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Admin

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  1. The posts that were thread drift in here have been moved to the Engines forum:
  2. The quiz in the first post is an example of what needs to be created for a quiz...it isn't an actual quiz or at least it isn't at the moment In reference to your question, try a google search on non-Polished engine
  3. 5.1 Air masses An air mass is a relatively homogeneous body of air usually covering millions of square kilometres of the Earth's surface and perhaps around 20 000 feet thick; even extending to the tropopause. To be homogeneous, the air mass source region must be exclusively continental (dry air) or exclusively maritime (moist air). All air mass source regions lie in tropical (warm air) or polar (cold air) latitudes. The air masses originating there are modified by passage into — and interaction within — the mid-latitudes, so producing 'mid-latitude air'. The modification of the air mass, by heating or cooling from the surface it is passing over, will change stability. Additional heating will make moist air more unstable, while additional cooling makes moist air more stable. Low-level convergence produces upper-level instability and low-level divergence produces upper-level stability. The air masses, and their source regions, affecting the Australian climate are: Equatorial maritime: Hot, humid air with dewpoint around 25 °C, bringing monsoon conditions to northern Australia. Tropical maritime: Warm, humid air with dewpoint around 20 °C, bringing showers, rain and tropical cyclones. Tropical continental: The source region is northern Australia. Hot, dry air in summer, dewpoint around 0 °C, bringing heat waves to southern Australia. Warm, dry air in winter, dewpoint around 4 °C. Southern Ocean maritime: Cool, moist air with dewpoint around 10 °C, bringing clouds, rain and drizzle to southern Australia. Antarctic polar continental/maritime: Cold, moist air with dewpoint around 5 °C, bringing cold outbreaks to southern Australia with snow and sleet. (South of Australia, the coastline of Antarctica lies north of the Antarctic Circle with the ice pack extending to about 60°S, only 1200 km from Tasmania). Frontal zones, or fronts, separate air masses of different characteristics. They usually extend from the surface to the middle troposphere, and occasionally to the upper troposphere. Within the frontal zone, changes of temperature, pressure, density and wind velocity are large compared to changes outside the frontal zone. In section 4 we established that the Antarctic front is the boundary region between the intensely cold Antarctic polar continental air and the warmer, moister polar maritime air. Also that the polar fronts are the major frontal regions of the southern hemisphere — mixing between polar air, mid-latitude air and returning tropical air. The Antarctic and polar fronts are quasi-stationary frontal regions, and may extend for several thousand nautical miles. They are distinct from the mobile cold fronts that directly affect southern Australia's daily weather patterns. The diagrams below indicate typical positions of the air masses, and the polar and Antarctic fronts, in the summer and winter seasons. 5.2 Extra-tropical cyclones The effect of the potential energy stored in the zone of strong surface temperature gradient in the polar frontal regions, with the cold air masses pushing north-west and wedging under the warmer air pushing south-east, is that the polar fronts spawn a series of migratory depressions south and west of Australia — typically in latitudes 35°S – 45°S. The depressions tend to be intense — surface pressures below 940 hPa with gradients of 50 hPa over 1500 km have been recorded. These transient depressions forming in the westerly wind belt (also known as cold-core cyclones, lows, storm depressions or, more correctly, extra-tropical cyclones) — often with embedded, smaller-scale storms — are the principal cause of day-to-day weather changes in southern Australia. A common theory for the development of these extra-tropical cyclones is that the interaction of the air masses cause a disturbance to develop on the line of the polar front. This initiates the process of converting the potential energy of the strong temperature gradient into the kinetic energy of a developing extra-tropical cyclone, so distorting the polar front into a wave-like configuration. The extent of each wave/trough is dependent on which air mass is stronger at that point. A wave crest may develop into an extra-tropical cyclone after several days (see following diagrams A to G) forcing southward movement of the warm air and northward movement of the cold air as mobile fronts. The intense, mobile cold front moves at 15–30 knots, faster than the warm front which it may eventually overtake to form an occluded front. That may then lead to an intensified storm. The development of the low also requires that the mass of the vertical column of air over the area is reduced by mass divergence, thus reducing the surface pressure. Consequently, the upper-air Rossby waves — and the jet streams — support and direct (and may enhance) the development of surface cyclones and other features. The maturing storm depression usually moves south-east to about 60°S – 65°S, into the Ross Sea and the sub-polar low belt. Here, cut off from the warmer moister air, it decays. Depressions may have a life cycle of one week or so. Some primary depressions may head north-east into the high-pressure belt. As they are then isolated from the westerly wind belt, they are consequently termed cut-off lows. Depressions tend to travel in groups of three or four, creating large eddies in the westerly wind belt. Secondary depressions occur on the trailing arm of the primary low cold front, and may curve north-east before decaying or swinging to the south-east. These secondary lows are often fast-developing, intense, short-lived storms. The spring-time msl analysis (below) from the World Meteorological Centre, Melbourne, shows the synoptic features in a polar projection of half the southern hemisphere, from the prime to the 180° meridians. It covers the area of southern Africa at the left, the Indian and Southern oceans, Antarctica at the bottom, and Australia/New Zealand at the right. The planetary-scale synoptic features displayed are the Antarctic polar high and the two anticyclones of the sub-tropical high belt extending a ridge right across the chart and centred at 35°S — also with a spur extending south to link into the polar high. There are also three or four centres of low pressure in the sub-polar low belt just off the Antarctic coastline at 65°S, each associated with an extensive front — some extending for maybe 3000 nautical miles. These are the polar fronts. There are about four migratory lows in the westerly wind belt at 55°S, one at 150°E and a group around 30°E — each associated with mobile cold and warm fronts. The unusual element is the long trough (the dashed line) extending from north-west Australia into the Tasman Sea and the Southern Ocean. The front passing over the south-east corner of Australia brought with it a cold outbreak of polar maritime air. The diagrams below are a four-day msl pressure forecast issued by the Australian Bureau of Meteorology [BoM]. Note the position of the fragmentary warm fronts well south of the mainland, and the frontal trough systems between the highs. A wide selection of the Bureau's daily msl analysis and prognosis charts can be viewed at BOM charts. In winter, intense primary depressions can develop at rates of one hPa per hour with the pressure gradient steepening towards the centre. Lows also develop in regions where no significant surface temperature gradient exists. They develop from the interaction of airstream flow and consequential frontal development. Weak lows may also form on the lee side of the Great Dividing Range. Occasionally a cold-core high — which unlike a warm-core high, decreases in intensity with height — will form in the southern polar maritime air mass behind a cold front. They are usually short-lived, as the upper levels are warmed by subsidence, and the system moves north-east and merges with the high pressure belt. However, such highs behind an intense low can direct a major cold outbreak of sub-Antarctic air into south-eastern Australia. If the cold-core anticyclone stays in the Southern Ocean and persists, it may form a blocking high, which interrupts and diverts the normal movement of the mobile cyclones. The same result is achieved if a warm-core high extends further south than normal. 5.3 Mobile cold fronts The mobile cold fronts, which develop with the extra-tropical cyclones, are typically 5000 feet deep at the nose and expand with depth. They may be 150 to 800 nm long and advance eastward at speeds of 15 to 40 knots — as indicated on the surface chart below. Mesoscale fronts may be much smaller. Small but sharp fronts also develop in the middle and upper troposphere. Warm fronts occur in the region where warm, less dense air is moving in the general direction of the south pole and sliding up over the semi-stationary colder, denser air. The resultant slope is in the region of 1:100 to 1:300. Cold fronts — where colder, denser air is pushing under semi-stationary, warmer air — have a typical slope of 1:60, but the warmer air is tending to ascend slantwise across the slope of the cold front. As the extra-tropical cyclones generally develop south of Australia — and the consequent warm fronts move south — the passage of a warm front over the mainland is rare. Part of a weak warm front may pass over Tasmania from a low developing in the south-east mainland corner or in Bass Strait. Such warm front occurrences over land are fragmentary, weak and transient. The BoM surface chart below shows a weak warm front forming at the south-east mainland corner, it subsequently disappeared within 24 hours. Similarly occluded fronts are rare occurrences in Australia; so, the remainder of this section deals solely with the structure and effects of cold fronts. The presence of a front does not of itself imply cloud formation and rain. Convergence is necessary to produce rain, and when the front is remote from a depression, then convergence may be absent. Cold fronts moving northward into south-west Queensland are usually shallow and diffused but may trigger a surge in the prevailing easterlies. The two diagrams below show the cross-section of typical summer cold fronts. The upper diagram is that of an active summer cold front. When the low pressure system weakens, or the cold front trails towards the high pressure region, the air aloft subsides and warms, the upper cloud disappears and the front weakens — as shown in the lower diagram. Note that the diagrams greatly exaggerate the frontal slope. In winter, if the normal pattern of eastward movement is halted then cold fronts will cross south-east Australia every few days. They are usually relatively weak but with widespread cloud bands, low cloud bases and showery precipitation. Some winter cold fronts may be vigorous and fast moving, with embedded thunderstorms and a narrow band of cloud and precipitation. Such winter fronts are usually associated with a very deep depression forming further north than usual. Cross-section of an unstable cold front When an active cold front moves north-east — particularly in spring and summer — a subsidence may occur in the cold air behind the frontal zone, which causes the frontal zone to bulge ahead of its surface position. Thus, the lifting of the warm air occurs ahead of the frontal surface position and is accompanied by increased instability — the nose of the cold front pushes up a bow wave that creates lift similar to orographic lift. Depending on the moisture content of the lifted air, thunderstorms — or even a squall line — may form ahead of the front. The sequence of events associated with the passage of such a front moving at 25 knots (but without a squall line) might be as follows: In the transition zone ahead of the front, warm to hot north to north-westerly winds freshen, pressure is falling and cirrus clouds are moving from the west, three to six hours prior to passage of the front; this is followed by lowering cloud (Ac, As and Ns). Some rain occurs just ahead of the front, then thunderstorms and violent gusts, and the temperature drops suddenly as the frontal zone passes. In the cold air behind the front, the clouds and showers clear quickly, the wind backs to south/south-west and the pressure rises. There may be a number of pressure changes in the transition zone ahead of any cold front, usually including wind squalls. The airflow in the zone is very unstable, producing large changes in wind velocity — both horizontal and vertical — and distinct lines of convection cells, which may form a squall line particularly in spring and summer. 5.4 Synoptic isobaric features East coast lows and cut-off lows Depressions forming off south-west and south-east Australia tend to be large, deep and slow moving. They may dominate the local weather system, bringing heavy rain for several days, particularly in the cooler season. These depressions may be cut off from the westerly wind belt by a high pressure cell or ridge to their south. Deep cut-off low off Western Australia coast Slow moving, cut-off low — eastern coast Blocking pairs About ten times per year a semi-stationary system of high and low pressure cells, located in the Tasman Sea, can block the normal easterly procession of the highs and lows. The blocking pairs occur most frequently in winter with the low pressure cell or trough closer to the equator and the high pressure cell on the polar side, both out of their normal zone. (The high could be a warm-core high that has drifted south-east or a persistent cold-core high). A strong north/south wind is set up between them and the upper, westerly wind flow is split — with one part passing on the northern side of the blocking pair and the other part passing on the southern side. Blocking pairs can cause abnormal weather patterns in south-east Australia. Persistent and recurring pairs lead to low rainfall and drought conditions. 5.5 The north-west cloud band The north-west cloud band is a frequent feature in satellite weather images, typically extending over 2500 nm and existing for two to four days. Most occurrences disintegrate after six days. It originates in a convective system in the Indian Ocean south and west of Indonesia, where tropical maritime air flowing poleward on the western flank of a high pressure ridge — extending through eastern and northern Australia — conflicts with a pre-frontal trough of colder, drier air extending from southern Australia into north-western Australia. The maritime air is forced to rise, producing heavy stratiform cloud that eventually extends from the convective source (which continues to feed moisture into the system) to south-eastern Australia. The phenomenon occurs once or twice a month during the colder months. The vertical extent of the cloud band increases toward the south-east with a lowering base and an increasing height of the tops. Two or three times a year a fully active band will present cloud cover right across Australia, extending — unbroken — from very low levels to above 20 000 feet and joining with a low pressure system in the south-east corner. Heavy rain is often associated with the bands and conditions less than standard visual meteorological conditions [VMC] can exist for days. STRICT COPYRIGHT JOHN BRANDON AND RECREATIONAL FLYING (.com)
  4. 4.1 General global circulation As the Earth rotates at a constant rate and the winds continue, the transfer of momentum between Earth–atmosphere–Earth must be in balance and the angular velocity of the system maintained. (The atmosphere is rotating in the same direction as the Earth but westerly winds move faster and easterly winds move slower than the Earth's surface. Remember, winds are identified by the direction they are coming from not heading to!) The broad and very deep band of fast-moving westerlies in the westerly wind belt, centred around 45°S (but interrupted at intervals by small, migrating lows moving east — not shown in the diagram above) lose momentum to the ocean through surface friction, resulting in the Southern Ocean's west wind drift surface current. The equatorial easterlies or trade winds and, to a lesser extent the polar easterlies, gain momentum from the Earth's surface. That gain in momentum is transferred, to maintain the westerlies, via large atmospheric eddies and waves — the sub-tropical high and the sub-polar low belts. These eddies and waves are also part of the mechanism by which excess insolation heat energy is transferred from the low to higher latitudes. Globally, the equatorial low pressure trough is situated at about 5°S during January and about 10°N during July. Over the Pacific Ocean the trough does not shift very far from that average position — but due to differential heating it moves considerably further north and south over continental land masses. In Australia the trough will sometimes approach Alice Springs — latitude 23°S in the hot centre of the continent. The average summer msl pressure chart shows the position of the three most intense low pressure areas of the trough over South America, Africa and Australia/Papua-New Guinea. The low-level air moving towards the trough from the sub-tropical high belts at about 30°S and 30°N is deflected by Coriolis, and forms the south-east and north-east trade winds. Coriolis effect deflects air moving towards the equator to the west and air moving away from the equator to the east. Thus, when the north-east trade winds cross the equator in the southern summer, they turn to become the north-west monsoon which brings the 'Wet' to northern Australia. 4.2 Cross-section of tropospheric circulation 4.3 The intertropical convergence zone and the Hadley cell The trade winds converging at a high angle at the equatorial trough, the 'doldrums', form the intertropical convergence zone [ITCZ]. The air in the trade wind belts is forced to rise in the ITCZ and large quantities of latent heat are released as the warm, moist, maritime air cools to its condensation temperature. About half the sensible heat transported within the atmosphere originates in the 0–10°N belt, and most of this sensible heat is released by condensation in the towering cumulus rising within the ITCZ. A secondary convergence zone of trade wind easterlies — the South Pacific convergence zone — branches off the ITCZ near Papua-New Guinea, extends south-easterly, and shows little seasonal change in location or occurrence. Over land masses the trade winds bring convective cloud, which develops into heavy layer cloud with embedded thunderstorms when the air mass is lifted at the ITCZ. The ITCZ is the 'boiler room' of the Hadley tropical cells, which provide the circulation that forms the weather patterns and climate of the southern hemisphere north of 40°S. The lower-level air rises in the ITCZ then moves poleward at upper levels — because of the temperature gradient effect — and is deflected to the east by Coriolis, at heights of 40 000 – 50 000 feet, while losing heat to space by radiative cooling. The cooling air subsides in the sub-tropical region, warming by compression and forming the sub-tropical high pressure belt. Part of the subsiding air returns to the ITCZ as the south-east trade winds thus completing the Hadley cellular cycle. (The system is named after George Hadley [1685-1768], a British meteorologist who formulated the trade wind theory.) At latitudes greater than about 30°S the further southerly movement of Hadley cell air is limited by instability, due to conservation of momentum effects, and collapses into the Rossby wave system. The Hadley cell and the Rossby wave system — combined with the cold, dry polar high pressure area over the elevated Antarctic continent — dominate the southern hemisphere atmosphere. Fifty per cent of the Earth's surface is contained between 30°N and 30°S, so the southern and northern Hadley cells directly affect half the globe. 4.4 The sub-tropical anticyclones The subsiding high-level air of the Hadley cells forms the persistent sub-tropical high pressure belt, or ridge, that encircles the globe and which is usually located between 30°S and 50°S. Within the belt there are three semi-permanent year-round high-pressure centres in the South Indian, South Pacific and South Atlantic oceans. In summer, anticyclonicity also peaks in the Great Australian Bight. In winter the high-pressure belt moves northward, the high in the Bight extends and migrates into a large, semi-permanent winter anticyclone over southern Australia. The Indian Ocean centre produces about 40 anticyclones annually which, as they develop, slowly pass from west to east, with their centres at about 38°S in February and about 30°S in September. The anticyclones, or warm-core highs, are generally large, covering 10° of latitude or more, roughly elliptical, vertically extensive and persistent, and with the pressure gradient weakening towards the centre. The anticyclones are separated by lower-pressure troughs. Winds move anticlockwise around the high, with easterlies on the northern edge and westerlies on the southern edge. Air moving equatorward on the eastern side is colder than air moving poleward on the western side. The high-level subsiding air spreads out, chiefly to the north and south of the ridge due to the higher surface pressures in the east and west. Thus the position of the sub-tropical high belt dominates Australian weather. In summer, when it is centred just south of the continent, sub-tropical easterlies cover much of Australia, with monsoonal movement in the north. In winter the belt, being further north, allows the strong, cold fronts that are embedded in the westerlies to affect southern Australia (refer to section 5.2). 4.5 The Antarctic polar high and the sub-polar low belt The lowest surface temperatures on Earth occur at the Antarctic continent, at minus 80 °C or less. The very dry air allows any long-wave radiation to escape without any appreciable atmospheric warming. The cold-core Antarctic polar high is quite shallow — 5000 to 10 000 feet deep — which decreases in intensity with height, and has a very steep inversion and an extensive upper-level low aloft; the combination of high pressure and low temperatures producing very dense air. The air moving in an anti-clockwise direction around the anticyclone produces the surface outflow belt of polar easterlies. But, over the high-altitude icecap, tropospheric circulation consists of mid and upper-level inflow and katabatic outflow in a shallow surface layer. (A monthly mean katabatic wind of 58 knots has been recorded at Commonwealth Bay.) Very cold air masses and minor highs can split off the main Antarctic air mass — following passage of a major cyclone — and move northwards in winter, bringing the very cold Antarctic continental/maritime air towards Australia. By contrast, due to the Antarctic ice cap elevation of 6000 to 13 000 feet, Southern Ocean storms usually do not penetrate the Antarctic region south of Australia and surface pressure mainly depends on elevation. A series of deep lows — usually centred between 50°S and 60°S and tending further south during the equinoctial periods (the Antarctic sub-polar low belt) — surround the Antarctic polar high, the boundary between the two systems is formed by the polar easterlies. This boundary between the intensely cold continental air and the warmer, moister polar maritime air is termed the Antarctic front. 4.6 Rossby waves and the westerly wind belt Upper westerlies blow over most of the troposphere between the ITCZ and the upper polar front. They are concentrated in the westerly wind belt where they undulate north and south in smooth, broad waves. These waves comprise one, two or three semi-stationary, long wave, peaks and troughs. They occur during each global circumnavigation and have a number of distinct mobile short waves; each about half the length of the long waves. The amplitude of these mobile Rossby waves, as shown on upper atmosphere pressure charts, varies considerably and can be as much as 30° of latitude. Then the airflow, rather than being predominantly east/west, will be away from or towards the pole. The gradient wind speed in the equatorward swing will be super-geostrophic and the speed in the poleward swing will be sub-geostrophic.The poleward swing of each wave is associated with decreasing vorticity and an upper-level high pressure ridge and the equatorward swing is associated with increasing vorticity and an upper trough. Downstream of the ridge, upper-level convergence occurs, with upper-level divergence downstream of the trough. This pattern of the Rossby waves in the upper westerlies results in compensating divergence and convergence at the lower level. This is accompanied by vorticity and the subsequent development of migratory surface depressions — lows or cyclones (cyclogenesis) — and the development of surface highs or anticyclones (anticyclogenesis). The long waves do not usually correspond with lower-level features, as they are stable and slow moving, stationary or even retrograding. However, they tend to steer the more mobile movement of the short waves which, in turn, steer the direction of propagation of the low-level systems and weather. The swings of the Rossby waves carry heat and momentum towards the poles, and cold air away from the poles. The crests of the short waves can break off, leaving pools of cold or warm air, which assist in the process of heat transfer from the tropics. Wave disturbances at the polar fronts perform a similar function at lower levels. An upper-level pool of cold air — an upper low or cut-off low or upper air disturbance — will lead to instability in the underlying air. The term cut-off low is also applied to an enclosed region of low surface pressure that has drifted into the high pressure belt, i.e. cut off from the westerly stream, or is cradled by anticyclones and high pressure ridges. Similarly the term cut-off high is also applied to an enclosed region of high surface pressure cut off from the main high pressure belt (refer to 'blocking pairs') and to an upper-level pool of warm air that is further south than normal — also termed upper high. Air thickness charts show the vertical distance between two isobaric surfaces. Usually, 1000 hPa is the lower, and the upper may be 700 hPa, 500 hPa or 300 hPa. The atmosphere in regions of less thickness — upper lows — will be unstable and colder, whereas regions of greater thickness — upper highs — tend to more stability. On these charts, winds blow almost parallel to the geopotential height lines. 4.7 Southern polar fronts The polar fronts, a series of separate fronts globally distributed in the Southern Ocean, are the major frontal zones of the southern hemisphere. They mix between polar air, mid-latitude air and returning tropical air (refer to diagram 4.2). The very cold, dense air moving from the Antarctic high pressure cell and which is deflected by Coriolis into easterlies, contacts the warmer, moister Southern Ocean air moving away from the sub-tropical high pressure belt and which is deflected by Coriolis into westerlies. The returning tropical air is the upper-level air flowing from the Hadley cell, which subsides behind the front and returns to the sub-tropical region at lower levels. Polar fronts are quasi-stationary and generally located about 45°S, but move with the seasons. 4.8 Upper-level jet streams Upper air flow in the Hadley cell moves to about 30°S latitude while cooling and eventually subsiding, forming the sub-tropical high pressure belt or ridge. Applying the principle of conservation of momentum: the rotation at the equator is 464 metres/second while at 30°S the surface rotation is 402 m/sec. Thus at 30°S a molecule of upper air transported from the equator has a surplus momentum of 62 m/sec or 122 knots. This surplus momentum forms the westerly sub-tropical jet stream, with an average velocity of 120 knots — the upper stream represented in the following diagram from The Weather Company www.weatherzone.com.au. The polar front jet streams are embedded in the upper-level westerlies, snaking north and south daily and seasonally with the movement of the polar front depressions. They exist because of the strong thermal gradient in that area and they are regions of maximum upper-level air mass transport. As they meander polewards and equatorwards with the general upper air waves, they tend (by their sheer mass) to steer the movement of major low-level air masses. This encourages development of surface pressure features, and intensification of pre-existing features, by the concentrated convergence/divergence within the jet stream. The jet streams are stronger in the winter when the polar front is closest to the equator. The image indicates the position of the sub-tropical and polar front jet streams on 29 August 2009. Jet streams are not continuous but can be as much as 3000 – 5000 km long, 100 – 300 km wide and 7000 – 10 000 feet deep. About 60% of the width tends to be on the equatorial side of the core, which is located near the tropopause. Over Australia, core wind speeds normally range from 60 – 150 knots, but occasionally reach 200 knots. The wind speeds usually decrease by 3 – 6 knots per 1000 feet above and below the core, but the rate may reach 20 knots per 1000 feet. Horizontally, the wind speeds are diminished by about 10 knots per 100 km distance from the core. Jet stream cirrus may form on the equatorial side of the core. STRICT COPYRIGHT JOHN BRANDON AND RECREATIONAL FLYING (.com)
  5. Hi, the site is desperately looking for an aviation learned person to act as or Quiz Master. All you need to do is come up with quizzes of about 10 or so questions each and send them to me. They need to be multiple choice questions with at least one correct answer and an approx time it should take a person to complete. For example: Questions and Answers 1. Select from the following choices the answer that is NOT one of the four forces acting on an aircraft in flight. A. Thrust B. Speed C. Drag D.Lift 2. If you are flying into a direct headwind of 28 knots, at a true airspeed of 156 knots, what is your ground speed? A. 156 knots, as your groundspeed is not affected by wind B. 184 knots, as wind and true airspeed is additive C. 128 knots, because TAS minus headwind component = GS D. Cannot determine from the data given 3. You're taking off in a tailwheel aircraft with a non-Polish engine. As you begin your takeoff roll, you use no rudder displacement. On which side of the runway will you most likely depart the prepared surface prior to getting airborne? A. Left B. Right C. Neither, as the aircraft will track straight with use of ailerons only D. Unable to determine the answer without knowing the wind direction 4. As a general rule, as ambient temperature increases, aircraft performance increases. A. True B. False 5. Hydroplaning is when the aircraft tires lose traction with the runway surface due to rain or standing water during takeoff or landing. Which of the following formulae can be used to determine the speed at which hydroplaning will occur? A. .6 times the stall speed with takeoff flaps B. 9 times the square root of the tire pressure C. Aircraft weight divided by the square root of the tire footprint in sqare inches D. Cannot be determined, as hydroplaning speed varies with the tread pattern just like in your car 6. There are OLD pilots and there are BOLD pilots, but there are few OLD, BOLD pilots! A. True B. False 7. Name the two factors which affect Density Altitude. A. Pressure altitude and gross weight B. Gross weight and temperature C. Engine power and flap setting D. Temperature and pressure altitude 8. Your friend flies his single engine plane into Beloit Airport for the Spring Fling Pancake Breakfast and Auto Show. After he shuts down in the parking area, he tosses you a rag and asks your help in cleaning bugs off the plane. The leading edges of the wings are covered with bug splats, but there are no bugs at all on the front of the propeller. Why not? A. Bugs can "see" the propeller and will avoid it at any cost. B. The propeller "blows" them out of the way so they impact the wings instead C. Tractor propellers are pitched such that the first surface that contacts the air (and bugs) as the plane moves forward is the back side of the propeller blades D. The propeller power pulses project a vibration ahead of the plane that bugs don't like and naturally avoid E. None of the above 9. What is the minimum number of hours prior to flying that a pilot may consume alcohol? A. Half an hour B. 4 hours for beer or wine; 8 hours for hard liquor C. 8 hours from "bottle to throttle" D. 24 hours 10. Pilots who fly tricycle gear airplanes are sissies. A. True B. False PLEASE, if you feel you would like to contribute to the learning of pilots and just create some fun quizzes by being the Quiz Master then URGENTLY let me know...thanks for any help you can give
  6. Harrison Ford - Legend of Aviation - from interview by RJ McHatton Inventive Productions (the Autobiography Company) http://www.inventiveproductions.com
  7. 3.1 Cloud formation Generally, upward motion of moist air is a prerequisite for cloud formation, downward motion dissipates it. Ascending air expands, cools adiabatically and, if sufficiently moist, some of the water vapour condenses to form cloud droplets. Fog is likely when moist air is cooled not by expansion but by contact with a colder surface. Water vapour generally needs something to condense onto to form liquid. Common airborne condensation nuclei are dust, smoke and salt particles; their diameter is typically 0.02 microns (micrometres) but a relatively small number may have a diameter up to 10 microns. Maritime air contains about one billion nuclei per cubic metre (typically salt), while polluted city air contains many more. The diameter of a cloud droplet is typically 10 to 25 microns and the spacing between them is about 50 times the diameter — perhaps 1 mm — with maybe 100 million droplets per cubic metre of cloud. The mass of liquid in an average density cloud is approximately 0.5 gram per cubic metre. Above the freezing level in the cloud, some of the droplets will freeze if disturbed by contact with suitable freezing nuclei or with an aircraft. Freezing nuclei are mainly natural clay mineral particles, bacteria and volcanic dust, perhaps 0.1 microns in diameter but up to 50 microns. There are rarely more than one million freezing particles per cubic metre; thus there are only enough to act as a freezing catalyst for a small fraction of the cloud droplets. Most freezing occurs at temperatures between –10 °C and –15 °C. The balance of the unfrozen droplets remains in a supercooled liquid state, possibly down to temperatures colder than –20 °C. Eventually, at some temperature warmer than –40 °C, all droplets will freeze by self-nucleation into ice crystals, forming the high-level cirrus clouds. In some cases, fractured or splintered ice crystals will act as freezing nuclei. The ice crystals are usually shaped as columnar hexagons or flat plate hexagons. Refer to sections 3.5.2 and 12.2.2. Condensation of atmospheric moisture occurs when: the volume of air remains constant but temperature is reduced to dewpoint; e.g. contact cooling and mixing of different layers the volume of an air parcel is increased through adiabatic expansion evaporation increases the vapour partial pressure beyond the saturation point a change of both temperature and volume reduces the saturation vapour partial pressure. 3.2 Cloud classification 3.2.1 Cloud genera Cloud forms are based on ten main genera, conventionally grouped into three altitude bands — high, medium and low — plus a vertically developed group. About 90% of atmospheric moisture exists below 20 000 feet with 50% or more in the band below 6500 feet. The altitudes included in each band are dependent on the thickness of the troposphere at nominal locations — tropical, temperate or polar. These are: Cloud altitude bands Tropical Australia Temperate Australia Antarctic High 20 000–60 000 16 000–43 000 10 000–26 000 Medium 6500–26 000 6500–23 000 6500 –13 000 Low 0–6500 0–6500 0–6500 High clouds A two-letter code is used to identify cloud genera in meteorological reports, observations and aviation area forecasts. Cirrus [CI] (Latin for 'curl'): white patches, banners, threads or delicate filaments of ice crystals. They often appear in patches of individual 'generating heads' with streaks of crystals falling from them thus forming comma-shaped or hooked 'mares' tails'. Cirrus clouds may merge into CS or CB. They are formed by widespread ascent, but sometimes by upper level turbulence in a smaller area. Cirrostratus [CS]: a thin, transparent, amorphous, whitish veil of smooth or sometimes finely fibrous appearance, appearing over much of the sky at very high altitudes. They create the appearance of halos about the sun or moon. Cirrostratus may merge into CC or possibly AS, and are formed by widespread ascent and may thicken when preceding a cold front. Cirrocumulus [CC]: thin, white patches, sheets or rows with small, regularly arranged elements or cloudlets in the form of grains or ripples, which may be merged or separate; sometimes with an appearance like fish scales — a 'mackerel sky'. The apparent width of elements is less than one degree. Cirrocumulus elements may merge together to form CS or separate into CI mares' tails. CC are produced by turbulence aloft — often associated with a front or upper-level disturbance. Medium-level clouds Altostratus [AS]: grey/bluish sheet, with coverage of possibly 8 oktas, of uniform appearance. They are often striated or fibrous, having parts thin enough to reveal a vague sun without any halo but possibly a corona. Altostratus often merges into NS. They are caused by widespread ascent and are usually associated with a front or upper-level disturbance. Altocumulus [AC]: white/grey patches, bands or sheets of regularly arranged globular elements (sometimes called mackerel sky) — waves or rows with light shading, closely packed or merged. The element width is 2 to 5 degrees. (A finger width at arm's length is approximately 2 degrees; the spread between the tips of the little finger and thumb when a hand is splayed is about 22 degrees.) Altocumulus often shows coloured patches (irisation) around elements when illuminated by the sun or moon; a corona may be visible. They are usually caused by turbulence and are not associated with a change in the weather. Nimbostratus [NS] (from the Latin 'nimbus' = cloud, aureole): thick, dense, dark grey layer, often with a ragged or diffused base, with continuous precipitation. Coverage is often 8 oktas. Scud (pannus) may form beneath it. Invariably they occur at medium level, but usually extend to high level and merge with AS; they may also extend to low levels and envelop hills. Nimbostratus are produced by widespread ascent. Low-level clouds Stratocumulus [SC]: grey/whitish patches, sheets or layers of separate or partly merged globular masses or rolls with dark shading and generally irregular appearance. If regularly arranged, the separate elements have apparent width exceeding 5 degrees. Coverage is often 8 oktas and may be penetrated by large CU or CB. Stratocumulus are probably the most frequently seen cloud in south-eastern Australia and are most frequent in winter anticyclones — 'anticyclonic gloom' — when moist air is trapped under an inversion. They are particularly noticeable around Melbourne. Stratus [ST] (Latin = spread, laid down): grey, uniform layer with fairly even base from which drizzle may descend. The sun outline may be visible. Stratus envelops low hills. They sometimes appear in ragged patches, which are produced by frictional turbulence or possibly orographic ascent. Cumulus [CU] (Latin = heap): white, heaped tops with generally grey, horizontal bases. Form is usually sharply outlined but may be ragged if evaporating. Vertical development varies greatly with atmospheric buoyancy, and bases can be at low or medium levels. Cumulus are formed by convection or possibly orographic ascent. Vertically developed clouds Cumulonimbus [CB]: heavy, dense cloud with massive vertical development, bases at low or medium levels, with tops possibly reaching (even overshooting) the tropopause. They may have a 'boiling' appearance during their vertical development stage. The base is usually very dark with lighter inflow areas. They are associated with heavy showers or virga — precipitation that evaporates before reaching the surface. Frequently low, ragged, turbulence cloud is mixed beneath it. Cumulonimbus are produced by vigorous convection. Refer to section 3.6. For more information on the types and dangers of thunderstorms read sections 9.4 through 9.7. Towering cumulus [TCU]: CU with cauliflower appearance, often of great vertical extent. Properly known as cumulus congestus [CU CON]. Cloud structure and composition Cloud type Height of base Vertical extent Composition Associated precipitation CI 20 000 + usually thin* ice crystals fall streaks CS 20 000 + usually thin ice crystals nil CC 20 000 + usually thin crystals/droplets nil AS 6000 – 20 000+ up to 15 000 usually crystals, occasionally mixed rain/snow AC 6000 – 20 000 usually thin usually droplets to –10 °C, some crystals to –30 °C occasionally mixed rain, drizzle NS 0 – 8000+ merges into AS water droplets steady rain, snow, ice pellets SC 1500 – 4000 500 – 3000 mainly droplets down to –15 °C rain, drizzle, virga ST 0 – 2000 200 – 1000 usually water droplets drizzle CU, TCU 1500 – 15 000 up to 15 000 water droplets rain showers CB 1500 – 5000 15 000 – 35 000+ mainly droplets to –15 °C, mixed at lower temperatures rain/snow showers/virga, hail, ice pellets *With fall streaks, the vertical extent of CI may exceed 5000 feet Photographs and more information on cloud classes and identification techniques can be found at the Australian Severe Weather website. 3.2.2 Cloud species Each of the cloud genera are subdivided into species by the addition of a common species descriptor (with a three-letter code), according to cloud shape and structure. Fibratus [FIB]: CI and CS in the form of long, irregularly curved or nearly straight parallel filaments, but without tufts or hooks. CI FIB, CS FIB Spissatus [SPI]: dense or thickened CI plumes or CS, often originating from, or the remnants of, a CB anvil. Generally has a stormy appearance, looking greyish when viewed towards the sun. CI SPI, CS SPI Uncinus [UNC] (Latin = hook): CI with filaments that are hooked or comma-shaped. 'Mares tail cirrus'. Ice crystals are forming at the high point of the fall streak where a small tuft of cloud may appear — the generating head. The crystals forming the tail are falling through atmospheric layers of varying wind velocity and persist for quite a while before evaporating. CI UNC Nebulosus [NEB]: CS and AS as an indistinct veil lacking any detail. Also applied to low amorphous ST — lifted fog. CS NEB, AS NEB, ST NEB Stratiformus [STR]: AC and SC, occasionally CC, spread out into an extensive sheet or layer. CC STR, AC STR, SC STR Lenticularis [LEN]: (from the Latin 'lentil shaped') AC of orographic standing wave origin, sometimes CC or SC; occurs as a biconvex shape with a sharp margin, and often elongated if produced by a long ridge. They sometimes display iridescence. May form in long bands parallel to the Great Dividing Range and extend 50 to 100 nm downstream, towards the east; see mountain waves. When there are alternating layers of drier and moister air a tall, well-developed lenticularis formation may resemble an inverted stack of dinner plates, occasionally seen in the mountain areas of south-eastern Australia. CC LEN, AC LEN, SC LEN Castellanus [CAS]: having a turreted or crenellated appearance and connected to a common cloud base line. They are generally AS (but forming AC), or sometimes SC, CI or CC, signifying increasing instability. AC CAS may precede the development of CB. Floccus [FLO] (Latin = tuft of wool): CI, CC or particularly AC occurring in chaotic form, like a flock of sheep, each unit having a ragged base and a small cumuliform tuft above; 'thundery skies'. Often accompanied by virga. If developing CU reach this humid and unstable layer then energetic CB may develop. Fractus [FRA]: ST or CU shreds with broken, ragged or wispy appearance, associated with formation or dispersion of low cloud. CU FRA often appears early in the morning, rising only slightly above the condensation level; they are also found in precipitation under CB. ST FRA is much darker than CU FRA when found under CB. ST FRA normally forms below NS or AS, and derives moisture from evaporating raindrops or surface water. Uplift from near-surface turbulence may produce ST FRA, particularly in areas of rising ground or low hills. If forming without overlying cloud, ST FRA forewarns of worsening low-level visibility and ST formation. Pannus or scud is a mix of CU FRA and ST FRA. Humilis [HUM] (Latin = lowly): CU with small development and usually flattened at an inversion that is not far above the condensation level — 'fair weather CU'. Lifetime is 5 to 45 minutes. CU HUM Mediocris [MED] (Latin = of middle degree): CU of intermediate vertical growth, occurring at no more than 3000 feet. They have tops showing small protuberances that are not actively growing. CU MED Congestus [CON] (Latin = piled up): CU with cauliflower appearance, often of great vertical extent, perhaps 10 000 feet; generally known as towering CU [TCU]. Freezing does not occur. CU CON may produce heavy showers or microbursts, the latter particularly so in northern Australia. Calvus [CAL] (Latin = bald): developing CB prior to anvil stage, but at least some of its upper part is losing its CU outline due to freezing. CB CAL Capillatus [CAP] (Latin = hair): CB with distinct icy, upper fibrous or striated cirriform appearance. Frequently anvil-shaped, or untidy plumes, or disordered cirrus mass. CB CAP 3.2.3 Cloud varieties Each of the cloud genera and species can be further classified into varieties by use of a common descriptor for element arrangement, transparency, etc. Intortus [IN]: irregularly curved or tangled CI. Vertebratus [VE]: CI looking like fish bone, ribs or vertebrae. Lacunosus [LA]: thin CC or AC with regularly spaced, net-like holes or a honeycomb appearance. Undulatus [UN]: parallel undulations in patches, sheets or layers of CC, CS, AC, AS, SC or ST caused by waves in the airstream. Radiatus [RA]: broad, parallel bands of CI, AC, AS, CU or SC appearing to converge towards a radiation point on the horizon, or both horizons. Duplicatus [DU]: more than one layer of CI, CS, AC, AS or SC at slightly different levels. The winds at each layer are usually blowing in slightly different directions. Translucidus [TR]: AC, AS, SC or ST in large sheets thin enough to show position of the sun or moon. Perlucidus [PE]: AC or SC in broad layers or patches with small lanes that allow the sky to be seen. Opacus [OP]: AS, AC, SC or ST that completely masks the sun or moon. 3.2.4 Accessory clouds There are three cloud types that only exist in association with one of the main cloud genera: Pileus (Latin = cap, hood, like mushroom cap): a short-lived, smooth lenticular cloud appearing in a humid stable layer above a CB or TCU when the rising thermal deflects the moving air in the layer up and over into the condensation level. Further CB or TCU development will push through the cap cloud, which may hang on as a temporary collar. There is a good photograph of such an event in the Sydney Storm Chasers website. In strong shear conditions, the cap cloud may form downwind. Velum (Latin = veil): a thin, wide and persistent sheet of cloud accompanying a CB or TCU and forming in a humid, stable layer. Velum is dark in contrast to the convective cloud that generally rises through it. Pannus (Latin = piece of cloth): a mix of CU FRA and ST FRA, or just a lump of ST. Scud rapidly forms or reforms generally at lower levels under precipitating CU, AS, CB or NS bases in turbulent lifting conditions, particularly when air rises rapidly at the edge of cool moist outflow, or a downburst or in upflow caused by the topography — and exacerbated by evaporation of moisture from forest canopies. Scud changes size and shape constantly, and may be drawn into the cloud base. Flight in a locality where pannus is forming — scud running — is a very dangerous activity for aviators. 3.2.5 Cloud features Some notable cloud features are: Incus (Latin = anvil): the anvil of a large CB, particularly a multicell or supercell storm, which has spread out, usually when upper-level winds are light. A severe storm attains maximum vertical development when the updraught reaches a stable layer which it is unable to break through — often the tropopause — and the cloud top spreads horizontally in all directions to form an overhanging anvil. The photograph and text below appeared in the "NSW Lightning Bolt" of August 1997 — produced by the Severe Weather Section of the Bureau of Meteorology, NSW. That anvil had a spread of about 30 km. The rollover around the underside of the anvil indicates rapid expansion. "Rose's magnificent photo (below) of a storm cloud near Millthorpe in NSW is familiar to many Bureau staff from the 1996 Weather Calendar, a 1995 Bureau Christmas card, and the new thunderstorm poster. The story of how the photo came to be taken may attract the writers at the Disney Studios. Rose relates the tale: '... my son Ian phoned to tell me about the clouds and to ask if I had a spare film, as his camera was empty. I tied a film to our kelpie's collar and sent him down the hill to Ian. Meanwhile, Ian's daughter Melanie was cycling up to get the film ... by the time they both met Ian the cloud had started to break up. Fortunately by then I had climbed two fences and taken the two shots ...' " Arcus (Latin = arch, bow or curve): a shelf-like cloud indicating the inflow region at the leading edge of a thunderstorm or a squall line. If conditions are very humid the shelf cloud will be a low, thick, curved and well-formed cloud bank. If there is a sharp, severe gust front there may be a vortex indicated by twisting scud under, and leading up to, the shelf. A roll cloud, like a horizontal tube, may develop if the leading edge of the shelf speeds up and detaches. SC, AC roll clouds are also associated with mountain waves and solitary waves. Granitus: a localised cloud (always forming below the lowest safe altitude [LSALT] marked on aeronautical charts) enclosing and obscuring a large chunk of land, usually in the form of a hill or peak. Granitus is sometimes known as 'stuffed CU', which refers to both the solid content and the consequences of entering such a cloud. Wall cloud: a localised, possibly rotating, lowering from a CB cloud base. Situated at the main updraught with a diameter ranging from 0.5 km to 5 km. Refer to section 9.5. The Sydney Storm Chasers website has many images of thunderstorm features. There are good photos of wall clouds, arcus, pannus and mammatus. Mammatus: hard, downward protuberances, pouches or bulges from the underside of a CB anvil (frequently) or CI, CC, AS, AC or SC, indicating descending pockets of small droplets or ice crystals. The sinking, saturated air is cooler than the air around it. As it sinks it warms, but warming is retarded because some of the heat is used in evaporating cloud droplets in the saturated air. If more energy is required for evaporation than is generated by adiabatic warming, then the air and the cloud pouches will continue to sink and will elongate the protuberances. The mamma associated with CI and CC are very shallow, forming undulations in the cloud trails. Mamma associated with CB are an indication of a dissipating storm rather than severe turbulence. Fall streaks: virga-like showers of ice crystals or snowflakes from CI generating heads, which sink at rates up to 0.5 m/sec but slowing as they sublimate. As they sink through several thousand feet they become deflected by falling into winds of lower velocity, or slow through sublimation, and thus appear to trail back from the parent head as hooks, mares' tails, etc. Dense streaks combined with a strong drop in wind speed produce jet-stream banners — CI features that stream with the wind. AS and most stable cloud features lie across the wind. Billow clouds: AC and AS found in a series of regular bands with clear areas between of similar width, occurring most frequently at 15 000 to 25 000 feet. At other times the upper surface (usually but could be the lower surface) of the cloud may have regular wave-like troughs and crests – undulatus. When a higher-level inversion occurs, the upper and lower air layers are generally stable. If there is a significant difference in wind velocity between the layers then there is vertical wind shear at the interface, and a phenomenon known as 'Kelvin-Helmholtz shearing instability' causes the formation of long but short-lived waves across the interface — in much the same way as ocean waves — which grow in amplitude until they curl up and break. The waves produce an extensive but shallow area of clear air turbulence. If sufficient moisture exists, the waves become visible as Kelvin-Helmholtz billows. Billows always move with the wind so that in wave clouds they appear to move from the front to the rear of the formation, evaporating in the troughs and re-condensing in the crests. Kelvin-Helmholtz instability produces the ripples seen when a light wind blows across a pond of water. Pyrocumulus: CU initiated by bushfire thermal activity. Ray Kennedy's photograph below shows a CU CON building above the brown smoke during the Gippsland bushfires on New Year's Day 1998. 3.2.6 Stratospheric clouds Nacreous (mother-of-pearl) clouds are rare, high-latitude, stratospheric clouds resembling CC LEN or AC LEN. Small patches are occasionally formed in winter, usually in stationary standing waves, and often in the lee of mountain ranges, which provide abrupt uplift. They usually occur in the ozone layer at about 25 km with temperatures down to –80°C or –90°C. Nacreous clouds are probably composed of spherical ice crystals about one to two microns diameter. Brilliant iridescence is shown at angular distances up to 40 degrees from the sun, and green and pink colours predominate. These clouds are brightest at sunset but are rarely seen in daylight. Noctilucent clouds [NLC] are rare, tenuous, mesospheric cloud formations only seen from higher-latitude locations, normally around 40° to 60° south, against a twilit (nautical and astronomical) sky in summer. Sufficient contrast for observation occurs when the sun is between 6° and 16° below the horizon with maximum contrast at 10° when solar illumination and light scatter is at the maximum. They are seen close to the sunward horizon and extend maybe 20° above, along the twilight arch, although the clouds can be seen at a much higher elevation. The clouds appear to be near the mesopause at about 80 km and are moving with the zonal easterlies. They resemble high CI with pronounced band or wave structures, commonly herring-bone, bluish-white to pure white with yellow beneath. They are probably composed of cosmic dust with thin ice deposition, saturation of traces of water vapour being reached through orographic waves resonated from the earth's surface, or possibly oxidation of atmospheric methane. The Australian Severe Weather website has many excellent images grouped into cloud classifications, cloud features and atmospheric phenomena. Also the Cloud Appreciation Society website is well worth a visit. 3.2.7 ICAO / WMO Cloud continuity scale SKC — sky clear, no cloud. FEW — few clouds, one to two oktas cover. SCT — scattered, 3 – 4 oktas cover. Clear intervals between clouds predominate. BKN — broken, 5 – 7 oktas. Cloud masses predominate. OVC — overcast, 8 oktas. Continuous, no clear intervals. 3.3 Lifting sources There are four main processes that provide the lifting source for moist air to form cloud: convection frictional turbulence orographic ascent convergence or widespread ascent. 3.3.1 Convection When air flows over a surface heated by solar radiation, the surface contact layer is heated by conduction, and some of the heat is transported upward by molecular motion and small turbulent eddies. If the incoming energy is sufficient, the temperature in the lower layer increases and thermals rise from the heated contact layer — initially as bubbles of buoyant air, and then develop as columns with 100 – 300 metre diameters. The strength of the thermal depends on the heating: Thermal vertical velocity Thermal strength Knots Feet/min Metres/sec Weak 1 – 2 100 – 200 0.5 – 1 Moderate 2 – 6 200 – 600 1 – 3 Strong 6+ 600+ 3+ Circling within a thermal (thermalling) is a prime source of uplift for soaring paragliders, hang gliders and sailplanes, and particularly so in the summer. In hot, dry areas of Australia, thermals exceeding 1000 feet/min are common. The rising thermal cools at about the DALR of 3 °C/1000 feet and if it reaches dewpoint — the convection or lifting condensation level — cumulus will form. They are initially maintained by a series of random rising eddies, but if developed enough can draw in surrounding moist air and maintain itself, in a steady organised upward flow, from the release of the latent heat of condensation. If the cloud has enough energy to pass the freezing level it may develop into a rain and wind storm, and possibly a CB. Refer to section 3.6. In most instances the air providing the water vapour for convective cloud growth comes from within the friction layer. When thermal turbulence of sufficient intensity to penetrate above the friction layer is present, and the condensation level lies above the friction layer, then isolated convective cloud — fair weather cumulus CU HUM — is formed with clear-cut bases and tops to the limit of penetration. A subsidence inversion above the condensation level may limit the vertical extent, with the cloud spreading out in broken SC. Night cooling also has the effect of spreading the cloud into broken SC. Air warmed by advection over a warm surface, particularly the sea, in a summer anticyclone provides ideal conditions for development of fair weather cumulus. 3.3.2 Frictional turbulence An airstream flowing over ground or water produces a turbulent layer, up to 500 feet deep in light winds or 3000 feet plus in strong winds. The vertical eddies within this friction layer or boundary layer transport air from the upper level to the surface, adiabatically warmed to a temperature above that of the surface air. Similarly surface air is transported to the upper level, cooling adiabatically to temperatures below that of the upper level. Thus, as the turbulent mixing continues, the lower level is warmed and the upper level is cooled until the temperature lapse rate through the layer equals the DALR and the layer is in neutral stability — providing the air remains unsaturated. An inversion is formed at the top of the friction layer. A pre-existing inversion, e.g. a subsidence inversion, will strengthen the process. Thermal turbulence will also be present. The deep, turbulent mixing also has the effect of evening-out the moisture content throughout the layer and if the humidity mixing ratio is high enough a mixing condensation level will be reached within the friction layer. If the lapse rate of the layer above the friction layer is stable, then layer cloud will form with its base at the mixing condensation level and its top at the inversion. Thus the thickness of the cloud layer will vary from very thin to possibly 3000 feet. If the upper air layer is unstable then cloud development would not be halted at the inversion and convective cloud would probably develop. If the wind is light the layer cloud would tend to ST, otherwise SC with undulations in the lower surface continually forming, with breaks where cloud is being evaporated in the down currents. ST FRA may also form with local variations in humidity, temperature and turbulence. Cloud produced by frictional turbulence is not usually associated with precipitation except perhaps for drizzle from dense layers. 3.3.3 Orographic ascent Orography is the branch of physical geography concerned with mountains. An airstream encountering a topographic barrier (i.e. hill, ridge, valley spur, mountain range) is forced to rise, in a broad cross-section from at or near the surface to the upper levels, and cools adiabatically. If the lift and the moisture content are adequate, condensation occurs at the lifting condensation level and cloud is formed on or above the barrier. Stratus is formed if the air is stable, whilst cumulus forms if the air is slightly unstable. If there is instability in depth, coupled with high moisture, CB may develop (refer to section 3.6). Solar heating of ridges may cause the adjacent air to be warmer than air at the same level over the valleys; thus the ridge acts as a higher-level heat source, increasing buoyancy and accentuating the mechanical lifting. The orographic lifting of an airstream provides gliders with the opportunity for ridge or hill soaring. Sea breezes crossing relatively small topographic barriers at the coastline (e.g. cliffs) may provide quite smooth uplift. Orographic cloud — cap cloud — in stable conditions tends to form continuously on the windward side of mountain ridges, but clears on the lee side. Lenticular cloud may also form a high cap above a hill when there is a layer of near saturated air aloft; orographic lifting causes condensation, and descent causes evaporation. A mountain wave may form — particularly in a sandwiched, stable layer — resulting in the formation of a series of lenticular clouds. 3.3.4 Convergence and widespread ascent The air in the centre of a low pressure centre, trough or heat trough is lifted by convergence, as is the air in the inter-tropic convergence zone. The air in the broad area ahead of a cold front is lifted by the frontal action. Generally the air rises very slowly, possibly one to five feet/minute, and cools. If moist enough, the air condenses at the lifting condensation level producing extensive layers of stratus-type cloud: NS, AS, CS and CI. However active or fast-moving fronts may nose the air up much more rapidly, leading to CB development. 3.4 Fog Fog [FG] is defined as an obscurity in the surface layers of the atmosphere that is caused by a suspension of water droplets, with or without smoke particles, and which is defined by international agreement as being associated with visibility less than 1000 metres. If the visibility is between 1000 and 5000 metres then the obscurity is mist — meteorological code BR, from the French brouillard = mist. Radiation fogs are the prevalent fogs in Australia, with occurrence peaking in winter. They are caused by lowering of the ground temperature through re-radiation into space of absorbed solar radiation. Radiation fogs mainly occur in moist air on cloudless nights within a high-pressure system, particularly after rainfall. The moist air closest to the colder surface will quickly cool to dewpoint with condensation occurring. As air is a poor conductor, a light wind of 2–6 knots will facilitate the mixing of the cold air throughout the surface layer, creating fog. The fog itself becomes the radiating surface in turn, encouraging further cooling and deepening of the fog. An increase in atmospheric pollution products supplies extra condensation nuclei to enhance the formation of fog; i.e. smog. A low-level inversion forms and the contained fog may vary from scattered pools in surface depressions to a general layer 1000 feet in depth. Calm conditions will result in a very shallow fog layer, or just dew or frost. The fog droplets sink at about 1 cm/sec. Surface winds greater than 10 knots may prevent formation of the inversion; the cooled air is mixed with the warmer air above, and so does not cool to dewpoint. If the forecast wind at 3000 feet is 25 knots or more, the low-level inversion may not form and fog is unlikely (refer to 'spread' in section 1.5). In winter, radiation fog may start to form in the evening and persist to midday — or later if the sun is cut off by higher-level cloud and/or the wind does not pick up sufficiently to break up the low-level inversion. Advection fog may occur when warm, moist air is carried over a surface that is cooler than the dewpoint of the air. Cooling and some turbulence in the lower layer lowers temperature to dewpoint and fog forms. Sea fogs drifting into New South Wales coastal areas are advection fogs that are formed when the sea surface temperature is lower than the dewpoint, but with a steady breeze to promote air mixing. Dewpoint can be reached by both temperature reduction and by increased water vapour content through evaporation. Advection fogs will form in valleys open to the sea when temperature falls in the evening, and when combined with a sea breeze of 5 – 15 knots to force the air upslope. Thick advection fogs may be persistent in winter, particularly under a mid-level cloud layer. Shallow evaporation fogs or steaming fogs result from the immediate condensation of water vapour that has just evaporated from the surface into near-saturated air. Steaming from a sun-warmed road surface after a rain shower demonstrates the process. Sea smoke or frost smoke is an evaporation fog occurring in frigid Antarctic air moving over relatively warm waters, thereby prompting evaporation into the cold air which, in turn, quickly produces saturation. Freezing fog is a fog composed of supercooled water droplets that freeze on contact with solid objects; e.g. parked aircraft. When near-saturated air is very cold, below –24 °C at sea level to –45 °C at 50 000 feet, the addition of only a little moisture will produce saturation. Normally, little evaporation takes place in very cold conditions but release of water vapour from engine exhausts, for instance, can quickly saturate calm air (even though the engine exhaust heat tends to lower the relative humidity) and will produce ice fog at the surface or condensation trails [contrails] at altitude. If the temperature is below –40 °C, ice crystals form directly on saturation. Contrails persist if relative humidity is high but evaporate quickly if low. Distrails occur when the engine exhaust heat of an aircraft flying through a thin cloud layer dissipates a clear trail. Frontal fog or rain-induced fog occurs when warm rain evaporates at surface level in light wind conditions and then condenses to form fog. 3.5 Precipitation 3.5.1 Rain [RA] and drizzle [DZ] Cloud droplets tend to fall but their terminal velocity is so low, about 0.01 metres/sec, that they are kept aloft by the vertical currents associated with the cloud construction process; but droplets will evaporate when coming into contact with the drier air outside the cloud. Some of the droplets are larger than others and consequently their falling speed is greater. Larger droplets catch up with smaller ones and merge or coalesce with them, eventually forming raindrops. Raindrops grow with the coalescence process and reach maximum diameters — in tropical conditions — of 4–7 mm before air resistance disintegrates them into smaller raindrops; this starts a self-perpetuating process. It takes about one million cloud droplets to form one raindrop. The terminal velocity of a 4 mm raindrop is about 9 metres/sec. Only clouds with extensive depth, 3000 feet plus, will produce rain (rather than drizzle). But very small, high clouds — generating heads — may produce trails of snow crystals, which evaporate at lower levels — fall streaks or virga. Drizzle forms by coalescence in stratiform clouds with depths possibly less than 1000 feet and with only weak vertical motion — otherwise the small (0.2 – 0.5 mm) drops would be unable to fall. It also requires only a short distance or a high relative humidity between the cloud base and the surface — otherwise the drops will evaporate before reaching the surface. Terminal velocity approximates 1–2 metres/sec. Light drizzle [–DZ]: visibility greater than 1000 metres Moderate drizzle [DZ]: visibility 500–1000 metres Heavy drizzle [+DZ]: visibility less than 500 metres Light rain showers [–SHRA]: precipitation rate under 2 mm/hour Moderate rain showers [SHRA]: 2–10 mm/hour Heavy rain showers[+SHRA]: more than 10 mm/hour Light rain [–RA]: under 0.5 mm/hour, individual drops easily seen Moderate rain [RA]: 0.5–4 mm/hour, drops not easily seen Heavy rain [+RA]: more than 4 mm/hour, rain falls in sheets Weather radar reports precipitation according to the reflectivity level: 1 – light precipitation 2 – light to moderate rain 3 – moderate to heavy rain 4 – heavy rain 5 – very heavy rain, hail possible 6 – very heavy rain and hail, large hail possible Scotch mist is a mixture of thick cloud and heavy drizzle on rising ground, formed in conditions of weak uplift of almost saturated stable air. 3.5.2 Snow [SN] At cloud temperatures colder than –10 °C where both ice and supercooled liquid water exist, the saturation vapour pressure over water is greater than that over ice. Air that is just saturated with respect to the supercooled water droplets will be supersaturated with respect to the ice crystals, resulting in vapour being deposited onto the crystal (refer to section 1.5). The reduction in the amount of water vapour means that the air is no longer saturated with respect to the water droplets. To achieve saturation equilibrium again, the water droplets begin to evaporate. Thus ice crystals grow by sublimation and water droplets lessen, i.e. in mixed cloud the ice crystals grow more rapidly than the water droplets. Snow is frozen precipitation resulting from ice crystal growth, and falls in any form between small crystals and large flakes. This is known as the Bergeron-Findeison theory and probably accounts for most precipitation outside the tropics. Snow may fall to the surface or, more often, melt below the freezing level and fall as rain. Snowflakes are built by snow crystals colliding and sticking together in clusters of several hundred — known as aggregation. Most aggregation occurs at temperatures just below freezing, as the snow crystals tend to remain separate at colder temperatures. 3.5.3 Hail and other ice forms The growing snow crystals acquire a fall velocity relative to the supercooled droplets. Growth also continues by collision and coalescence with supercooled droplets forming ice pellets [PE]. The process is termed accretion, or opaque riming if the freezing is instantaneous incorporating trapped air, or glazing if the supercooled water freezes more slowly as a clear layer. A similar process occurs with airframe icing. The ice pellets in turn grow by coalescing with other pellets and further accretion — these are termed hail [GR] when the diameter exceeds 5 mm. The size reached by hailstones before falling out of the cloud depends on the velocity and frequency of updraughts within the cloud. Hail is of course a hazard to aviation, particularly when it is unexpected; for example hail falling from a CB anvil can appear to fall from a clear sky. Snow grains [SG] are very small, flattened, opaque ice grains, less than 1 mm and equivalent to drizzle. Snowflakes that, due to accretion, become opaque, rounded and brittle pellets, 2 – 5 mm diameter, are called snow pellets or graupel [GS]. Sleet is transparent ice pellets less than 5 mm diameter that bounce on impact with the ground. Sleet starts as snow, partially melting into rain on descent through a warm layer, then refreezing in a cold near-surface layer. The term is sometimes applied to a snow/rain mixture or just wet snow. Diamond dust [IC] is minute airborne ice crystals that only occur under very cold (Antarctic) conditions. When raindrops form in cloud-top temperatures warmer than –10 °C the rain falls as supercooled drops. Such freezing rain or drizzle striking a frozen surface, or an aircraft flying in an outside air temperature [OAT] at or below zero, will rapidly freeze into glaze ice. Freezing rain is responsible for the ice storms of North America and northern Europe, but the formative conditions differ from the preceding. 3.5.4 The seeder – feeder mechanism Any large-scale air flow over mountain areas produces, by orographic effect, ice crystals in cold cloud tops. By themselves, the falling crystals would cause only light drizzle at the ground. However, as the crystals fall through the low-level mountain top clouds they act as seed particles for raindrops that are formed by coalescing cloud droplets with the falling crystals, producing substantial orographic rainfall in mountain areas. Aerial cloud seeding involves introducing freezing nuclei (silver-oxide crystals with a similar structure to ice crystals) into parts of the cloud where few naturally exist, in order to initiate the Bergeron-Findeison process. 3.6 Thunderstorm development Like CU, surface heating may provide the initial trigger to create isolated CB within an air mass but the initial lift is more likely to be provided by orographic ascent or convergence effects. In the formative stages of a CB, the cloud may have an updraught pulse of 1000–2000 feet/min. The rising parcel of air reaches altitudes where it is much warmer than the surrounding air, by as much as 10 °C, and buoyancy forces accelerate the parcel aloft possibly reaching speeds of 3000–7000 feet/min. Precipitation particles grow with the cloud growth. The upper levels of the cloud gain additional energy from the latent heat released from the freezing of droplets, and the growth of snow crystals and hailstones. When the growth of the particles is such that they can no longer be suspended in the updraught, then precipitation — and its associated drag downdraught — occurs. If the updraught path is tilted by wind shear or veer, rather than vertical, then the precipitation and its downdraught will fall away from the updraught, rather than back down through it (consequently weakening or stopping the updraught) and a co-existing updraught/downdraught may become established. An organised cell system controlling its environment and lasting several hours may evolve. Middle-level dry air from outside the cloud is entrained into the downdraught of an organised cell. The downdraught is further cooled by the dry inflow air evaporating some of its water and ice crystals, and tends to accelerate downwards in vertical gusts. At the same time, the downdraught maintains the higher horizontal momentum it gained at upper levels from the higher forward speed of the storm at that height. When the cold, plunging air nears the surface, the downburst spreads out in all directions as a cold gust front or squall. This is strongest at the leading edge of the storm and weakest towards the trailing edge. Each organised cell system contains an updraught / downdraught core. Beneath this is the outflow region containing the rain shield. The core is bounded by the downdraught gust front, a flanking line with a dark, flat base. Underneath this is the inflow region of warm, moist air. The CU and TCU generated by the inflow within the flanking line are the genesis of new cells. Within the core, the condensation of moisture from the inflow region produces rain, hail and snow and the associated downdraught to the outflow region. When the cool air outflow exceeds and finally smothers(or undercuts and chokes off) the inflow, then the storm dissipates. High moisture content in the low-level air with dry, mid-level air and atmospheric instability are required to maintain CB development. The amount of precipitation from a large storm is typically 200 000 tonnes but severe storms have produced 2 million tonnes. Anvils may take several forms: Cumuliform: forms when a very strong updraught spreads rapidly and without restriction. Back-sheared: the cloud top spreads upwind, against the high-level flow, this indicates a very strong updraught. Mushroom: a rollover or lip around the underside of an overhanging anvil, which indicates rapid expansion. Overshooting top: a dome-like protusion through the top of an anvil, which indicates a very strong updraught pulse. The overshooting top in large tropical storms has been known to develop into a 'chimney' form, towering maybe 10 000 feet into the stratosphere, with an extensive plume cloud extending downwind from its top. Such clouds transfer moisture to the stratosphere. The Australian Bureau of Meteorology Web site has a storm spotters' guide. Parts 1 and 2 briefly describe the structure and types of thunderstorms likely to be encountered in Australia. For further information on clouds, fog and precipitation consult the University of Manchester's Intute, an online catalogue of internet resources in Earth sciences. 3.7 Flight in cloud or without external visual references The human vestibular system When walking, a person's prime sense of orientation is provided by visual references. When vision is severely degraded, the vestibular system in the inner ears, which senses motion and gravity (thus roll, pitch and yaw), generally allows us to keep our balance when walking without using visual references. However, the vestibular system is not designed for high speed or angular motion, and cannot be used as an in-flight back-up system; i.e. you cannot close your eyes and continue to fly straight and level. Motion of the fluid within the ears' semicircular canals is affected by inertia and will feed quite erroneous prompts to the brain, resulting in various types and levels of vertigo. For example, without the external visual references of clear sky, terrain or a horizon, forward deceleration tends to give a pitching-down sensation whilst forward acceleration gives a pitching-up sensation. Once settled into a constant rate turn, the sensation is of not turning at all; but when the turn is halted, the sensation is then of turning in the opposite direction. In addition, the vestibular system will not detect slow rates of bank, so that if the aircraft is banking at the rate of one or two degrees per second the vestibular system will not send any prompts to the brain — it will consider the aircraft is still flying straight and level, while any associated speed changes may provide contrary sensations. For example, if the aircraft is slowly banking and accelerating in a descending turn, the sensation may well be one of pitching-up. Spatial disorientation Aircraft accidents caused by spatial disorientation are usually fatal and occur when VFR flight is continued in adverse visibility conditions — cloud, fog, smoke, haze, showers, oncoming darkness and combinations thereof. Pilots who have not been trained to fly solely by visual reference to the flight instruments in a 'blind flying' panel will soon find themselves experiencing spatial disorientation should they, inadvertently or deliberately, enter cloud where the external visual references — by which they normally orient themselves in visual meteorological conditions — are lost. The same applies to any atmospheric condition or in adverse weather where the visual references (horizon [principally], terrain and clear sky) are lost or just significantly reduced — smoke from bushfires or extensive burning of sugar cane, for example. Even a pilot who is well experienced in flying in instrument meteorological conditions may occasionally experience a phenomenon called 'the leans'. This usually occurs when the aircraft has been inadvertently allowed to slowly bank a few degrees and the pilot then makes a quick correction to level the wings. The vestibular system doesn't register the initial bank but does register the wing levelling as an opposite direction bank (away from a wings-level attitude) — and the pilot's brain produces a leaning sensation while also perceiving from the instrument readings that the aircraft is flying straight and level. The reaction — which can persist for quite a while — may be for the pilot to lean sideways in her/his seat so that everything feels right! Read the section titled 'Pressing on in deteriorating conditions' in the Flight Planning and Navigation Guide. For more information on the vestibular functions and effects, google the terms 'vestibular spatial disorientation' in a web search. STRICT COPYRIGHT JOHN BRANDON AND RECREATIONAL FLYING (.com)
  8. In line with the proposed Site Menu Structure: What's New Forums Clubs Blogs Events Media - with sub sections of Gallery, Videos, Articles, Aviation News Resources - with sub sections of Downloads, Maps, Links, Tutorials, Tools and Calculators, Quizzes Reference - with sub sections of Aircraft, On This Day, Famous People, plus any other reference items Commerce - with sub sections of Classifieds, Suppliers, Pilot Shop, Product Reviews Members - with sub sections of Leader board, Online Users, Staff, Site Support (as it is now) Off Topic I have now created the new Resources Section. In this section, available by clicking Resources on the main menu, you will find the sub sections for Downloads, Tutorials, Google Earth Maps for Airstrips, Airports and Members. Coming soon to this section will be all the different Pilot Tools and Calculators and a whole new Quizzes sub section In the Media Section we are still building the Articles and Aviation News sub sections
  9. Version 1.0.0

    5 downloads

    Crosswords are a fun way of quizzing your knowledge on some of the subjects and topics you will encounter whilst learning to fly. Suitable for both new and qualified private pilots. Note, there are two files in the download, 1 for the actual crossword puzzle and 2, the answers
  10. Version 1.0.0

    9 downloads

    This is a flight planner created in an Excel spreadsheet
  11. Sir Charles Edward Kingsford Smith, MC, AFC (9 February 1897 – 8 November 1935), often called by his nickname Smithy, was an early Australian aviator. In 1928, he made the first trans-Pacific flight from the United States to Australia. He also made the first non-stop crossing of the Australian mainland, the first flights between Australia and New Zealand, and the first eastward Pacific crossing from Australia to the United States; and, also, made a flight from Australia to London, setting a new record of 10.5 days. Early and personal life Charles Edward Kingsford Smith was born on 9 February 1897 at Riverview Terrace, Hamilton in Brisbane, Queensland, Australia, the son of William Charles Smith and his wife Catherine Mary (née Kingsford, daughter of Richard Ash Kingsford, a Member of the Queensland Legislative Assembly and mayor in both Brisbane and Cairns municipal councils). His birth was officially registered and announced in the newspapers under the surname Smith, which his family used at that time. The earliest use of the surname Kingsford Smith appears to be by his older brother Richard Harold Kingsford Smith, who used the name at least informally from 1901, although he married in New South Wales under the surname Smith in 1903. In 1903, his parents moved to Canada where they adopted the surname Kingsford Smith. They returned to Sydney in 1907. Kingsford Smith first attended school in Vancouver, Canada. From 1909 to 1911, he was enrolled at St Andrew's Cathedral School, Sydney, where he was a chorister in the school's cathedral choir, and then at Sydney Technical High School, before becoming an engineering apprentice with the Colonial Sugar Refining Company at 16. Kingsford Smith married Thelma Eileen Hope Corboy in 1923. They divorced in 1929. He married Mary Powell in December 1930. Shortly after his second marriage he joined the New Guard, a radical monarchist, anti-communist, and allegedly fascist-inspired organisation. World War I and early flying experience In 1915, he enlisted for duty in the 1st AIF (Australian Army) and served at Gallipoli. Initially, he performed duty as a motorcycle dispatch rider, before transferring to the Royal Flying Corps, earning his pilot's wings in 1917. In August 1917, while serving with No. 23 Squadron, Kingsford Smith was shot down and received injuries which required amputation of two toes. He was awarded the Military Cross for his gallantry in battle. As his recovery was predicted to be lengthy, Kingsford Smith was permitted to take leave in Australia where he visited his parents. Returning to England, Kingsford Smith was assigned to instructor duties and promoted to Captain. On 1 April 1918, along with other members of the Royal Flying Corps, Kingsford Smith was transferred to the newly established Royal Air Force. On being demobilised in England, in early 1919, he joined Tasmanian Cyril Maddocks, to form Kingsford Smith, Maddocks Aeros Ltd, flying a joy-riding service mainly in the North of England, during the summer of 1919, initially using surplus DH.6 trainers, then surplus B.E.2s. Later Kingsford Smith worked as a barnstormer in the United States before returning to Australia in 1921. He did the same in Australia and also flew airmail services, and began to plan his record-breaking flight across the Pacific. Applying for a commercial pilot's licence on 2 June 1921 (in which he gave his name as 'Charles Edward Kingsford-Smith'), he became one of Australia's first airline pilots when he was chosen by Norman Brearley to fly for the newly formed West Australian Airways. During the First World War, Ken Richards had been the observer in Kingsford Smith's plane in France. Later Richards moved to Cowra, New South Wales. Kingsford Smith owned an old Avro plane and in 1922 flew to Cowra to see his old comrade. Kingsford Smith and Richards flew under the Cowra traffic bridge. They also attempted to fly under the nearby railway bridge, but Richards fortunately noticed the telephone lines and pulled the aircraft away only seconds from impact. 1928 Trans-Pacific flight In 1928, Kingsford Smith and Charles Ulm arrived in the United States and began to search for an aircraft. Famed Australian polar explorer Sir Hubert Wilkins sold them a Fokker F.VII/3m monoplane, which they named the Southern Cross. At 8:54 a.m. on 31 May 1928, Kingsford Smith and his 4-man crew left Oakland, California, to attempt the first trans-Pacific flight to Australia. The flight was in three stages. The first, from Oakland to Wheeler Army Airfield, Hawaii, was 3,870 kilometres (2,400 mi), taking an uneventful 27 hours 25 minutes (87.54 mph). They took off from Barking Sands on Mana, Kauai, since the runway at Wheeler was not long enough. They headed for Suva, Fiji, 5,077 kilometres (3,155 mi) away, taking 34 hours 30 minutes (91.45 mph). This was the most demanding portion of the journey, as they flew through a massive lightning storm near the equator. The third leg was the shortest, 2,709 kilometres (1,683 mi) in 20 hours (84.15 mph), and crossed the Australian coastline near Ballina before turning north to fly 170 kilometres (110 mi) to Brisbane, where they landed at 10.50 a.m. on 9 June. The total flight distance was approximately 11,566 kilometres (7,187 mi). Kingsford Smith was met by a huge crowd of 26,000 at Eagle Farm Airport, and was welcomed as a hero. Australian aviator Charles Ulm was the relief pilot. The other crewmen were Americans, they were James Warner, the radio operator, and Captain Harry Lyon, the navigator and engineer. The National Film and Sound Archive of Australia has a film biography of Kingsford Smith, called An Airman Remembers, and recordings of Kingsford Smith and Ulm talking about the journey. A stamp sheet and stamps, featuring the Australian aviators Kingsford Smith and Ulm, were released by Australia Post in 1978, commemorating the 50th anniversary of the flight. A young New Zealander named Jean Batten attended a dinner in Australia featuring Kingsford Smith after the trans-Pacific flight and told him "I'm going to learn to fly." She later convinced him to take her for a flight in the Southern Cross and went on to become a record-setting aviator, following his example instead of his advice ("Don't attempt to break men's records – and don't fly at night", he told her in 1928 and remembered wryly later). 1928 Trans-Tasman flight After making the first non-stop flight across Australia from Point Cook near Melbourne to Perth in Western Australia in August 1928, Kingsford Smith and Ulm registered themselves as Australian National Airways (see below). They then decided to attempt the Tasman Sea crossing to New Zealand not only because it had not yet been done, but also in the hope the Australian Government would grant Australian National Airways a subsidised contract to carry scheduled mail regularly. The Tasman had remained unflown after the failure of the first attempt in January 1928, when New Zealanders John Moncrieff and George Hood had vanished without trace. Kingsford Smith's flight was planned for take off from Richmond, near Sydney, on Sunday 2 September 1928, with a scheduled landing around 9:00 a.m. on 3 September at Wigram Aerodrome, near Christchurch, the principal city in the South Island of New Zealand. This plan drew a storm of protest from New Zealand churchmen about the "sanctity of the Sabbath being set at naught." The mayor of Christchurch supported the churchmen and cabled a protest to Kingsford Smith. As it happened, unfavourable weather developed over the Tasman and the flight was deferred, so it is not known whether or how Kingsford Smith would have heeded the cable. Accompanied by Ulm, navigator Harold Arthur Litchfield, and radio operator Thomas H. McWilliams, a New Zealander made available by the New Zealand Government, Kingsford Smith left Richmond in the evening of 10 September, planning to fly overnight to a daylight landing after a flight of about 14 hours. The 2,600 kilometres (1,600 mi) planned route was only just over half the distance between Hawaii and Fiji. After a stormy flight, at times through icing conditions, the Southern Cross made landfall in much improved weather near Cook Strait, the passage between New Zealand's two main islands. At an estimated 241 kilometres (150 mi) out from New Zealand, the crew dropped a wreath in memory of the two New Zealanders who had disappeared during their attempt to cross the Tasman earlier that year. There was a tremendous welcome in Christchurch, where the Southern Cross landed at 0922 after a flight of 14 hours and 25 minutes. About 30,000 people made their way to Wigram, including many students from state schools, who were given the day off, and public servants, who were granted leave until 11 a.m. The event was also broadcast live on radio. While the New Zealand Air Force overhauled the Southern Cross free of charge Kingsford Smith and Ulm were taken on a triumphant tour of New Zealand, flying in Bristol Fighters. The return to Sydney was made from Blenheim, a small city at the north of the South Island. Hampered by fog, severe weather and a minor navigational error, the flight to Richmond took over 23 hours; on touchdown the aircraft had enough fuel for only another 10 minutes flying. "Coffee Royal" incident On 31 March 1929, en route from Sydney to England, the Southern Cross with Kingsford Smith at the helm made an emergency landing on a mudflat near the mouth of the Glenelg River, in the Kimberley region of northern Western Australia. The Southern Cross was found and rescued after a fortnight's searching, with George Innes Beard, Albert Barunga and Wally from the Kunmunya Mission the first overland party to reach the downed aircraft. While on their way to help with the search two friends of Kingsford Smith crash landed in the Tanami Desert in Central Australia and died of thirst and exposure on 12 April 1929. The pair, Keith Vincent Anderson and Henry Smith "Bobby" Hitchcock, had been flying a Westland Widgeon plane named Kookaburra. Many sections of the media and public felt that the forced landing of the Southern Cross, which was dubbed the "Coffee Royal" incident after the brew of coffee and brandy which the crew had drunk while awaiting rescue, had been a publicity stunt and that Kingsford Smith was responsible for the two deaths. An official inquiry was convened into the incident, fuelled by the media speculation. One of the criticisms levelled at Kingsford Smith was that he could have been spotted and rescued much more quickly had he set a fire with engine oil. The foundation for the attack was not tested by the inquiry at the time but Dick Smith (no relation) rediscovered the landing site in 1981 and carried out an experiment burning brush with and without engine oil and found that the latter actually created a more visible effect as viewed from the air against the dark mud and surface terrain; Kingsford Smith had been right. Despite Kingsford Smith being exonerated by the inquiry, his reputation within Australia never fully recovered during his lifetime. The bodies of Anderson and Hitchcock were later recovered from the Tanami Desert. Hitchcock's body was returned to Perth for burial at Karrakatta Cemetery, while Anderson's body was returned to Sydney. Over 6000 mourners attended Keith Anderson's funeral. It was an elaborate affair befitting a national hero. Anderson was buried at Rawson Park, Mosman, on 6 July 1929. A grand memorial was later erected at the gravesite in his honour. Australian National Airways In partnership with Ulm, Kingsford Smith established Australian National Airways in 1929. The passenger, mail and freight service commenced operations flying between Sydney, Brisbane and Melbourne, in January 1930, with five aircraft but closed after crashes in March and November the next year. Later flights After collecting his 'old bus', Southern Cross, from the Fokker aircraft company in the Netherlands where it had been overhauled, in June 1930 he achieved an east-west crossing of the Atlantic from Ireland to Newfoundland in 31½ hours, having taken off from Portmarnock Beach (The Velvet Strand), just north of Dublin. New York gave him a tumultuous welcome. The Southern Cross continued on to Oakland, California, completing a circumnavigation of the world, begun in 1928. In 1930, he competed in an England to Australia air race, and, flying solo, won the event taking 13 days. He arrived in Sydney on 22 October 1930. In 1931, he purchased an Avro Avian he named the Southern Cross Minor, to attempt an Australia-to-England flight. He later sold the aircraft to Captain W.N. "Bill" Lancaster who vanished on 11 April 1933 over the Sahara Desert; Lancaster's remains were not found until 1962. The wreck of the Southern Cross Minor is now in the Queensland Museum. Also in 1931, Smith began developing the Southern Cross automobile as a side project. In 1933, Seven Mile Beach, New South Wales, was used by Kingsford Smith as the runway for the first commercial flight between Australia and New Zealand. In 1934, he purchased a Lockheed Altair, the Lady Southern Cross, with the intention of competing in the MacRobertson Air Race. He was unable to make it to England in time for the start of the race, and so flew the Lady Southern Cross from Australia to the United States instead; the first eastward crossing of the Pacific Ocean by aircraft. Disappearance and death Kingsford Smith and co-pilot John Thompson "Tommy" Pethybridge were flying the Lady Southern Cross overnight from Allahabad, India, to Singapore, as part of their attempt to break the England-Australia speed record held by C. W. A. Scott and Tom Campbell Black, when they disappeared over the Andaman Sea in the early hours of 8 November 1935. Aviator Jimmy Melrose claimed to have seen the Lady Southern Cross fighting a storm 150 miles from shore and 200 feet over the sea with fire coming from its exhaust. Despite a search for 74 hours over the Bay of Bengal by test pilot Eric Stanley Greenwood, OBE, their bodies were never recovered.[44] Eighteen months later, Burmese fishermen found an undercarriage leg and wheel, with its tyre still inflated, which had been washed ashore at Aye Island in the Gulf of Martaban, 3 km (2 mi) off the southeast coastline of Burma, some 137 km (85 mi) south of Mottama (formerly known as Martaban). Lockheed confirmed the undercarriage leg to be from the Lady Southern Cross. Botanists who examined the weeds clinging to the undercarriage leg estimated that the aircraft lies not far from the island at a depth of approximately 15 fathoms (90 ft; 27 m). The undercarriage leg is now on public display at the Powerhouse Museum in Sydney, Australia. In 2009, filmmaker and explorer Damien Lay stated he was certain he had found the Lady Southern Cross. The location of the claimed find was widely misreported as "in the Bay of Bengal". However, the 2009 search, was in fact, at the same location where the landing gear had been found in 1937, at Aye Island in the Andaman Sea. Kingsford Smith was survived by his wife, Mary, Lady Kingsford Smith, and their three-year-old son Charles Jnr. Kingsford Smith's autobiography, My Flying Life, was published posthumously in 1937 and became a best-seller. Following The Joint Australian Myanmar Lady Southern Cross Search Expedition II (LSCSEII) in 2009, Lay conducted a total of ten further expeditions to Myanmar to recover wreckage from the site. In 2011, Lay claimed to have found the wreckage, but that claim has been widely disputed, and no evidence confirming the claim has been forthcoming. The location of the site, approximately 1.8 miles off the coast of Myanmar, has never been publicly released. Lay has worked closely with both the Kingsford Smith and Pethybridge families since 2005. The privately funded project was supported by the government and people of Myanmar. As of December 2017, Lay was still searching for parts of the Lady Southern Cross. Honours and legacy In 1930 Kingsford Smith was the inaugural recipient of the Segrave Trophy, awarded for "Outstanding Skill, Courage and Initiative on Land, Water [or] in the Air". Kingsford Smith was knighted in the 1932 King's Birthday Honours List as a Knight Bachelor. He received the accolade on 3 June 1932 from His Excellency Sir Isaac Isaacs, the Governor-General of Australia, for services to aviation and later was appointed honorary Air Commodore of the Royal Australian Air Force. In 1986, Kingsford Smith was inducted into the International Air & Space Hall of Fame at the San Diego Air & Space Museum. The major airport of Sydney, located in the suburb of Mascot, was named Kingsford Smith International Airport in his honour. The federal electorate surrounding the airport is named the Division of Kingsford Smith, and includes the suburb of Kingsford. His most famous aircraft, the Southern Cross, is now preserved and displayed in a purpose-built memorial to Kingsford Smith near the International Terminal at Brisbane Airport. Kingsford Smith sold the plane to the Australian Government in 1935 for £3000 so it could be put on permanent display for the public. The plane was carefully stored for many years before the current memorial was built. Kingsford Smith Drive in Brisbane passes through the suburb of his birth, Hamilton. Another Kingsford Smith Drive, which is located in the Canberra district of Belconnen, intersects with Southern Cross Drive. Opened in 2009, Kingsford Smith School in the Canberra suburb of Holt was named after the famous aviator, as was Sir Charles Kingsford-Smith Elementary School in Vancouver, British Columbia, Canada. He was pictured on the Australian $20 paper note (in circulation from 1966 until 1994, when the $20 polymer note was introduced to replace it), to honour his contribution to aviation and his accomplishments during his life. He was also depicted on the Australian one-dollar coin of 1997, the centenary of his birth. Albert Park in Suva, where he landed on the trans-Pacific flight, now contains the Kingsford Smith Pavilion. A memorial stands at Seven Mile Beach in New South Wales commemorating the first commercial flight to New Zealand. Qantas named its sixth Airbus A380 (VH-OQF) after Kingsford Smith. KLM named one of its Boeing 747s (PH-BUM) after Kingsford Smith. A trans-Encke propeller moonlet, an inferred minor body, of Saturn is named after him. Australian aviation enthusiast Austin Byrne was part of the large crowd at Sydney's Mascot Aerodrome in June 1928 to welcome the Southern Cross and its crew following their successful trans-Pacific flight. Witnessing this event inspired Byrne to make a scale model of the Southern Cross to give to Kingsford Smith. After the aviator's disappearance, Byrne continued to expand and enhance his tribute with paintings, photographs, documents, and artworks he created, designed or commissioned. Between 1930 and his death in 1993, Byrne devoted his life to creating and touring his Southern Cross Memorial. Source: Wikipedia
  12. Admin

    Aviation Terms

    This list of Aviation Terms contains those that are most frequently used. To have one added to the list please let me know...thanks AGL - Above Ground Level, as a measurement of altitude above a specific land mass, and differentiated from MSL. ADF - Automatic Direction Finding via automated radio. ADI - Attitude direction indicator. Shows the roll and pitch of the aircraft. AFCS - Automatic flight control system that provides inputs to the fight controls to assist the pilot in maneuvering and handling the aircraft. AFT - Referring to the rear of the aircraft. AI - Altitude indicator. Displays the aircraft's altitude above sea level. Aileron - The movable areas of a wingform that control or affect the roll of an aircraft by working opposite one another-up-aileron on the right wing and down-aileron on the left wing. AIM - Airman's Information Manual - A primary FAA publication whose purpose is to instruct airmen about operating in the US airspace system. ADC - Air Data Computer - A primary sensor-based navigation data source. AGR - Air-Ground Ranging - Straight-line distance from the aircraft to a point on the ground. ATC - Air Traffic Control - A service operated by the appropriate authority to promote the safe, orderly, and expeditious flow of air traffic. Airfoil - The shape of the wing when looking at its profile. Usually a teardrop shape. Airframe - The fuselage, booms, nacelles, cowlings, fairings, and airfoil surfaces of an aircraft. Airspeed - The speed of an aircraft relative to its surrounding air mass. See: calibrated airspeed; indicated airspeed; true airspeed. Airspeed Indicator - An onboard instrument which registers velocity through the air, usually in knots. Different from ground speed. AIS - Aeronautical Information Service. ALS - Approach light system. A lighting system installed on the approach end of an airport runway and consists of a series of lightbars, strobe lights, or a combination of the two that extends outward from the runway end. ALT - Short term for Altitude. Altimeter - An onboard instrument which senses air pressure in order to gauge altitude. Altimeter Setting - The barometric pressure reading used to adjust a pressure altimeter for variations in existing atmospheric pressure. Altitude - Height of an aircraft, usually with respect to the terrain below. Angle of Attack - The angle between the chord line of the wing of an aircraft and the relative wind. Annual - Mandatory inspection of airframe and power plant that occurs every 12 months. AO - Aircraft Operator. AOPA - Aircraft Owner and Pilot's Association. APP - Approach (Control). Approach Speed - The recommended speed contained in aircraft manuals used by pilots when making an approach to landing. ARCID - Aircraft Identification. ATA - Actual Time of Arrival. As opposed to ETA (Estimated Time of Arrival) used in filing a flight plan. ATD - Actual Time of Departure. As opposed to ETD (Estimated Time of Departure) used in filing a flight plan. ATIS - Automated Terminal Information Service usually containing vital information on wind direction, velocity, pressure readings, and active runway assignment for that particular airport. Attitude - The primary aircraft angles in the state vector; pitch, roll, and yaw. Attitude Indicator - A vacuum powered instrument which displays pitch and roll movement about the lateral and longitudinal axes. ADF - Automatic Direction Finding - A basic guidance mode, providing lateral guidance to a radio station. Equipment that determines bearing to a radio station. Autopilot - A method of an automatic flight control system which controls primary flight controls to meet specific mission requirements. Autorotation - A rotorcraft flight condition in which the lifting rotor is driven entirely by action of the air when the rotorcraft is in motion. AVGAS - Aviation Gasoline (piston aircraft fuel). Bernoulli Effect - Airflow over the upper surface of an airfoil causes suction (lift) because the airstream has been speeded up in relation to positive pressure of the airflow on the lower surface. CAS - Calibrated Airspeed - The indicated airspeed of an aircraft, corrected for position and instrument error. CAS is equal to true airspeed in standard atmosphere at sea level. Camber - The convex or concave curvature of an airfoil. CAT - Clear Air Turbulance. CAVU - Ceiling and Visibility Unlimited; ideal flying weather. Ceiling - The heights above the earth's surface of the lowest layer of clouds or obscuring phenomena that is reported as "broken," "overcast," or "obscured". CG - Center of Gravity - The longitudinal and lateral point in an aircraft where it is stable; the static balance point. Chord - The measurable distance between the leading and trailing edges of a wingform. CTAF - Common Traffic Advisory Frequency - A frequency designed for the purpose of carrying out airport advisory practices while operating to or from an airport without an operating control tower. The CTAF may be a UNICOM, Multicom, FSS, or tower frequency and is identified in appropriate aeronautical publications. Controlled Airspace - An airspace of defined dimensions within which air traffic control service is provided to IFR flights and to VFR flights in accordance with the airspace classification. Controlled airspace is a generic term that covers Class A, B, C, D, and E airspace. Crabbing - A rudder-controlled yawing motion to compensate for a crosswind in maintaining a desired flight path, as in a landing approach. Dead Reckoning - The process of estimating one's current position based upon a previously determined position, or fix, and advancing that position based upon known speed, elapsed time, and course. Deadstick - Descending flight with engine and propeller stopped. Departure Stall - A stall in the takeoff configuration with power. Deviation (Magnetic) - The error of a Magnetic Compass due to inherent magnetic influences in the structure and equipment of an aircraft. Directional Gyro - A panel instrument providing a gyroscopic reading of an aircraft's compass heading. DME - Distance Measuring Equipment, a radio navigation device that determines an aircraft's distance from a given ground station, as well as its groundspeed and time to/from the station. Drag - The resisting force exerted on an aircraft in its line of flight opposite in direction to its motion. Dry Weight - The weight of an engine exclusive of any fuel, oil, and coolant. Elevator - The movable part of a horizontal airfoil which controls the pitch of an aircraft, the fixed part being the Stabilzer. ETA - Estimated time of arrival. ETD - Estimated time of departure. FBO - Fixed-Base Operator. A commercial operator supplying fuel, maintenance, flight training, and other services at an airport. FAR - Federal Air Regulations. Flap - A movable, usually hinged airfoil set in the trailing edge of an aircraft wing, designed to increase lift or drag by changing the camber of the wing or used to slow an aircraft during landing by increasing lift. Flare - A control wheel maneuver performed moments before landing in which the nose of an aircraft is pitched up to minimize the touchdown rate of speed. Flight Envelope - An aircraft's performance limits, specifically the curves of speed plotted against other variables to indicate the limits of speed, altitude, and acceleration that a particular aircraft cannot safely exceed. Flight Plan - Specified information relating to the intended flight of an aircraft, filed orally or in writing with an FSS or an ATC facility. FSS - Flight Service Station - Air traffic facilities which provide pilot briefing, enroute communications and VFR search and rescue services, and assist lost aircraft. Fuselage - An aircraft's main body structure housing the flight crew, passengers, and cargo and to which the wings, tail and, in most single-engined airplanes, engine are attached. GA - General Aviation - That portion of civil aviation which encompasses all facets of aviation except air carriers holding a certificate of public convenience and necessity from the Civil Aeronautics Board and large aircraft commercial operators. Glass Cockpit - Said of an aircraft's control cabin which has all-electronic, digital and computer-based, instrumentation. Glider - An unpowered aircraft capable of maintaining altitude only briefly after release from tow, then gliding to earth. Glide Scope - (1) The angle between horizontal and the glide path of an aircraft. (2) A tightly-focused radio beam transmitted from the approach end of a runway indicating the minimum approach angle that will clear all obstacles; one component of an instrument landing system (ILS). GPS - Global Positioning System; satellite-based navigation, rapidly replacing dead reckoning methods. Gross Weight - The total weight of an aircraft when fully loaded, including fuel, cargo, and passengers; aka Takeoff Weight. Ground Control - Tower control, by radioed instructions from air traffic control, of aircraft ground movements at an airport. Ground Effect - Increased lift generated by the interaction between a lift system and the ground when an aircraft is within a wingspan distance above the ground. It affects a low-winged aircraft more than a mid- or high-winged aircraft because its wings are closer to the ground. Ground Speed - The actual speed that an aircraft travels over the ground its "shadow speed"; it combines the aircraft's airspeed and the wind's speed relative to the aircraft's direction of flight. IFR - Instrument Flight Rules, governing flight under instrument meteorological conditions. ILS - Instrument Landing System. A radar-based system allowing ILS-equipped aircraft to find a runway and land when clouds may be as low as 200' (or lower for special circumstances). IAS - Indicated Air Speed - A direct instrument reading obtained from an air speed indicator uncorrected for altitude, temperature, atmospheric density, or instrument error. Compare calibrated airspeed and true airspeed. IMC - Instrument Meterological Conditions - Meteorological conditions expressed in terms of visibility, distance from clouds, and ceiling less than minimal specified for visual meteorological conditions (VMC). Knot - One nautical mile, about 1.15 statute miles (6,080'); eg: 125kts = 143.9mph. Lift - The force exerted on the top of a moving airfoil as a low-pressure area [vacuum] that causes a wingform to rise. airfoils do not "float" on air, as is often assumed - like a boat hull floats on water - but are "pulled up" (lifted) by low air pressures trying to equalize. Lift-Drag Ratio - The lift coefficient of a wing divided by the drag coefficient, as the primary measure of the efficiency of an aircraft; aka L/D ratio. Liquid Compass - A non-electronic, calibratable compass floating in a liquid as a panel instrument; aka wet compass. Load Factor - The proportion between lift and weight commonly seen as g (sometimes capitalized) - a unit of force equal to the force of gravity times one. LORAN - Long Range Navigation System - Utilizes timing differences between multiple low-frequency transmissions to provide accurate latitude/longitude position information to within 50'. LTA - Lighter-than-air craft, generally referring to powered blimps and dirigibles, but often also includes free balloons. Magnetic Compass - The most common liquid-type compass, capable of calibration to compensate for magnetic influences within the aircraft. Magnetic Course - Compass course + or - deviation. Magnetic North - The magnetic North pole, located near 71° North latitude and 96° West longitude, that attracts a magnetic compass which is not influenced by local magnetic attraction. MAG - Magneto - An accessory that produces and distributes a high-voltage electric current for ignition of a fuel charge in an internal combustion engine. MSL - Mean Sea Level. The average height off the surface of the sea for all stages of tide; used as a reference for elevations, and differentiated from AGL. METAR - Acronym in FAA pilot briefings and weather reports simply means an "aviation routine weather report". NDB - Non Directional Beacon - An LF, MF, or UHF radio beacon transmitting non-directional signals whereby the pilot of an aircraft equipped with direction finding equipment can determine his bearing to or from the radio beacon and "home" on or track to or from the station. PAR - Precision Approach Radar, a ground-radar-based instrument approach providing both horizontal and vertical guidance. Pattern - The path of aircraft traffic around an airfield, at an established height and direction. At tower-controlled fields the pattern is supervised by radio (or, in non-radio or emergency conditions by red and green light signals) by air traffic controllers. Flying an entire pattern is called a 'Circuit'. PIC - Pilot in Command - The pilot responsible for the operation and safety of an aircraft during flight time. Pitch - Of the three axes in flight, this specifies the vertical action, the up-and-down movement. Pitot Tube - More accurately but less popularly used, Pitot-Static Tube, a small tube most often mounted on the outward leading edge of an airplane wing (out of the propeller stream) that measures the impact pressure of the air it meets in flight, working in conjuction with a closed, perforated, coaxial tube that measures the static pressure. Roll - Of the three axes in flight, this specifies the action around a central point. Rotorcraft - A heavier-than-air aircraft that depends principally for its support in flight on the lift generated by one or more rotors. Includes helicopters and gyroplanes. Rudder - The movable part of a vertical airfoil which controls the YAW of an aircraft; the fixed part being the fin. Scud - A low, foglike cloud layer. Service Ceiling - The height above sea level at which an aircraft with normal rated load is unable to climb faster than 100' per minute under Standard Air conditions. Sideslip - A movement of an aircraft in which a relative flow of air moves along the lateral axis, resulting in a sideways movement from a projected flight path, especially a downward slip toward the inside of a banked turn. Sink, Sinking Speed - The speed at which an aircraft loses altitude, especially in a glide in still air under given conditions of equilibrium. Skid - Too shallow a bank in a turn, causing an aircraft to slide outward from its ideal turning path. Slip - Too steep a bank in a turn, causing an aircraft to slide inward from its ideal turning path. Slipstream - The flow of air driven backward by a propeller or downward by a rotor. Squawk Code - A four-digit number dialed into his transponder by a pilot to identify his aircraft to air traffic controllers. Stabilizer - The fixed part of a horizontal airfoil that controls the pitch of an aircraft; the movable part being the elevator. Stall - (1) Sudden loss of lift when the angle of attack increases to a point where the flow of air breaks away from a wing or airfoil, causing it to drop. (2) A maneuver initiated by the steep raising of an aircraft's nose, resulting in a loss of velocity and an abrupt drop. TAS - True Air Speed - True Air Speed. Because an air speed indicator indicates true air speed only under standard sea-level conditions, true air speed is usually calculated by adjusting an Indicated Air speed according to temperature, density, and pressure. Thrust - The driving force of a propeller in the line of its shaft or the forward force produced in reaction to the gases expelled rearward from a jet or rocket engine. Opposite of drag. Torque - A twisting, gyroscopic force acting in opposition to an axis of rotation, such as with a turning propeller; aka Torsion. Touch-and-Go - Landing practice in which an aircraft does not make a full stop after a landing, but proceeds immediately to another take-off. Transponder - An airborne transmitter that responds to ground-based interrogation signals to provide air traffic controllers with more accurate and reliable position information than would be possible with "passive" radar; may also provide air traffic control with an aircraft's altitude. Trim Tab - A small, auxiliary control surface in the trailing edge of a wingform, adjustable mechanically or by hand, to counteract ("trim") aerodynamic forces on the main control surfaces. Turn & Bank Indicator - Primary air-driven gyro instrument, a combined turn indicator and lateral inclinometer to show forces on an aircraft in banking turns. Also referred to as "needle & ball" indicator, the needle as the gyro's pointer and a ball encased in a liquid-filled, curved tube. Uncontrolled Airspace - Class G Airspace; airspace not designated as Class A, B, C, D or E. UNICOM - Universal Communication - A common radio frequency (usually 121.0 mHz) used at uncontrolled (non-tower) airports for local pilot communication. Useful Load - The weight of crew, passengers, fuel, baggage, and ballast, generally excluding emergency or portable equipment and ordnance. V - Velocity - Used in defining air speeds, listed below: VA = Maneuvering Speed (max structural speed for full control deflection) VD = Max Dive Speed (for certification only) VFE = Max Flaps Extended Speed VLE = Max Landing Gear Extended Speed VLO = Max Landing Gear Operation Speed VNE = Never Exceed Speed VNO = Max Structural Cruising Speed VS0 = Stalling Speed Landing Configuration VS1 = Stalling Speed in a specified Configuration VX = Best Angle of Climb Speed VXSE = Best Angle of Climb Speed, one engine out VY = Best Rate of Climb Speed VYSE = Best Rate of Climb Speed, one engine out VASI - Visual Approach Slope Indicator - A system of lights on the side of an airport runway that provides visual descent guidance information during the approach to a runway. Venturi Tube - A small, hourglass-shaped metal tube, usually set laterally on a fuselage in the slipstream to create suction for gyroscopic panel instruments. Now outdated by more sophisticated means. VFR - Visual Flight Rules that govern the procedures for conducting flight under visual conditions. The term is also used in the US to indicate weather conditions that are equal to or greater than minimum VFR requirements. Also used by pilots and controllers to indicate a specific type of flight plan. VMC - Visual Meteorological Conditions - Expressed in terms of visibility, distance from clouds, and ceiling equal to or better than specified minima. VOR - VHF OmniRange - A ground-based navigation aid transmitting very high-frequency (VHF) navigation signals 360° in azimuth, on radials oriented from magnetic nort. The VOR periodically identifies itself by Morse Code and may have an additional voice identification feature. Voice features can be used by ATC or FSS for transmitting information to pilots. VSI - Vertical Speed Indicator. A panel instrument that gauges rate of climb or descent in feet-per-minute (fpm). Also called the Rate Of Climb Indicator. Yaw - Of the three axes in flight, this specifies the side-to-side movement of an aircraft on its vertical axis, as in skewing. Yoke - The control wheel of an aircraft, akin to a automobile steering wheel.
  13. Admin

    ATC Phrases

    The following are the most common ATC phrases "Cleared to taxi" When told by ground control or tower that you are cleared to taxi, the controller has given you instruction to taxi along taxiway centerlines according to taxiway markings. It is important to repeat all controller instructions and runway crossing instructions, as you may be told to "hold short" of a specific runway and wait for further instructions. "Position and hold" or "Line up and Wait" (AUS) The tower expects you to taxi onto runway centerline and maintain a stopped position while the aircraft in front of you gains separation or clears the runway. It is important that, prior to crossing the hold-short lines, you verify your instructions, verify runway of use, and scan extended final for traffic. "Cleared for takeoff" The tower controller is the only authority to clear you for takeoff at a controlled airfield. Repeat back your takeoff clearance and call sign, as well as scan final for traffic. The tower may request other specific instructions, so listen closely to your takeoff clearance. "Enter closed traffic" The tower has acknowledged the pilot's intention to perform successive operations involving takeoffs and landings or low approaches where the aircraft does not exit the traffic pattern. "Cleared for the option" When you are cleared for the option you have been given permission to either do a touch-and-go, make a low approach, missed approach, stop and go, or full-stop landing. If requesting this clearance, the pilot should do so upon establishing downwind on a VFR traffic pattern. "Cleared touch-and-go" When authorized by the tower, the touch-and-go procedure allows the pilot to land on the runway, reconfigure the airplane and perform a takeoff to re-enter the traffic pattern. If requesting this approach the pilot should do so upon establishing downwind on a VFR traffic pattern. "Cleared low approach" A low approach clearance allows the pilot to perform a simulated emergency landing or normal landing down to the runway environment (100' AGL) and then perform a go-around to re-enter or depart the pattern. If requesting this approach you should do so upon establishing downwind on a VFR traffic pattern. "Cleared stop-and-go" A stop-and-go clearance allows the pilot to land on the runway, come to a full stop, and then takeoff on the remaining length of runway. The pilot must be aware of runway lengths and takeoff distance requirements. This procedure can be beneficial in keeping costs lower when performing night currency. If requesting this clearance the pilot should do so upon establishing downwind on a VFR traffic pattern. "Cleared to land" When given clearance to land the tower has authorized you to land on the runway in use. The phrase "cleared to land" gives you immediate use of that runway, unless the tower advises that you are in sequence for landing ("number two to land, number three, etc..."). After advising approach or tower that you are inbound for landing at your destination you do not have to make any further request for clearance to land. "Land-and-hold-short" The land-and-hold-short procedure requires the pilot to perform an accurate landing on the runway so that the pilot can stop the aircraft before reaching an intersecting runway, intersecting taxiway, or construction area. If you are unable to comply with landand-hold-short operations, you may request clearance for a different runway. "Make Short Approach" Used by ATC to have a pilot to alter their traffic pattern so as to make a short final approach. If unable to execute a short approach, simply tell the ATC so. "Parking with me" Under normal conditions you would exit the runway at the first available taxiway, stop the aircraft after clearing the runway, and call ground control for instructions if you have not already received them. If the controller says "parking with me", he or she has given you clearance to taxi to your destination. "Caution: wake turbulence" This call from ATC advises the pilot of the potential for encountering wake turbulence from departing or arriving aircraft. "Frequency change approved" You've reached the edge of the controller's airspace and may change your radio to your next frequency. "Proceed direct" You may turn to the direct heading of your destination (often followed by this heading). Usually used by ATC once you've been vectored clear of other traffic in the area. "Report position" The controller wants to pinpoint your position relative to the airport. You should report altitude, distance, and direction. For example: "8081G is five miles southwest of the airport at one thousand two hundred feet" "Expedite" ATC would like you to hurry up whatever it is that you're doing; taking off, landing, climbing, descending, or taxiing to your destination. "Ident" ATC request for a pilot to use his aircraft transponder identification feature (usually an IDENT button). This helps the controller to confirm an aircraft identity and position. "Squawk" Followed by a squawk code or function button on the transponder. ATC issues individual squawk codes to all aircraft within radar service in order to differentiate traffic. "Go around" Pilots receiving this transmission should abandon their approach to landing. Additional instructions from ATC may then follow. Unless otherwise instructed, VFR aircraft executing a go around should overfly the runway while climbing to pattern altitude, then enter the traffic pattern by way of the crosswind leg. "Watch for Traffic..." Usually followed by the direction and distance of the traffic, you should immediately scan for it with "Looking for traffic" and report back to the controller whether you have the aircraft in sight or not. "Extend Downwind" While this may seem obvious, the controller wants you to continue straight on your downwind until he or she tells you to turn base (often followed by "I'll call your base"). In all likelyhood you're going to have a long final. Keep course and scan for other traffic.
  14. Birth of a NOTAM NOTAM start life as messages on the Aeronautical Fixed System (AFS). They are received centrally at the UK NOTAM office at London Heathrow from originators within the UK and from foreign NOTAM offices. AIS staff check and edit the NOTAM if necessary and they are then placed in the transmit queue for transmission to all UK NOTAM recipients. These include ATC offices, some airlines, briefing services etc. There is no central world-wide NOTAM database, databases are built up individually by users from the incoming message stream. ICAO NOTAM format The format of NOTAM is defined in Annex 15 to the International Convention on Civil Aviation. An explanation of the format can be found here. Here is a typical NOTAM and its decode. A1484/02 NOTAMN Q) EGTT/QMRXX/IV/NBO/A/000/999/5129N00028W005 A) EGLL B) 0208231540 C) 0210310500 EST E) RWY 09R/27L DUE WIP NO CENTRELINE, TDZ OR SALS LIGHTING AVBL Notam Decoder A1484/02 - one letter to indicate the Series, a 4-digit NOTAM number followed by a stroke and two digits to indicate the year. NOTAMN - Suffix N Indicates this is a new NOTAM. Other options are R for NOTAM replacing another or C for one cancelling another. Q) EGTT/QMRXX/IV/NBO/A/000/999/5129N00028W005 This is the "Q" or qualifier line, it always starts Q) and contains the following fields, each separated by a stroke. FIR (here EGTT, London FIR) NOTAM Code, a 5 letter code starting with Q, defined in Annexe 15. Here QMR indicates that it concerns a Runway. XX indicates that remaining detail is in Plain Language. In this particular case the text shows that certain runway lighting is unavailable. Strictly speaking under ICAO rules this should have appeared as separate NOTAM for each type of lighting. QLCAS is the code for centreline lighting u/s QLZAS is the code for Touch Down Zone lighting u/s and QLAAS is the code for Approach Lighting u/s (note in all cases AS indicates unserviceable). The use of QMRXX here is a sensible compromise that reduces the number of NOTAM from three to one. A full list of codes is included in ICAO document 8126 (Aeronautical Information Services Manual). IV - Indicates that this is significant for IFR and VFR traffic NBO - indicates for immediate attention of aircraft operators, for inclusion in PIB's and Operationally significant for IFR flights A - Indicates scope, here Aerodrome, others are E (en-route) or W (nav warning) 000/999 - lower and upper limits expressed as a flight level. In this case it has been left as the default as it is not applicable. 5129N00028W005 - Indicates the geographical centre and radius of influence, always this number of digits. In this case the radius is 5 n.m. A) EGLL - ICAO indicator of the aerodrome or FIR (London Heathrow) can include more than one FIR B) 0208231540 - Date/time group (UTC) when this NOTAM becomes effective C) 0210310500 EST - Date/time group (UTC) when the NOTAM ceases to be effective. Note "EST" means "estimated" (NOT Eastern Standard Time!). All NOTAM with EST remain in force until cancelled or replaced. E) RWY 09R/27L DUE WIP NO CENTRELINE, TDZ OR SALS LIGHTING AVBL - text of the notam using ICAO abbreviations. Decode of this is "Runway 09/27 due to work in progress no centreline, touchdown zone or simple approach lighting system available" Here's the whole thing again A1484/02 NOTAMN Q) EGTT/QMRXX/IV/NBO/A/000/999/5129N00028W005 A) EGLL B) 0208231540 C) 0210310500 EST E) RWY 09R/27L DUE WIP NO CENTRELINE, TDZ OR SALS LIGHTING AVBL and here's the same thing as it appears in the PIB produced by ANAIS AGA : FROM 02/08/23 15:40 TO 02/10/31 05:00 EST A1484/02 E)RWY 09R/27L DUE WIP NO CENTRELINE, TDZ OR SALS LIGHTING AVBL You can see that the Q line is omitted entirely, A) has been stripped out because it appears as the header to the section and B) and C) have been reformatted and placed in the first line. AGA has been derived from the Q Code "QMR" (see Annex 15) INTERNATIONAL NOTAM (Q) CODES This appendix is to be used to interpret the contents of coded international NOTAM's. A NOTAM code group contains five letters. The first letter is always the letter "Q'' to indicate a code abbreviation for use in the composition of NOTAM's. The second and third letters identify the subject being reported. (See Second and Third Letter Decode Tables). The fourth and fifth letters identify the status of operation of the subject being reported. (See Fourth and Fifth Letter Decode Tables). THE NOTAM CODE DECODE SECOND AND THIRD LETTERS AGA Lighting Facilities (L) Code Signification Uniform Abbreviated Phraseology LA Approach lighting system (specify runway and type) apch lgt LB Aerodrome beacon abn LC Runway center line lights (specify runway) rwy centreline lgt LD Landing direction indicator lights ldi lgt LE Runway edge lights (specify runway) rwy edge lgt LF Sequenced flashing lights (specify runway) sequenced flg lgt LH High intensity runway lights (specify runway) high intst rwy lgt LI Runway end identifier lights (specify runway) rwy end id lgt LJ Runway alignment indicator lights (specify runway) rwy alignment indicator lgt LK Category II components of approach lighting system (specify runway) category II components apch lgt LL Low intensity runway lights (specify runway) low intst rwy lgt LM Medium intensity runway lights (specify runway) medium intst rwy lgt LP Precision approach path indicator (PAPI) (specify runway) papi LR All landing area lighting facilities ldg area lgt fac LS Stopway lights (specify runway) swy lgt LT Threshold lights (specify runway) thr lgt LV Visual approach slope indicator system (specify type and runway) vasis LW Heliport lighting heliport lgt LX Taxiway centre line lights (specify taxiway) twy centreline lgt LY Taxiway edge lights (specify taxiway) twy edge lgt LZ Runway touchdown zone lights (specify runway) rwy tdz lgt THE NOTAM CODE DECODE SECOND AND THIRD LETTERS AGA Movement and Landing Area (M) Code Signification Uniform Abbreviated Phraseology MA Movement area mov area MB Bearing strength (specify part of landing area or movement area) bearing strength MC Clearway (specify runway) cwy MD Declared distances (specify runway) declared dist MG Taxiing guidance system tax guidance system MH Runway arresting gear (specify runway) rwy arst gear MK Parking area prkg area MM Daylight markings (specify threshold, centre line, etc.) day markings MN Apron apron MP Aircraft stands (specify) acft stand MR Runway (specify runway) rwy MS Stopway (specify runway) swy MT Threshold (specify runway) thr MU Runway turning bay (specify runway) rwy turning bay MW Strip (specify runway) strip MX Taxiway(s) (specify) twy THE NOTAM CODE DECODE SECOND AND THIRD LETTERS AGA Facilities and Services (F) Code Signification Uniform Abbreviated Phraseology FA Aerodrome ad FB Braking action measurement equipment (specify type) ba measurement eqpt FC Ceiling measurement equipment ceiling measurement eqpt FD Docking system (specify AGNIS, BOLDS, etc.) dckg system FF Fire fighting and rescue fire and rescue FG Ground movement control gnd mov ctl FH Helicopter alighting area/platform hel alighting area FL Landing direction indicator ldi FM Meteorological service (specify type) met FO Fog dispersal system fog dispersal FP Heliport heliport FS Snow removal equipment snow removal eqpt FT Transmissometer (specify runway and, where applicable, designator(s) of transmissometer(s)) transmissometer FU Fuel availability fuel avbl FW Wind direction indicator wdi FZ Customs cust THE NOTAM CODE DECODE SECOND AND THIRD LETTERS COM Communications and Radar Facilities (C) Code Signification Uniform Abbreviated Phraseology CA Air/ground (specify service and frequency) a/g fac CE En route surveillance radar rsr CG Ground controlled approach system (GCA) gca CL Selective calling system (SELCAL) selcal CM Surface movement radar smr CP Precision approach radar (PAR) (specify runway) par CR Surveillance radar element of precision approach radar system (specify wavelength) sre CS Secondary surveillance radar (SSR) ssr CT Terminal area surveillance radar (TAR) tar THE NOTAM CODE DECODE SECOND AND THIRD LETTERS COM Instrument and Microwave Landing System (I) Code Signification Uniform Abbreviated Phraseology ID DME associated with ILS ils dme IG Glide path (ILS) (specify runway) ils gp II Inner marker (ILS) (specify runway) ils im IL Localizer (ILS) (specify runway) ils liz IM Middle marker (ILS) (specify runway) ils mm IO Outer marker (ILS) (specify runway) ils om IS ILS Category I (specify runway) ils I IT ILS Category II (specify runway) ils II IU ILS Category III (specify runway) ils III IW Microwave landing system (MLS) (specify runway) mls IX Locator, outer (ILS) (specify runway) ils lo IY Locator, middle (ILS) (specify runway) ils lm THE NOTAM CODE DECODE SECOND AND THIRD LETTERS COM Terminal and En Route Navigation Facilities (N) Code Signification Uniform Abbreviated Phraseology NA All radio navigation facilities (except...) all rdo nav fac NB Nondirectional radio beacon ndb NC DECCA decca ND Distance measuring equipment (DME) dme NF Fan marker fan mkr NL Locator (specify identification) l NM VOR/DME vor/dme NN TACAN tacan NO OMEGA omega NT VORTAC vortac NV VOR vor NX Direction finding station (specify type and frequency) df THE NOTAM CODE DECODE SECOND AND THIRD LETTERS RAC Airspace Organization (A) Code Signification Uniform Abbreviated Phraseology AA Minimum altitude (specify en route/crossing/safe) mnm alt AC Class B, C, D, or E Surface Area ctr AD Air defense identification zone (ADIZ) adiz AE Control area (CTA) cta AF Flight information region (FIR) fir AH Upper control area (UTA) uta AL Minimum usable flight level mnm usable fl AN Area navigation route rnav route AO Oceanic control area (OCA) oca AP Reporting point (specify name or Coded designator) rep AR ATS route (specify) ats route AT Class B Airspace tma AU Upper flight information region (UIR) uir AV Upper advisory area (UDA) uda AX Intersection (INT) int AZ Aerodrome traffic zone (ATZ) atz THE NOTAM CODE DECODE SECOND AND THIRD LETTERS RAC Air Traffic and VOLMET Services (S) Code Signification Uniform Abbreviated Phraseology SA Automatic terminal information service (ATIS) atis SB ATS reporting office aro SC Area control centre (ACC) acc SE Flight information service (FIS) fis SF Aerodrome flight information service (AFIS) afis SL Flow control centre flow ctl centre SO Oceanic area control centre (OAC) oac SP Approach control service (APP) app SS Flight service station (FSS) fss ST Aerodrome control tower (TWR) twr SU Upper area control centre (UAC) uac SV VOLMET broadcast volmet SY Upper advisory service (specify) advisory ser THE NOTAM CODE DECODE SECOND AND THIRD LETTERS RAC Air Traffic Procedures (P) Code Signification Uniform Abbreviated Phraseology PA Standard instrument arrival (STAR) (specify route designator) star PB Standard VFR arrival std vfr arr PC Contingency procedures contingency proc PD Standard instrument departure (SID) (specify route designator) sid PE Standard VFR departure std vfr dep PF Flow control procedure flow ctl proc PH Holding procedure hldg proc PI Instrument approach procedure (specify type and runway) inst apch proc PL Obstacle clearance limit (specify procedure) ocl PK VFR approach procedure vfr apch proc PM Aerodrome operating minima (specify procedure and amended minimum) opr minima PN Noise operating restrictions noise opr restrictions PO Obstacle clearance altitude oca PP Obstacle clearance height och PR Radio failure procedure radio failure proc PT Transition altitude transition alt PU Missed approach procedure (specify runway) missed apch proc PX Minimum holding altitude (specify fix) mnm hldg alt PZ ADIZ procedure adiz proc THE NOTAM CODE DECODE SECOND AND THIRD LETTERS Navigation Warnings: Airspace Restrictions (R) Code Signification Uniform Abbreviated Phraseology RA Airspace reservation (specify) airspace reservation RD Danger area (specify national prefix and number) ..d.. RO Overflying of ... (specify) overflying RP Prohibited area (specify national prefix and number) ..p.. RR Restricted area (specify national prefix and number) ..r.. RT Temporary restricted area tempo restricted THE NOTAM CODE DECODE SECOND AND THIRD LETTERS Navigation Warnings: Warnings (W) Code Signification Uniform Abbreviated Phraseology WA Air display air display WB Aerobatics aerobatics WC Captive balloon or kite captive balloon or kite WD Demolition of explosives demolition of explosives WE Exercises (specify) exer WF Air refueling air refueling WG Glider flying glider flying WJ Banner/target towing banner/target towing WL Ascent of free balloon ascent of free balloon WM Missile, gun or rocket firing frng WP Parachute jumping exercise (PJE) pje WS Burning or blowing gas burning or blowing gas WT Mass movement of aircraft mass mov of acft WV Formation flight formation flt WZ model flying model flying THE NOTAM CODE DECODE SECOND AND THIRD LETTERS Other Information (O) Code Signification Uniform Abbreviated Phraseology OA Aeronautical information service ais OB Obstacle (specify details) obst OE Aircraft entry requirements acft entry rqmnts OL Obstacle lights on ... (specify) obst lgt OR Rescue coordination centre rcc THE NOTAM CODE DECODE FOURTH AND FIFTH LETTERS Availability (A) Code Signification Uniform Abbreviated Phraseology AC Withdrawn for maintenance withdrawn maint AD Available for daylight operation avbl day ops AF Flight checked and found reliable fltck okay AG Operating but ground checked only, awaiting flight check opr awaiting fltck AH Hours of service are now hr ser AK Resumed normal operations okay AM Military operations only mil ops only AN Available for night operation avbl night ops AO Operational opr AP Available, prior permission required avbl ppr AR Available on request avbl o/r AS Unserviceable u/s AU Not available (specify reason if appropriate) not avbl AW Completely withdrawn withdrawn AX Previously promulgated shutdown has been cancelled promulgated shutdown cnl THE NOTAM CODE DECODE FOURTH AND FIFTH LETTERS Changes (C) Code Signification Uniform Abbreviated Phraseology CA Activated act CC Completed cmpl CD Deactivated deactivated CE Erected erected CF Operating frequency(ies) changed to freq change CG Downgraded to downgraded to CH Changed changed CI Identification or radio call sign changed to ident change CL Realigned realigned CM Displaced displaced CO Operating opr CP Operating on reduced power opr reduced pwr CR Temporarily replaced by tempo rplcd by CS Installed installed CT On test, do not use on test, do not use THE NOTAM CODE DECODE FOURTH AND FIFTH LETTERS Hazard Conditions (H) Code Signification Uniform Abbreviated Phraseology HA Braking action is ... ba is 1)Poor 2)Medium/Poor 3)Medium 4)Medium/Good 5)Good HB Braking coefficient is ... (specify measurement device used) brkg coefficient is HC Covered by compacted snow to depth of cov compacted snow depth HD Covered by dry snow to a depth of cov dry snow depth HE Covered by water to a depth of cov water depth HF Totally free of snow and ice free of snow and ice HG Grass cutting in progress grass cutting HH Hazard due to (specify) hazard due HI Covered by ice cov ice HJ Launch planned ... (specify balloon flight identification or project Code name, launch site, planned period of launch(es)_date/time, expected climb direction, estimate time to pass 18,000 m (60,000 ft), together with estimated location) launch plan HK Migration in progress migration inpr HL Snow clearance completed snow clr cmpl HM Marked by marked by HN Covered by wet snow or slush to a depth of cov wet snow depth HO Obscured by snow obscured by snow HP Snow clearance in progress snow clr inpr HQ Operation cancelled ... (specify balloon flight identification or project Code name) opr cnl HR Standing water standing water HS Sanding in progress sanding HT Approach according to signal area only apch according signal area only HU Launch in progress ... (specify balloon flight identification or project Code name, launch site, date/time of launch(es), estimated time passing 18,000 m (60,000 ft), or reaching cruising level if at or below 18,000 m (60,000 ft), together with estimated location, estimated date/time of termination of the flight, and planned location of ground contact when applicable) launch inpr HV Work completed work cmpl HW Work in progress wip HX Concentration of birds bird concentration HY Snow banks exist (specify height) snow banks hgt HZ Covered by frozen ruts and ridges cov frozen ruts and ridges THE NOTAM CODE DECODE FOURTH AND FIFTH LETTERS Limitations (L) Code Signification Uniform Abbreviated Phraseology LA Operating on auxiliary power supply opr aux pwr LB Reserved for aircraft based therein reserved for acft based therein LC Closed clsd LD Unsafe unsafe LE Operating without auxiliary power supply opr without aux pwr LF Interference from interference from LG Operating without identification opr without ident LH Unserviceable for aircraft heavier than u/s acft heavier than LI Closed to IFR operations clsd ifr ops LK Operating as a fixed light opr as f lgt LL Usable for length of...and width of... usable length/width LN Closed to all night operations clsd night ops LP Prohibited to prohibited to LR Aircraft restricted to runways and taxiways acft restricted to rwy and twy LS Subject to interruption subj intrp LT Limited to limited to LV Closed to VFR operations clsd vfr ops LW Will take place will take place LX Operating but caution advised due to opr but caution due THE NOTAM CODE DECODE FOURTH AND FIFTH LETTERS Other (XX) Code Signification Uniform Abbreviated Phraseology XX Where 4th and 5th letter Code does not cover the situation, use XX and supplement by plain language (plain language following the NOTAM Code)
  15. Area Forecasts For Operations At or Below 10,000 Feet The Area Forecast system is designed primarily to meet the needs of pilots of general aviation. There is an emphasis on plain language and brevity in a simple, easy to read format. The system provides for the routine issue of forecasts for designated areas (see map below) and the prompt issue of amendments when prescribed criteria are satisfied. More detail of the area forecast boundaries with place locations is contained in Airservices Australia's Planning Chart Australia (PCA). There may be variations in commencement of validity between different regions, and between those times when daylight saving is or is not operating. However the following principles apply: the standard validity period is twelve hours but this may vary from state to state. an area forecast covering daylight hours will be available as soon as practicable in the morning. area forecasts are not prepared for those times when air traffic volume is so low as not to justify routine issues. In these cases a route forecast will service any individual flights. area forecasts will generally be available a minimum of one hour before commencement of validity. Message Structure Message Identifier The forecast is identified as AREA FORECAST unless the forecast is an amendment in which case it will be denoted AMEND AREA FORECAST. In the case of amended area forecasts, all individual sections that are amended will be annotated with AMD preceding the section heading. Validity Period The validity period is written DDHHMM TO DDHHMM, where DD is the day of the month and HHMM is the time in hours and minutes UTC. Area Number The relevant forecast area is specified by an area forecast district number. These are given in more detail on the current Airservices Australia's Planning Chart Australia. Note that Areas 24, 87 and 88 are only designated for the purpose of Area QNH. Any flights in these areas can be provided with a route forecast. Overview The overview will highlight any conditions which may inhibit safe operations for pilots flying under visual flight rules, and will make reference, where necessary, to any spatial and temporal variations. It will assist the pilot in making the following types of decisions: Are the meteorological conditions Visual Meteorological Conditions (VMC), marginal, Instrument Flight Rules (IFR) or too poor for flying? Is it better to plan for a coastal or inland track? If bad weather is encountered, what is the contingency plan? Return? Change altitude? Change heading? Land immediately? Subdivisions Area forecasts may be divided into spatial, temporal or weather-related subdivisions. Spation subdivisions are given using PCA (Planning Chart Australia) or lat/lon coordinates Winds and Temperatures Upper level winds are given for 2000 (or 3000 in elevated regions), 5000, 7000, 10 000, 14 000 and 18 500 feet. The expected mean wind direction is given in three figures to the nearest ten degrees True, followed by a solidus (/), followed by the mean wind speed in two figures to the nearest five knots, 290/40. CALM and VRB05 (wind direction variable at 5 knots) are used when appropriate. A REMARKS section may be included below the WIND section to provide further information on winds. Upper level temperatures are given for 10 000, 14 000 and 18 500 feet. These are given in whole degrees Celsius, following the forecast of the upper wind for the level concerned. e.g. 290/40 PS08, 300/50 ZERO, 360/10 MS10. The abbreviation PS is used for positive temperatures, and MS (minus) is used for negative temperatures. Cloud The inclusion of cloud is restricted to: any CB or TCU. any cloud with a base at or below 5000 feet above the highest terrain in the area covered by the forecast. any cloud layer of more than 4/8 (broken or overcast) amount with base at or below 20 000 feet above MSL. any cloud associated with any forecast precipitation, moderate or severe icing and moderate or severe turbulence. Cloud amount is given using the following abbreviations: FEW - Few (1 to 2 oktas) SCT - Scattered (3 to 4 oktas) BKN - Broken (5 to 7 oktas) OVC - Overcast (8 oktas) ...except for cumulonimbus and towering cumulus, for which amount is described as: ISOL - Isolated OCNL - Occasional (well separated) FRQ - Frequent (little or no separation) EMBD - Embedded (in layers of other cloud) Cloud type is given using the following abbreviations: CU - Cumulus SC - Stratocumulus CB - Cumulonimbus TCU - Towering cumulus ST - Stratus AS - Altostratus AC - Altocumulus NS - Nimbostratus If subdivisions are used and one or more subdivisions have no cloud associated with it, the format used is NIL CLOUD. When CU and SC, or AC and AS, occur together at similar heights, they are combined, i.e. CU/SC or AC/AS. Cloud base and tops are given in feet above MSL (mean sea level). Weather Weather information relating to the layer below 21 000 feet above MSL is given following the word 'WEATHER'. If subdivisions are used and one or more subdivisions have no weather associated with it the format is, WEATHER A: NIL. Visibility Horizontal visibility is given in metres to the nearest 100 metres up to and including 5000 metres, and in whole kilometres above that value. Forecast visibilities of 50 metres or less are given as 'ZERO'. The forecast value is followed by the units used e.g. '8KM' or '1000M'. Significant variations of visibility are included. If the visibility is forecast to be above 10 kilometres throughout the area, the words 'UNRESTRICTED' or 'GOOD' are used. Vertical variations of horizontal visibility, which might prevent flight under VMC conditions, are significant. For example, information is supplied on the depth of layers affected by drizzle, haze and dust storms, and the levels of haze layers under inversions. Visibility variations with these phenomena is given. Freezing Level Freezing level is the height, in feet, above MSL of zero degrees Celsius. Reference is made to any variations in height greater than 1000 feet, and to the occurrence of more than one freezing level. Icing The icing section gives information on the expected occurrence of moderate or severe icing in cloud (including convective cloud), or precipitation, in the layer below 20 000 feet above MSL. The height above MSL of the bottom and top of the layer is given as, for example, MOD IN RA 5000/8000. When the layer of icing is expected to extend above 20 000 feet, descriptions such as MOD ABOVE 14000 are used. Turbulence This section provides information on moderate or severe turbulence including turbulence associated with convective cloud. The height above MSL of the bottom and top of any layer(s) is given as, for example, MOD IN CLOUD 12000/16000 When the turbulence is expected to extend to ground level, descriptions such as BELOW 8000 are used. When the turbulence is expected to be confined to clouds, descriptions such as MOD IN CLOUD BELOW 8000 are used. When the turbulence is expected to extend above 20 000 feet, descriptions such as SEV ABOVE 15000 are used. Critical Locations These are locations such as gaps in mountain ranges which are frequently used by general aviation aircraft. Currently, critical location forecasts are appended to Area Forecasts for Bowral and Mt Victoria (NSW) on AREA 21; Mt Victoria and Murrurundi (NSW) on AREA 20; and Kilmore Gap (Vic) on AREA 30. Critical location forecasts are written in a mixture of plain language and TAF format making reference as necessary to cloud, visibility and weather. CAVOK is used to indicate visibility greater than 10 KM, cloud ceiling above 5000 FT above ground level and nil significant weather. Remarks This section will include any relevant information not included elsewhere in the forecast. Abbreviations and Codes Used in Area Forecasts AC - Altocumulus AC/AS - Altocumulus and Altostratus with bases at the same level AS - Altostratus AMD - Amendment BKN - Broken CAVOK - Cloud and visibility and weather ok. CB - Cumulonimbus CU - Cumulus CU/SC - Cumulus and Stratocumulus with bases at the same level DZ - Drizzle EMBD - Embedded FEW - Few FG - Fog FM - From (only used in Critical Locations section) FRQ - Frequent GR - Hail GS - Small Hail INTER - Intermittent variations (only used in Critical section Locations) ISOL - Isolated MOD - Moderate NS - Nimbostratus OCNL - Occasional OVC - Overcast RA - Rain SC - Stratocumulus SCT - Scattered SEV - Severe SH - Shower SN - Snow ST - Stratus TCU - Towering Cumulus TEMPO - Temporary variations (only used in Critical Locations section) TS - Thunderstorm Z - Code for UTC (universal time) Example
  16. METAR/SPECI A METAR is a routine report of meteorological conditions at an aerodrome. A SPECI is a special report of meteorological conditions, issued when one or more elements meet specified criteria significant to aviation. SPECI is also used to identify reports of observations recorded ten minutes following an improvement (in visibility, weather or cloud) to above SPECI conditions. Location The location is indicated by either the ICAO (International Civil Aviation Organization) location indicator or another approved abbreviation. Date/Time The day of month and the time of the report is given in UTC (Coordinated Universal Time) using six figures followed by the letter Z. The first two digits are the day of the month; the following 4 digits are the time in hours and minutes, e.g. 291741Z (time of report is 1741 on the 29th of the month UTC). AUTO The abbreviation AUTO will be included when the report contains only automated observations. Surface Wind The wind direction is given in degrees true, rounded to the nearest 10 degrees. A variable wind direction is given as VRB. The wind speed, given in knots (KT), is the mean value over the sampling period which is normally ten minutes. The maximum wind speed during the sampling period is reported when it exceeds the mean speed by 10 knots or more. It is indicated by the letter G which is followed by the gust value, e.g. a wind direction of 280°, with a mean speed of 20 knots and a maximum gust of 31 knots, is given as 28020G31KT. Visibility The horizontal visibility is given in metres up to 9000 metres; with 9999 being used to indicate a visibility of 10 kilometres or greater. When the visibility is estimated manually (i.e. by an observer), two groups may be reported when the visibility is not the same in different directions. In these cases, the higher visibility will be given first, followed by the minimum visibility and its direction (using one of the eight points of the compass) from the observing station e.g. 9000 2000N. When visibility is given by an automated sensor (in fully AUTOmated reports), only one group is reported. The value is followed by the letters NDV (Nil Directional Variation) to indicate that, as there is only one visibility sensor in place, any directional variation in visibility that may exist cannot be detected. Weather Weather phenomena are reported using the codes listed in the tables: Code Weather Descriptor MI - Shallow BC - patches PR - partial DR - drifting BL - blowing SH - showers FZ - freezing TS - thunderstorm Code Weather Phenomena DZ - drizzle RA - rain GR - hail SN - snow SG - snow grains DU - dust SA - sand SS - sandstorm DS - dust storm GS - small hail/snow pellets PL - ice pellets FG - fog BR - mist FU - smoke HZ - haze PO - dust devil SQ - squall FC - funnel cloud VA - volcanic ash IC - ice crystals PL - ice pellets Intensity is indicated for precipitation, blowing dust/sand/snow, dust storm and sandstorm by appending: the prefix - for light, e.g. -DZ the prefix + for heavy, e.g. +RA no prefix for moderate, e.g. SHRA One or more codes may be grouped, e.g. +TSGR, -TSRASN NOTE When precipitation is reported with TS, the intensity indicator refers to the precipitation, e.g. -TSRA = thunderstorm with light rain. Well-developed dust/sand whirls (dust devils) and funnel clouds are reported using the indicator + An observation may provide an indication of weather in the vicinity of the aerodrome, i.e. between 8 and 16KM of the aerodrome reference point. In these cases, the weather code is prefixed with the abbreviation VC (vicinity), e.g. VCTS. Cloud Cloud information is reported from the lowest to the highest layers in accordance with the following rules: 1st group: the lowest layer regardless of amount. 2nd group: the next layer covering more than 2 oktas of the sky. 3rd group: the next higher layer covering more than 4 oktas of the sky. Extra groups: for cumulonimbus and/or towering cumulus clouds, whenever observed and not reported in any of the above. Cloud amount is described using the codes in the table: Code - Cloud Amount SKC - sky clear FEW - few (1 to 2 oktas) SCT - scattered (3 to 4 oktas) BKN - broken (5 to 7 oktas) OVC - overcast (8 oktas) NSC - nil significant cloud NCD* - nil cloud detected * NCD is reported (in fully automated reports only) when a cloud sensor detects nil cloud (a human observer will report SKC when the sky is clear. Cloud height is given as a three-figure group in hundreds of feet above the aerodrome elevation, e.g. cloud at 700 feet is shown as 007. Cloud type is identified only for cumulonimbus and towering cumulus, e.g. FEW030CB, SCT045TCU. When an individual layer is composed of cumulonimbus and towering cumulus with a common base, the cloud is reported as CB only. If the sky is obscured, due to, for example, bushfire smoke, human observers will report the vertical visibility (when it can be estimated) in lieu of cloud. It is reported with the prefix VV followed by the vertical visibility in hundreds of feet, e.g. the group VV003 reports an estimated vertical visibility of between 300 and 399 feet (values are rounded down to the next hundred foot increment). CAVOK The abbreviation CAVOK (Cloud and Visibility OK) is used when the following conditions are observed simultaneously: Visibility is 10 kilometres or more; No cloud below 5000 feet or below the highest 25NM minimum sector altitude, whichever is the higher, and no cumulonimbus and no towering cumulus; and No weather of significance to aviation, i.e. none of the weather phenomena listed in the weather tables above. Temperature Air temperature and dew point values are rounded to the nearest whole degree. Negative values are indicated by M (minus) before the numeral, e.g. 34/M04 Pressure (QNH) The QNH value is rounded down to the next whole hectopascal and is given using four figures prefixed by Q, e.g. 999.9 is given as Q0999 Supplementary Information Supplementary information is used to report: Recent Weather - significant weather observed since the last report but not at the time of observation is given after the prefix RE, e.g. RERA. Wind Shear - reports of wind shear experienced on take-off or landing are given after the indicator WS, e.g. WS RWY16. Remarks The Remarks section (indicated by RMK) may contain the following: Quantitative information on past rainfall is given in millimetres in the form RFRR.R/RRR.R or RFRR.R/RRR.R/RRR.R. The former, e.g. RF00.2/004.2, gives the rainfall recorded in the ten minutes prior to the observation time, followed by the rainfall recorded in the period since 0900 local time. The second format, e.g. RF00.2/003.0/004.2, gives the rainfall recorded in the ten minutes prior to the observation, followed by the rainfall in the sixty minutes prior to the observation, followed by the rainfall recorded in the period since 0900 local time. Information of operational significance not reported in the body of the message, for example: information about significant conditions (such as bushfires and distant thunderstorms) beyond the immediate vicinity of the aerodrome, any BKN or OVC low or middle cloud present at or above 5000 feet when CAVOK has been included in the body of the message, CLD:SKY MAY BE OBSC may be reported in fully automated reports when the ceilometer (cloud sensor) detects nil cloud and the visibility sensor estimates horizontal visibility as being less than 1000 metres Elements of report not available Where an element of a report is not available, solidi will be reported in lieu of the missing element, e.g. //// for visibility, // for weather and ////// for cloud. SPECI Criteria SPECI is used to identify reports of observations when conditions are below specified levels of visibility and cloud base; when certain weather phenomena are present; and when temperature, pressure or wind change by defined amounts (outlined in the table on the right). SPECI is also used to identify reports of observations recorded 10 minutes following an improvement in visibility, weather or cloud to METAR conditions. Element And Criterion Wind Direction - Changes of 30° or more, the mean speed before or after the change being 20KT or more Wind Speed - Changes of 10KT or more, the mean speed before or after the change being 30KT or more Wind Gust Gusts of 10KT or more above a mean speed of 15KT or more Gust exceeds the last reported gust by 10KT or more Visibility - When the horizontal visibility is below the aerodrome’s highest alternate minimum visibility* Weather - When any of the following begins, ends or changes in intensity: thunderstorm hailstorm mixed snow and rain freezing precipitation drifting snow fog (including shallow fog, fog patches and fog at a distance) dust storm sand storm squall funnel cloud moderate or heavy precipitation Cloud - When there is BKN or OVC cloud below the aerodrome's highest alternate minimum cloud base* Temperature - When the temperature changes by 5°C or more since last report Pressure - When the QNH changes by 2hPa or more since last report Other Upon receipt of advice of the existence of wind shear The incidence of any other phenomenon likely to be significant *Where no descent procedure is established for an aerodrome, the aerodrome’s alternate ceiling and visibility are 1500 feet and 8 kilometres respectively. METAR/SPECI Examples METAR YPPH 221130Z 28012G23KT 9000 -SHRA FEW005 BKN050 27/22 Q0999 RETS RMK RF00.6/003.4 DISTANT TS REPORT EXPLANATION METAR Routine meteorological observation YPPH ICAO location indicator for Perth Airport 221130Z Time of observation is 1130 on the 22nd of the month UTC 28012G23KT Wind from the west (280 degrees True) at 12 knots; gusting to 23 knots 9000 Visibility is 9 kilometres. -SHRA Present weather is light rain shower FEW005 There are 1 to 2 oktas of cloud with base at 500 feet BKN050 There are also 5 to 7 oktas of cloud with base at 5000 feet 27/22 The air temperature is 27°C; the dewpoint temperature is 22°C Q0999 The QNH is between 999 and 999.9 hectopascals RETS Recent weather was a thunderstorm RMK Remarks section follows RF00.6/003.4 0.6 mm of rain has fallen in the last 10 minutes; 3.4 mm has fallen since 0900 local time DISTANT TS Distant thunderstorm (greater than 16 kilometres from the aerodrome reference point) SPECI YSCB 171515Z AUTO 22015G25KT 9000NDV // NCD 13/09 Q1003 RMK RF00.8/003.0 REPORT EXPLANATION SPECI Special meteorological observation (for wind gust) YSCB ICAO location indicator for Canberra Airport 171515Z Time of observation is 1515 on the 17th of the month UTC AUTO This report is fully automated 22015G25KT Wind from the southwest (220 degrees True) at 15 knots, gusting to 25 knots 9000NDV Visibility is 9000 metres; from a single visibility sensor, therefore no directional variation (NDV) in visibility can be detected // Present weather is unavailable NCD Nil cloud has been detected (by ceilometer) 13/09 The air temperature is 13°C; the dewpoint temperature is 09°C OVC110 There are also 8 oktas of cloud with base at 11 000 feet Q1003 The QNH is between 1003 and 1003.9 hectopascals RMK Remarks section follows RF00.8/003.0 0.8 mm of rain has fallen in the last 10 minutes; 3.0 mm has fallen since 0900 local time
  17. SIGMETs are issued to provide urgent advice to aircraft of actual or expected weather developments or trends that are potentially hazardous. SIGMETs are issued to advise of the occurrence or expected occurrence of the following phenomena: Code and Description OBSC TS - Obscured thunderstorm(s) EMBD TS - Frequent thunderstorm(s) SQL TS - Squall line thunderstorms OBSC TSGR - Obscured thunderstorm(s) with hail EMBD TSGR - Embedded thunderstorm(s) with hail FRQ TSGR - Frequent thunderstorm(s) with hail SQL TSGR - Squall line thunderstorms with hail TC - Tropical cyclone SEV TURB - Severe Turbulence SEV ICE - Severe icing SEV ICE FZRA - Severe icing due to freezing rain SEV MTW - Severe mountain wave HVY DS - Heavy duststorm HVY SS - Heavy sandstorm VA - Volcanic ash RDOACT CLD - Radioactive Cloud Pilots in command of aircraft encountering any of the above phenomena not notified by SIGMET advices must report details of the phenomena in an AIREP SPECIAL. SIGMET for thunderstorms are only issued when they are: obscured (OBSC) by haze or smoke embedded (EMBD) within cloud layers frequent (FRQ), i.e. with little or no separation between clouds and covering more than 75% of the area affected squall line (SQL) thunderstorms along a line of about 100 nautical miles or more in length, with little or no separation between clouds SIGMET for thunderstorms and tropical cyclones do not include reference to icing and turbulence as these are implied as occurring with thunderstorms and tropical cyclones. Responsibility for the issuance of SIGMET within Australian FIRs SIGMETs for volcanic ash are the responsibility of the Volcanic Ash Advisory Centre, Darwin. SIGMETs for tropical cyclones are the responsibility of the Tropical Cyclone Advisory Centres in Perth, Darwin and Brisbane. SIGMETs for turbulence and icing above FL185 are the responsibility of the Aviation Weather Centre, Melbourne. SIGMET for all other phenomenon are the responsibility of the Meteorological Watch Offices located in Perth, Darwin, Adelaide, Hobart, Melbourne, Sydney, Brisbane and Townsville. SIGMET Structure Bulletin Identification WCAU01 for SIGMET on tropical cyclones WVAU01 for SIGMET on volcanic ash cloud WSAU21 for SIGMET for other phenomena Originating Office (WMO Indicator) The World Meteorological Organisation (WMO) location indicators for Australian Meteorological Watch Offices are: APRM - Adelaide Regional Forecasting Centre APRF - Perth Regional Forecasting Centre ABRF - Brisbane Regional Forecasting Centre ASRF - Sydney Regional Forecasting Centre ADRM - Darwin Regional Forecasting Centre AMRF - Melbourne Regional Forecasting Centre AMHF - Hobart Regional Forecasting Centre ABTL - Townsville Meteorological Office AMMC - Melbourne Aviation Weather Centre Note: These differ from the ICAO indicators (beginning with Y) used elsewhere in the message. Issue Date/Time Issue date/time is given in UTC in the form DDHHMM, where DD is day of month, and HHMM is time in hours and minutes. Flight Information Region Gives the abbreviation for the FIR (YMMM or YBBB) in which the phenomenon is located. Identifier The message identifier is SIGMET. Daily Sequence Number The four-character sequence number consists of: a two-letter designator to indicate the general location of the event (as given in the two maps below), and a two-digit number, giving the sequence number of SIGMETs issued by the relevant office within the FIR (Brisbane or Melbourne) since 0000 UTC. The tropical cyclone and low-level SIGMET two-letter designators and their associated geographical extent are: The high-level (above FL185) icing and turbulence SIGMET two-letter designators and their general associated geographical extent are: Validity Period The validity period is given in the format DDHHMM/DDHHMM, where DD is the day of the month and HHMM is the time in hours and minutes UTC. Tropical cyclone and volcanic ash SIGMETs can have a validity of up to six hours. SIGMETs for other phenomena can be valid for up to four hours. Originating Office (ICAO Indicator) The International Civil Aviation Organization (ICAO) location indicators for Australian Meteorological Watch Offices are: YPRM - Adelaide Regional Forecasting Centre YPRF - Perth Regional Forecasting Centre YBRF - Brisbane Regional Forecasting Centre YSRF - Sydney Regional Forecasting Centre YPDM - Darwin Regional Forecasting Centre YMRF - Melbourne Regional Forecasting Centre YMHF - Hobart Regional Forecasting Centre YBTL - Townsville Meteorological Office YMMC - Melbourne Aviation Weather Centre Flight Information Region This gives the abbreviation and full name for the FIR in which the phenomenon is located. Meteorological Information This section includes: type of phenomenon observed or forecast location, both horizontal and vertical extents movement or expected movement expected change in intensity SIGMET for tropical cyclone and volcanic ash cloud include a forecast position for the end of the validity period message status Cancel SIGMET If during the validity period of a SIGMET, the phenomenon for which the SIGMET is no longer occurring or is no longer expected, the SIGMET is cancelled by issuing a SIGMET with the abbreviation CNL in lieu of meteorological information. SIGMET Status The status line indicates whether the SIGMET is: NEW - the SIGMET is for a new phenomenon. REV - the SIGMET reviews an earlier SIGMET for the phenomenon. CNL - cancels a current SIGMET. The following abbreviations are used in SIGMET: Code and Description A - Altitude ABV - Above APRX - Approximately BLW - Below CNL - Cancel DS - Dust storm EMBD - Embedded FIR - Flight Information Region FCST - Forecast FL - Flight level FRQ - Frequent FZRA - Freezing rain GR - Hail HVY - Heavy ICE - Icing INTSF - Intensifying LOC - Location MOV - Moving NC - No Change (intensity) OBS - Observed OBSC - Obscured RDOACT CLD - Radioactive cloud REV - Review SEV - Severe SQL - Squall line SS - Sand storm STNR - Stationary STS - Status TC - Tropical cyclone TS - Thunderstorm TURB - Turbulence VA - Volcanic ash WI - Within (area) WKN - Weakening (intensity) Z - Universal Time SIGMET Examples WSAU21 AMMC 180357 YMMM SIGMET MM01 VALID 180439/180839 YMMC- YMMM MELBOURNE FIR SEV TURB FCST WI S3200 E12800 - S3200 E13000 - S4700 E13600 - S4700 E13400 FL260/400 MOV E 25KT NC STS:NEW WSAU21 AMMC 180720 YMMM SIGMET MM02 VALID 180720/180839 YMMC- YMMM MELBOURNE FIR CNL SIGMET MM01 180439/180839 STS:CNL SIGMET MM01 180439/180839 WCAU01 APRF 180217 YMMM SIGMET PH01 VALID 180215/180815 YPRF- YMMM MELBOURNE FIR TC ILSA OBS AT 0000Z S1330 E11324 CB TOP FL500 WI 120NM OF CENTRE MOV WSW 17KT INTSF FCST 0815Z TC CENTRE S1418 E11036 STS:NEW WVAU01 ADRM 200100 YBBB SIGMET BT04 VALID 200100/200700 YPDM- YBBB BRISBANE FIR VA ERUPTION LOC S0416 E15212 VA CLD OBS AT 200100Z A100/180 APRX 120NM BY 40NM S1130 E14530 - S1330 E14900 - S1030 E15030 - S0830 E14700 - S1130 E14430 MOV SW 20KT FCST 0700Z VA CLD APRX S110 E144530 - S1230 E14930 - S1050 E15130 - S0800 E14700 - S1130 E14400 STS:REV SIGMET BT03 191900/200100
  18. Aerodrome Forecast (TAF) A TAF is a coded statement of meteorological conditions expected at an aerodrome and within a radius of five nautical miles of the aerodrome reference point. Explanation of TAF Elements Identifier and Description TAF - Aerodrome Forecast TAF AMD - Amended Aerodrome Forecast TAF COR - Corrected Aerodrome Forecast TAF .. CNL - Cancels Aerodrome Forecast TAF .. NIL - Aerodrome Forecast will not be issued PROV TAF - Provisional Aerodrome Forecast Location The location is given by either an ICAO location indicator or an approved Airservices Australia abbreviation. Issue Time The issue time of the TAF is expressed in a six-figure group followed by the code letter Z, e.g. 202230Z, which gives an issue time of 2230 on the 20th day of the month UTC. Validity The period of validity is given in the format ddhh/ddhh, where dd is day of the month and hh is hour UTC, e.g. 2100/2206, which gives a 30 hour validity period from 0000 the 21st to 0600 on the 22nd UTC. Note that 00 is used to indicate periods of validity beginning at 0000 UTC; and 24 is used to indicate periods of validity ending at 2400 UTC. Wind The wind direction is given in degrees True, rounded to the nearest 10 degrees. A variable wind direction is given as VRB (used when the forecasting of a mean wind direction is not possible). The wind speed is given in knots (KT). The maximum wind gust is included, after the letter G, if it is expected to exceed the mean by 10 knots or more, e.g. a wind direction 280° True, with a mean speed of 20 knots, and a maximum gust of 30 knots, is given as 28020G30KT Visibility The horizontal visibility is given in metres in increments of 50 metres when visibility is forecast to be less than 800 metres; in increments of 100 metres when forecast to be 800 metres or more but less than 5,000 metres; and in increments of 1,000 metres when forecast to be 5,000 or more but less than 10,000 metres . Visibility is always given in a four figure group: eg 500 metres is given as 0500. Forecast visibilities of 10 kilometres or more are given as 9999. Visibility is not given when CAVOK is forecast. Weather Forecast weather is expressed using the following abbreviations: MI - shallow BC - patches PR - partial DR - drifting BL - blowing SH - showers FZ - freezing TS - thunderstorm DS - duststorm GS - small hail/snow pellets DZ - drizzle FG - fog RA - rain BR - mist GR - hail FU - smoke SN - snow HZ - haze SG - snow grains PO - dust devil DU - dust SQ - squall SA - sand FC - funnel cloud SS - sandstorm VA - volcanic ash IC - ice crystals PL - ice pellets Intensity is indicated for precipitation, blowing dust/sand/snow, duststorms and sandstorms. In these cases, the weather group is prefixed by - for light and + for heavy; moderate intensity has no prefix, e.g. +TSRA means thunderstorm with heavy rain; DZ means moderate drizzle; -RA means light rain. After a change group, if the weather ceases to be significant, the weather group is replaced by NSW (nil significant weather) or CAVOK if appropriate. Cloud Cloud information is given from the lowest to the highest layers in accordance with the following rule: 1st group: the lowest layer regardless of amount. 2nd group: the next layer covering more than 2 oktas. 3rd group: the next higher layer covering more than 4 oktas. Extra group for cumulonimbus and towering cumulus when forecast but not at any of the layer heights given above. Cloud amount is given using the following abbreviations: SKC - sky clear FEW - few (1 to 2 oktas) SCT - scattered (3 to 4 oktas) BKN - broken (5 to 7 oktas) OVC - overcast (8 oktas) NSC - nil significant cloud Cloud height is given as a three-figure group in hundreds of feet above the aerodrome, e.g. cloud at 700 feet above the aerodrome is shown as 007. Cloud type is identified only for cumulonimbus and towering cumulus, e.g. FEW030CB, SCT040TCU. CAVOK The abbreviation CAVOK (Ceiling and Visibility and weather OK) is used when the following conditions are forecast simultaneously: Visibility is 10 kilometres or more, No cloud below 5000 feet or the highest 25 nautical mile minimum sector altitude, whichever is the higher; and no cumulonimbus or towering cumulus at any height, No weather of significance to aviation, i.e. none of the weather listed in the weather table Significant Changes and Variations (FM, BECMG, INTER, TEMPO) Significant changes and variations will be included when the changes and variations are expected to satisfy the amendment criteria. It should be noted that these changes relate to improvements as well as deteriorations. The term FM is used when one set of prevailing weather conditions is expected to rapidly change to a different set of prevailing weather conditions. The indicator is the beginning of a self-contained forecast, with the new conditions applying until the end period of the forecast or until the commencement time of another FM or BECMG group. The term BECMG is used when one set of prevailing weather conditions is expected to gradually change to a different set of prevailing weather conditions. The indicator is the beginning of a self-contained forecast, with the new conditions applying until the end period of the forecast, or until the commencement time of another BECMG or FM group. Following any change group (FM or BECMG) there will be information on wind, visibility, weather and cloud; except when CAVOK is given or when fog is forecast. Following any change group (FM or BECMG) where there is nil significant weather forecast the abbreviation NSW is used. In some cases where the sky is forecast to be clear after a change group the abbreviation SKC is used. The terms TEMPO and INTER are used to indicate significant temporary or intermittent variations from the prevailing conditions previously given in the TAF. TEMPO is used for periods of 30 minutes or more but less than 60 minutes. INTER is used for periods less than 30 minutes. Change and variation groups (FM, BECMG, TEMPO, INTER) are not introduced until all information necessary to describe the initial forecast conditions of wind, visibility, weather and cloud have been given. Variation groups (TEMPO, INTER) follow at the end of all change groups (FM, BECMG) and before any PROB or TURB. PROB The term PROB[%] is used if the estimated probability of occurrence is 30 or 40 percent (probabilities of less than 30% are not given), and is only used with reference to thunderstorms or poor visibility (less than the alternate minimum) resulting from fog, mist, dust, smoke or sand. If the estimated probability of occurrence is greater than or equal to 50 percent, reference is made to the phenomenon in the forecast itself, not by the addition of a PROB. When using PROB with thunderstorms, INTER and TEMPO are also included whenever possible to indicate the probable duration. Where PROB is used without one of these, the likely period of occurrence will be deemed to be one hour or more. For example: PROB30 INTER 1205/1211 5000 -TSRA BKN040CB indicates a 30% probability of deteriorations of less than 30 minutes due to thunderstorms with light rain between 0500 and 1100 UTC on the 12th. PROB40 TEMPO 1102/1113 3000 TSRA BKN040CB indicates a 40% probability of deteriorations of 30 minutes or more but less than 60 minutes due to thunderstorms with moderate rain between 0200 and 1300 UTC on the 11th. PROB30 1005/1014 1000 +TSRA BKN040CB indicates a 30% probability of deteriorations of one hour or more due to thunderstorms with heavy rain between 0500 and 1400 UTC on the 10th. RMK RMK (remarks) precedes Turbulence (if forecast) and Temperatures and QNH Turbulence Special reference is made in TAF to hazardous turbulence that may endanger aircraft or adversely affect their safe or economic operation. The TAF contains information on commencement time (FMddhhmm), the expected intensity (moderate [MOD] or severe [SEV]) and the vertical extent (BLW.... FT). TILLddhhmm is used to indicate the cessation of the turbulence when this is expected before the end of the TAF validity. Air Temperature Temperature, preceded by the letter T, is given in whole degrees celsius using two figures. If the temperature is below zero Celsius, the value is prefixed by the letter M (minus). In Australia, forecasts of air temperature are given at three-hourly intervals, for a maximum of nine hours, from the time of commencement of validity of the forecast. They are given for the times HH, HH+3, HH+6 and HH+9, where HH is the time of the commencement of the TAF validity. They are point forecasts for these times but are valid for, in the case of the first value, ninety minutes after the time point HH; and, for subsequent values, ninety minutes each side of the time point. QNH QNH, preceded by the letter Q, is given in whole hectopascals using four figures. In Australia, forecasts of QNH are given at three-hourly intervals, for a maximum of nine hours, from the time of commencement of validity of the forecast. They are given for the times HH, HH+3, HH+6 and HH+9, where HH is the time of the commencement of the TAF validity. They are point forecasts for these times but are valid for, in the case of the first value, ninety minutes after the time point HH; and, for subsequent values, ninety minutes each side of the time point. TAF Examples Example 1 TAF YMAY 022230Z 0300/0312 35010KT CAVOK FM030800 31018KT 9999 SHRA BKN025 OVC100 INTER 0308/0312 31020G40KT 3000 +TSRA BKN010 SCT040CB RMK FM030600 MOD TURB BLW 5000FT T 23 24 28 33 Q 1012 1013 1014 1009 Decoded: TAF - Aerodrome Forecast YMAY - ICAO location indicator for Albury Airport 022230Z - TAF issued at 2230 on the 2nd day of the month UTC 0300/0312 - Validity period of TAF is from 0000 to 1200, on the 3rd day of the month UTC 35010KT - Wind will be from the north (350 degrees True) at 10 knots CAVOK - Cloud, visibility and weather ok FM030800 - Significant changes to the mean conditions are expected to commence from 0800 on the 3rd UTC, and to persist (at least) until the end of the forecast period Note that there will be intermittent variations to these new mean conditions (refer INTER below) 31018KT - Wind will be from the northwest (310 degrees True) at 18 knots 9999 - Visibility will be 10 kilometres or more SHRA - Weather will be moderate showers of rain BKN025 - Cloud will be broken (5 to 7 oktas) with base at 2500 feet above the aerodrome OVC100 - There will also be overcast cloud (8 oktas) with base at 10000 feet INTER 0308/0312 - There will be intermittent (periods of less than 30 minutes) variations to the previously given mean conditions. Period of INTER is 0800 to 1200 on the 3rd UTC 31020G40KT - Intermittently the wind will be from the northwest (310 degrees True) at 20 knots gusting to 40 knots 3000 - Visibility will be 3000 metres +TSRA - Weather will be thunderstorms with heavy rain BKN010 - Cloud will be broken (5 to 7 oktas) with base at 1000 feet above the aerodrome SCT040CB - There will also be 3 to 4 oktas of cumulonimbus cloud with base at 4000 feet RMK - Remarks section follows FM030600 MOD TURB BLW 5000FT - From 0600 on the 3rd UTC, expect moderate turbulence below 5000 feet T 23 24 28 33 - Forecast air temperatures at 00, 03, 06 and 09 UTC are 23, 24, 28 and 33 Q 1012 1013 1014 1009 - Forecast QNH at 00, 03, 06 and 09 UTC are 1012, 1013, 1014 and 1009. Example 2 TAF COR YMLT 212240Z 2200/2218 31015G28KT 6000 -RA BKN010 OVC100 TEMPO 2209/2218 2000 +TSRA BKN005 SCT040CB RMK T 25 21 18 15 Q 1014 1013 1013 1011 Decoded: TAF - Aerodrome Forecast COR - This TAF is a correction to the previously issued TAF YMLT - ICAO Location Indicator for Launceston Airport 212240Z - TAF issued at 2240 on the 21st day of the month UTC 2200/2218 - Validity period of TAF is from 0000 until 1800 on the 22nd of the month UTC 31015G28KT - Mean wind is expected to be from 310 degrees True at 15 knots with gusts to 28 knots 6000 - Visibility will be 6000 metres -RA - Weather will be light rain BKN010 - Cloud will be broken (5 - 7 octas), with base at 1000 feet above the aerodrome OVC100 - There will also be overcast cloud, with base at 10,000 feet above the aerodrome TEMPO 2209/2218 - There will be temporary variations (periods of 30 to 60 minutes), to the previously given mean conditions, during the period 0900 to 1800 on the 22nd. 2000 - Visibility will be 2000 metres +TSRA - Weather will be thunderstorms with heavy rain showers BKN005 - There will be broken (5 to 7 oktas) cloud with base at 800 feet above the aerodrome SCT040CB - There will also be scattered (3 to 4 oktas) cumulonmbus cloud with base at 2000 feet above the aerodrome RMK - Remarks section follows T 25 21 18 15 - Forecast air temperatures at 06, 09, 12 and 15 UTC are 25, 21, 18 and 15 Q 1014 1013 1013 1011 - Forecast QNH at 06, 09, 12 and 15 UTC are 1014, 1013, 1013 and 1011 Example 3 TAF AMD YMML 292330Z 3000/3106 14008KT 9999 NSW SCT030 FM301100 14003KT 3000 HZ BKN009 PROB40 3017/3023 0400 FG RMK T 14 15 17 14 Q 1016 1014 1013 1014 Decoded: TAF - Aerodrome Forecast AMD - This TAF amends the previously issued TAF YMML - ICAO location indicator for Melbourne Airport 292230Z - TAF issued at 2230 on the 29th day of the month UTC 3000/3106 - Validity period of TAF is from 0000 on the 30th until 0600 on the 31st UTC 14008KT - Mean wind is expected to be from the southeast (150 degrees True) at 8 knots 9999 - Visibility will be 10 kilometres or more NSW - There will be nil significant weather SCT030 - Cloud will be scattered (3 to 4 oktas), with base at 3000 feet above the aerodrome FM301100 - Significant new mean conditions are expected from 1100 on the 30th UTC; 14003KT - Mean wind is expected to be from 150 degrees True at 3 knots 3000 - Visibility will be 3 kilometres HZ - Weather will be haze BKN009 - Cloud will be broken (5 to 7 oktas), with base at 900 feet above the aerodrome PROB40 3017/3023 - There is a 40% probability of conditions being the following during the period 1700 to 2300 on the 30th: 0400 - Visibility of 400 metres FG - Fog RMK - Remarks section follows T 14 15 17 14 - Forecast air temperatures at 00, 06, 09 and 12 UTC are 14, 15, 17 and 14 Q 1016 1014 1013 1014 - Forecast QNH at 00, 06, 09 and 12 UTC are 1016, 1014, 1013 and 1014
  19. It has been a good last few weeks for the site in our quest to having the greatest single repository of all information a recreational aviator needs to enjoy their flying safely and being more informed. All the Aircraft listings from the old site have now been migrated and @red750 is doing a great job on adding more and more aircraft into the aircraft section to act as a reference point on all the different aircraft out there...thanks Red More and more Events are getting added to the Event Calendar by @Old Koreelah helping us all to know what events we may like to attend in our flying activities, thanks O'K We have a new site Homepage that hopefully portrays an inviting message to all who visit us and hopefully get them to join in. The Clubs section has been renamed to "Groups" to reflect more of what that feature provides...still a little more work to do on that one Slowly we are getting the John Brandon Tutorials into the site which meets our objective of pilot education...give these a read to keep the information fresh to make our flying safer. I have also been slowly migrating many of the videos from the old site over to here. We now have the Maps section which not only adds all the Airstrips into a Google Earth Map but also site users that will enable members to perhaps go for a fly and meet up with other site members and form new friendships all having the same interest in recreational flying Thanks to the great @Ahmed Zayed the site has an amended Whats New, an accepted new site theme and many other improvements, some obvious and others not so obvious like enhancements with the Facebook and Twitter login, core software upgrades, Weekly Email, and many more so a huge thanks to Ahmed. And above all thanks to you the user for your great contributions to the site and creating an enjoyable environment and let's not forget the fantastic work that the Moderators do in supporting that enjoyable environment What's happening next... Ahmed and I are looking into bringing the Aviation News section back and are exploring different ways to bring the latest aviation news to everyone here. This will also support the new Articles System and Special Picks of Interest system I have commenced work with an IPS guru on server performance. I have been waiting for 6 months for him to become available and today we started the exchange of finer details for him to start work in a few weeks. This may see us end up with 3 servers spread across the world that continually exchange data so a user will experience fast performance no matter where they are in the world so hopefully we will see a greater international audience contributing to the discussions we have here on Recreational Flying (.com). So, I will continue with the Tutorial migration and the Video migration plus start experimenting with many different new sections like Famous Aviators, On This Day, Aviation Product Reviews and more. Also on the agenda is to migrate Clear Prop into the site but a Payment Gateway needs to be developed first before that happens. Hope this post keeps you in the loop on the site/resource moving forward and as ALWAYS, any suggestions on how we can improve the site for you is always appreciated...thanks
  20. 2.1 Insolation and atmospheric temperature Insolation The Earth's surface and the atmosphere are warmed mainly by insolation — incoming solar electromagnetic radiation. The amount of insolation energy reaching the outer atmosphere is about 1.36 kilowatts per m². About 10% of the radiation is in the near end of the ultraviolet range (0.1 to 0.4 microns [micrometre]), 40% in the visible light range ( 0.4 to 0.7microns), 49% in the short-wave infrared range (0.7 to 3.0 microns ) and 1% is higher energy and X-ray radiation; see 'The electromagnetic wave spectrum' below. The X-rays are blocked at the outer atmosphere, and most of the atmospheric absorption of insolation takes place in the upper stratosphere and the thermosphere. There is little direct insolation warming in the troposphere, which is mostly warmed by contact with the surface and subsequent convective and mechanical mixing; see 'Tropospheric transport of surface heating and cooling' below. On a sunny day 75% of insolation may reach the Earth's surface; on an overcast day only 15%. On average, 51% of insolation is absorbed by the surface as thermal energy — 29% as direct radiation and 22% as diffused radiation; i.e. scattered by atmospheric dust, water vapour and air molecules; see 'Light scatter'. About 4% of the radiation reaching the surface is directly reflected, at the same wavelength, from the surface back into space. Typical surface reflectance values, or albedo, are shown below: Soils 5–10% Desert 20–40% Forest 5–20% Grass 15–25% Snow, dependent on age 40–90% Water, sun high in sky 2–10% Water, sun low in sky 10–80% In the insolation input diagram shown below it can be seen that about 26% of insolation is directly reflected back into space by the atmosphere but 19% is absorbed within it as thermal energy, with much of the UV radiation being absorbed within the stratospheric ozone layer. Clouds reflect 20% and absorb 3%, and atmospheric gases and particles reflect 6% and absorb 16%. Altogether some 70% of insolation is absorbed at the Earth's surface and in the upper atmosphere, but eventually all this absorbed radiation is re-radiated back into space as long-wave (3 to 30 microns) infrared. The result of radiation absorption and re-radiation is that the mean atmospheric surface temperature is maintained at 15 °C. Terrestrial radiation The surface–atmosphere radiation emission diagram below shows that some 6% of input is lost directly to space as long-wave infrared from the surface. Atmospheric O2, N2, and argon cannot absorb the long-wave radiation. Also there is a window in the radiation spectrum between 8.5 and 11 microns where infrared radiation is not absorbed to any great extent by the other gases. About 15% of the received energy is emitted from the surface as long-wave radiation, and absorbed by water vapour and cloud droplets within the troposphere, and by carbon dioxide in the mesosphere. This is actually a net 15%; the total is much greater but the remainder is counter-balanced by downward long-wave emission from the atmosphere. Radiation emitted upwards into space, principally nocturnal cooling, is re-radiated from clouds (26%) plus water vapour, O3 and CO2 (38%). The atmosphere then has a net long-wave energy deficit, after total upwards emission (64%) and absorption (15%). This is equivalent to 49% of solar input and a short-wave insolation excess of 19% (16% + 3% absorbed) resulting in a total atmospheric energy deficit equivalent to 30% of insolation. Energy balance The surface has a radiation surplus of 30% of solar input: 51% short wave absorbed less 21% long wave emitted. This surplus thermal energy is convected to the atmosphere by sensible heat flux (7%) and by latent heat flux (23%). (The 'flux' is a flow of energy). The latent heat flux is greater because the ratio of global water to land surface is about 3:1. Over oceans, possibly 90% of the heat flux from the surface is in the form of latent heat. Conversely over arid land, practically all heat transfer to the atmosphere is in the form of sensible heat. Overall the earth—atmosphere radiation/re-radiation system is in balance. But between latitudes 35°N and 35°S more energy is stored than re-radiated, resulting in an energy surplus. But between the 35° latitudes and the poles there is a matching energy deficit. There is also a diurnal and a seasonal variation in the radiation balance. The average daily solar radiation measured at the surface in Australia is 7.5 kW hours/m² in summer and 3.5 kW hours/m² in winter. All substances emit electromagnetic radiation in amounts and wavelengths dependent on their temperature. The hotter the substance, the shorter will be the wavelengths at which maximum emission takes place. The sun, at 6000 K, gives maximum emission at about 0.5 microns in the visible light band. The Earth, at 288 K, gives maximum emission at about 9 microns in the long-wave infrared band. Tropospheric transport of surface heating and cooling The means by which surface heating or cooling is transported to the lower troposphere are: by conduction — air molecules coming into contact with the heated (or cooled) surface are themselves heated (or cooled) and have the same effect on adjacent molecules; thus an air layer only a few centimetres thick becomes less (or more) dense than the air above by convective mixing — occurs when the heated air layer tries to rise and the denser layer above tries to sink. Thus small turbulent eddies build and the heated layer expands from a few centimetres to a layer hundreds, or thousands, of feet deep depending on the intensity of solar heating; see 'Convection'. Convective mixing is more important than mechanical mixing for heating air, and is usually dominant during daylight hours. In hot, dry areas of Australia the convective mixing layer can extend beyond 10 000 feet by mechanical mixing — where wind flow creates frictional turbulence; see 'Frictional turbulence.. Mechanical mixing dominates nocturnally when surface cooling and conduction create a cooler, denser layer above the surface — thus stopping convective mixing. If there is no wind mechanical mixing cannot occur, see 'Fog'. The term (planetary) boundary layer is used to describe the lowest layer of the atmosphere, roughly 1000 to 6000 feet thick, in which the influence of surface friction on air motion is important. It is also referred to as the friction layer or the mixed layer. The boundary layer will equate with the mechanical mixing layer if the air is stable and with the convective mixing layer if the air is unstable. The term surface boundary layer or surface layer is applied to the thin layer immediately adjacent to the surface, and part of the planetary boundary layer. Within this layer the friction effects are more or less constant throughout, rather than decreasing with height, and the effects of daytime heating and night-time cooling are at a maximum. The layer is roughly 50 feet deep, and varies with conditions. Heat advection Advection is transport of heat, moisture and other air mass properties by horizontal winds. Warm advection brings warm air into a region. Cold advection brings cold air into a region. Moisture advection brings moister air and is usually combined with warm advection. Advection is positive if higher values are being advected towards lower values, and negative if lower values are being advected towards higher; e.g. cold air moving into a warmer region. Advection into a region may vary with height; e.g. warm, moist advection from surface winds while upper winds are advecting cold, dry air. 2.2 Electromagnetic wave spectrum The electromagnetic spectrum stretches over 60 octaves, the frequency doubling within each octave. For example, the frequencies in octave #18 range from 68.58 MHz to 137.16 MHz — which includes the aviation VHF NAV/COM band. In a vacuum, electromagnetic waves propagate at a speed close to 300 000 km/sec. The frequency can be calculated from the wavelength thus: Frequency in kHz = 300 000/wavelength in metres Frequency in MHz = 300/wavelength in metres or 30 000/ wavelength in centimetres Frequency in GHz = 30/wavelength in centimetres The very high frequency [VHF] band used in civil aviation radio communications lies in the 30 to 300 MHz frequency range — thus the 10 metre to 1 metre wavelength range. The other civil aviation voice communications band is in the high frequency [HF] range; 3 to 30 MHz or 100 to 10 metres. The amplitude of the wave is proportional to the energy of vibration. The table below shows the wave length ranges — beginning in nanometres [nm] and progressing through micrometres/microns [µm], millimetres, metres and kilometres — and the associated radiation bands. 2.3 Tropospheric global heat transfer Precipitation is less than evaporation between 10° and 40° latitudes — the difference being greatest at about 20°. Polewards and equatorwards of these bands precipitation is greater than evaporation. The transfer of atmospheric water vapour, containing latent heat, is polewards at latitudes greater than 20° and equatorwards at lower latitudes. Most of the vertical heat transfer is in the form of latent heat, but possibly 65% of the atmospheric horizontal transfer is in the form of sensible heat following condensation of water vapour. Horizontal latent heat transfer occurs primarily in the lower troposphere. The general wind circulation within the troposphere and the water circulation within the oceans transfers heat from the energy surplus zones to the energy deficit zones, thereby maintaining the global heat balance. About 70% is transferred by the atmosphere and 30% by the oceans. The large mid-latitude eddies, and the cyclones and anticyclones in the broad westerly wind belt that flows around the southern hemisphere, play a particularly important part in the transfer of the excess heat energy from low to high latitudes and in the mixing of cold Antarctic air into the mid-latitudes. 2.4 Temperature lapse rates in the troposphere The temperature lapse rates in the troposphere vary by latitude, climatic zone and season, and vary between less than 0 °C/km (i.e. increasing with height) at the winter poles to more than 8 °C/km over a summer sub-tropical ocean. In the mid-latitudes the temperature reduces with increasing height at varying rates, but averages 6.5 °C/km or about 2 °C per 1000 feet. However, within any tropospheric layer, temperature may actually increase with increasing height. This reversal of the norm is a temperature inversion condition. If the temperature in a layer remains constant with height then an isothermal layer condition exists. At night, particularly under clear skies, the air in the mixed layer cools considerably, but the long-wave radiation from the higher levels is weak and the air there cools just 1 °C or so. Consequently a nocturnal inversion forms over the mixed layer, the depth of which depends on the temperature drop and the amount of mechanical mixing;see 'Fog'. Tropospheric average temperature lapse rate profile The altitude of the tropopause, and thus the thickness of the troposphere, varies considerably. Typical altitudes are 55 000 feet in the tropics with a temperature of –70 °C and 29 000 feet in polar regions with a temperature of –50 °C. Because of the very low surface temperatures in polar regions and the associated low-level inversion, the temperature lapse profile is markedly different from the mid-latitude norms. In mid-latitudes the height of the troposphere varies seasonally and daily with the passage of high and low pressure systems. In the chart above, an exaggerated environmental temperature lapse rate profile has been superimposed to illustrate the temperature layer possibilities — starting with a superadiabatic lapse layer at the surface, a normal lapse rate layer above it then a temperature inversion layer and an isothermal layer. 2.5 Adiabatic processes and lapse rates An adiabatic process is a thermodynamic process where a change occurs without loss or addition of heat, as opposed to a diabatic process in which heat enters or leaves the system. Examples of the latter are evaporation from the ocean surface, radiation absorption and turbulent mixing. An adiabatic temperature change occurs in a vertically displaced parcel of air due to the change in pressure and volume (see the gas equation in 'Gas laws and basic atmospheric forces') occurring during a short time period, with little or no heat exchange with the environment. Upward displacement and consequent expansion causes cooling; downward displacement and subsequent compression causes warming. In the troposphere, the change in temperature associated with the vertical displacement of a parcel of dry (i.e. not saturated) air is very close to 3 °C per 1000 feet, or 9.8 °C / km, of vertical motion; this is known as the dry adiabatic lapse rate [DALR]. As ascending moist air expands and cools in the adiabatic process, the excess water vapour condenses after reaching dewpoint and the latent heat of condensation is released into the parcel of air as sensible heat, thus slowing the pressure-induced cooling process. This condensation process continues while the parcel of air continues to ascend and expand. The process is reversed as an evaporation process in descent and compression. The adiabatic lapse rate for saturated air, the saturated adiabatic lapse rate [SALR], is dependent on the amount of moisture content, which is dependent on temperature and pressure. The chart below shows the SALR at pressures of 500 and 1000 mb (hPa), and temperatures between –40 °C and +40 °C. The chart shows that on a warm day (25 °C) the SALR near sea level is about 1.2 °C / 1000 feet. At about 18 000 feet — the 500 hPa level — the rate doubles to about 2.4 °C / 1000 feet. The environment lapse rate [ELR] is ascertained by measuring the actual vertical distribution of temperature at that time and place. The ELR may be equal to or differ from the DALR or SALR of a parcel of air moving within that environment. In the atmosphere, parcels of air are stirred up and down by turbulence and eddies that may extend several thousand feet vertically in most wind conditions. These parcels mix and exchange heat with the surrounding air thus distorting the adiabatic processes. If the rate of ground heating by solar radiation is rapid, the mixing of heated bubbles of air may be too slow to induce a well-mixed layer with a normal DALR. The ELR, up to 2000–3000 feet agl, may be much greater than the DALR. Such a layer is termed a superadiabatic layer, and will contain strong thermals and downdraughts. 2.6 Atmospheric stability Atmospheric stability is the air's resistance to any disturbing effect. It can be defined as the ability to resist the narrowing of the spread between air temperature and dewpoint. Stable air cools slowly with height and vertical movement is limited. If a parcel of air, after being lifted, is cooler than the environment, the parcel — being more dense than the surrounding air — will tend to sink back and conditions are stable. The temperature of unstable air drops more rapidly with an increase in altitude, i.e. the ELR is steep. If a lifted parcel is warmer, and thus less dense than the surrounding air, the parcel will continue to rise and conditions are unstable. Unstable air, once it has been lifted to the lifting condensation level, keeps rising through free convection. Instability can cause upward or downward motion. When saturated air containing little or no condensation, is made to descend then adiabatic warming causes the air to become unsaturated almost immediately and further descent warms it at the DALR. If the ELR lies between the DALR and the SALR, a state of conditional instability exists. Thus, if an unsaturated parcel of air rises from the surface, it will cool at the DALR and so remain cooler than the environment, and conditions are stable. However, if the parcel passes dewpoint during the ascent it will then cool at a slower rate and, on further uplift, become warmer than the environment and so become unstable. High dewpoints are an indication of conditional instability. The figure below demonstrates some ELR states with the consequent stability condition: ELR #1 is much greater than the DALR (and the SALR), thus providing absolute instability. This condition is normally found only near the ground in a superadiabatic layer — although a deep superadiabatic layer exists in the hot, dry tropical continental air of northern Australia in summer. ELR # 2 between the DALR and the SALR demonstrates conditional instability. It is stable when the air parcel is unsaturated, i.e. the ELR is less than the DALR; and unstable when it is saturated, i.e. the ELR is greater than the SALR. ELR #3 indicates absolute stability, where the ELR is less than the SALR (and the DALR). Neutral equilibrium would exist if the ELR equals the SALR and the air was saturated, or if the ELR equals the DALR and the air was unsaturated. The following diagram is an example of atmospheric instability and cloud development, and compares environment temperature and that of a rising air parcel with a dewpoint of 11 °C. The amount of energy that could be released once surface-based convection is initiated in humid air is measured as convective available potential energy [CAPE]. CAPE is measured in joules per kilogram of dry air. It may be assessed by plotting the vertical profile of balloon radiosonde readings for pressure, temperature and humidity on a tephigram (a special meteorological graph format); and also plotting the temperatures that a rising parcel of air would have in that environment. On the completed tephigram, the area between the plot for environment temperature profile and the plot for the rising parcel temperature profile is directly related to the CAPE, which in turn is directly related to the maximum vertical speed in a cumulonimbus [Cb] updraught. One form of aerological diagram is used to determine the stability of the atmosphere — and thus potential thermal activity — by plotting the ELR from radiosonde data and comparing that with the DALR and SALR lines on the diagram. For more information go to the aviation section of the Australian Bureau of Meteorology website and look in the 'Sports Aviation' box for 'How to use the Aerological Diagram'. While there also look in the 'Learning' box for the 'Aviation eHelp' section. 2.7 Convergence, divergence and subsidence Synoptic scale atmospheric vertical motion is found in cyclones and anticyclones, and is caused mainly by air mass convergence or divergence from horizontal motion. Meteorological convergence indicates retardation in air flow with an increase in air mass in a given volume due to net three-dimensional inflow. Meteorological divergence, or negative convergence, indicates acceleration with a decrease in air mass. Convergence is the contraction and divergence is the spreading of a field of flow. If, for example, the front end of moving air mass layer slows down, the air in the rear will catch up — converge — and the air must move vertically to avoid local compression. If the lower boundary of the moving air mass is at surface level, all the vertical movement must be upward. If the moving air mass is just below the tropopause, all the vertical movement will be downward because the tropopause inhibits vertical motion. Conversely, if the front end of a moving air mass layer speeds up, then the flow diverges. If the air mass is at the surface, then downward motion will occur above it to satisfy mass conservation principles. If the divergence is aloft, then upward motion takes place. Rising air must diverge before it reaches the tropopause, and sinking air must diverge before it reaches the surface. As the surface pressure is the weight per unit area of the overlaying column of air, and even though divergences in one part of the column are largely balanced by convergences in another, the slight change in mass content of the overriding air changes the pressure at the surface. The following diagrams illustrate some examples of convergence and divergence: Note: referring to the field of flow diagrams above, the spreading apart (diffluence) and the closing together (confluence) of streamlines alone do not imply existence of divergence or convergence, as there is no change in air mass if there is no cross-isobar flow or vertical flow. (An isobar is a curve along which pressure is constant, and is usually drawn on a constant height surface such as mean sea level.) Divergence or convergence may be induced by a change in surface drag; for instance, when an airstream crosses a coastline. An airstream being forced up by a front will also induce convergence. For convergence / divergence in upper-level waves, refer to Rossby waves. Some divergence / convergence effects may cancel each other out; e.g. deceleration associated with diverging streamlines. Developing anti-cyclones — 'highs' and high pressure ridges are associated with converging air aloft, and consequent wide-area subsidence with diverging air below. This subsidence usually occurs from 20 000 down to 5000 feet, typically at the rate of 100 – 200 feet per hour. The subsiding air is compressed and warmed adiabatically at the DALR, or an SALR, and there is a net gain of mass within the developing high. Some of the converging air aloft rises and, if sufficiently moist, forms the cirrus cloud often associated with anti-cyclones. As the pressure lapse rate is exponential and the DALR is linear the upper section of a block of subsiding air usually sinks for a greater distance (refer to section 2.1 ISA table) and hence warms more than the lower section. If the bottom section also contains layer cloud, the sinking air will only warm at a SALR until the cloud evaporates. Also, when the lower section is nearing the surface, it must diverge rather than descend and thus adiabatic warming stops. With these circumstances it is very common for a subsidence inversion to consolidate at an altitude between 3000 and 6000 feet. The weather associated with large-scale subsidence is almost always dry. However, in winter, persistent low cloud and fog can readily form in the stagnant air due to low thermal activity below the inversion, producing 'anti-cyclonic gloom'. In summer there may be a haze or smoke layer at the inversion level, which reduces horizontal visibility at that level — although the atmosphere above will be bright and clear. Aircraft climbing through the inversion layer will usually experience a wind velocity change. Developing cyclones, 'lows' or 'depressions' and low-pressure troughs are associated with diverging air aloft and uplift of air, leading to convergence below. There is a net loss of mass within an intensifying low as the rate of vertical outflow is greater than the horizontal inflow, but if the winds continue to blow into a low for a number of days, exceeding the vertical outflow, the low will fill and disappear. The same does not happen with anti-cyclones, which are much more persistent. A trough may move with pressure falling ahead of it and rising behind it, giving a system of pressure tendencies due to the motion but with no overall change in pressure, i.e. no development, no deepening and no increase in convergence. 2.8 Momentum, Coriolis effect and vorticity Momentum definitions Angular velocityThe rate of change of angular position of the rotating Earth = W = 7.29 x 10–5 radians per second. (One radian = 57.2958°, 2p radians = 360°) or, the rate of angular rotation around a cyclone or anticyclone = w. (A rotor that spins at 1000 rpm has twice the angular velocity of one spinning at 500 rpm). Tangential angular velocityThe tangential angular velocity of a point on the Earth's surface is the product of its radial distance (r) from the Earth's rotational axis and W = Wr. The radial distance from the rotational axis is zero at the poles increasing to maximum at the equator. Angular momentumThe angular momentum of a point on the Earth's surface is the product of the tangential angular velocity and mass (m), and the radial distance from the rotational axis =mWr². If mass is presumed at unity then angular momentum = Wr². Or, angular momentum for a rotating air mass is the product of w and the radius of curvature = wr. Conservation of angular momentumThe principle of conservation of angular momentum states that the total quantity of energy (mass x velocity) of a system of bodies; e.g. Earth–atmosphere, not subject to external action, remains constant. Friction reduces the angular momentum of an air mass rotating faster than the Earth, e.g. a westerly wind, but the 'lost' omentum is imparted to the Earth, thus the angular momentum of the Earth–atmosphere system is conserved. Coriolis effect Coriolis effect (named after Gaspard de Coriolis, 1792 – 1843) is a consequence of the principle of conservation of angular momentum. The Coriolis or geostrophic force is an apparent or hypothetical force that only acts when air is moving. A particle of air or water at 30° S is rotating west to east with the Earth's surface at a tangential velocity of about 1450 km/hour. If that particle of air starts to move towards the equator, the conservation principle requires that the particle continue to rotate eastward at 1450 km/hour even though the rotational speed of the Earth' surface below it is accelerating as the particle closes with the equator, which is rotating at 1670 km/hour. Tangential eastward velocity at the Earth's surface Equator 1670 km/hour 464 metres/sec 15° South 1613 km/hour 448 metres/sec 30° South 1446 km/hour 402 metres/sec 45° South 1181 km/hour 328 metres/sec 60° South 835 km/hour 232 metres/sec 75° South 432 km/hour 120 metres/sec 90° South 0 km/hour 0 metres/sec Thus air or water moving towards the equator is deflected westward relative to the Earth's surface. Conversely, air moving from low latitudes, with high rotational speed and momentum, is deflected eastward, i.e. as a westerly wind, when moving to higher latitudes with lower rotational speeds. The Coriolis force is directed perpendicular to the Earth's axis, i.e. in a plane parallel to the equatorial plane, so it has maximum effect on horizontal air movement at the poles and no effect on horizontal air movement at the equator. The direction of its action is perpendicular to the particle velocity and to the left in the southern hemisphere, i.e. standing with your back to the wind the Coriolis effect will be deflecting the wind direction to the left (to the right in the northern hemisphere). The rate of turning, or curvature, of a moving particle of air or water is proportional to 2VW sine f, where V is the north/south component of the particle's velocity and f is the latitude. Because sine 90° = 1 and sine 0° = 0, then the Coriolis must be at maximum at the poles and zero at the equator, as expressed above. The Coriolis effect stops turning the moving air only when it has succeeded in turning it at right angles to the force that initiated the movement — a pressure or thermal gradient. The Coriolis parameter, f = 2W sine f, is the local component of the Earth's rotation about its axis that contributes to air circulation in the local horizontal plane. It is assumed negative in the southern hemisphere and positive in the northern hemisphere. Vorticity Vorticity or spin is the measure of rotation of a fluid about three-dimensional axes. Vorticity in the horizontal plane, i.e. about the vertical axis, is the prime concern in planetary scale and synoptic scale systems. Relative vorticity is taken as horizontal motion, relative to the Earth's surface, about the local vertical axis and is measured as circulation per unit area. It is assumed to be negative if cyclonic and positive if anticyclonic. Relative vorticity z = 2w. Absolute vorticity is the relative vorticity plus the Coriolis parameter — which is maximum at the poles and zero at the equator. Relative vorticity is related to horizontal divergence and convergence through the principle of conservation of angular momentum. In the cyclonic movement of air around a low pressure system the fractional decrease in horizontal area due to convergence is matched by a fractional increase in spin, thus conserving the angular momentum. With both increasing vorticity and convergence at lower levels, the vertical extent of the air column is stretched adiabatically and the upper-level divergence lifts to higher levels. Conversely, in anticyclonic rotation, the fractional increase in the surface area of the system, due to lower level divergence, is matched by a fractional decrease in spin. With decreasing vorticity and divergence at a lower level, the vertical extent of the air column shrinks adiabatically and the upper level convergence sinks to lower levels. The relationship is expressed in the principle of conservation of potential absolute vorticity equation: Coriolis parameter + relative vorticity / vertical depth of the air column ( D ) = constant or, f + z / D = constant Thus as the Coriolis at a given southern latitude is constant and negative, a reduction in the depth of a column at that latitude requires z to become more positive with consequent anticyclonic rotation. Conversely, an increase in depth requires z to become more negative with consequent cyclonic rotation. The principle accounts for the development of wave patterns in upper air flow. The cyclonic curvature of the isobars can be seen on surface synoptic charts resulting from the easterly / south-easterly trade wind encountering the mountain ranges along the north Queensland coast. The initial reduction in vertical depth as the airstream encounters the barrier, followed by the increase in depth on the western side, induces anticyclonic and cyclonic curvature. 2.9 Thermal gradients and the thermal wind concept The rate of fall in pressure with height is less in warm air than in cold, and columns of warm air have a greater vertical extent than columns of cold air. Consider two adjacent air columns having the same msl pressure; the isobaric surfaces (surfaces of constant pressure) are at higher levels in the warm air column, which result in a horizontal pressure gradient from the warm to the cold air — this increases with height, i.e. the temperature gradient causes increasing wind to higher levels. The horizontal pressure gradient increases as the horizontal thermal gradient increases — this is known as the thermal wind mechanism. The isobaric surface contours vary with height so the geostrophic wind velocity above a given point also varies with height. The wind vector difference between the two levels above the point — the vertical wind shear — is called the thermal wind, i.e. the wind vector component caused by temperature difference rather than pressure difference. On an upper air thickness chart which indicates the heat content of the troposphere, the thermal wind is aligned with the geopotential height lines or with the isotherms on an upper-air constant pressure level chart (isobaric surface chart), and the thicker (warmer) air is to the left looking downwind. *Note: a geopotential height line is a curve of constant height, i.e. the height contours relating to an isobaric surface — 850 or 500 hPa for example — usually shown as metres above mean sea level. Thickness charts are similar but show the vertical difference in decametres (i.e. tens of metres, symbol 'dam') between two isobaric surfaces — usually 1000 hPa and 500 hPa. See the national weather and warnings section of the Australian Bureau of Meteorology and view the weather and wave maps. An isopleth is the generic name for all isolines or contour lines. An isotherm is a curve connecting points of equal temperature and is usually drawn on a constant pressure surface or a constant height surface. The speed of the thermal wind is proportional to the thermal gradient; the closer the contour spacing, the stronger the thermal wind. If the horizontal thermal gradient maintains much the same direction through a deep atmospheric layer — for instance there are no upper level highs or lows, and the gradient is strong with the colder air to the south — then the thermal wind will increase with height, eventually becoming a constant westerly vector. The resultant high-level wind will be high speed and nearly westerly. Generally, colder air is to the south so that the thermal wind vector tends westerly. But if the horizontal thermal gradient reverses direction with height, then an easterly thermal wind will occur above that level and the upper-level westerly geostrophic wind speed will decrease with height. Because the direction of the thermal gradient is reversed above the tropopause, the thermal wind reverses to easterly. The horizontal thermal gradient is at maximum just below the tropopause, where the jet stream occurs. At latitude 45° S a temperature difference of 1 °C in 100 km will cause an increase in thermal wind of 10 m/sec (or about 20 knots) for every 10 000 feet of altitude — giving jet stream speeds at 30 000 feet, ignoring geostrophic wind. Temperature contrasts between air masses at the polar front will be greatest during winter, giving the strongest jet stream. STRICT COPYRIGHT JOHN BRANDON AND RECREATIONAL FLYING (.com)
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  24. Thanks mate, I just tried it and it works ok so not sure exactly what you may be referring to: On the Recreational Flying (.com) site: 1. Click Off Topic in main menu column takes you to the Whats Up Australia site in a new tab 2. Click Off Topic in the sub menu on the Whats New page takes you to the Whats New on the Off Topic site On the Whats Up Australia site: 1. Click Rec Flying on the sub menu on the Whats Up Australia site takes you to the Recreational Flying (.com) home page in the same tab Is there something that's not working right elsewhere?
  25. Thanks all, the new Home Page is now up, hope you like it and as always, any suggestions on improvements are greatly appreciated
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