John Brandon

The Ops Manual (an RA-Aus copyright) is certainly available to persons or organisations who are not members of the association. The price is $38.50 plus $5.50 postage but updates not included. Mail the office with your cheque! cheers John (Brandon)

Yes Mike, quite true, I would be wary too. Hence the reference to Bob Hoover who did a lot of very thrilling air displays in the Shrike Commander.

Thanks Mike, It's very interesting that both aircraft seem to have suffered exactly the same simultaneous negative g outer wing separations at or near the main spar splice joints. The Tasmanian final accident investigation report appears to favour the autopilot control of the elevator trim tabs over-riding an inexperienced pilot's manual attempts to pull the nose up. Even if the Victorian aircraft suffered a runaway electric trim or autopilot the pilot's 1000 hours or so in that aircraft type would lead to the expectation that such situations would be countered before nearing Vne. Will just have to wait until the investigation is concluded but can't help thinking turbulence played a significant role. The Shrike Commander has 6.5 degrees wing washout and one thing that all recreational pilots should bear in mind is that wing washout really compounds negative loads at high speed. The following is an extract from the safety article appearing in the November 2007 issue of the RA-Aus magazine. Wing washout: handy at low speed, not so good at high speed! Wings incorporating geometric washout have a significantly lower aoa towards the wing tips. At high speed when the wing is flying at low aoa there are high aerodynamic loads over the wings but the outer sections could well be flying at a negative aoa and the reversed load in that area, or just a badly distributed load due to the wing shape, will bend the wingtips down, possibly leading to outer spar fracture. cheers John PS I wonder what Bob Hoover thinks of this? Didn't he borrow a Shrike Commander from Essendon for his famous display after CASA gave him a licence and a poke in the eye to FAA?

Found the report, thanks Alf and Vince. I could have sworn that accident happened at least five years ago, just proves time accelerates as you age. cheers John

Some time recently (I guess within the past 10 years) an aircraft departed Essendon at night for some point north carrying (I think) urgently needed aircraft spares. The aircraft disappeared from the Airservices plot somewhere around Mangalore and was later found to have suffered inflight breakup due to severe turbulence. I seem to recall that it was a Shrike Commander but I can't find any reference to it in the ATSB accident investigation reports. Does anyone have any information which would enable me to find the report? cheers John Brandon

Or being aviators who never carry 4 figure trig tables in the cockpit we could just apply the 1-in-60 rule thus: 2 X 60/68 = 1.76 = about 2 degrees or, 10 X 60/82 = 7.3 = about 7 or 8 degrees Bendorn, the 1-in-60 rule provides a rule of thumb based on the reasonably accurate assumption that the sine of any angle, up to about 45°, is equal to 0.01666 times (or 1/60) the number of degrees. e.g sine 30° is 0.01666 x 30=0.5 or 30/60 = 0.5. The sine is the ratio – in any approximate right angle triangle – of the side opposite the angle, to the hypotenuse (the longest side), thus the 1-in-60 rule is very handy in the mental arithmetic of flight theory and basic navigation as the angles involved are usually less than 45°. For angles up to 15° or 20° the tangent (opposite side/adjacent side) is practically the same value as the sine. For angles between 50° and 75° the sine is about 1/70 times the number of degrees, and for angles between 75° and 90° the sine approaches unity. cheers John

I would very much doubt that broadcasting for help as a private citizen in an emergency, by whatever means is at hand, could be classified as an offence. You have a valid reason for carrying your airband transceiver if you like to listen to the traffic while bushwalking and, providing you don't use your aircraft station identity in the emergency broadcast [which could confuse everyone], I see no problem whatsoever. cheers John

Yes, if caught. Transgressions of the Class Licence should not be encouraged or condoned, it brings our association into disrepute. I wrote the material that Slarti referred to avoid such transgressions, which, by the way could also be most unrewarding for the transgressor. Use the CB band if you must transmit to non-aeronautical stations. cheers John

Sorry for the delayed reply, it was our fortnightly shopping day yesterday — big trip into Albury. Vb and Vc are not the same but are derived from the 'corners' of the aircraft gust envelope. B is Vb, C is Vc and D is Vd. Vb is related to the 66 fps gust velocity required to be considered by designers of commuter category aircraft. Va doesn't appear in the gust envelope only the manoeuvring envelope [or the combined envelope] at corner A. in the combined envelope Vb would be between Va and Vc and, I guess, closer to Va than Vc. I've added a V-n diagram which might be helpful but the quality is not the best. The Vb gust line is the 66 fps line for commuter category, the Vc and Vd gust lines are the 50 fps and 25 fps lines respectively for all categories. cheers John

Thanks Mark but they haven't turned up yet - 10.00 pm John

Thanks for that. It is interesting that the T6/24 Airtourer AFM doesn't mention handling in turbulence but at least it does provide Va for normal and aerobatic category. Vb, the design speed for maximum gust intensity, still exists in FAR23.335 though it's unlikely to be specified by the designer of an aircraft below 6000 lb. Probably more applicable to the higher end commuter category. Seems to me that most FAR23 and FAR23 Appendix A light singles stick with just Va as a speed to fly in "turbulence' but I'd like to see something from the European designed JAR23 and CS-VLA aircraft. cheers John John

G'day J430, You have not responded to my query and are departing from the thread, however, in response here are the first few paragraphs of the article Im working on: 6.1 Defining turbulence and wind shear It is usual to classify all the changes in atmospheric motion that significantly disturb aircraft flight as turbulence but in some wind shear events there may be no air turbulence involved. It is difficult to define the degree of turbulence or the load effects of shear in a way that is meaningful to a recreational aviation pilot. Measuring by the airflow velocity change or the gust velocity measured in feet per second doesn't really enable the pilot to judge how turbulent the conditions are in her/his circumstances, particularly so if the instrument panel is not equipped with an accelerometer. However the following is partly based on an old ICAO turbulence scale which, though classifying by the induced positive or negative accelerations [only as measured near the aircraft cg] does provide a descriptive definition of sorts appropriate for 3-axis aeroplanes but perhaps not flexible wing weight-shift aircraft and certainly not meaningful for our powered parachutists. Very low – below 0.05g; light pitch, yaw and roll oscillations experienced. Low – 0.05 to 0.2g; might include light 'chop' i.e. slight, rapid, rhythmic bumps and oscillations without significant changes in altitude or attitude. Like driving a boat through a choppy sea. Also known as 'cobblestoning' — like driving at moderate speed on a corrugated gravel road. Moderate – 0.2 to 0.5g; turbulence is becoming significant and the ride produces strong intermittent uncomfortable jolts with attitude upsets and airspeed variations but aircraft remains in control. Head hitting cockpit roof structure if clearance small or harness allows. Severe – 0.5 to 1.5g; aircraft handling in all axes made difficult but not dangerous [if occupants and objects properly secured] except near the surface. Large abrupt changes in altitude/attitude with significant variations in indicated airspeed. Cockpit instruments difficult to read mainly because of problems with re-focus. Very severe – above 1.5g; aircraft violently tossed about combined with extreme handling difficulty, structural damage possible. The wake vortices from larger aeroplanes or the rotor downwash from helicopters add another form of turbulence extremely hazardous to all recreational aircraft particularly because of strong rotational effects leading to sudden height loss. Such vortices must be anticipated and avoided. Wind shear – in aviation terms wind shear is a sudden but sustained “variation in wind along the flight path of a pattern, intensity and duration, that displaces the aircraft abruptly from its intended path and sufficiently that substantial and timely control action is needed” and is probably the greatest hazard to flight at low levels in visual meteorological conditions but its effect is short-lived. The flight path displacement is initiated by a substantial change in lift generation associated with the aircraft's inertia [see note 1 following]. The shearing action between air layers with substantially differing velocities — or vertical gusts and their surrounds — may also induce strong turbulent eddies or breaking waves at the shearing level or interface." cheers John

G'day all, I am currently writing the safety articles for the July and August issues of the RA-Aus journal and need a little information regarding the statements made in various light aircraft POH/Flight Manuals about operations in turbulence. For example the POH for the Piper PA32, a six seat, 300 hp retrac in FAR23 'normal' category states: "In keeping with good operating practice used in all aircraft, it is recommended that when turbulent air is encountered or expected, the airspeed should be reduced to maneuvering speed [i.e. Va] to reduce the structural loads caused by gusts and to allow for inadvertent speed build-ups which may occur as a result of the turbulence or of distractions caused by the conditions." Would you mind checking your POH and advising if essentially the same is stated or if more options are added or if it is substantially different? cheers John Brandon

1. The term "on the step" generally refers to waterborne operations where an aircraft taking off or taxiing fast is using the hydrodynamic lift from the 'planing hull' [the hull portion forward of the transverse step] to support it rather than using the buoyancy of the whole 'displacement hull'. When on the step water drag is at its lowest and the centre of buoyancy is close to the step so that the pilot can rock the hull forward and back so assisting the break-out when water conditions are calm. When alighting the aim is to touch down "on the step". 2. The term "on the step" was also fashionable for a while prior to 30 or 40 years ago when people were debating the transition from climb to cruise. The thing to bear in mind in that transition is that unless you use extra power [i.e. greater than cruise power] to accelerate the aircraft from climb speed to cruise speed then it is going to take a long time to accelerate to that cruise speed normally reached at your selected engine settings. Some aircraft may just not get there if altitude is held. So normally you facilitate the acceleration by leveling off near cruise altitude, maintaining climb power until cruise speed is reached then reducing to the cruise settings. Or you can do it by extending the climb, setting cruise power and then using the potential energy of height to supply the energy for acceleration to cruise speed at cruise height. Probably the best practice [but not for passengers] is a combination of both; i.e. continuing the climb for maybe 200 feet past the required cruise altitude then pushing over enough to unload the wings a little [perhaps to 0.6 to 0.8g] so that induced drag is reduced while maintaining climb power, thereby enabling the fastest acceleration to the required cruise speed. If done nicely cruise altitude, maximum cruise speed for that setting and cruise power all come together quickly and at the same time. cheers John Brandon

In regard to the premature internet publication of the ops manual you will have to blame me, your independent web service volunteer author. I had the pdfs in order to start preparation of the CD for official release and distribution of the manual and made a mis-judgement in making the ops manual publicly available. The Canberra staff were not involved in that decision. cheers John Brandon

Have to inform you that the online ops manual issue 6 has now been removed. It will be reinstated when the CD is distributed to members. I will start working on the CD tonight which will be posted to Lynn Jarvis Thursday. Lynn has volunteered to do all the necessary work to convert it into a publishable format. The CD will contain the two manuals plus my online tutorials. The reason for the withdrawal was that it was creating far more telephone calls to Mick Poole than he could cope with so please give him and the others in the office a break for a couple of months. cheers John

The RA_Aus intent regarding publication/distribution of ops manual issue 6 and tech manual issue 3 is unclear [to me anyhow]. For all previous issues the printed manuals distributed free to every member and available at a price to non-members was regarded as the "official" document and the format appearing on the web site was "unofficial" and meant for single section access only. It was/is assumed that members are reasonably conscientious and have absorbed the general content of the manuals so that, if their official copy is not to hand, they can readily access any section of current interest from the on-line version. For example following an inflight structural failure away from home base the pilot might wish to access section 4.10 online to see the means of reporting that failure to ATSB. That single section access to the web site versions, which has existed since web site inception, also encourages non-members to purchase the manuals rather than download for free, which makes sense to me. Regarding the apparent date anomaly you must all be aware by now that nothing moves fast when dealing with aviation regulation. The July date is correct it is just that the unfortunate RA-Aus staff having expended considerable effort in apparently getting a task concluded then have to debate the subject with our regulatory masters for six months before they say OK you can now publish it. How many realise that it is now 11 years since the AUF and the others involved started development of CASR Part 103 and still the Notice of Final Rule Making has not been released. The whole regulatory change process that the RA-Aus staff take up on your behalf is extremely frustrating to them and I believe there is a lack of realisation of that amongst the members. John Brandon

I put the Operations Manual issue 6 on the website yesterday. See www.raa.asn.au/opsmanual/index.html John Brandon

There is some confusion in the use of terms in this thread so perhaps a couple of definitions might assist. Inertia is the property of a body resisting any change in motion, or continuing in the same state of rest or state of motion relative to the Earth's cg. The mass of a body is a measure of its inertia i.e. its resistance to being accelerated or decelerated by an applied force increases with mass; a heavier aircraft has more inertia than a lighter one, so is more resistant to random displacement forces — atmospheric turbulence. As long as an aircraft's mass remains unchanged so will its inertia whether it is at rest or moving i.e. any motion [speed] or pulling g has absolutely no effect on an aircraft's inertia. Momentum on the other hand is mass [inertia if you like] multiplied by speed and for an aircraft in flight the speed is the true airspeed. Momentum is the property that allows you to trade airspeed for altitude, following engine failure for example. I think someone stated that an aircraft cruising at 45 knots into a 45 knot headwind would have zero kinetic energy, that is not correct. Kinetic energy relates to mass multiplied by speed squared and the speed for an aircraft in normal flight is the true airspeed, so any airspeed above Vs1 can still be swapped for gravitational potential energy even if the aircraft was moving backwards relative to the ground. Groundspeed is only used in the kinetic energy equation when you want to calculate the work to be done [i.e. the kinetic energy expended] to bring the aircraft to a halt on the ground. cheers John Brandon

Might I suggest those who contemplate carrying children in ultralights read section 3.4 of a document I've prepared for the March issue of the RA-Aus journal. It can be found at www.raa.asn.au/nonlinked/deceleration.html ; I also suggest you google 'child restraint system aircraft' cheers John

I'm currently finishing off the safety feature article for the February and March issues of Recreational Aviation Australia. This article deals with the problems of landing too fast in an emergency. I would be interested to hear from anyone who has put an ultralight, or any light aircraft, through a properly constructed farm fence. As you may know each strand of a four or five strand barbed wire cattle fence is usually strained up to 100 kg and the 2.5 mm mild steel wires each have a breaking strain around 3000 newtons [300 kg force]. The 4 point barb clusters are spaced at 10 cm. From the damage I've seen to a four wheel drive vehicle which was allowed to roll downhill through my boundary fence breaking through the top four wires I conclude the damage to an aircraft and occupants might be horrific. I don't think an ultralight moving at 25 knots would break through such a fence nor would it stretch mild steel barbed wire very far and of course there's always the chance of hitting an intermediate post. When the fence is struck at an angle the barbs act as a very effective chain saw. cheers John

Mode S allows 24 bits for the unique ID so 16.8 million. Here's a little more about Mode S, for more see www.raa.asn.au/comms/safety.html#transponder 6.3 Aircraft radar beacon transponders Transponders are specialised radio devices forming the airborne part of the Air Traffic Control Radar Beacon System [ATCRBS or "at-crabs"]. Transponders respond to a 1030 MHz interrogation pulse, from an Air Traffic Control secondary surveillance radar [sSR], by returning a high energy 1090 MHz pulse which strengthens the radar return signal. (Primary radar surveillance exists only within about 50 nm of the major civilian and military airports but such radars don't interrogate airborne transponders, SSR range is at least 100 nm from the radar unit.) In addition the response from transponders fitted to smaller civilian aircraft normally consists of a 12 bit identity/status code plus a 12 bit altitude reading [in units of 100 feet] which appear on the controller's SSR screen with the aircraft 'paint'. Civilian units with this identity [Mode A] plus altitude encoding [Mode C] interrogation response capability are known as Mode 3 A/C [or just Mode A/C] transponders. The transponder receives the Mode C altitude data from an altitude encoding altimeter or from a blind encoder; the latter probably being an electronic device with a pressure transducer connected to the static vent feed. Both types of units send pressure altitude not altimeter indicated altitude. (Some encoders are also capable of supplying altitude data to a GPS – "baro-aiding".) The 12 bit identity code is separated into four 3-bit numerals using octal rather than decimal notation, thus each numeral will be in the range 0 – 7, i.e. the numerals 8 and 9 will not appear in any identity/status code. The standard four digit identity code 'squawked' by VFR aircraft is '1200' until radio contact with Air Traffic Services, who might then instruct the pilot to squawk an assigned individual code e.g. 4367 – the maximum number of pilot-selected identity codes available for assignment at any one time is only 4096. The Mode A/C surveillance system is very limited. The transponders carried by regular passenger transport aircraft use a 24 bit identity code allowing a total of 16.8 million individual addresses. Thus every aircraft can be permanently assigned a unique address, usually based on the aircraft's country of registration and registration number. Consequently those aircraft can be selectively addressed by ground stations or other aircraft. This message format is called Mode S [for 'selective address'] but the transponders also have the normal Mode A/C functions. Currently in Australia the main Mode S transponder function is to allow aircraft equipped with Traffic Alert and Collision Avoidance Systems to 'talk' directly with each other thereby enabling mutual resolution of potential traffic conflicts; see below. Such transponders also act as the aircraft's digital modem terminal for data upload/download and distribution. Mode S can also provide faster more accurate ATC surveillance provided the ground radars are of the fast single pulse interrogation type. Many [most?] of the Australian SSRs are not monopulse radars and thus need to be replaced; this expensive requirement is prompting an accelerated implementation of ADS-B instead of new radars. John Brandon

The RPL proposal is not something new, it has been in official existence at least since 1998, it appeared in the Part 61 discussion paper released in 2000. In Part 61 [Flight crew licence structure] it has nothing to do with any sport pilot concept. I believe it is primarily meant to tidy up the ICAO regulatory anomaly where currently Australian SPL [i.e. student pilot licence] holders who have passed the General Flying Progress Test are allowed to carry passengers when operating in the vicinity of their home base. The US FAA also released an RPL in the '90s but I think that was a fizzer. I would be interested to know if some organisation is trying to add a Sport Pilot Licence [in addition to the RPL] to the Part 61 proposal. By the way there is no existing Sport Pilot 'Licence' associated with LSA, in the US it is a Sport Pilot Certificate which in concept is practically identical to the RA-Aus Pilot Certificate. John Brandon

Isn't that the proposed Recreational Pilot Licence not a Sport Pilot Licence or Certificate?