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Lost procedure

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8.7 Lost procedure


There are occasions during a cross-country flight when the pilot is uncertain about the aircraft's position, particularly when there are considerable distances between verifiable landmarks and a near-track landmark has not come into view. If proper flight planning and checking procedures are followed, and actual versus planned flight progress is continually monitored and recorded, then probably the only way to become really lost — in fine weather and reasonable visibility — is if an en route heading adjustment is incorrectly calculated or implemented, or if a turning point is overflown without noticing.


There are a few rules that must be followed if thought to be lost or caught in a difficult situation;


1. Fly the aeroplane! You must not concentrate all attention on the navigation problem — keep the normal scan going otherwise you can readily lose control of the aircraft.


2. If the ETA at the next waypoint has not yet, or only recently, lapsed then hold the heading — resist the temptation to start wandering about searching for landmarks.


3. However, if the ETA at the waypoint has long passed then choose a landmark below the aircraft, log the time and then orbit the landmark while you carry out a quick recheck of the running log and previous mental DR, and start the procedure detailed in the next paragraph. But don't forget rule 1: "Fly the aeroplane!". There is no point in wasting fuel while doing this so reduce power and airspeed to the best endurance setting for a safe flight speed. If no obvious error is found that will provide the basis for a position estimate then proceed with rule 4.


4. Check the time elapsed since the last position fix and estimate the distance covered in that time. On the chart draw a line of position [LOP] across the track (the original or an intercept) at the estimated distance from the last fix. The line should extend about 1 nm either side of track, for each 5 minutes flown since the fix; i.e. if it is 30 minutes since your last positive fix then the line will extend roughly 6 nm either side. Then draw a rough circle with the LOP as the diameter (see diagram below) — your most probable position [MPP] is somewhere within that circle of uncertainty. Find the most prominent features on the map within the circle and then try to locate them on the ground. The 1 nm per 5 minutes is based on ground speeds around 50 or 60 knots; if ground speeds are around 100 knots then make it 2 nm per 5 minutes. 'Most probable' means maybe an 80% chance.


5. If below 3000 feet agl then climb a little, cloud base permitting. The theoretical line-of-sight distance at 4000 feet agl is 65 nm all round. This provides sufficient coverage to pick up all the major landmarks — near and middle distance — which aren't concealed by terrain or atmospheric conditions. If climbing takes you above an inversion layer you may find surface visibility is better just below the inversion. Remember that on a bright day, scattered cloud shadows may make some landmarks difficult to pick up even if relatively close. Reduce power to best endurance.


6."Read from ground to map!" Normally in flight, the navigator should be continually identifying features on the map and waiting for the next one to come up on track, within an estimated time. When uncertain of position, the procedure is reversed — look for two or more large features on the ground and then identify features on the chart that are in the same juxtaposition. Prominent line features are best although, quite often, a spot feature is easily identified — for example the names of grazing or farming properties are shown on the charts and their owners, particularly those with an airstrip, often paint the name on a roof, in large letters. If you see a prominent line feature, then fly along it until you can derive a fix from an intersect or a verifiable landmark.


7. If necessary "assess the wind!" Whilst over the orbiting landmark turn onto a quadrantal heading, e.g. north, and fly that heading for one minute then turn 90°, e.g. west, and fly that for one minute. Systematically scan the surrounds for an identifiable landmark, starting with the area closest to the aircraft then moving out to the middle distance. Repeat for two more anticlockwise turns and after 4 minutes have elapsed you should arrive back near the starting point. If you have held to the headings and the timing, then the ground distance and direction of the arrival point from the orbiting landmark should provide a reasonable estimate of the wind velocity; e.g. if the arrival point is about 1 nm north-west then the wind speed must be 15 knots from the south-east. Of course if you are a poor judge of ground distance (which applies to many/most of us) then the indicated wind speed is not calculable but at least you know the direction and have a gross indication of the speed.




8."Start an expanding square search!" Starting over the orbiting landmark turn onto a quadrantal heading, e.g. north, and fly that heading for 2 minutes then turn 90°, e.g. west, and fly that for 2 minutes. Log the times and headings. Systematically scan the surrounds starting with the area closest to the aircraft then moving out to the middle distance. Repeat for two more legs but fly these for 3 minutes each. The next 2 legs are flown for 4 minutes each and so the expanding pattern is repeated, extending each pair by one minute, until a position is pinpointed or you are well outside the circle of uncertainty and a precautionary landing might be a wise action. Do not fly around in increasing circles, always fly planned (and logged) headings and durations.


Prepare for a precautionary landing


9. "Don't stay up too late!" Be prepared to make a precautionary landing well before the fuel content reaches the 30-minute reserve figure and well before oncoming twilight reduces visibility at ground level. You need to ensure that a precautionary landing isn't downgraded to a forced landing because of fuel exhaustion. Try to select a suitable site near a house. Remember after you have landed you still have to secure the aircraft, protect it from stock (cattle licking the skin do a lot of damage) and perhaps get some help — very difficult in the bush and near impossible in the dark!


A 'precautionary' landing is an emergency landing under power at a prepared landing ground or some other suitable, but unprepared, site. If you have read your insurance policy carefully you may find that damages claims are limited if you make a precautionary landing at a 'non-prepared landing zone'.


There are many circumstances where a precautionary landing is a wise move. Among them are:


  • deteriorating weather
  • oncoming darkness
  • fuel reaching reserve level
  • lost and you decide to obtain help on the ground
  • engine running rough (although this might be considered a forced landing)
  • occupant illness or a frightened passenger.



The technique for precautionary landings at other than a prepared landing ground is essentially the same as that for short field landingsexcept that additional low-level passes should be made to check the hazards, taking particular care in locating and avoiding wires. Map out the landing/run-out path and also determine the escape route in the event of an aborted landing.


And lastly:


10."Communicate!" Share the problem.


Source: http://www.recreationalflying.com/tutorials/navigation/enroute.html#lost



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