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Usually you will have a rough idea of the direction of home base and can turn towards it, while continuing to search for prominent landmarks. “DF steers” are available from ATC in many areas and provided you are within radio range a heading to fly will be freely offered. Do not be too proud or afraid to ask for assistance.
If you have no idea of the direction to fly, set up a triangular pattern at endurance speed settings, at the highest practical altitude, to alert the radar network. If shortage of fuel becomes a problem, land to conserve remaining fuel.
In an extreme emergency, if there is absolutely nowhere to land, you should broadcast a MAYDAY distress message on 121.5 MHz giving the helicopter type, the nature of the emergency, the amount of fuel left, the assistance required, and your immediate intentions. Listen out on the same frequency for instructions.
Pilot Navigation
One advantage of the helicopter over other aircraft is its ability to land in unimproved locations. Do not exhaust your fuel supply by continuing to fly; select a suitable field near habitation if possible, and land preserving sufficient fuel to return to base. A thorough map study on the ground may re-orientate you, but do not take off again if you are still unable to positively fix your location.
Reciprocal Track
For one reason or another, such as a diversion to an alternate, it may be necessary to calculate a track to take you over the route you have just flown. An easy method for mentally calculating the reciprocal of a heading is to add 200 to headings less than 180 degrees and then subtract 20. For headings of more than 180 degrees subtract 200 and then add 20.
Once on the reciprocal track, the allowance for wind will be opposite to that used outbound. If 10 degrees was added to the outbound track to allow for drift, it will now be subtracted from the reciprocal track to obtain a compass heading. This heading should be adequate until a new and more accurate one is calculated. Turn the chart 180 degrees, map read back to a known fix, and then resume normal navigation either back to the point of departure or to an alternate destination.
Low Level Navigation
There may be an occasion, during a cross-country flight, that will necessitate low-level navigation. Some of the flying on your flight test may also be done at low level. Special mention is therefore made now of low-level map reading.
The greatest difference in navigating at cross-country altitudes lower than usual is the restricted field of view at low level, which becomes extremely limited when flying over rough or hilly terrain. This, combined with the greater attention that must be given to handling the helicopter, cuts down the time you have to positively identify your landmarks and checkpoints as they come up. Since you cannot hope to continually compare your checkpoints with the chart to assist identification, you must pick unique, easily recognizable features. Line features, such as railway lines or roads, that run 90 degrees to the track are used as check-points, and those that run to the turning point are used as lead-in lines.
During low-level navigation flight, you have to be on the lookout for obstacles such as TV and radio antennas, power lines, factory chimneys, and sharply rising ground. The set-heading procedure should be carried out if possible, before descending to the low-level altitude, and navigation should be strictly confined to map reading. Log keeping is impossible because of the urgent need to keep a good lookout. Check outside frequently if altitude is critical, to avoid flying into the ground. If you become uncertain of your position, if possible climb as high as necessary to give yourself an extended field of view and try to identify a landmark.
Remember that when you are doing cockpit checks you must not bury your head in the cockpit. Complete the first item and then pause to have a thorough look around; complete the next item and look around again; continue in this way until the check has been fully covered. If your low-level navigation technique is to be a success, you must develop good handling habits, so that most of your time can be devoted to checking your position and to look out.
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直升机飞行训练手册 HELICOPTER FLIGHT TRAINING MANUAL(43)
