User Guide

of the circulating vortex ring destroys most of the main rotor’s lift, and you cannot escape
by raising the collective – you will only pump energy into the ring’s circulation. You are
already descending too fast to escape downwards and outrun it. The only way out is to use
the cyclic to move laterally, because lateral movement disrupts the vortex, just as vertical
movement maintains it.
Coping with Reduced Power
If you lose an engine in a powerful twin-engined helicopter like the Comanche or the Hokum
you can still fly, land and take off, provided that you don’t try to lift heavy weights in hot and
high conditions or leap tall buildings at a single bound. The keys to achieving this are
translational lift and ground effect. Every time you raise the collective for more lift you put
more strain on the surviving engine, and the rotor speed may slow to dangerous levels.
Ground effect multiplies your main rotor lift and may let you hover with reduced power.
It also provides a convenient low-friction environment in which to accelerate to a speed
where translational lift can let you climb out of ground effect. When approaching for a
landing, or descending and decelerating for any other reason, let yourself gently down at a
shallow angle or a low speed, or both. The ground effect cushion is no deeper than your
main rotor diameter.
If you cannot even hover in ground effect, you may still be able to achieve a running
landing, if space is available. The approach is flown very like a low speed approach to a
runway in a fixed-wing aircraft. Just as in an aircraft, you round out your descent by pulling
smoothly back on the cyclic before you touch the ground so that you kiss it gently rather than
crash into it at an angle. At the same time you must avoid plunging your tail-rotor into the
ground.
If you’re running out of horizontal speed but close to the ground you can probably afford to
raise the cyclic to slow the last seconds of descent. If you run out of forward speed and rotor
rpm at the same time, you’d better hope that you don’t have too far to fall.
Running takeoffs are also possible if space, surface and wind direction permit. The idea
here is to accelerate on the ground to a speed where translational lift will let you lift off and
(you hope) climb. If you can’t climb out of ground effect then you need a clear run to a lower
altitude, or another rolling landing. Failing these, you’re in trouble.
Autorotations
If a helicopter loses all engine power in flight, it can still be landed without serious
damage or injury provided that the pilot does everything right, and there is a clear space in
the right place for a landing. The technique and options vary according to your height when
power is lost.
1) Loss of Power at Altitude
The standard Autorotation procedure assumes that the helicopter is flying at 500 feet / 150
meters or more. The key technique is to preserve the rotational energy stored in the main
rotor system (treating it as a giant flywheel) until it can be used up in the last few seconds
of flight to halt your descent and lower the helicopter more or less smoothly to the ground.
GROUND SCHOOL
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