User Guide

tail swings out across the wind, the length of the lever-arm increases and so does the

turning force. Factors 2 and 3 both reach their maximum when the helicopter is broadside-

on to the wind, as it is when you’re flying sideways.

Because the tail fin exerts no turning effect when pointing straight into the relative wind (and

the helicopter’s fuselage is generating little or no more drag than it does when flying forwards)

it is possible to accelerate to much higher speeds in backwards than in sideways flight.

The catch comes when the tail turns out of line. The moment any turning force is generated,

it tends to turn the helicopter even further off the wind, generating even more turning force,

and so on in a vicious circle. At high speeds this happens so quickly that you have very little

time to correct the swing, and if you are moving faster than your maximum stable sideways

speed, once the swing goes beyond a certain point you don’t have enough tail-rotor thrust

to stop it anyway.

At this point you’ve lost control of the turn, which is almost exactly like a handbrake turn or

U-turn in a car. The helicopter swaps ends in an instant, the main rotor blades flap and

thrash madly, and if you’re lucky they don’t smash the cockpit canopy or chop off the tail

boom as the rotor disc tries to re-align itself with the suddenly and violently changing

attitude of the rotor mast.

It is possible (and even potentially tactically useful) to perform milder variants of this

manoeuvre under control, but work up to it cautiously. Approach it as you would approach

the problem of performing a backflip while whirling a sharp sword around your head.

Hazards and Emergencies:

Landing on Slopes

When necessary, it is entirely possible to land safely on a smooth moderate slope, but the

technique needs practice. Though at first sight it might seem natural to land facing up the

slope, the preferred direction is sideways, facing into the wind. If you don’t think the

helicopter will be stable standing across the slope, then the slope is too steep, and you

must find somewhere else.

Approach as normal, but slow your final descent so that you hover with your uphill wheel

just touching the ground. Now very gently lower the collective, and as the helicopter leans,

move the cyclic in the opposite direction so that the rotor disc remains horizontal. Once both

wheels are on the ground, carefully lower the collective to transfer the weight to the wheels,

keeping the rotor disc horizontal, to oppose the pull of gravity, rather than tilting it to match

the cross-slope.

Take-off can be accomplished by simply reversing the landing drill. The important things are

to keep the rotor disc horizontal and to use a very delicate touch on the collective when the

wheels are on the ground.

Retreating Blade Stall

We have already talked about the difference in lift developed by the advancing and

retreating blades of the main rotor in horizontal flight, which is due to the difference in their

effective airspeeds. Lift is directly and sensitively proportional to airspeed, but for any given

GROUND SCHOOL