Helicopter Engine-Off Landings

If the Helicopter Engine Fails, Auto-rotation Is Required

Apr 21, 2008

Many people believe that if the engine stops in a helicopter, it simply falls out of the sky. An instructor explains that this is not true, and describes what to do.

Many people think that if the engine fails in a helicopter, the occupants have had it: the aircraft will simply drop like a stone, killing everybody inside it. However, this is simply not true. Auto-rotation enables the helicopter to land under control.

Instant Descent

In a helicopter, the turning of the rotors keeps the aircraft flying. Normally it is the engine which keeps those rotors turning. But it does not have to be the engine, and if it fails, something else is needed to prevent the rotors slowing down. This can be achieved by putting the helicopter into an instant descent.

As soon as there is any indication of a problem with the engine, the pilot lowers the collective lever as far as possible. This takes the pitch off the rotor blades, and the helicopter begins to go downwards. When this occurs, air from below keeps the rotors turning. It is a similar process to the working of a windmill, or even a sycamore leaf.

What Is Auto-rotation?

The helicopter is now established in what is known as ‘autorotation’. It will descend quite quickly, typically at around 1700ft/min. But it will be coming down under control, and the pilot can choose where to go, can turn, can decide whether to speed up or slow down, and finally he or she can turn into wind and select a safe landing site.

So at a height of about 40 feet, the pilot starts a gentle flare to arrest the rate of descent. Then a few feet from the ground the helicopter is leveled, and at the last moment the collective lever is raised to cushion the landing. If this is done correctly, the helicopter will land gently on the ground, and the occupants can exit from it quite normally.

Is it Very Difficult?

This sounds easy, and it is not, in fact, all that difficult. It does not feel to the pilot -- or his or her passengers -- as though the helicopter is falling out of the sky. Helicopter students learning auto-rotations do not finish each lesson staggering or looking green. In fact, many pilots positively enjoy practicing auto-rotations, and claim that it is great fun. Most of them do practice them quite often, so that if they ever have a real engine failure, they will be able to walk away safely…and even use the helicopter again afterwards.