Autorotations: Always Have A Bailout Plan

Being able to perform autorotation landings is an important milestone in your growth as a helicopter pilot. Outright power failures are pretty uncommon for electric-powered helis, but there are still cases where a quick autorotation can save the day in the event of a problem like a stripped main gear or tail-drive failure. Not only that, but autorotations are challenging and fun!

- Jim Ryan

HOW IT WORKS

In an autorotation, the main rotor is unpowered. By dropping collective to slightly negative pitch, air flowing through the rotor disc causes the blades to spin on their own, or “autorotate.” With no power to the rotor, there’s no longer any blade torque, so autorotations are an effective emergency procedure not only for powertrain failures but also for tail-rotor problems.

As the helicopter descends, the main rotor will spin close to or even faster than normal rpm. The spinning rotor is like a flywheel, storing up inertial energy. As the heli nears the ground, you pull collective to slow the descent and make a soft landing. Timing is crucial; as you pull collective, the rotor inertia decays rapidly and rpm will quickly drop below the threshold for sustained flight. So the goal is to set it down fast. When you time it right, autos look very cool.

CHOOSING A PRACTICE MACHINE

The first step is to choose your practice helicopter. Biggerhelis make for much easier autorotations because of their longer, heavier blades and lower head speed. I’ve seen pilots learn autos with 360-size helis, but it’s a challenge. In my opinion, the ideal machine for mastering autos is a durable helicopter in the 550 to 600 class, preferably one with tough wide-stance landing gear. A 600 is big enough to store a good deal of kinetic energy in the rotor but small enough that damage should be relatively minor if you make a poor landing. Normally, with a 600, almost any crackup or rollover means repairs, but the most common error in an auto is letting rpm drop too low. With the power off and the blades spinning slowly, you’re much less likely to do any real damage. I’ve bounced pretty hard on autos and even flopped the heli over on its side, with no more damage than perhaps a dinged tail boom.

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