I get AOPA’s ePilot newsletter every day. Today it has an article called Rotorcraft Rookie: Advanced autorotations. The first paragraph reads:
Now, it’s been waaaaaay too long since I’ve had the discretionary funds to fly a helicopter; but autorotations were always my favourite thing to do in a heli. Here’s a very good article on autorotations: Autorotative Flight (Or Yes Virginia, A Heli Can Glide!).
Many people wonder, ‘What happens if your engine quits in a helicopter? Do you fall out of the sky?’ Fortunately, you don’t fall out of the sky. Well, you do; but it’s a controlled fall. The key is to maintain rotor RPM. The Robinson R22s and Schweizer 300s (aka TH-55 for you Army types) have ‘low inertia’ rotor systems. Basically, the rotors aren’t very heavy. Without power, they slow down very quickly unless drag is reduced immediately. During our practice autorotations in training, I’d lower the collective as soon as the power was chopped. Usually there was a ‘3-2-1’ countdown, but sometimes the instructor would chop the power unexpectedly. Those were annoying, since there were mountains to climb over and it takes time to climb 2,500 feet after an autorotation in a low-powered helicopter on a hot day with two big guys in it. I had the collective down in half a second in the unexpected power chops. It becomes automatic.
Hovering autos are different. In that case, you don’t want to lower the collective immediately. If you do, you’ll gain altitude and then run out of lift when you’re five feet in the air. If your engine quits when you’re hovering, you need to wait one second before you raise the collective to cushion your landing. Telling someone you have one second to lower the collective if you have a power failure in flight before you lose rotor RPM and plummet to a nasty death sounds like a very short time. When you’re hovering three feet above the ground and have to wait a second, it seems a very long time indeed.
A mundane post, I know. But I thought I’d share the article.