ben1000
Senior Heliman
Location: Gilbert, Arizona
| Howdy...
As I understand it:
An autorotation bearing is a one-way bearing that is like the free-wheel on a mountain bike. If you stop pedaling, the bike keeps going... On a heli, if the engine stops, the main rotor keeps turning without having to turn the main gear and the clutch gear, and the engine (if the clutch fails). If your clutch locks up in flight and the engine quits (which I've had happen) the blades can keep going, rather than stopping because of the drag of the engine turning...
A driven tail basically means that the tail is driven from the main shaft and not from the main gear. This means that if the engine quits, the tail rotor keeps going as long as the main rotor keeps going. On some heli's (like the nexus), if the engine quits, the tail rotor stops too, even though the main blades keep going.
This is not as bad a problem as it sounds, because if the engine quits, so does all the torque that the tail rotor is trying to correct, so the tail will likely just weathervane into the wind in this situation. But it does mean that you have to land the heli in whatever orientation the tail ends up in, whereas with a driven tail, you have full control over the tail even if the engine quits, and thus can land the heli in any direction you like, or even perform tricks like piroetting auto-rotations.
Hope that helps...
(Is it me, or are my answers getting REALLY long-winded these days :-)
Regards,
Ben1000 |
