What is autorotation???[&:]

where the motor is killed or quits and you land without power.

check out you tube for some vids of it.

Autorotation is probably the best thing out there. It ranks above fire, electricity, and sliced bread hands down.

Like mrasmm says, it's when the engine dies on you (or is shut off purposefully when training) but you're still able to land safely. Basically, during decent, you change the pitch of your blades so that they catch the air and start turning. The purpose of this is to get enough blade rotation so that at a certain distance above the ground you change your blades' pitch again so that now they're creating some lift for you (this is called a flair) and slows your plummet down to safe landing speeds. Again, like mrasmm suggests, YouTube has some great examples of this, both real and R/C helis.

Auto rotation is when you reduce the pitch of the blades down to zero.
Also allowing the blades turn faster then the engine speed is called auto rotation.
Gyro copters are all auto rotation machines.
When a helicopter loses an engine the pilot can (on most small choppers) let the rotors free wheel and try to land the craft with the rotors free wheeling.
When your about 10 feet from the ground you pull back the cyclic control and the blades titling back will act like a big super drag chute and if you do every thing right you can land it with no or little damage
We usually call it a controlled crash.
Some good info here
Vegas/ http://cybercom.net/~copters/pilot/autorotation.html

_____________________________

Vegas/
The only Easy Day Was Yesterday.

thanx

If you mix the 3 answers given you might be able to understand what an "auto" is.

1. No need to shut down or kill the engine. There is a function on most radio controllers to bring the engine to IDLE and leave it there, not reacting to what the throttle stick is doing. Remeber that the throttle stick on the radio is shared by the pitch function.

2. The angle of the blades is decreased to something less than zero degrees. Is actually closer to -4 degrees. Zero degrees will not create enough energy on the blades to perform a successful flare and landing.

So let's review;

1. You intentionally flip your Throttle HOLD switch on your radio (bring engine to IDLE) or your engine dies (emergency auto).
2. Inmediately bring the pitch stick down to about -4 degrees. Some people prefer even more blade deflection. I use close to -10.
3. As the heli drops to the ground, the air passing thru the rotor disk, maintains or increases the rotational energy of the blades.
4. As you approach the ground, (no set altitude as all helis are different) you increase the blade pitch back to a little over hover deflection and "arrest" the fall, and any forward movement. This is called the FLARE.
5. If you did it right, you should have enough energy left in the blades to settle softly to the ground. (Landing)

Rafael

or how about this =P
http://en.wikipedia.org/wiki/Autorotation

Does this feature exist on a real helicopter? Real means, pasenger helicopter or military helicopter.

yes yes it does =) On every one that I know about. On the smaller ones that are belt drive, they just release the tension on the belts. On the larger heli's they have one way bearings