This is not a glitch or a problem. You're using the wrong collective set.

Go into your configuration and switch to helicopter controls...

You'll see two sets of collectives.

Collective Up
Collective Down

and at the bottom

Collective Up (Analogue)
Collective Down (Analogue)

The top ones will force a hover when controls are released, which makes it more ideal for keyboard users, the bottom set allows full range of your slider (aka Throttle).

The current issue isn't that we don't have autorotation, we do. The main issue is that the blades INSTANTLY lock when you're hit for some reason... In arma 2, if you lose your mrot/eng, you'll still have enough spin to perform an autorotation.