Turning it on through addAction wouldn't really make sense. The issue is that the engine can turn on when I don't want it to.

The reason I opened this ticket is because I do not want the engine to turn on by pressing the "collective up" key, as it prevents proper voluntary autorotations, such as landing after tail rotor loss (it is possible to land with the engine on, but an autorotation is the way to go).
Pressing "collective up" or "move forward" for cars is also not a realistic (or even remotely believable) way to turn an engine on.

Bumping this to update on the situation with the latest devbuild:
Since autorotations are back, and also due to the tweaks in the flight model of helicopters, it would be a really useful addition to turn the engine on only through the action menu, as it would allow for autorotation landings after a tail rotor loss.
As of now, you perform an autorotation normally, then when you try to cushion the landing, the engine turns back on, and the helicopter starts spinning wildly due to the broken tail rotor.

While it may not be useful for ground vehicles, helicopters would really benefit from it (but then it would make sense to add this to all vehicles).

Simply put, if the engine of a helicopter fails for whatever reason, the helicopter is able to auto-rotate to the ground.
If the main rotor is damaged, lift is greatly reduced, or even completely lost if the rotor is destroyed, and the helicopter will indeed fall like a rock.

As has been stated, the main issue is that any AA missile will damage ALL the hit points of the helicopter, when they should usually only partly damage it.

The "collective down landing" issue is probably due to the way collective is implemented: it's merely a force that depends on the key you press, so my guess is that when you land while pressing Z, that force will stick the helicopter to the ground, which is indeed not the way it should be.

I'm not entirely against extreme banks, as people will complain that they "keep falling out of the sky", but it does look extreme.

As for AA, I can see the radar blinking, but there is no alarm sound, which makes it difficult to react in time to deploy flares.

Actually, having a coaxial rotor doesn't mean the helicopter can 360 at all speeds. At high speeds, the aerodynamics force the helicopter to the lowest-drag profile, which is facing forward. It would require a lot of power to overcome this.
Also, not having a tail rotor doesn't mean it's easier to turn: yaw is achieved by changing pitch independently on both rotors (same as cyclic input), which shouldn't be as powerful as an entire (albeit small) rotor. It does help with stability, though. The Ka-50 also has a tail rudder to help turning.

The Comanche's ability to fly sideways up to 100 knots from forward flight is a special feature, which probably gives a great power boost to the tail rotor.

Great improvement overall, very good job on that!

A few things, though:

• Collective is indeed to unresponsive. There is supposed to be a slight delay between input and reaction, but it is too high now (maybe somewhere halfway between now and before the update?).

• Acceleration is now much more sensible for all helicopters, but top speeds are too low (they were too high before, though). It is difficult to reach 200 km/h without collective input with just about any helicopter, and even collective up makes it difficult to reach 250 km/h (which should be possible for any helicopter, with more or less ease depending on the helicopter).

-Autorotations are back, yay! The only problem is the angle required to keep the blades spinning: pitching down even 5 degrees, even when descending, starts stalling the rotor. On the other hand, you can autorotate vertically (from a hover), which is impossible due to the Vortex Ring State. What you could do to simulate this would be to start stalling the rotor when the angle between the blades and your velocity nears 75-90 degrees.
Pitching down, especially with low airspeed, is actually the only way to start an autorotation. Then you have to establish a good attitude depending on your descent, usually between -5 degrees (down) to +10 degrees (up). Lower angles would indeed stall the rotor over time.
Another problem with autorotations is the low speed of the helicopters currently: it's difficult to keep a good forward velocity without stalling the rotor (but as I said, it's currently possible to autorotate with zero forward velocity).
Autorotation airspeed is usually around 65 to 85 knots (100-120 to 160 km/h), depending on the helicopters.

• Bleeding speed in tight turns is nice, but the effect seems to be exaggerated a bit: even in long turns, you lose a lot of forward velocity.

As I said before, great improvement overall, can't wait to see the next tweaks/fine-tuning!

Overall feeling is still much the same as before the update.
The only difference I noticed (but I can't compare anymore) is that the Blackfoot seems to accelerate a bit more reasonably.

I also tried autorotations in the devbuild, but didn't notice any difference.
Thanks for keeping us in the loop, I'll wait for the next tweaks.

Quickstops are possible, but you need to set minimum collective quite a while before you can actually stop; this is the proper behavior of a helicopter, though.

Another important issue is the top speed: world record top helicopter speed is somewhere around 400 km/h, yet we can easily fly faster in Arma, and much, much faster when diving. Generally speaking, helicopters tend to accelerate a bit too much, and often reach impossible speeds.

Thanks for keeping us informed.
I'll gladly give feedback as soon as changes are made to them.

Although it would be kinda cool, PiP is different from proper reflections: the image you see is seen from a predefined angle, and does not depend on where you stand.
What I mean is that you would only be able to see what's directly in front of the mirror.

I believe Vichard meant hovering low enough to have skids touching the water.
In this situation, the engine goes red pretty fast and then the helicopter will indeed crash in the water.

Yep, crossing fingers is not how autorotations are done :P

The problem is that higher altitudes mean the rotor will have more time to slow down, while it should keep rotating due to the air flowing through the rotor.

As I said before, it worked really well in 0.58, but is broken in 0.60.

Bumping this as it still hasn't been reviewed/acknowledged/assigned.
It would be an issue if proper autorotations weren't back for the beta, with the new helicopters that will be available.

This issue is now also present in the latest stable version, 0.60.
Helicopters cannot autorotate anymore.

Since issue 0009007 has been closed very quickly as duplicate, I will simply post here: this issue is NOT present in the current stable build, but IS present in the latest devbuild (0.61.105957).

I agree with nmdanny's point 2, but not so much with point 1.

Pilots are not supposed to eject form their helicopter, and ejecting supposedly takes more time than just teleporting the character outside.
In real life, the Ka-50 features an ejection seat, but I don't think any other pilots have parachutes.