Wow, so I just came on here hoping to get an answer to this! sweet!

To be clear, holding the trimmer button is -for all intent and purpose- like temporarily engaging the FD?

I'm guessing this is so that the autopilot never has to work very hard (read: outside a few degrees of stick-center) to maintain stability)?

Side question: under what flight conditions would the 'zeroed out' trim setting apply? It seems to always result in a VERY aggressive rearward pitch.

I don't consider the positioning of the trim reset helpful, beyond recentering your stick's center when using a non-FF stick when it gets all out of whack.

There is one instance that it works wonderfully. If you have two engines out and need to autorotate, if you don't want to go through a conventional autorotational descent, I found out that the Ka-50 in BS2 will act as a "parachute". If you allow the Ka-50 to enter a vertical or near-vertical autorotation, and then max out the collective and reset the trim, the aircraft will somehow maintain stability and a controlled vertical auto-descent and land soft enough for you to survive. It will collapse the landing gear, but will nonetheless be survivable.

I tried this multiple times. Each time the rotors slowed down to dangerous levels until enough downward velocity built up, the rotors will cone to an extreme, and the aircraft will kind of sway back and forth like a leaf sometimes. If you don't have the gear down, or can't lower it, don't try this cuz you'll just explode on impact. I would also recommend jettisoning your wing stores to make yourself lighter.

This whole procedure goes against all my real-world experience in helos, but I've never flown or had any knowledge about coaxials besides what's in the DCS BS manual. Whether the real-life Ka-50 can do this, no telling.

There's only 2 I can think of:

A) you've lost track of your simulated trim position. Reset the trim, stabilize the flight - then trim again immediately.

b) Parked.

The only time I have used that myself is when I'm down on the ground taxing and need to have "neutral" control of aircraft for turning onto taxi way etc. without having to worry about the aircraft running away from me.

I never use it in flight.

Use of the RCTRL-Enter controls indicator should be mandatory IMO. It will give you feedback on the control positions that a real pilot would feel instinctively, which DCS cannot convey.

There would be no need to Reset the trim, as you now have the knowledge to keep the trim from going crazy.

Nate