Wacky trimmer - bug or feature?

[AlphaOneSix]

That's actually quite nicely modelled in DCS Blackshark, helo gets very unstable quick if there is any wind and trimmer pushed down.

 

When I fly the BS, I hold down the trimmer button for the duration of any maneuver. I have held it down for up to 30 seconds at a time. I have never experienced any instability.

[EinsteinEP]

mdee, I also get great performance from holding the Trimmer button down during maneuvers. Like Alpha mentions above, it's the most frequently used button when I fly and I often hold it for great periods of time - wind or no wind. The only instabilities I've regularly encountered were due to autopilot wind-up (due to me not Trimming effectively), being in an unexpected autopilot mode (dang, wonder how long I left that Route mode switch on?), or having critical pieces shot off the helicopter (hmm...that rotor blade sure looked mighty important...).

 

If you could post a track of the behavior you're experiencing, it would be great to review. Perhaps there is something else going on...

[mdee]

 

If you could post a track of the behavior you're experiencing, it would be great to review. Perhaps there is something else going on...

 

Track is up a couple of posts above. Observe when I press and release, helo jumps up (or down) When I do the same pull and press - hold and release, helo doesn't jump. These are not big corrections or anything. It feels like AP is kicking in too slow when you press and release quickly and assumes slightly different flight parameters than ordered by releasing a button. Maybe this is how KA50 AP works, I don't know, but it feels weird, and if this is for real, I feel sorry for KA50 pilots ;)

 

Pressing and holding trim button basically disables AP, I'd rather not do that too often, might as well fly in permanent FD mode, can't imagine that in combat and/or gusty wind with turbulences. I am not that skilled.

[AlphaOneSix]

Pressing and holding trim button basically disables AP, I'd rather not do that too often, might as well fly in permanent FD mode, can't imagine that in combat and/or gusty wind with turbulences. I am not that skilled.

 

This is why the trimmer button on all helicopters is placed in a location that makes it very easy to push. I use one of the Fire buttons on my X-52 (forget the name, the one on top closest to my thumb).

[StrongHarm]

There is also the case where you have the stick overtrimmed before you engage auto-pilot. For instance, if I have the stick trimmed all the way forward so I can achieve top speed, then I set autopilot, the autopilot will only need 75% forward trim to maintain. When I go to retrim with autopilot still set, as soon as I hit the trim button the nose will fall with a quick jerk. So, it could be the difference between what route mode has set and the manually trimmed position. I like to use the axis indicator like Frederf.

[EinsteinEP]

mdee,

 

I thought I had posted a response, but must have goobered it, cuz it doesn't show up here...

 

I reviewed your track and have the following observation: in normal autopilot mode without any modes enabled, when you release the Trimmer button, the autopilot "reads" your current attitude (pitch, bank, heading) and attempts to hold that attitude even if you move the controls around afterwards.

 

For example, at 12:04:40 in your track, you press/release the Trimmer button with about a 5° nose down attitude. The autopilot now is set to maintain that atttitude. You then pull the cyclic back and pull the nose up to 5° nose UP. You can see the autopilot "fighting" you and it gives its full 20% cyclic forward to put the nose where you told it to keep it: 5° DOWN.

 

When you press the Trimmer button again at 12:04:50, that 20% cyclic disappears, so, to the rotors, it looks like the cyclic got bumped 20% back, hence the nose "jump" up.

 

Remember that when you release the Trimmer, the autopilot is trying to hold that attitude. If you want to change that attitude, press and hold the Trimmer button, then release it when you have your desired attitude.

 

I recommend you fly with FD on all the time for a while: get used to how the system responds WITHOUT autpilot feedback (other than stability augmentation). Then the autopilot responses seem less mysterious.

 

Good luck!

[mdee]

mdee,

 

For example, at 12:04:40 in your track, you press/release the Trimmer button with about a 5° nose down attitude. The autopilot now is set to maintain that atttitude. You then pull the cyclic back and pull the nose up to 5° nose UP. You can see the autopilot "fighting" you and it gives its full 20% cyclic forward to put the nose where you told it to keep it: 5° DOWN.

 

 

Good luck!

Thank you very much for your response, I fully understand what you say. Trouble is I do not pull cyclic back, I just let go of the stick to neutralize it, because I haven't got force feedback stick and this is how it was demonstrated in producer notes. All the rest is autopilot/game trim mechanism, I don't do anything.

 

Watch producer notes at 3:39 when he says ".. release it, center the stick". He gets the same kind of jump.

 

I flew a helicopter numerous times as a passenger next to a pilot and just recently had a chat with a couple of them and this is not how the trim works. Trim keeps cyclic in position to neutralize the forces and autopilot tries to stabilize ordered flight parameters. It's of course not a point it and fly directly where you point, there are small changes etc, but if conditions don't change abruptly there is definitely no 5-10 percent jump after you lock the cyclic using the trimmer. It wasn't K50 helicopter tho. By the way they also told me that it's discouraged to hold the trimmer and move the cyclic, they never do that.

 

Anyway, I got used to it and it doesn't really matter if this is real K50 thing (I feel pity for the pilots tho ;) ) or in game implementation flaw.

 

Thanks a lot for looking at my track!

[EinsteinEP]

Thank you very much for your response, I fully understand what you say.

Glad to help!

Trouble is I do not pull cyclic back, I just let go of the stick to neutralize it, because I haven't got force feedback stick and this is how it was demonstrated in producer notes. ... Watch producer notes at 3:39 when he says ".. release it, center the stick". He gets the same kind of jump.

Yeah, the "old" Trimmer system only gives you about 0.5 sec to return your non-FFB controls (cyclic AND rudder!) to zero. If they're not at zero at that time, then you get a "bump". It's REALLY hard to get no bump at all, although with some practice/coordination, you can reduce the bump size to a pretty small amount - small enough to not impact your flight much.

 

Control bump is a limitation of this Trimmer implementation and, as you point out, is NOT present in real helos (they have the ultimate force feedback sticks and pedals!). ED removed the bump behavior with the "central" Trimmer method in 1.0.1: instead of waiting for a set amount of time then accepting control inputs, this new method will ignore your inputs until the non-FFB controls are centered, thus, no bump. The achille's heel of this approach is that it will literally ignore your input FOREVER if you don't center the controls up, even as you sprial down, screaming, crashing into the ground, a flaming ball of fire. To make it worse, centering the cyclic after releasing the Trimmer button is easy and intuitive, but many pilots forget they also need to center their RUDDER inputs too, resulting in what appears to be control lock-out ("My cyclic was centered, what gives?").

 

Personally, I'd prefer a hybrid of the two methods - the central method with a timeout, say 1.0 sec - but, in the meantime, I prefer to fly with the old method and live with the bump, since I, too, frequently forget to center my rudder pedals.

Edited February 3, 2010 by EinsteinEP