Autopilot and Trim

[Slant]

I'm noticing a couple things:

1. Autopilot does not seem to use the trim system anymore. When I am in level flight, engage the autopilot altitude hold and make a speed change, disengaging the autopilot will have the nose pitch up or down depending on the speed change. I do not think this is right. Test: 300KIAS to 250 or 350 and then disengage. (Apparently this is intentional, as the autopilot is only using a fraction of trim speed, see below)

2. The trim hat seems to be much more aggressive now. When I could happily keep on clicking the nose up or down to fine tune my trim (and still would never quite get it perfectly right lol), now it's giving me massive (like 5° pitch up or down) nose pitch changes per click. It's very imprecise, crude even. Very difficult to get the proper trimmed state like this.

Can anyone else confirm this behaviour or am I imaginging things? It's like with all these drag/performance changes, something about trimming compensating for these changes was left out and feels out of whack.

Or is this just how it was and I just need to get used to it?

Edited October 25, 2021 by Slant

[draconus]

Quote

Known issue: the AP is currently slightly off and we are working to correct itl

 

[Slant]

Hmm, I did not see Victory's response. Apparently I have to rethink how I fly this beast. Trimming is a bitch at the moment, though. I can barely stabilize the a/c.

Having thought about it some more: It doesn't make any sense to me still.

 

There are two ways I can engage the altitude hold, both have to meet the criterial of basically achieving level flight. Either I trim the a/c out and that should accomplish what Victory said, or I can be a dirty cheat and just hold the stick to achieve level flight. If I understand Victory correctly, the latter should result in a pitch movement the second I engage autopilot and let go of the stick, as the trim system can't keep up with making the correction that I require. Or does altitude hold use direct input and bypasses the trim system? Seems wrong to me, honestly. But I am not an engineer...

 

What's happening now is that altitude hold will hold the a/c in level flight no matter what, if I just meet the initial conditions. That should not work, if I understand this correctly.

Edited October 25, 2021 by Slant

[draconus]

As I understand (and read) all AP modes use auto-trimming but the servos are slow and cannot keep up with bigger changes of speed or aircraft config.

[Slant]

I understand.

What I'm seeing is that I can put an untrimmed a/c into level flight, engage the ap and it'll hold the a/c in level flight. When I disengage the ap, I get a massive pitch up or pitch down movement. Where is that coming from? If you think about what you said, the a/c should either be trimmed for whatever state it's in when coming out of ap, or it should fail to hold altitude altogether. It shouldn't hold altitude and then return to the untrimmed state it was in before engaging altitude hold.

I feel like I'm having a hard time explaining.

[draconus]

I thought the quote:

Quote

Known issue: the AP is currently slightly off and we are working to correct itl

would end the discussion. No need to explain further