Trim Issues

[Cam]

JGregory, MJRHealth,

I have just done some more testing to try and get to the bottom of the Trim issue I reported for both  V1.6.3 and V1.6.4. To recap, Trim works great when AP is not engaged - the Trim gauge moves and the DataRef changes as it should. However, after Take-Off with a Nose High attitude (ie climbing to height), if I engage the AP the Trim gauge and DataRef stay where they were when AP was engaged and do not move until AP is disengaged.

The trick to duplicating the issue is to be in a nose-high position when AP is engaged (ie climb-out). If in level flight when AP is engaged, there will be no issues.

If the Trim was in a high nose-up position when AP is disengaged (but aircraft in level flight), the aircraft  jolts to a nose-up attitude. I ensured that I was using the correct les command for the trim switch and I ensured that no other switches had trim assigned.

I have taken some screen shots at various speeds and flap settings (with DataRef)Log.txt, which are attached along with the log (2 flights).

Any advice would be appreciated.

Thanks

Log.txt

[mjrhealth]

Im going to do another flight tomorrow , all went to poop, wouldnt capture ILS  GS was red, was in level flight disconnected to manually land nose went up but was trimmed for level flight, probably should of restarted after activation, Try again tomorrow. It may be something to do with the throttle latch as if you lock it before you drop flaps it wont let you, disengaging than re engaging wont fix it, second time i disengaged it flaps went to full as i think i had used flap lever trying to figure out what was  going on. Like I said tomorrow

[JGregory]

4 hours ago, Cam said:

I have just done some more testing to try and get to the bottom of the Trim issue I reported for both  V1.6.3 and V1.6.4. To recap, Trim works great when AP is not engaged - the Trim gauge moves and the DataRef changes as it should. However, after Take-Off with a Nose High attitude (ie climbing to height), if I engage the AP the Trim gauge and DataRef stay where they were when AP was engaged and do not move until AP is disengaged.

The trick to duplicating the issue is to be in a nose-high position when AP is engaged (ie climb-out). If in level flight when AP is engaged, there will be no issues.

If the Trim was in a high nose-up position when AP is disengaged (but aircraft in level flight), the aircraft  jolts to a nose-up attitude. I ensured that I was using the correct les command for the trim switch and I ensured that no other switches had trim assigned.

I have taken some screen shots at various speeds and flap settings (with DataRef)Log.txt, which are attached along with the log (2 flights).

Any advice would be appreciated.

Thanks

 

Your trim is indicating significant nose-up in ALL of these screenshots !  Try trimming for neutral prior to engaging the autopilot.

[Cam]

8 hours ago, JGregory said:

Your trim is indicating significant nose-up in ALL of these screenshots !  Try trimming for neutral prior to engaging the autopilot.

This is mainly an issue on climb-out. After takeoff I follow the FD bars and trim to the set climb speed. I then engage the AP. The trim position you see on the screen shots is where it is at for the trimmed climb speed. 
Are you suggesting that I should not trim for climb out speed and hold it manually till AP engagement? Seems counterintuitive. I have always flown the Saab this way and not had a problem till this version. 
Notwithstanding, you will see that the trim DataRef does not change at all in any of the screen shots. I would have thought that it would move when I used the AP VS mode to climb and descend. it appears locked at whatever position it was at when AP is engaged. 

cheers 

[JGregory]

43 minutes ago, Cam said:

This is mainly an issue on climb-out. After takeoff I follow the FD bars and trim to the set climb speed. I then engage the AP. The trim position you see on the screen shots is where it is at for the trimmed climb speed. 
Are you suggesting that I should not trim for climb out speed and hold it manually till AP engagement? Seems counterintuitive. I have always flown the Saab this way and not had a problem till this version. 
Notwithstanding, you will see that the trim DataRef does not change at all in any of the screen shots. I would have thought that it would move when I used the AP VS mode to climb and descend. it appears locked at whatever position it was at when AP is engaged. 

cheers 

Why is the trim at max up in the first picture with A/P disengaged?  Did you move the trim to that position before takeoff?  

We do not manipulate the ap and trim interaction in any way.  If it is different from 1.5 then it might be changes that Austin or Philipp have introduced over the last couple of years.  However, since most users are not reporting this I tend to think there is something else going on here.

Edited March 31, 2021 by JGregory

[Cam]

24 minutes ago, JGregory said:

Why is the trim at max up in the first picture with A/P disengaged?  Did you move the trim to that position before takeoff?  

We do not manipulate the ap and trim interaction in any way.  If it is different from 1.5 then it might be changes that Austin or Philipp have introduced over the last couple of years.  However, since most users are not reporting this I tend to think there is something else going on here.

I set the trim for takeoff to 1.5. I then retrim on climb out, after accelerating,  to maintain my climb speed. I then engage the AP and the trim does not move from there.

I thought the trim DataRef and gauge would change during AP operation as weight and CoG changed. I manually changed the CoG from one extreme to the other and there was no change in either the gauge or DataRef. My recollection is that the trim gauge moved as the AP retrimmed to account for CoG changes during flight. 

[sirtopper]

I can confirm there is something not right with elevator trim indicator and dataref when the autopilot has control. They do not alter at all while the autopilot has control. When you then disconnect the autopilot because the trim is not synced up with the autopilot trim setting there is sudden jump in aircraft pitch as it adjusts to elevator pitch trim reading. 

[Cam]

44 minutes ago, sirtopper said:

I can confirm there is something not right with elevator trim indicator and dataref when the autopilot has control. They do not alter at all while the autopilot has control. When you then disconnect the autopilot because the trim is not synced up with the autopilot trim setting there is sudden jump in aircraft pitch as it adjusts to elevator pitch trim reading. 

Thank you sirtopper. 

[JGregory]

OK guys, I think I found the problem.  Should be a fix in the next update

Edited April 1, 2021 by JGregory

[mjrhealth]

38 minutes ago, JGregory said:

OK guys, I think I found the problem.  Should be a fix on the next update

Cool it wasnt us.

[iGoApp]

Cool it wasn't iGoDispatch. 

[mjrhealth]

31 minutes ago, mjrhealth said:

Cool it wasnt us.

Was doing flight and watching trim which wasnt changing, trying to get screenshots, glad  its sorted

[Cam]

1 hour ago, mjrhealth said:

Was doing flight and watching trim which wasnt changing, trying to get screenshots, glad  its sorted

Thanks for the input guys. 

[Cam]

1 hour ago, iGoApp said:

Cool it wasn't iGoDispatch. 

Nope. Your app is great. 

[mjrhealth]

Funny thing after last update broke ils, and a few other things,  deleted folder completely and reinstalled, behaved itself, but AP trim still not showing, though that round didnt get the nose up on AP disconnect

[Cam]

23 minutes ago, mjrhealth said:

Funny thing after last update broke ils, and a few other things,  deleted folder completely and reinstalled, behaved itself, but AP trim still not showing, though that round didnt get the nose up on AP disconnect

It appears to depend on your trim setting on AP engagement. If your straight and level it would likely be fine, but trimmed for a 140kt climb and then engaging AP will lock the trim in a high nose-up position and give you grief when you disengage AP. Anyway, looks like a problem has been found so that’s good. 
I might try what you did with the directory as I sometimes overshoot VOR/LOC capture. 

Edited April 1, 2021 by Cam