Excessive pitch after AP disconnect

Hi,

Got Mike Stone's Rockwell Saberliner and have installed excellent Horst Paetzold panel. The aircraft with this panel is amazing, flies and handles great but when AP is disconnected, in particular from the approach hold, the aircraft pitches up and is difficult to level. I saw many old posts on this subject, but is there any new remedy to fix this jolt?

Any advise appreciated

Thanks,

Peter,

I do not know if this is a "new" remedy but have you trimmed out your Saberliner before you switch on it's AP ?

Does this plane handle correctly, e.g. directly after take off and during level flight without the AP being switched on ?

Regards

Hans

Peter,

 

I do not know if this is a "new" remedy but have you trimmed out your Saberliner before you switch on it's AP ?

Does this plane handle correctly, e.g. directly after take off and during level flight without the AP being switched on ?

 

Regards

 

Hans

If it's not trimmed before applying AP, then it deffo won't be when you disconnect.... ALWAYS check your trim first!

Thanks Hans.

I installed the trim gauge and the trim is OK before AP engagement. Also the plane hand flies great.

I found out that when I push the yoke down (key 8) just before the AP disconnect, the aircraft stays reasonably in level and does not pitch up. So there seems to be a remedy.

I also tried a different AP to no avail. I think that some tweaks in aircraft.cfg could fix this, did some straight forward adjustments in [flight_tuning] duplicating figures from aircraft which does not pitch up after AP disconnect to no avail.

Read someplace that it also might be a model issue.

Interesting stuff.

Cheers

Peter,

I became inquisitive as a result of your posting and downloaded the Sabreliner + the separate panel and it's update. Got it all flying .... and .... as you say, under manual control it flies very well indeed. Switching the normally functioning AP on and off, does not cause any of the pitching as you mention.

Also, when on any auto-captured ILS approach and taking over manually just befor landing, the plane does not misbehave in any way either.

I was testing this aircraft in it's basic form as downloaded and without any edits of my own but with a maximum 30% fuel load, more or less as is normal for landing.

I'm using a Saitek yolk with a separate throttle quadrant and pedals. My trimming is done via a tumbler switch on the yolk and could therefore be more exact than what I understand, happens via your key 8. I therefore do not need an extra "trimgauge" as you mention.

All in all, I find no real problems with this plane, nor with it's separately downloaded panel, nor with the combination of the two.

Good luck.

Hans

Many Thanks Hans for looking into this.

It probably has to do with my way of flying. As embarrassing as it sounds, and after 17 years with FS4, I still use the keyboard to fly. Can use it blindfolded by now:)

It is obvious that, in my case, the trimming is the issue but as mentioned, I can get around it.

I was amazed by the realism of the panel, great job by Horst.

Cheers,

The only thing I can now think of is that you decrease the "elevator trim" figure in the plane's "Flight tuning" section in it's aircraft.cfg file, especially if your problem is only with this plane and not with any of your others.

Again, good luck and regards.

Hans

Thanks Hans,

Have reduced the elevator_trim_effectiveness =0.400, and it helped, also noted that when I disconnect the speed hold prior to AP disconnect it helps.

Actually had this issue with few aircraft (have about 150 flyables), some hold the descent angle great after the AP disconnect and some not (dive or pitch up). It is definitely a trim issue and I should probably finally graduate to a more sophisticated setup.

Cheers,

Hi,

Have you checked the A/P settings in the Miscellaneous tab in FSUIPC?

There might be something there to remedy your problem.

Regards,

DDP.

Many Thanks for all your input gents but looks like Dirk (DDP) offered a solution, which helped:

In FSUIPC Miscellaneous section, I have checked the box at "Center elevator on AP alt change" and it did the trick.

The aircraft now flies nice and level after AP disconnect and also follows the glide path on AP disconnect from the ILS Approach hold.

As mentioned got 100s of flyables, so will check some more aircraft, but looks like this is a solution.

Further to below:

Centre elevator on AP Alt change makes FSUIPC centre (zero) the elevator input when the Autopilot ALT hold mode is

enabled or disabled. This is mainly of use for keyboard flyers, where the original keyboard-set value for the elevator is

retained, ineffectively, whilst the A/P controls the vertical modes, but which then undesirably re-asserts itself when the

A/P control is relinquished. This option is only displayed when running FS2004, where it is most needed.