The FS9 autopilot uses "trim" to hold an altitude as well as for climbs and descends. Real-world pilots tell me that this is not the way autopilots work on real-world aircraft.Because of this, one of the problems I have with FS9 when I disengage the A/P is that the aircraft jumps up or down, sometimes on short final, which is not very nice. In a real-world aircraft, once you trim your aircraft, it will remain trimmed, and the autopilot will not un-trim your plane, so when you disengage your A/P, you plane continues to fly smoothly without jumping up or down, climbing or descending unexpectedly.Is there a way to make FS9 not use trim to control the autopilot? How do other FS9 simmers maintain their aircraft flying smoothly when they disconnect the A/P on final approach--when I disconnect the A/P, my aircraft usually goes into a climb or descend instead of continuing on a smooth flight path like the real-world airplanes?Thank you in advance,Kerke

It is a glitch that MS should really resolve as it defeats the object of trim, but the effect is lessened if you are in trim BEFORE you engage the AP. But there is no alternative.I disengage the AP before short finals to ensure I can manually correct trim before touchdown and on the bigger stuff I will switch the a/p off once landing configuration has been achieved and stabilised, but then in my GA flying I have only rarely had the use of autopilots and I'm used to hand-flying!Allcott

Here is a report that contains your scenerio in real aircraft:http://www.ntsb.gov/ntsb/brief.asp?ev_id=2...207X04942&key=1If I recall the piper malibu had lots of troubles with trim when disconecting the autopilot.Suggest you do a google search on "autopilot trim".Both of the autopilots on my planes-an stec 50 on my debonair, and a century on my Baron-require the plane to be trimmed before engaging the autopilot. The stec-will even "tell" you after you have engaged altitude hold when an out of trim condition occurs-but you have to manually trim the out of balance condition yourself.http://mywebpages.comcast.net/geofa/pages/rxp-pilot.jpg

On the 727, pitch autopilot controls both the elevator position and also drives the auotpilot/cruise stabilizer trim motor. There is a problem in FS when trim is assigned to an axis. I think the latest FSUIPC (pay version) has a corrective for this.scott s..

The use of the Stec-50 in FS9 causes the elevator trim to act like an STEC 60-2 with the auto trim feature. I think this is confusing the RealityXP stec-50. Is there a way to edit the aircraft.cfg to disable the default elevator auto trim?Also is there a way to shut of the RealityXP Stec-50 with the keyboard Z key (on short final I don't want to be using the mouse to shut off the red switch or push the on/off switch on the face of the stec-50).Comancheguru

Class A a/c (i.e. a/c with variable incidence tailplanes) autopilots actually change and maintain attitude with trim not elevator actuators. For this reason they employ a synchroniser that re-trims the aircraft when you select and deselect the A/P to prevent control ######. The A/P will not engage if this system is not functioning and will trip out if it fails.Autoland systems also re-trim the a/c to start the flare at 50', again the elevator is actuated. It would be bad practice to select A/P to re-trim for two reasons: 1) Re-triming in RL is 10000000 times easier than in FS so is not an issue 2) Switching A/P on and off would cause extra wear and tear.

If you'd like an FS aircraft with an autopilot that works correctly using control surface inputs, look no further than the PMDG 737 - you can even see the yoke move in the VC when the AP is on.