Hello,I fly with AP on , when I switch AP off (mostly in final phase for manual landing) the aircraft stalls, some times it goes down very fast, very difficult to recover. I have this reaction with all aircrafts.Do you have the same?Any suggestion?Thanks in advance

Had the same experience with 2004 (and to some extent with 2002). I fly mostly the Baron, and would fly final at 95 Kts--more realistic than MS's 100Kts they recommend. But, at 95Kts.--also had a severe pitch-down when disengaging the autopilot. Found that keeping the final airspeed at the "Microsoft" recommended 100Kts. or above resulted in a perfectly trimmed aircraft at autopilot disengage-then reduce speed. You will also notice that at less than recommended final approach speed, the aircraft will not follow the glide slope, but will fall below by at least one dot, as if the autopilot is not putting in enough up elevator trim. This is the reason it pitches down upon dis-engagement. This is even more aggravated with the Lear45 and other high performance aircraft. MSFS final approach speeds are generally too high as compared with the real aircraft. For example--the Lear 45 routine approach speed (Final) is 115-125 Kts.--MSFS recommends 140 Kts. You can expect a severe pitch down at anything less than 140Kts. Trying to land the Lear at 140 Kts. is a real testy experience!!-it still wants to fly, and will!It must be the algorithms in the respective air files that require some compromises over the full performance range of the aircraft.Recommend keeping you final approach speed reasonally close to MSFS recommended. Then reduce airspeed. Try disengaging the AP a bit further out on final to give you time to adjust airspeed with power/trim to achieve a more realisic touch-down configuration. Hope this helps.

>Hello,>I fly with AP on , when I switch AP off (mostly in final phase>for manual landing) the aircraft stalls, some times it goes>down very fast, very difficult to recover. I have this>reaction with all aircrafts.>Do you have the same?>Any suggestion?>Thanks in advancePerhaps because you didn't trim properly before applying the a/p in the first place? I used to have this problem until I was shown that you must manually trim the aircraft BEFORE switching the a/p on, or else you're storing up problems for later. The reason is that MS chose to run the pitch command for the a/p from the trim, not the elevator! Crazy, but they did it.Allcott

Interesting, Allcott!Tried your tip by flying four coupled ILS approaches with varying final approach speeds. (100Kts.,95Kts.,90Kts.,&85Kts., in the Baron.)Before each approach, on downwind, the airplane was trimmed level, then AP turned on. All approaches were then flown with the AP.(Approach) When flying the approach at the lower final airspeeds (say 90Kts. in the Baron) your advice seemed to help, as the plane would dip below the GS for a bit, then trim up and come very close to the GS at about 150' AGL. In all cases, (even 85Kts.) there was no pitch change, or trim correction required, when the AP was de-coupled. There is something to this, "accumulated error" if the plane is not trimmed out correctly in the early phase of the flight before the AP is applied. So I am now trimming the plane out to the rate of climb set in the AP after T/O before coupling the AP. This seems to help somewhat after final approach AP decouple.ThanksBaron58tcP.S. Since (most)all GA aircraft have mechanical primary controls (i.e. cables or push rods/torque tubes), the AP controls the trim tabs, as they are electrically controlled, and therefore accessable to the AP.

Hello Allcott,Thanks for the suggestion, it works !

>>P.S. Since (most)all GA aircraft have mechanical primary>controls (i.e. cables or push rods/torque tubes), the AP>controls the trim tabs, as they are electrically controlled,>and therefore accessable to the AP.I'm not familiar with ALL types of autopilots for GA aircraft, but the types I do know, are connected to flight surfaces (elevator/ailerons) through mechanical linkages such as a rod from the A/P servo to an elevator or aileron bellcrank.Then----- the autopilot may be able to sense an out of trim situation in which it can control a trim tab; or it might just display an out of trim light; or have nothing to do with trim at all.Best advice is to be trimmed before engaging the autopilot, whether it be in climb, cruise, or descent. I always keep trimmed & have little trouble when disengaging the A/P.Edit --Now that I said all that............ how is the auto-pilot tied to a Piper PA-28 Archer? I attempted to look it up, but didn't find the answer.L.Adamson

When I am wrong, best to admit it and get on with life:I am wrong:LAdamson: You are right. Autopilots control (through servos) the primary flight controls. My belated research concentrated on GA aircraft--mostly manufacturers of AP's for experimental aircraft. All rcommended (insisted) on trim-out before engagement of the A/P. Sorry-no Piper Archer information.I am wrong:Allcott: You are right. MSFS uses trim only for the autopilot. On a coupled final approach (Baron), any airspeed less than 100Kts will cause the airplane to sink below the glide slope. Reason: The elevator trim tabs do not have enough elevator authority to maintain proper pitch attitude. (Obvious-as the the elevator trim is full nose up at this point, and has exerted all the elevator deflection possible.)I am right (in general): MSFS does not allow realistic (or low) final approach speeds because trim tab control cannot exert sufficient elevator deflection to maintain the glide slope, even if the aircraft is capable of doing so.Solution: None: The benefit of this thread, (started by Emile-thanks)and this forum in general is to learn more about the characteristics (eccentricities) of MSFS and understand how to cope with them. Sooo---keep the final airspeed up to MSFS specs, or decouple the AP and fly it yourself. (My choice)Thanks Emile, LAdamson, Allcott