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Aircraft stalling under autopilot at altitude >20,000ft

DavidRS Guest

Hi,

I hope someone can help me with an issue I've been having for a while. Often when I'm flying on autopilot at FL230 or higher, the aircraft will suddenly pitch up and then stall. Sometimes I will catch it but the only way to recover is disengage AP and manually fly but it feels like the trim is set in such a way that the aircraft pitches up and to maintain level flight I have to have the stick pushed forward almost to its limits. Sometimes I can't save the flight and will go into an aerodynamic stall and that's it. Not even pitching down and increasing throttle saves the aircraft.

I have tried various things like the trim and requesting lower altitudes and making sure the pitot heat is on but nothing seems to stop it. There doesn't seem to be any pattern to it and it affects all aircraft if in AP mode. The problem is really irritating and I can't enjoy long distance flights (at least not if cruise altitude is over FL230). I have the realism setting quite high and crash detection and aircraft stress on as well. I'd rather not reduce the realism as that somewhat takes away the enjoyment but if that what it takes then so be it.

Pro Member First Officer
lionlicker First Officer

Which aircraft is this? What is it's practical cruise ceiling? Are you using autothrottle. Are you thinning the mixture correctly?

DavidRS Guest

It occurs on all commercial airliners regardless of manufacturer so cruise ceiling will vary but the problem starts usually at FL230-FL250 so well within limits. By this point I will have probably switched to autothrottle and I try to keep the rate of climb at 1900-2100ft/min.

Pro Member First Officer
lionlicker First Officer

This may have occurred because some aspects of the autopilot are enabled and others are not. The fpm varies from sea level up to cruise level. Typical jets may start with 3500 fpm at sea level and by the time they reach 36000 ft they can only manage about 1000 fpm.

DavidRS Guest

Lionlicker - many thanks for the tip. I'll give that a go and ignore the ATC instructions to hurry up and get to altitude!

Pro Member Trainee
Gary (garyv440) Trainee

Having this same issue whenever I activate the master AP switch for any model plane..lately I have been trying to get the 737 AP to work…...it almost seems its reversed  as when I turn it  on,   the plane is uncontrollable, and off I  can fly smoothly…any tips?  

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