With various planes, I think all of a recip prop design I am occasionally getting a strange stall if in fact that is actually what is happening. This may have happened with a jet or turbojet, but this old memory does not remember it. It doesn't happen often enough (yet at least) to be a big problem, but I would like to know what is causing it.For example, climbing out from takeoff with a rate of climb of only 500 FPM, Normal climb IAS, full power, flaps and gear retracted, when I reach 3,000 to 4,000 feet on autopilot I get a drastic descent. I can look in spot view and see that the plane is in a little more than a normal nose up attitude when this occurs and see the cycle begin. The plane will recover after loosing altitude and begin the climb again like a normal reaction after a stall, but will overshoot the autopilot rate of climb setting and go into a stall/recovery cycle over and over again until a final crash occurs.The strangest item when this occurs which makes me wonder if it is a legitimate stall or may be something else happening, is that the moment she breaks and the descent begins, MP and RPM look like somebody cut the throttle and then through recovery they increase back up to set ratings. (No speed control on the autopilots in question).I think this happened at least once on careful manual climb with the autopilot deactivated, but have not been able to duplicate it again. I have been able to disable the autopilot and recover manually with what may or may not have been this one exception. (Old memory again)When I restart FS9 and try to exactly duplicate the flight conditions, everything is fine and works flawlessly.Has anybody else seen this animal and/or have any idea what causes it?Thanks:RTH

Update:For what it might be worth, I now turn fsmeteo off before beginning a final approach. Since I have done this, I have not had the problem described in the original post happen again. This makes little difference to anything weatherwize as current conditions are retained, and there is little probability that there would be significant change in the ten to fifteen mins. the approach will add.For anyone implementing third party weather, I would suggest giving this a try if you are seeing this problem occur. MSFS originated weather may do the same thing, I don't know; but I am not sure there is a way to retain your current weather conditions without leaving it on. Time will tell if this was the problem, but again, this seems to be the solution thus far (for me at any rate).Good luck and happy flying:RTH

You might check your aircraft.cfg file under [Autopilot] VS and set your VS speed to 700fpm or so. Also check your .air file, it may have the same statement to change. I think sometimes that setting tries to over- ride the trim adjustment that you set manually in autopilot.John

>Update:>>For what it might be worth, I now turn fsmeteo off before>beginning a final approach. Since I have done this, I have not>had the problem described in the original post happen again.>This makes little difference to anything weatherwize as>current conditions are retained, and there is little>probability that there would be significant change in the ten>to fifteen mins. the approach will add.Maybe it's related to icing. Have you tried turning anti-ice and pitot heat on?Marco