Berserk Autopilot in F5 View

[Guest grognard4]

I apologize if this has been addressed before on this forum, but I searched and couldn't find a reference to it:When I turn on the autopilot with an altitude lock (only), and then switch to the F5 external view, invariably after a short time (usually under 30 seconds) the autopilot goes berserk. Usually it puts the plane in a steep dive. I have to turn off the autopilot to recover (if I haven't slammed into the ground first). The workaround is to always turn off the autopilot before switching to the external view, but that's easy to forget.Has anyone else experienced this, and is there a fix? I have flown Flight Unlimited 3 (with the Flight 2 scenery added) off and on for many years on two different PCs (the first with Windows 98, many years ago), and this has happened on both machines. My current PC is running Windows XP Pro with service pack 3.

[agtim 0]

Which plane are you using for that ? It must be plane dependent then when I tried it with the P51D - using autopilot by key a and Alt a the plane is stable even in F5 for far more than minutes.:-wave Andrehttp://forums.avsim.net/user_files/193441.jpg

[Guest grognard4]

Thanks for checking into it, Andre. I hadn't thought about it being aircraft-specific. I'm pretty sure it has happened with all aircraft, but now that you mention it, perhaps it has been more frequent with Flight 3 aircraft than with Flight 2 aircraft. It will happen very consistently with the the Mooney or Renegade, for instance.Rick

[Guest R_Driscoll]

If what you're seeing is increasing nose-up, followed by sudden violent bank to one side and corkscrew downwards motion, then what you're seeing is an autopilot-induced stall. This happens if the autopilot is engaged on a low power setting without autothrottle (i.e. setting an airspeed), and is a real-life effect. It has nothing to do with the external view, but to do with settings that the plane cannot maintain.What happens is that with altitude lock on but inadequate power, the autopilot increases angle of attack to maintain sufficient lift to keep the plane at the required level. Recipe for a stall, usually fatal at low altitude. To avoid, never use external view if your speed is not constant or increasing.I have flown the Mooney and Renegade often, and I believe the autopilot is working correctly within its limits. But from your description, this is the most likely explanation.Robert.

[Guest grognard4]

Thanks Robert. What you say makes sense, although it would seem that the effect would also occur while I was in an internal view, which has never been the case. Also, it has occured after long periods of level flight at high cruising speeds. Finally, I don't believe there has been "increasing nose up" before things get crazy. But hey, I'll experiment with it and see what happens!Rick

[Guest grognard4]

I ran some experiments, and found that the problem most often occurs after I have held down the joystick trigger (button 1 on my CH Fighterstick USB) to pan up or down while in the F5 external view. When I let go of the button and stick, the plane pitches violently up or down. When I switch to internal view, I find that the elevator trim indicator has started moving rapidly toward full-down or full-up. I can only gain control by turning off the autopilot and hand-trimming the aircraft back to a "normal" trim range.At no time did I press the backspace key to invoke auto-trim. I did not switch to external view until the aircraft was trimmed out straight and level with the RPMs near the "top of the green". The problem has never occurred when the autopilot is off, no matter how much I pan up, down, or sideways. Weather settings make no difference. The problem is not aircraft-specific. My latest experiments were conducted using the Piper Arrow as well as the Mooney.The problem can't be with the joystick, because the same problem occurred many years ago while I was using an analog Thrustmaster control system.