Autopilot Acted Up last night (CIV)

[PonyDriver]

For some reason, about half way through my flight in the CIV Mustang, the autopilot started acting up. All of the sudden, while holding altitude, the nose of the plane went UP-and-DOWN, Over and over...kind of like in some wave pattern or something. I looked down and saw the elevator trim wheel turning forward and back...all by itself. Disconnecting the autopilot stopped the sickening ride, but it came right back after I turned it back on.

Only thing I could think that caused it...too much fuel in FUS tank? But I was actually burning fuel FROM that tank..

Hmmm

[NL451MG]

What weather were you using? What were your framerates? Any other programs using SimConnect? Those are usually what mess with the autopilots on my aircraft.

[robert41]

I get this with a heavy load of fuel in the aft tank. It calms down after burning the fuel down.

[Lewis - A2A]

Yes this is correct as the fuel burns, you will have to be careful due to the known instability with certain fuel loads. The issue can be affected by external factors of course too such as turbulence and weather which would hinder an off balance aircraft too.

thanks,
Lewis

[NL451MG]

I never would have thought fuel, but I always burn the wing tanks before the fuselage though.

[EnDSchultz]

I never would have thought fuel, but I always burn the wing tanks before the fuselage though.

That's probably your issue. A full fuselage tank puts the aircraft's center of gravity way aft, so much that the plane is on the verge of instability. This results in oscillations in the autopilot when trying to hold altitude. Always burn the fuselage tank first, and in the mean time, it seems like pitch hold does not suffer from the oscillation problem, so you can use that mode to more or less hold altitude while the fuselage tank burns.

[NL451MG]

I never would have thought fuel, but I always burn the wing tanks before the fuselage though.

That's probably your issue. A full fuselage tank puts the aircraft's center of gravity way aft, so much that the plane is on the verge of instability. This results in oscillations in the autopilot when trying to hold altitude. Always burn the fuselage tank first, and in the mean time, it seems like pitch hold does not suffer from the oscillation problem, so you can use that mode to more or less hold altitude while the fuselage tank burns.

'I'm not the OP lol. Nor have I had any issues with stability while burning the wing tanks first. Either way, I usually save the fuselage tank for my approaches and landings. Fuel flows into the left tank first (I can't remember the reason why) at roughly 10 gallons per hour, so you want to use left first. But that's on the real P-51s.

[EnDSchultz]

I'm not the OP lol. Nor have I had any issues with stability while burning the wing tanks first. Either way, I usually save the fuselage tank for my approaches and landings. Fuel flows into the left tank first (I can't remember the reason why) at roughly 10 gallons per hour, so you want to use left first. But that's on the real P-51s.

Ahaha...I'll just be over here with my foot in my mouth.

[NL451MG]

Ahaha...I'll just be over here with my foot in my mouth.

Lol. It happens to all of us at least once.

[Tomas Linnet]

and don't forget to switch to the left tank once in while as the A2A P51-D also(of course) return some fuel to the left wing tank.

[NL451MG]

and don't forget to switch to the left tank once in while as the A2A P51-D also(of course) return some fuel to the left wing tank.

Yep. Left is always the first one I burn, then I switch to the right and keep that going to keep them balanced or until almost empty. Then I use the fuselage tank.

[Alan_A]

You guys sure you want to burn the wing tanks before the fuselage tank? Read this thread, then decide.

[Lewis - A2A]

Yes you should be burning the fuse tank first to keep stability with the aircraft, it'll help your flying no end. During the war many pilots still burned the fuse and drop tanks first switching between them, sacrificing some range but increasing flight stability should they find a fight. The Mustang isnt the best to try and dogfight in when shes got a full load in the fuse.

thanks,
Lewis