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#2551445 - 07/16/08 12:09 AM FSX autopilot and altitude hold.
Powerwise Offline
Member

Registered: 01/26/08
Posts: 139
Loc: Northern Ontario, Canada
So, I started out on an IFR flight from my hometown to a city an hour east of here. I was instructed to climb to and maintain 5000 feet. My autopilot worked fine, climbing me up to 5000 feet at a VS of 400. The Cessna then levelled out at 5000, after which I turned to intercept the VOR heading.

But then my autopilot stopped working so well. It will no longer maintain altitude, or even fly my assigned VS. It's as if, for some reason, I'm just manually pitching the aircraft up and down, without the altitude functions of my autopilot. I looked for some kind of "center trim" function in the controls, but couldn't find anything. I also centered the trim on my joystick, but unfortunately my plane decided to take a nosedive, prompting ATC to start #%&*$#. Is it something I did with my joystick/trim that is affecting my autopilot? Is there some type of procedure to get the autopilot functioning again?

Thanks alot,

me.

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#2566031 - 08/11/08 01:56 AM Re: FSX autopilot and altitude hold. [Re: Powerwise]
Powerwise Offline
Member

Registered: 01/26/08
Posts: 139
Loc: Northern Ontario, Canada
Hmm, I quite possibly did not phrase my question too well, in which case I apologize :P.But since this problem is still plaguing me, I guess I'll give it another try.

So I'm flying my plane manually right now at my assigned altitude (5000 feet). I punch in an altitude of 5000 feet into my autopilot, and activate the AP and the altitude hold functions. But my plane will not stay at altitude, instead relying only on my elevator trim inputs. It's just like flying manually, attempting to trim up and down just perfectly (next to impossible). It's not just regular oscillations that take place under AP's flight envelope, it's raw trim and will continue either up or down just as if under manual flight.


I guess I just don't understand the pitch well enough. Should I centre my trim before going into autopilot? If I do that, I lose the trim that was keeping me level. Arrrghh. It's probably something stupid (very stupid) I'm missing but in weeks of flying I haven't figured it out yet.

If anybody has any input at all, it would be much appreciated.

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#2566034 - 08/11/08 02:30 AM Re: FSX autopilot and altitude hold. [Re: Powerwise]
Rick.50cal Offline

Lifer

Registered: 10/25/99
Posts: 21415
 Originally Posted By: Powerwise
Hmm, I quite possibly did not phrase my question too well, in which case I apologize :P.But since this problem is still plaguing me, I guess I'll give it another try.

So I'm flying my plane manually right now at my assigned altitude (5000 feet). I punch in an altitude of 5000 feet into my autopilot, and activate the AP and the altitude hold functions. But my plane will not stay at altitude, instead relying only on my elevator trim inputs. It's just like flying manually, attempting to trim up and down just perfectly (next to impossible). It's not just regular oscillations that take place under AP's flight envelope, it's raw trim and will continue either up or down just as if under manual flight.


I guess I just don't understand the pitch well enough. Should I centre my trim before going into autopilot? If I do that, I lose the trim that was keeping me level. Arrrghh. It's probably something stupid (very stupid) I'm missing but in weeks of flying I haven't figured it out yet.

If anybody has any input at all, it would be much appreciated.


What's your airspeed? If you are flying in level flight that's approaching "clean stall speed", then your AP won't be able to do much. At 5000 feet, you may have to have either less than maximum weight, and also have the air/fuel mixture changed from sea level, to get the airspeed required.

Now, you shouldn't need to center the trim before turning on the AP, although it doesn't hurt, and probably would in fact help make the transition a little smoother... but the AP "flies" the plane using the trim functions anyway, so if your plane is already trimmed when you turn on the AP, the change should be minimal.

That said, I wonder if the problem/solution is much simpler than that: make SURE you not only have the AP actually activated(left-most button "AP"), but then actually activate the "Altitude Hold" on the AP too (right-most bottom button "ALT"), as it's not on by default.


Edited by Rick.50cal (08/11/08 02:33 AM)
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#2566054 - 08/11/08 05:37 AM Re: FSX autopilot and altitude hold. [Re: Rick.50cal]
eonel Offline
Member

Registered: 12/12/01
Posts: 453
Loc: Zurich, Switzerland
I have had the same problem on occassion. Uncontrollable nose pitching up & down until you breech maximum speed & crash. All with the autopilot turned on & behaving normally for the last hour.

I was thinking the problem was related to ActiveSkyX. It started happening when I downloaded the latest Service Pack for ActiveSkyX. My thinking was ActiveSkyX could be changing air pressure/wind too rapidly and the autopilot was trying to adjust for that.

But it happens so infrequently & I have no evidence that it is ActiveSkyX. Would be interested if you're also using ActiveSkyX.

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#2566464 - 08/11/08 06:34 PM Re: FSX autopilot and altitude hold. [Re: eonel]
Powerwise Offline
Member

Registered: 01/26/08
Posts: 139
Loc: Northern Ontario, Canada
I am actually using ActiveSkyX, as a matter of fact.

Rick.50cal: Even if I set the AP to 2000 feet or so, or adjust my fuel-air mixture perfectly (or using automixture) I have the same problem. I'm wondering if maybe it's a problem with the X-52 or something.

ETA (actually this isn't edited because I haven't even posted yet!): The autopilot did the same thing in FS9, but then started working. Blah. I think I'm just going to try and reinstall the whole shebang.

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