Aircraft Ossilating up and down while crusing

[michaelb15]

I just downloaded Tom Ruths AMAZINGLY well modeled Airbus A300, and I took it out for a nice long range flight From Heathrow, to Kennedy Intl.

Because it was such a long flight, and the long flight was pushing the range limits of the A300, I was crusing at only mach .65, at fl 380, in order to conserve as much fuel as possible.

Well anyway, it started crusing fine, for the first few hours everything was perfect. But then once the fuel started dipping below 40% or 40,000 lbs the plane started ossilating up and down between 37,700 feet, and 38,300 feet. I tried taking off the autopilot, and leveling out at fl 380, and then turn it back on, and within seconds it was back to the ossilations.

It seems that the trim is over sensitive, and because its so sensitive, the autopilot was majorly overcorrecting.

Is there any ways I can fix this? Its a reallly beautiful aircraft otherwise.. like realllly beautiful.. it gives Payware a run for the money. (no pun intended)

This is a borrowed SS showing just how amazing the virtual cockpit is.. (its Tom ruths' 717, but the A300 is just as well modeled, if not better)

[Knick]

aircraft.cfg file.

I think it should mention something like trim effectiveness.

It's in the same section as aileron effectiveness and rudder effectiveness.

Lower the value.


Edit: Of course make a back up of the original before you do anything

[mfaulisi]

Are you speeding up the sim rate?  I had that issue with one of my planes, but only if I sped up the rate.  Once I put it at real time it was fine again.

[michaelb15]

Ok I will try that cfg edit..

I am not speeding up sim rate. Ive actually never tried that feature.. I like my long flights.. it makes the landings critical 

[Brett_Henderson]

Since it cruised stable until the fuel burned off.. I'd say it's a load problem.. ie.

[Dave71K]

I have had this exact same problem but with T Ruth a340 when flying long haul. Heathrow to Hong Kong for example.
The plane starts oscillating up and down with the vertical speed needle going all over the place.  I'm not aware of what causes it initially but once it starts it seems that the autopilot constantly tries to over compensate and gets it wrong.

The solution I have found is I have to disengage autopilot regain control and then manually adjust trim to get the aircraft into straight and level flight again. If you do not set the trim correctly manually the autopilot basically panics and starts going wild again and can't catch up. Once trim is set I can then normally reengage the autopilot with no problem.
I hope this helps!