Altitude Hold

[Wiganlad]

Installed the Piper Comanche 250 into Prepar3D V4, up and flying ok, just a issue with the Alt hold, when engaged the airplane nose drops ( 2000-2500'/pm) and then starts oscillating but takes awhile to settle down.

I7 4770 4.4o/c
gpu 980ti
W7

[alan CXA651]

Hi.
Check your trimmed out prior to engaugeing , to see if thats the fault.
regards alan.

[Lewis - A2A]

Yes, check you are all trimmed out as best you can prior to engaging otherwise you will be chasing the beeps all over the sky.

thanks,
Lewis

[Wiganlad]

Thanks for your reply Lewis., had another try, disconnected the Saitek trim wheel, abit better, just noticed the overhead trim adjuster is not aligning I'm seeing a -% when the marker is in the up band.
bob

[mallcott]

Thanks for your reply Lewis., had another try, disconnected the Saitek trim wheel, abit better, just noticed the overhead trim adjuster is not aligning I'm seeing a -% when the marker is in the up band.
bob

It is what it is, lots of old aircraft have had trim adjusted, weights added and removed and just plain old wear and tear so that zero no longer means zero.

The important thing is to trim the aircraft manually before applying the autopilot and, on a long flight where the CofG may change as a result of fuel burn, disable the a/p on a regular basis and re-trim before re-applying.

[Wiganlad]

Done quite a few flights, although have been very careful in setting the trim before setting Alt hold, still getting a nose dive down to 2000ft/m and more.
have altered a couple setting in the aircraft.cfg file , elevator trim effectiveness and limits and now getting a reasonable set on the alt hold.

[Oracle427]

Bad idea to edit the cfg file. The A2A sim engine does not use the .cfg file the same way that a standard P3D model does. There may be all sorts of unintended consequences.

It would be better to try and eliminate components interfering with the normal behavior of the sim.

If you have a custom weather engine you should try turning that off to see if there is a difference.
You will also need to try loading the sim with a stock aircraft such as the F22 and then changing over to the Comanche once in sim. Launching right into the Comanche, or any other complex add-on for that matter, can cause all sorts of handling issues.

It is also important to check that the aircraft is in good condition in the maintenance hangar.

Lastly, I wonder if there is operator error with the autopilot. How are you confirming that you have actually engaged alt hold mode on the STEC?

[Wiganlad]

Bad idea to edit the cfg file. The A2A sim engine does not use the .cfg file the same way that a standard P3D model does. There may be all sorts of unintended consequences.

It would be better to try and eliminate components interfering with the normal behavior of the sim.

If you have a custom weather engine you should try turning that off to see if there is a difference.
You will also need to try loading the sim with a stock aircraft such as the F22 and then changing over to the Comanche once in sim. Launching right into the Comanche, or any other complex add-on for that matter, can cause all sorts of handling issues.

It is also important to check that the aircraft is in good condition in the maintenance hangar.

Lastly, I wonder if there is operator error with the autopilot. How are you confirming that you have actually engaged alt hold mode on the STEC?

I will revert back and try your suggestion with loading the F22 first.
its in good shape in the hanger.
the alt hold id light is showing

[Wiganlad]

Bad idea to edit the cfg file. The A2A sim engine does not use the .cfg file the same way that a standard P3D model does. There may be all sorts of unintended consequences.

It would be better to try and eliminate components interfering with the normal behavior of the sim.

If you have a custom weather engine you should try turning that off to see if there is a difference.
You will also need to try loading the sim with a stock aircraft such as the F22 and then changing over to the Comanche once in sim. Launching right into the Comanche, or any other complex add-on for that matter, can cause all sorts of handling issues.

It is also important to check that the aircraft is in good condition in the maintenance hangar.

Lastly, I wonder if there is operator error with the autopilot. How are you confirming that you have actually engaged alt hold mode on the STEC?

Yes that did it, loading the F22 first, thanks for the advice, only dropped about 150' and then held the altitude.

[Oracle427]

Some of the issues can be subtle when starting with a complex aircraft instead of a stock aircraft. I found that the C172 sometimes becomes very pitch sensitive if started directly in a default flight.

Enjoy!

[Lewis - A2A]

Yes initialisation issues occur when using complex simulations as default aircraft. Its why we always recommend against this unpredictable practice, that will work fine for some and cause issues and frustration for others.

Oracle is also correct, the cfg settings are set to tie in with our Accu-sim simulation engine running external to the main platform and creating the realistic simulation experience based upon our own first hand test flight programs.

thanks,
Lewis