MD-80s, MD-90 Development

Everything in connection with developing aircraft for FlightGear
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IAHM-COL
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Re: MD-80s, MD-90 Development

Postby IAHM-COL » Sun Sep 18, 2016 3:30 pm

I think I'll test.
So many 4 letter acronyms get my brain a hickup :P

For what I read above, I say MD82 or MD88 (I like analog navigation)
https://raw.githubusercontent.com/IAHM-COL/gpg-pubkey/master/pubkey.asc

R.M.S.
If we gave everybody in the World free software today, but we failed to teach them about the four freedoms, five years from now, would they still have it?

Octal450
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Re: MD-80s, MD-90 Development

Postby Octal450 » Sun Sep 18, 2016 3:37 pm

All can analog navigate, just switch the dial to the left of the pilots seat to "VOR"

Octal450
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Re: MD-80s, MD-90 Development

Postby Octal450 » Sun Oct 02, 2016 4:04 am

Upgraded EFD MD-90 cockpit has been removed since I can't find enough information to replicate it realistically.

KL-666
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Re: MD-80s, MD-90 Development

Postby KL-666 » Sun Oct 02, 2016 4:37 pm

I tested the one with the steam gauges of course (82). It flew fine manually (did a little circuit, take off and land), and i saw all the instruments i need to fly and navigate. Beautiful plane.

Next i tried to do a normal flight at fl 340 with autopilot of course. There a problem occurred. After changing heading 10 degrees, the autopilot started to roll left-right all the time. Full aileron deflection in 2-3 seconds from the one side to the other, and back and forth all the time. And staying in it, never getting less in the rolls. Not really a way i like to fly for a long time.

Maybe the autopilot plays fine with the route manager, but manual heading inputs are not appreciated by the autopilot.

Kind regards, Vincent

Octal450
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Re: MD-80s, MD-90 Development

Postby Octal450 » Mon Oct 03, 2016 2:30 am

Thanks for the report. I've never had this problem, but I'll check it out.
The AP shouldn't be allowed to roll the aileron more than 0.5 each way. (max is 1.0).

Josh

Octal450
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Re: MD-80s, MD-90 Development

Postby Octal450 » Mon Oct 03, 2016 5:41 pm

@KL-666
I've tried to solve it, can you give it another try?

Thanks,
Josh

KL-666
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Joined: Mon Sep 28, 2015 8:42 am

Re: MD-80s, MD-90 Development

Postby KL-666 » Mon Oct 03, 2016 7:59 pm

Yes, now it gets in the same aileron oscillation, but with 50% aileron deflection.

You can try yourself:
- take the 82
- do nothing with route manager, just climb on manual AP inputs
- be sure to be above fl 300 (there i know for sure it happens)
- change heading 10-20 degrees

Then you have your aileron oscillation.

Kind regards, Vincent

Octal450
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Re: MD-80s, MD-90 Development

Postby Octal450 » Tue Oct 04, 2016 1:54 am

I did this, and it works fine to me.
It was always limited to 50%.
I don't see any terrible roll oscillation. Could you save your FGTAPE or make YT video?

Sure the aileron is not smoothest, due to the FDM having a slight yaw issue. New FDMs will come eventually.

Josh

KL-666
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Joined: Mon Sep 28, 2015 8:42 am

Re: MD-80s, MD-90 Development

Postby KL-666 » Thu Oct 06, 2016 12:30 pm

I think i found the answer for the oscillating autopilot for some, but not for others. Just read this thread:

As you've guessed, the autopilots oscillate more at low frame rates.

Typically, they will have been tuned on the aircraft developers own machine, and so will work best at whatever frame rate the author had. If you have a significantly lower frame rate, IIRC the autopilot ends up over-correcting, and so oscillates.

https://forum.flightgear.org/viewtopic.php?f=17&t=2974


So if the developer optimizes the autopilot for his 90 fps, and i come along with a meager 20-30 fps, then the autopilot will oscillate for me around the target bank. In bigger turns it has the time to slowly grow in amplitude, until the plane is totally out of control.

The best advise for developers would be to develop while using a low frame rate, so the autopilot works for everybody.

Kind regards, Vincent

Octal450
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Joined: Sun Oct 18, 2015 2:47 am

Re: MD-80s, MD-90 Development

Postby Octal450 » Thu Oct 06, 2016 4:18 pm

I test on my old PC with 15fps. Not the issue

You could be overspeeding. Keep in mind. The MD-80 has flaps up, then slats retract. In the analog cockpit, there is no indicator for slats (yet).


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