fix(a380x/flight model): Fix stall and auto rotate issues

[donstim]

Fixes #9269

Summary of Changes

1. Increases elevator authority and reduces pitch-up from engine thrust to : a) allow the envelope protection system to perform its intended function of preventing the airplane from stalling and b) allow the pilot to pitch the nose down for recovery.
2. Decreases the effectiveness of the trim system at takeoff speed conditions to prevent auto-rotation
3. Adjusts stable condition pitch angles to better match available data

Screenshots (if necessary)

References

Pitch angles and N1.zip

Additional context

Example takeoff showing no autorotation and stall prevention/recovery capability:
https://1drv.ms/v/s!Ajsy7Ey4_8uFgZZ7YVz0k8S3PINZ4Q?e=bjlT6m

Discord username (if different from GitHub): donbikes

Testing instructions

1. Test takeoffs at high, low, and medium weights with pitch trim properly set and takeoff speeds from SimBrief to verify no auto-rotation. (Note: At very low weights, the nosewheel may become unweighted just before Vr.)
2. Test going to high pitch angles/low speeds in all configurations to verify that stall is prevented and verify that recovery can be made by reducing the pitch angle by use of the elevator.
3. Test landings at low, medium, and high weights to verify that the THS does not reach its upward limit (10 degrees) during the approach/landing.

How to download the PR for QA

Every new commit to this PR will cause new A32NX and A380X artifacts to be created, built, and uploaded.

1. Make sure you are signed in to GitHub
2. Click on the Checks tab on the PR
3. On the left side, find and click on the PR Build tab
4. Click on either flybywire-aircraft-a320-neo or flybywire-aircraft-a380-842 download link at the bottom of the page

meant to hit request changes

[2hwk]

See changelog.md

[Saschl]

Quality Assurance Report

Discord Username : saschl
Aircraft : A380X
Tier of Testing : 2
Date : 04/11/2024

Testing Process:

Full flight EDDB - EGLL

• Takeoff and observe nose wheel. Could not observe premature lifting of nosewheel.
• Pitched up after takeoff and could always recover
• Triggered A/FLOOR situation and could recover
• Checked pitch angles during normal flight, seemed reasonable to me

Negatives:
N/A, great job!

Testing Results:
Passed

[outermarkerXXVII]

Have you checked the THS during approach and landing? I did a few landings at 360 tons, 35%CG and landed with a THS of ~3% so nearly FULL UP trim.

[donstim]

Have you checked the THS during approach and landing? I did a few landings at 360 tons, 35%CG and landed with a THS of ~3% so nearly FULL UP trim.

Thanks for the report. This will be fixed.

[aadee9940]

So i was testing this out yesterday, did a few stalls and from that point of view everything was good. But then when i transitioned to normal flight, autothrottle just did not respond.

I had autothrottle on, ap1 was not engaged. I selected speed 220 and put the levers into clb.

I was at 240 knots and expected the engines to drop thrust so i can slow down, instead what happens is as soon as I put the levers into clb, the engines go into toga regardless of what the speed target is.

The only way to get out of this is was to disconnect autothrottle completely.

[flogross89]

@aadee9940 Thanks for the test. ATHR should not be affected by this PR. Just to confirm, you were in selected speed mode? What did the left column of the FMA show? Should show SPEED and not THR CLB or A FLOOR.

[aadee9940]

@flogross89 hi, i loaded it up today with a clean install, seems like the issue is gone. Yesterday, the fma was refusing to show speed, it was stuck on thr clb. I tried it today again, and speed mode engages fine. Even with just athr and no ap1

Thank you.