feat(a380x/fctl): add flare law pitch up compensation

[lukecologne]

Fixes #10912
Fixes #10828

Summary of Changes

This PR adds the flare law pitch up compensation due to ground spoilers. A nose down command proportional to the ground spoiler command angle is introduced, up to 10° of nose down command at full deployment. This ensures a smooth derotation.

Also fix an incorrect input to the alternate law, where AOA was used instead of mach, leading to permanent nose down. The alternate law should now be properly usable.

Furthermore, a flawed alternate law reversion condition was fixed, where the alternate law would only revert if exactly one or two elevators, exactly 2 ailerons or exactly one rudder were failed. Now the law also reverts if more surfaces are failed. This was one part of the erroneous FD disengagement at hydraulic power available (i.e. during engine start), so this specific issue should be fixed. But there is still a problem with FD disengagement during law reversion, which should not occur. This issue is to be fixed in another PR.

Example for a manual landing where the pitch up compensation is visible: https://streamable.com/p1cj49

Cockpit API Changes

Screenshots (if necessary)

References

Additional context

Discord username (if different from GitHub):

Testing instructions

Check that during manual landings, the elevators introduce a nose down command during ground spoiler deployment.
Check that the alternate law reversion properly works, and that the alternate law no longer introduces a constant nose down command.

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

[Saschl]

Dev team QA report

Discord Username : saschl
Object of testing : #10902
Aircraft : A380X
Simulator : 2024
Tier of Testing : 1
Date : 24/08/2026

Testing Process:
Performed a few manual landings and verified no pitch up happens after spoiler deployment.

Notes:
Backpressure is needed to avoid the nose to slam into the ground. Pilots need to check whether the amount of backpressure is expected.

Media:

Microsoft.Flight.Simulator.2024.2026-08-24.00-09-03.-.Trim.mp4

landing.mp4

Testing Results:
Passed

[donstim]

I flew a number of manual landings with both full flaps and CONF 3. Also tried it in combination with #10851 and I like the compensation for the pitch-up due to ground spoiler deployment.