feat(athr/fadec): improved reverse thrust limit based on TOGA limit

[aguther]

Fixes #7967

Summary of Changes

This PR introduces an improved reverse thrust limit instead of the constant 45% N1 in the past. Right now, the reverse thrust limit is calculated in a percentage of the TOGA limit.

Screenshots (if necessary)

References

Additional context

Testing instructions

• test reverse thrust in different situations and environmental conditions; expectation is that N1 from the shown N1 limit can be achieved
• test that no excessive negative speed can be achieved with reverse thrust

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, click on the bottom PR tab
4. Click on either flybywire-aircraft-a320-neo or flybywire-aircraft-a380-842 download link at the bottom of the page

[2hwk]

Needs testing instructions before QA is ready to go

[donstim]

From a technical standpoint, if QA does not discover any issues, this PR looks good to go for me. The effect of reverse thrust on stopping distance is provided in the QRH for wet runways (runway condition code 5 -- good). (Such data is not available for dry runways because credit for the effect of reverse thrust is not allowed for dry runways as an additional safety margin.) Unfortunately, MSFS does not correctly simulate the braking friction on a wet runway. However, I was able to do so by manipulating the toe brake scalar.

For max manual braking after CONF FULL landing at 66 T at EHAM 18R on a wet runway without the use of reverse thrust, the stopping distance derived from the QRH is 2748 ft. By manipulating the toe brake scalar combined with using the MSFS rain weather condition, I achieved a stopping distance with the A32NX of 2741 ft. With reverse thrust, the stopping distance derived from the QRH is 2617 ft. Using the reverse thrust in this PR, the tested average (of 2 runs) A32NX stopping distance on a simulated wet runway is 2605 ft.

The autobrake situation is a bit more complicated in terms of simulating accurate wet runway stopping distances in MSFS. However, the effect of reverse thrust on those distances using the reverse thrust level in this PR appears to match the data well. Although the QRH does not have a shorter runway distance with reverse thrust for either the medium or low autobrake setting, the FlySmart EFB shows about a 30 m (96 ft) shorter stopping distance with medium autobrakes for the test condition. If the wet runway braking capability was correctly represented in MSFS, my tests show about a 140 ft shorter distance for autobrakes medium with reverse thrust. No difference exists at the autobrake low setting since the autobrake low deceleration target can be achieved without the use of reverse thrust. This is correctly replicated in MSFS with this PR.

I highly recommend merging this PR.

[2hwk]

@aguther Just need instructions for testers and we can set this as ready to test

[noonebling]

Quality Assurance Trainee Report

Discord : noonebling
Object of testing: 8565
Tier of Testing : 1
Date : 07/04/2024

Testing Process:
Tested reverse thrust in different situations and environmental conditions.

Negatives:
N/A

Testing Results:
Passed

Conclusions:
Works as expected

[2hwk]

QA pass label removed due to some late changes that require re-testing, also would like to see more QA trainees be able to run through this one while we wait for some large PR merges.

[donstim]

QA pass label removed due to some late changes that require re-testing, also would like to see more QA trainees be able to run through this one while we wait for some large PR merges.

What else is needed now to merge this?

[aguther]

From my side it's ready to go after a short test.