[Engines/EWD] - Negative Thrust limit value when toggling reverse thrust

[BravoMike99]

Aircraft Version

Experimental

Build info

{
    "built": "2023-04-14T14:28:11+00:00",
    "ref": "refs/heads/experimental",
    "sha": "49faa5cb317e1fa71bfa29cd18157dd2735b733c",
    "actor": "2hwk",
    "event_name": "manual",
    "pretty_release_name": "experimental:49faa5cb",
    "version": "v0.10.0-exp.49faa5c"
}

Describe the bug

Upon toggling reverse thrust, the thrust limit value becomes negative on the EWD.

Expected behavior

Thrust limit value to be positive

Steps to reproduce

1. Toggle reverse thrust (can be with engines on or off)
2. Observe the thrust limit value on the top right of the EWD.

References (optional)

E.g. : https://youtu.be/UQE-g7yrY3w?t=105

Additional info (optional)

No response

Discord Username (optional)

Bruno_pt99#5802

[tracernz]

Should be about 65% as well I think?

[donstim]

More info on this bug... Not only does the MREV rating limit N1 go to -45%, the maximum static reverse N1 I was able to achieve on the ground at KSEA was 41.0% Neither are correct.

I could not find anything in the engine or FADEC code for reverse thrust. PR #7762 turned off the reverse thrust capability within the default MSFS code, so it appears that reverse thrust is being simulated entirely through the changes introduced by PR #7762.

The MREV limit and actual reverse N1 shown on the EWD appears to come from lines 70-81 in: https://github.com/flybywiresim/aircraft/blame/master/fbw-a32nx/src/systems/instruments/src/EWD/N1Limit.tsx

I realize the data to enable a fully realistic simulation of Leap 1A-26 reverse thrust may not be available, but the N1 and MREV limit values being shown are not even close. The MREV limit, in particular, appears to be a constant because it did not change at all when I varied temperature, QNH, and engine bleeds. If you are going to use a constant value, which is not a good long term solution, I suggest using something like the 67.5% value from the video provided in the references above. The value achieved when the thrust lever is moved to the maximum reverse thrust position should also correspond to the MREV limit value.