fix(press): delta pressure calculation before adirs on

[mjuhe]

Summary of Changes

This PR fixes an issue with the pressurization system. When spawning at an airport high above sea level the delta pressure was not being calculated correctly and the safety valved opened (triggering the corresponding ECAM warning).

The pressurization system uses the outside static pressure from the ADIRS to calculate delta pressure. Before the system is powered, the delta P cannot be computed. Now before ADIRS power up, the ECAM system page shows "XX" for delta pressure, no warning comes on, and the safety valve does not open.

Screenshots (if necessary)

References

Additional context

Discord username (if different from GitHub): Commander Ga

Testing instructions

Spawn at an airport high above see level (KDEN for example). Before powering up the ADIRS, ensure the delta pressure is not shown on the ECAM (it shows "XX" as above). Observe the safety valve is closed and no warrning comes on.

When setting the ADIRS to align, after a few seconds the delta pressure indication comes on, and is 0.

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

[lukecologne]

Except the note I left above, looks to be good

[LunakisDev]

Quality Assurance Trainee Report

Discord: LunakisLeaks
Object of testing: #8648
Tier of Testing: 1
Date: 18/5/2024

Testing Process:

1. Spawned at KDEN
2. Started the aircraft
3. Checked if the delta pressure shows "XX"
4. Observed that the safety valve is closed and no warning comes on
5. ADIRS to align
6. Checked if the delta pressure indication comes on, and is 0

Negatives:
N/A

Testing Results:
Passed

Conclusions:
LGTM