fix: Update flight model info in fmgc guidance

[donstim]

Fixes #[issue_no]

Summary of Changes

This change updates the flight model information in the FMGC guidance section for use in computing vertical guidance parameters. This change will make the flight model information in the FMGC consistent with #6820.

Screenshots (if necessary)

References

Additional context

Discord username (if different from GitHub): donbikes#4084

Testing instructions

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[beheh]

I'm approving this from a technical side, because the form of the changes seem fine. I haven't cross-checked the numbers themselves.

[davidwalschots]

@donstim What kind of testing are you expecting on this item?

[donstim]

@donstim What kind of testing are you expecting on this item?

Fair question, but I don't have an answer. This PR was done as a courtesy to @BlueberryKing and anyone else who might be working on FMGC guidance that needs this information. I can provide some testing guidance for anyone who can access the baseDrag value computed by this file by inputting a CL value, but I don't think that would be doable by a typical QA tester. I would envision a 2-step test: 1) Ensure the computed baseDrag value matches values I can provide that were used to create the polynomials in the equations; and 2) Verify that the computed baseDrag value matches (within a tolerance) CD values shown in the Aircraft Editor Debug Speeds window in developer mode for any given flight condition.

I don't know what level of scrutiny the original flightmodel.ts file got that this PR modifies.

[tracernz]

I think this is one that really just needs review, although maybe @BlueberryKing can do some tests with his vnav branch.

[BlueberryKing]

I have been using this PR on the experimental-vnav branch. As expected, I have not noticed any breaking issues with it, which is the important part before merging this into master.

I would be happy to do a more comprehensive test on the functionality using the method @donstim described.

[tracernz]

I am inclined to just merge this. Any objections?

[BlueberryKing]

I am inclined to just merge this. Any objections?

Yeah, good to go from my side. Has not caused any issues on experimental.

[donstim]

Sorry for the delay. Finally getting back to this. Here are some inputs/outputs that can be used as a check:

FLAPS UP
CL = 0.29471, BaseDrag = 0.0213
For Mach = 0.78, CD Mach correction = 0.00122, CD with Mach correction = 0.02252

CL = 0.39013, BaseDrag = 0.023299
For Mach = 0.65, CD Mach correction = 0.0004, CD with Mach correction = 0.023699

CONF 1
CL = 0.84155, BaseDrag = 0.055432

CONF 1+F
CL = 1.07326, BaseDrag = 0.076367

CONF 2
CL = 1.00455, BaseDrag = 0.0.79944

CONF 3
CL = 1.07352, BaseDrag = 0.088355,

CONF FULL
CL = 1.22098, BaseDrag = 0.118748

[BlueberryKing]

Thank you very much! I will be checking these values.

[BlueberryKing]

I have now conducted the tests, both with the values @donstim provided as well as with the computed values in the simulator. The values lined up nicely for all configurations. 👍

[donstim]

Someone needs to add the Mach correction to BaseDrag. Otherwise, it will not be very accurate for flaps up high speed drag

.

[BlueberryKing]

I have now added the Mach correction factor into the flight model predictions. I tested this briefly and observed more conservative predictions, as would be expected since we now correctly account for an increase in drag at high Mach numbers.

In the images below we can see how the top of climb arrow moves further away with the Mach correction.

Without the Mach correction:

With Mach correction:

I reached my cruising altitude closer to the predicted top of climb with these changes. Good stuff!