fix(a380x/flight model): A380X Flight Model Update plus fix auto-rotate issue

[donstim]

Fixes #[issue_no]

Summary of Changes

General update to flight model plus:

1. Fixes auto-rotate issue
2. Updates flap and gear drag values to match pitch/power tables

Screenshots (if necessary)

References

Additional context

Discord username (if different from GitHub): donbikes

Testing instructions

1. Test different takeoff conditions to verify auto-rotate (complete nosewheel liftoff before VR) is fixed. (Note: I used full passenger payload with 25 T of fuel as the critical condition. I also checked the same payload with 10 T of fuel. Hopefully, there aren't any reasonable loadings that will result in auto-rotation.)
2. Test full flights, including use of BTV, to make sure there aren't any anomalies introduced.

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, flybywire-aircraft-a380-842 (4K) or flybywire-aircraft-a380-842 (8K) download link at the bottom of the page

[Ueeew]

@donstim If tested this PR when you opened it 1 or 2 week ago, so it might be a bit outdated but I wanted to give feedback. The auto rotation works really good and only at light weight It rotated a few knots before the actual rotate speed. This works really well. The flap modification didn’t work that good. Flap config 1 and 2 worked pretty much as before but on landing when deploying flap cfg 3 and then Full the aircraft generates from on moment to another so much lift that it needed to pitch down so drastically that you went from a normal (-1)° - 3°pitch, with Flap cfg 1 or 2, on an 3° glide-slope TO an 5° or more nose down dive to stay on this 3° glide-slope with cfg 3 and Full. What I want to say by that is that In my opinion Flaps cfg 3 and Full produced way to much lift, keep in mind that this might be fix until now. Maybe this feedback helps even though it’s 2 weeks old.

[donstim]

Thanks for the comments, but yes the version you tested is very much outdated. I continue to work with this on my own system and only occasionally update this PR. Even so, I don't think I've ever had the behavior you've described for CONF 3 and FULL.

I've chosen a more critical case for the auto rotate issue and have resolved it, but it requires an unacceptably high trim level during other phases of flight. Still working on it, but it's a very frustrating process that requires constant re-tuning of parameters every time one of the major parameters is changed.

[aadee9940]

Hi, I just did a flight taking off at 430T with a 55c Flex, 132, 147, 152.
The auto rotate behavior seems to be solved. As you know in the past the nose would begin to lift itself in the 140kts region, that is gone now.

In terms of the BTV, everything was fine. I did not catch anything odd.

Thank you for this fix.

[alepouna]

Giving an approval for QA flow to start

[utkrishtm]

@donstim Hey, I tested three scenarios: medium, no load, and extra-long haul load. Everything looks good so far. Are there any specific or additional scenarios you would like me to test before I submit my report? Thanks!

[donstim]

@donstim Hey, I tested three scenarios: medium, no load, and extra-long haul load. Everything looks good so far. Are there any specific or additional scenarios you would like me to test before I submit my report? Thanks!

No, that sounds great. Thank you!

[utkrishtm]

Quality Assurance Trainee Report

Discord Username : utkrishtm
Object of testing : #9728
Aircraft : A380X
Tier of Testing : 2
Date : 24/01/2025

Testing Process:

• Flight 1: RJAA 34L - RJFF 34 (2 hr) (Full Passenger Load + Cargo)

  • Block Fuel: 30.0T
  • ZFW: 370.3T ZFWCG: 31.5%
  • GW: 400.3T GWCFG: 33%
  • TO PERF: Flex: 66C Flaps: 1+F
  • V1: 142 VR: 149 V2: 154
  • LAND PERF: Flaps: FULL BTV: Yes
  • VLS: 137kts VAPP: 142kts

• Flight 2: RJFF 16 - VHHH 07R (4 hr) (No Passenger or Cargo Load)

  • Block Fuel: 40.5T
  • ZFW: 300.0T ZFWCG: 36.2%
  • GW: 340.5T GWCFG: 37%
  • TO PERF: Flex: 40C Flaps: 1+F
  • V1: 130 VR: 132 V2: 148
  • LAND PERF: Flaps: FULL BTV: Yes
  • VLS: 125kts VAPP: 137kts

• Flight 3: VHHH 07R - KORD 27C (14 hr) (Full Load, Breaking Limits)

  • Block Fuel: 186.0T
  • ZFW: 346.8T ZFWCG: 35.3%
  • GW: 532.8T GWCFG: 40%
  • TO PERF: Flex: 51C Flaps: 2
  • V1: 145 VR: 160 V2: 170
  • LAND PERF: Flaps: FULL BTV: Yes
  • VLS: 130kts VAPP: 138kts

Testing Results:
Passed

Negatives:

• I am not sure if it is specific to this build, but when trying to set up the BTV exit with Navigraph, the arrival airport does not show up. It prompts me to keep waiting for a long time. However, if I select the airport in the EFB and view some charts for that specific airport, then go back to set up the BTV and look at the airport on OANS, it sometimes appears. This seems like a weird anomaly that I encountered. I’ve included a video to demonstrate the issue.

• Entering values that exceed the limits should not be allowed. The maximum is 512T, but I was able to overload it to 532T. The fields should automatically adjust to only allow the max cargo or passenger load.

• During departure from VHHH with FLAPS 2, after takeoff, the airplane was pitching up a little more than intended. This could potentially lead to a stall. I’ve attached a video to illustrate this around 55 seconds into the video. It may have been caused by the weights not being within the flight envelope.

Conclusions:

• Overall, the experience was great. The issue has been resolved, and BTV works as expected in all scenarios with no change to its functionality.

Media:

• Each takeoff was recorded for detailed analysis. I have shown the FCTL page to highlight the inputs made either by me or the plane.
• The videos were long so I included them in a Google Drive so it could be watched easily. Please make sure to watch in 1080p for better visual clarity.
  https://drive.google.com/drive/folders/1yN_h1Hxfa0HudcbojFIPkCXRi-k4w5EI?usp=sharing

[aadee9940]

I know 2024 is not supported, but I am commenting just for tracking.
So i tried this in 2024, 390T and a 66c flex. The auto rotate issue reappears, and the stall after takeoff bug is back, this time it occurs at 2000ft all by itself, at this point i am pitching 10 degrees up.

It is really wierd, because with this exact build in 2020, nothing like that happens.
No auto rotate, no stall.

[donstim]

Quality Assurance Trainee Report

Discord Username : utkrishtm Object of testing : #9728 Aircraft : A380X Tier of Testing : 2 Date : 24/01/2025

Testing Process:

• Flight 1: RJAA 34L - RJFF 34 (2 hr) (Full Passenger Load + Cargo)

  • Block Fuel: 30.0T
  • ZFW: 370.3T ZFWCG: 31.5%
  • GW: 400.3T GWCFG: 33%
  • TO PERF: Flex: 66C Flaps: 1+F
  • V1: 142 VR: 149 V2: 154
  • LAND PERF: Flaps: FULL BTV: Yes
  • VLS: 137kts VAPP: 142kts

• Flight 2: RJFF 16 - VHHH 07R (4 hr) (No Passenger or Cargo Load)

  • Block Fuel: 40.5T
  • ZFW: 300.0T ZFWCG: 36.2%
  • GW: 340.5T GWCFG: 37%
  • TO PERF: Flex: 40C Flaps: 1+F
  • V1: 130 VR: 132 V2: 148
  • LAND PERF: Flaps: FULL BTV: Yes
  • VLS: 125kts VAPP: 137kts

• Flight 3: VHHH 07R - KORD 27C (14 hr) (Full Load, Breaking Limits)

  • Block Fuel: 186.0T
  • ZFW: 346.8T ZFWCG: 35.3%
  • GW: 532.8T GWCFG: 40%
  • TO PERF: Flex: 51C Flaps: 2
  • V1: 145 VR: 160 V2: 170
  • LAND PERF: Flaps: FULL BTV: Yes
  • VLS: 130kts VAPP: 138kts

Testing Results: Passed

Negatives:

• I am not sure if it is specific to this build, but when trying to set up the BTV exit with Navigraph, the arrival airport does not show up. It prompts me to keep waiting for a long time. However, if I select the airport in the EFB and view some charts for that specific airport, then go back to set up the BTV and look at the airport on OANS, it sometimes appears. This seems like a weird anomaly that I encountered. I’ve included a video to demonstrate the issue.
• Entering values that exceed the limits should not be allowed. The maximum is 512T, but I was able to overload it to 532T. The fields should automatically adjust to only allow the max cargo or passenger load.
• During departure from VHHH with FLAPS 2, after takeoff, the airplane was pitching up a little more than intended. This could potentially lead to a stall. I’ve attached a video to illustrate this around 55 seconds into the video. It may have been caused by the weights not being within the flight envelope.

Conclusions:

• Overall, the experience was great. The issue has been resolved, and BTV works as expected in all scenarios with no change to its functionality.

Media:

• Each takeoff was recorded for detailed analysis. I have shown the FCTL page to highlight the inputs made either by me or the plane.
• The videos were long so I included them in a Google Drive so it could be watched easily. Please make sure to watch in 1080p for better visual clarity.
  https://drive.google.com/drive/folders/1yN_h1Hxfa0HudcbojFIPkCXRi-k4w5EI?usp=sharing

Thanks for the thorough test. Thsi PR only affexts the flight model, so it can't cause the issues you had with OANS. Regarding staying within the operating limitations like weight, cg, speed, etc., just like the real airplane, complying with those limitations is the responsibility of the pilot/operator. The real airplane can also be overloaded.

I'm out of town and cannot see your videos well enough on my small phone to see what you're describing. If you're talking about pitch being more sensitive in CONF 2 than CONF 1+F during takeoff rotation such that the same input leads to higher than intended pitch angles, adjusting that will have to wait until the rotation law can be tuned. In any case, you should be able to pitch up to the highest pitch attitude attainable without being able to recover without stalling uncontrollably.

[donstim]

I know 2024 is not supported, but I am commenting just for tracking. So i tried this in 2024, 390T and a 66c flex. The auto rotate issue reappears, and the stall after takeoff bug is back, this time it occurs at 2000ft all by itself, at this point i am pitching 10 degrees up.

It is really wierd, because with this exact build in 2020, nothing like that happens. No auto rotate, no stall.

Thanks for the report. One more reason I guess not to use FS2024. Must be due to one of those completely undocumented flight model "improvements" people keep talking about where the same input parameters for 2020 lead to different results in 2024. Pretty hard to develop an airplane that way.

[Ueeew]

@donstim could you again merge the master in your PR request that its up.-to-date again. that would be great, thank you

[donstim]

Sorry, I am out of town for the next week. The web editor to resolve the conflicts on the changelog page does not well on my phone. Anyone should be able to do it.

[BravoMike99]

Sorry, I am out of town for the next week. The web editor to resolve the conflicts on the changelog page does not well on my phone. Anyone should be able to do it.

Done 👍