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I have an aircraft using the legacy flight model system - and the G Force variable from the simulation appears to be influenced by something within the legacy flight model system. This results in the G Force over-reading at low altitudes and under-reading at high altitude.
Could I ask the Asobo team to either double check their G Force calculation when the legacy FM system is in use - or advise which properties of the legacy flight model might influence the G Force calculation?
Many thanks.
Hello @Machtwo
Can you tell me which aircraft you used to produce this issue and possibly provide a package please?
I ran some tests with Asobo aircraft configured to allow legacy FM but couldn't reproduce the issue.
Regards,
Sylvain
Altitude always will effect how an aircraft performs because the astmopheric pressure. So I would suspect the G force to change with the same control movements as the aircraft will behave differently. Even when flaps are deployed this changes the G effects. See the flight_model.cfg for the settings.
[AIRPLANE_GEOMETRY]
positive_g_limit_flaps_up =4
positive_g_limit_flaps_down =2.8
negative_g_limit_flaps_up =-3.2
negative_g_limit_flaps_down =-2.4
None of the aircraft using modern flight model show this behavior. For example, the default A320 will show a G Force of 1G when flying straight and level at 5000ft. With legacy, the G Force displayed is 1.05g in the same circumstances.
Likewise at cruise, FL350 - default A320 shows a G Force of 1g. Legacy FM shows 0.91g.
If verified, it’s an interesting find. After exploring both modes, I doubt legacy « universe » beeing fundamentally different than modern flight model. Asobo just implemented a different way to compute flight forces acting on aircraft body. Try aircraft debug to display forces and you wanna see it looks quite similar in both modes.
If you are building sort of EFCS relying on g-load I see 2 solutions for your issue: one is computing yourself gload from trajectory and speed, second is making a measurement of local gload during a slew up to rebase your model. That one sounds a bit rushed though.
I see 2 solutions for your issue: one is computing yourself gload from trajectory and speed
This works fine. I'm more intrigued as to why the internal calculation might be influenced by configuration properties or the legacy fm system. Anything running on the modern system gives expected results. I wonder if Asobo might have any ideas as to what could be causing these discrepancies.
Here's an example in level cruise, FL380.
Would be interesting to know if constant G is actually variable with altitude as per reality
Hello @simfan
I was able to reproduce the issue.
An easier way to see it is to check the G Force value when you are static on ground; it shows 0.86
It occurs with legacy FM when you are beyond the max takeoff weight, which is the case with your default config.
You should get correct g force values in the 0 to 100% payload range.
We are checking where the problem comes from.
Regards,
Sylvain
I sent you guys an updated model with a payload within range which still exhibits the issue. It's a blocking issue for us so if you can look into it asap we'd really appreciate it.
Hi @FlyingRaccoon -
do we have any updates on this topic? We'd love to see a resolution and we're happy to provide assistance on it if you need.
Also- is it possible that you could share the formula that G FORCE is calculated with, for legacy model?
Thanks!
BUMP-ing this so we can perhaps get a reply on how the bug report is progressing?
It would help if we could at least be given the current formula used to calculate the G-FORCE variable (which is wrong for the legacy model) so we could perhaps figure out a way to re-do it using individual components.
Dear Asobo-
( @FlyingRaccoon @EPellissier @Boris_ )
can you please respond on this topic? Is it being looked at? We realize that you have certain priorities in your day-to-day but correspondence has been lacking and you have been replying on other topics immediately which does not give us confidence in how fast the matter will be looked into.
It's quite important that something as vital as a physical value which is absolutely necessary to develop an accurate aircraft autopilot simulation is fixed as soon as possible, if you wish to maintain your claim that you wish to have an accurate simulation and not a game.
We would really appreciate a response on our questions above - this issue is blocking our development efforts at the moment.
If you need us to use a different avenue of communication, please say so and we will, but we find the lack of response confusing, to say the least.
My apologies for the lack of feedback.
I have logged all the information at my disposal and the issue is being tracked, but it requires a core sim engineer to have a look.
They are very busy people and I don't expect them to be able to have a look in the short term.
I will update this post as soon as I have new information about this issue.
Regards,
Sylvain
This topic was reviewed by one of our core simulation engineers and here's what we found:
- The G force was incorrect on ground when the aircraft was heavy enough for the landing gear suspension to reach its stop position. Beyond that, the additional force was not accounted for in the G force calculation.
This was affecting all FM types and will be fixed in SU12
- The legacy fm was computing accelerations that were slightly off. The G Force was just a symptom.
With SU12, we will introduce a new parameter: legacy_fm_new_integration
When set to 1, a new acceleration integration will be done that will give correct accelerations and therefore G force.
It will be set 0 by default, to not impact existing aircraft that would have been configured based on these wrong accelerations.
Please test your aircraft when SU12 flighting begins to make sure you get the expected results and do not see any undesired side effects.
Regards,
Sylvain
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