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787 wings

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787 wings

Postby Alexis07 » Sat Jan 23, 2021 10:13 pm

When I flight the 787 the wings make strange movements and disappear, I Think is a bug someone knows the solution ?
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Re: 787 wings

Postby CaptB » Sat Jan 23, 2021 11:00 pm

I'm not sure if this is simulated in this model, but if it is, it's quite possible you are exceeding the g forces and the wing separates.
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Re: 787 wings

Postby V12 » Sun Jan 24, 2021 6:01 am

One of the available 787s has bug in the wingflex logic and this is result :

Image
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Re: 787 wings

Postby Alexis07 » Sun Jan 24, 2021 9:29 pm

Or when I put the simulation time x2 or x4 the wings desappear
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Re: 787 wings

Postby wkitty42 » Mon Jan 25, 2021 12:12 pm

patient: doctor! doctor! it hurts when i do this...
doctor: well, don't do that ;)
:mrgreen:
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: 787 wings

Postby Michat » Mon Jan 25, 2021 9:29 pm

That problem ocurred also when for some reason 4Gb RAM becomes full, new terrain loading, new metar data received.
It seems the algo is leaking, But I don't have any conclusion, my statement is based on pilot TICO experience long hauling the amazing 787 for years with a low spec PC.

This nice model deserves a solution since the wing flexer never worked properly.

In my oppinion the amont of flex is exagerated, compared to other sims where is fine, I believe these are more focus on flexible tip than a constant curve concept. Do we need another approach?. Let's wait for an expert to answer this question on how to solved this problem.

29.92 For Narendran. Thumbs up if you are on the Omega95' 787 in 2021 suffering the batwing effects.
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Re: 787 wings

Postby Ysop » Mon Jan 25, 2021 10:17 pm

It might be easiest to do research from photos and model by this. Deflection will be fairly proportional to lift. It will not be a constant curve.

Of course it is possible to calculate the deflection curve using lift distribution with the help of a structural software. But the amount of assumptions to be taken for such a composite wing is quite immense. Only if someone has access to a broken 787-wing ;-)
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Re: 787 wings

Postby V12 » Tue Jan 26, 2021 7:06 am

Michat :
In FG2018.X.Y I observed dramatical wing flex when FG downloaded new METAR and advanced weather steeply changed wind speed and direction. Then I used manual METAR input and changed 30 kts wind direction from full tailwind to full headwind. Result was same as on picture above. Discontinual change of the wind direction caused discontinual change of the lift, result was brief abnormal wing flex. But I never "lost" my wings.
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Re: 787 wings

Postby Michat » Thu Jan 28, 2021 3:52 am

You are right, thoses FGversion agnostic glitches is what we get too.

The logic is pretty we'll explained in the wiki http://wiki.flightgear.org/Wingflexer There are some parameters to tweak to get estimations and then watch the visual results.
From FGWiki: 777 wing in turbulence show about 2-3 Hz. (I didn't research 787 videos).

So maybe with some tweeks the 787 wing flex could be more credible. I wonder if the 777 WF is working. Also wish to know how the WF is performing on YASIM.

Although the math problem is solved., it will need a control protection algo on the run-time to avoid the computacional cascade loop that collapses the machine, ej with metar changes.

Math done. It will required a FG software eng hacker or similar to tackle the issue.

If anyone could tweak and test the787 and any Yasim WF model getting same bad results, that could be a good starting point to scale up the issue with a ticket in SF.

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