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Ground position drift

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Ground position drift

Postby fredsie » Sun Nov 11, 2018 8:31 am

This is not a problem so much as a curiosity, but I wonder if others have noticed it.
I start up a plane (doesn't matter which one) on a runway using the launcher. Then sometimes I forget and leave the sim running like this. Coming back after a few hours I see that the plane is now sitting in the grass between the runway and the taxiway. I checked the property browser and indeed there is a continual creep upwards of both latitude and longitude. Is there a known cause of this?
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Re: Ground position drift

Postby legoboyvdlp » Sun Nov 11, 2018 9:01 am

Is the engine running?

You can turn on the parking brake on most aircraft with "Shift + B".
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Re: Ground position drift

Postby FlugHund » Sun Nov 11, 2018 9:45 am

Yes, we've noticed. It's been there as for long as I can remember. The good news, at least for Helis based on YASim there is talk about a fix on the devel-ml.
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Re: Ground position drift

Postby WoodSTokk » Sun Nov 11, 2018 11:15 am

Not only for Helis. The fix should work on all yasim based aircrafts. Thats an old known bug in yasim (at least) and have to do with the wind and mass of aircraft.
You can shutdown the engines and engage the parking brake. If there is wind on the airfield, the aircraft will move more or less, depends on wind strength and mass of aircraft.
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Re: Ground position drift

Postby fredsie » Sun Nov 11, 2018 12:25 pm

Hmm. Weather manual, zero wind. Engines not running, parking brake on. Plane is the 757, not prone to moving in a light breeze, i'd imagine. :-) Still drifting.
I'm inclined to think there's some rounding going on as the sim model continually recalculates current position.
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Re: Ground position drift

Postby wkitty42 » Sun Nov 11, 2018 4:04 pm

yeah, it is certainly a YASIM thing... i saw it years back when i first installed 3.0.0 from the ubuntu repositories... when i landed here in these forums, i saw there was a newer version and that started my trip into building the latest code... building my own binaries didn't help with this particular problem, though... it can be seen in most all YASIM craft unless their maintainers have taken steps to fix the problem in the craft... i know several have been aware and discussed craft-side possible fixes... i don't know if any of those amounted to anything, though, and i rarely fly YASIM craft these days...
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Re: Ground position drift

Postby enrogue » Sun Nov 11, 2018 10:20 pm

It has to do with the way yasim calculates static friction with the ground. The patch in development completely changes it, but due to the fact that aircraft maintainers don't like things changing automatically it has to be made optional. We've been testing a slightly updated version of the original patch for a while now, and the new patch appears to work ok (it makes the change optional & per gear point), but it needs to be tested with more aircraft types - I'm working on it
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Re: Ground position drift

Postby Isaak » Mon Nov 12, 2018 8:40 am

Once the patch is implemented in FG I will make sure the 777 incorporates it. The required changes seem trivial.
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Re: Ground position drift

Postby sim » Mon Nov 12, 2018 11:08 am

Yes the drift if you hang about near the threshold of KSFO runway 28 will skew the plane's heading and eventually ditch you in the sea regardless of no engines running and parking brake applied. Hope this can be fixed but regard it as a curiousity and it may be Fightgears way of encouraging pilots to keep moving. ATC Tower won't appreciate planes hanging around there too long before departing skywards! 8)

Take a leaf out of Speedy's book and keep moving!
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