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YASim Issue with fuselage "cx" parameter

Good sims require good FDMs (the "thing" that makes an aircraft behave like an aircraft).

YASim Issue with fuselage "cx" parameter

Postby Colin Howell » Wed Mar 26, 2014 9:16 pm

YASim has a bug in its handling of the "cx" parameter for fuselages, which is supposed to be the drag factor for the X axis.

I've filed this as Issue 1427.

Because of how the code treats the "cx" parameter, it ends up being an overall drag factor for the fuselage, not restricted to the X axis like it should be.

This will affect any YASim aircraft which has a fuselage with a "cx" value different from 1. Fixing it is pretty simple, but may require retuning the aircraft if it was tuned for the old buggy behavior.
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Re: YASim Issue with fuselage "cx" parameter

Postby Philosopher » Wed Mar 26, 2014 10:40 pm

Hi Colin,

unfortunately, Chrome on my iPod crashed when I was about to post an reply to one of your merge requests...

Anyways, the gist was that, if I were a developer reviewing your code, I would like to see a plan so that old aircrt can remain unchanged (especially 3rd-party ones :(). It's really great that you're taking the time to investigate and fix these oversights/bugs, but I've seen the concern before, "what about the other aircraft?" So I would suggest to come up with something that allows these fixes to be gradually implemented, and my idea would be a simple versioning system, or tags to enable/disable each fix, and then display a warning if it's too new for the binary (might as well let the user try to fly it, so don't crash ;)). If you did that (and if I were a dev with more authority, and commit access to fg), I wouldn't hesitate to merge them (since you give rational explanations ;)).
Thanks,
Philosopher
(inactive but lurking occasionally...)
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Re: YASim Issue with fuselage "cx" parameter

Postby DFaber » Thu Mar 27, 2014 8:35 am

Hi Philosopher,

Philosopher wrote in Wed Mar 26, 2014 10:40 pm:It's really great that you're taking the time to investigate and fix these oversights/bugs, but I've seen the concern before, "what about the other aircraft?" So I would suggest to come up with something that allows these fixes to be gradually implemented, and my idea would be a simple versioning system, or tags to enable/disable each fix, and then display a warning if it's too new for the binary (might as well let the user try to fly it, so don't crash ;)).


I don't think there is a big number of Aircraft affected by these changes to justify an additional versioning scheme. I have tested the slat patch and the twist patch and found very little problems, in fact most cases I've seen saw an improvment. Of the 15 Aircraft I've tested the twist patch on, only two wouldn't start up at all.

I'm going to test this patch and report back.

Since we are at the beginning of the release cycle, I'd vote to apply these patches as is and don't make it too complicated. I guess Aircraft Devs are more keen on Yasim improvements than embarressed that they may have to touch their Airplane.

Greetings
Detlef Faber
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Re: YASim Issue with fuselage "cx" parameter

Postby Colin Howell » Tue May 06, 2014 8:23 pm

I forgot to report that the fix for this was accepted into GIT around a month ago. Sorry about that.

This fix is now governed by the recently-added YASim version system, described in this post. Thus it will only take effect for aircraft which specify a YASim version of "YASIM_VERSION_32" or later, including "YASIM_VERSION_CURRENT". Aircraft which don't specify any version will be unaffected.
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