Pitch "jerks"
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In looking at the behavior it almost seems like a rounding or float to integer conversion where some precision is lost and is noticeable when transitioning between positive and negative. But who knows. So frustrating that Asobo won't help trouble shoot a really popular add-on plane. Is there a way where we can help by contacting Asobo ourselves?
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Found a "tip" some time ago on the official forum, which seems to "work".
The source of the jerks seems to caused by these entries in the flightmodel.cfg:
aileron_up_drag_coef = 0.2
aileron_down_drag_coef = 3.9Simply comment these out and the jerks are gone.
;aileron_up_drag_coef = 0.2
;aileron_down_drag_coef = 3.9Probably not a scientific way yet it seems to works.
Any thoughts on this?
Marcel
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@mgr That would be odd if aileron drag modelling caused pitching moments like that. My guess is that these coeffecients are there to model adverse yaw. Anyways, I don't think I can do this mod since I bought my Arrow through the M$ marketplace :( Might be interesting to look at other plane's values for these settings.
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Also, that difference between up and down drag seems really high (20x drag coeff in the down direction). But not knowing how the sim treats those values, it is hard to say. I do also notice the excessive wagging on final which may be attributed to those settings. Can you try .2 and .39 and see what you get? If anyone can post these values for the Arrow II?
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@sender46 Might be, but hard to say since I don't know what these numbers actually mean to MSFS. Still interested in what these values are for the Arrows that don't have this issue is. If they are the same, then that might rule out this being the source of the issue (although it could be a contributing factor along with something else). Trying .39 and seeing what the effect is might be a useful exercise for someone that can do it (I can't because the Marketplace version doesn't give access to the parameters).
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@ajbarber In v0.10.3 these lines are:
aileron_up_drag_coef = 0.5
aileron_down_drag_coef = 2.8 ;3.9So still a high ratio of 0.5 to 2.8. I can't try changing mine to 0.39 at the moment.
Interesting that a number of other aircraft I've looked at don't even have those parameters in their flightmodel.cfg, e.g. Bonanza G36 Improvement Project v0.6.8, DA40-NGX Improvement Mod v0.9.0.1, Milviz Cessna C310R v0.1.0, FlySimWare Cessna C414AW Chancellor Beta 2.2.0, FlyByWire A32NX v0.8.0.
The only other aircraft I've found that does have those parameters included is the FlyingIron Spitfire L.F Mk IXc v1.2.0, which has them at these values (with a much lower ratio between the two):
aileron_up_drag_coef = 0.5
aileron_down_drag_coef = 1.0 -
@sender46 said in Pitch "jerks":
aileron_down_drag_coef
Defines the drag added by downwards[sic] aileron deflection. This parameter has a significant impact on adverse yaw. Increase downward deflection drag to get more adverse yaw. This parameter is multiplied by the aileron deflection angle. Default is 1. This can be scaled with the aileron_down_drag_scalar parameter in the [FLIGHT_TUNING] section and is further modified by internal coefficients.So it is 1 when not specified. Up default is .5. What are the values in the config for aileron_down_drag_scalar? The default for that is also 1.
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@ajbarber aileron_up_drag_scalar and aileron_down_drag_scalar are not specified in v0.10.3.
For whatever it's worth (maybe nothing, being a completely different aircraft), in the FlyingIron Spitfire L.F Mk IXc v1.2.0 they are specified as:
aileron_up_drag_scalar = 0.15
aileron_down_drag_scalar = 0.85Interested to hear what @Delta558 makes of @mgr's "tip" and what comparisons with other aircraft might mean.
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@sender46 The aileron up / down drag were added relatively recently because, as part of their wholesale removal of coefficients, they removed the setting which worked well in FSX. Unfortunately, the new version was not documented until very recently, and when the lines were added they were entirely undocumented - it was guesswork, no other option. That's why the 'up' setting is still default, the down setting was adjusted until some adverse yaw was seen. With further sim updates, it appears the effect has changed somewhat and I would agree that 2.8 may still be too large a figure, but if you use entirely the default figures then there was no adverse yaw present at all. We have no idea how they assign values to up drag and down drag for the game's internal calculations, so it's really just a case of adjusting until you find a setting that gives a reasonable reaction. Once again, this is because the core flight model of the game is not grounded in aerodynamic theory.
As to whether or not this is the reason for the 'pitch jerks' that are being discussed here, I doubt it and I think this topic (or other threads on this forum about it) predate the introduction of aileron up / down drag lines in the flight model.
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@delta558 said in Pitch "jerks":
... I think this topic (or other threads on this forum about it) predate the introduction of aileron up / down drag lines in the flight model.
Hmmmm :thinking_face: How can a "tip" to remove aileron up / down drag lines predate the introduction of those lines? If that was the case they wouldn't have been there to be removed.
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@sender46 This topic, the pitch jerking which has been the subject of a couple of threads, predates the introduction of the aileron up/down drag . . .
edit: the first comments about the pitch jerks that I can find date from April last year. The lines were introduced into the flight model in SU5, which I believe was late July.
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@ajbarber Voted up but I don't expect it to make any difference.
Quote from another forum: "They will probably just tell you that ...... they don’t support 3rd-party aircraft, or it will vanish in the black hole that is Zendesk’s bug report area."
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@sender46 said in Pitch "jerks":
Quote from another forum: "They will probably just tell you that ...... they don’t support 3rd-party aircraft, or it will vanish in the black hole that is Zendesk’s bug report area."
The first reply to the post said as much. Although, if it had a lot of votes, it would be hard to ignore.
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Just to say we have not given up on this, but have been checking and re-checking geometry and coefficients to see if something has slipped through. So far nothing has. The only thing that has made any difference appears to be the wing thickness ratio. Setting the wing to be as thick as an airliner's (roughly four times the actual thickness of the aircraft's wing) seems to give a slightly better / smoother ride, though who knows what else that will affect!
It's not an answer, it's not a fix, but frustratingly I have built the PA38 using the exact same technique as I always have and you can bet I'm watching for this behaviour now. So far, not a pitch jerk in sight.