But you're right. Reactions to gusts are the only times an AIRBORNE plane sees any sort of sidewind. But your reaction description misses one point. The plane will yaw in response to the "new" wind direction and as well it will accellerate until it is again in a balanced wind head on mode. When it flys out of the gust it treats the previous "steady state" as a NEW wind gust from the opposite direction.
No, I didn't miss this point, I just though I had already over simplified this duscussion. Guess we'll just keep simplifying. Yes, your correct that the second two airplanes need augmentation...again, tried to set up the most painfully simple case. Thanks for the added info for our veiwers though.
Mesae, Just because we learn how to calculate stability derivatives using terms like c_n_beta, doesn't mean that the ability or tendency to crab is not an effect of some stability characterisics. I'll ask you this, is crabbing a good thing? (you should answer..yes, it allows the airplane to maintain a ground track in the presence of a crosswind, see... its right here in my faa handbook) then I'll ask you this, Does yaw stability effect the airplane's natural tendency to reduce sideslip angle (you say yes again). Does this reduction in sideslip angle result in a crab angle? (you say yes, if there is a crosswind component) Then I say, doesn't this imply that yaw stability does have a relationship with crab angle, and thus staying on a ground track???? Then I say, that will be $50 for that lesson.
Sideslip angle, and not crab, is a term in yaw stability calculation.
no one said crab was used to calculate yaw stability parameters. crab is certainly related to flight path and heading...I don't think this topic is called "give us a bunch of definitions"
However, without placing a bunch of additional constraints on your final example, it cannot be said with certainty that the airplane will spin, since as far as we know, aurotation due to spinning requires at least a partial stall. Certainly, if no correction is applied, AND a stall ensued, a spin would likely occur, i.e. it depends on a lot of things that were not specified in your example. Departure due to yaw instability is not the same thing as spinning, especially not initially.
please don't go here. spin, crash, uncontrollable...you are smart enough to get the idea without venturing onto some other topic.
Again, I think the question still lingers, which airplane would you rather have (all other variable the same[this ones for you guys]) to maintain a ground track (say...for crop dusting). Which robust controller would be simplest to design (this one's for those of you talking flight controllers)? I'm not looking for definitions of crop dusting or various autopilot schemes here. I will not give up until someone states that SFG's reduce an airplanes ability to follow a ground track, or gives an adequate response to why they do or have no effect!