Hello, nice to meet you and I'm sorry for disturbing!
I would like some help from someone with a great experience like you. I'm a private pilot, heading towards my commercial license and I realized that I have some doubts regarding some flight regimes which I don't master on my own. I will try to summarize them below, I hope you could follow and help me.
The first issue I have is about stall and spin in bad weather/turbulence. For example, if suddenly the 15 kts headwind shifts its direction and becomes a tailwind, I will lose 30 kts of airspeed, right? If so, I don't get it if the result would be a stall or just losing lift and momentary have an increased rate of descent. Actually, I can't figure out on my own if the AOA would change even if the pilot maintains the same attitude during the windshear event.
The same problem for updrafts/downdrafts. As far as I know, these gusts momentary change the AOA and thus it would results a stall, right? What if hypothetically just one wing is affected by the gust? The result would be a spin? Or more likely a snap roll? All these scenarios are in the low and slowflight regimes i.e. takeoff/landing, because I guess this would be the most probable scenario to be problematical.
The next problem is about crosswind landings. We use to make stall landings in small airplanes, so, considering this and a kicking-the-crab in flare technique, you are uncoordinated close to stall when you kick the crab and use opposite aileron to prevent banking due to rudder use. How safe is this?
Also regarding stall, is there any difference between an accelerated stall and a dynamic one?
Thanks so much!
Hi Steve, In your first instance where the headwind changes to a tailwind. This is referred to as wind shear and has caused a few commercial airliners to crash during landing. The appropriate response when this happens is to increase pitch angle to stop the descent while applying all available power. The AOA will definitely change for the worse if constant attitude is maintained.
The downdraft problem is less of a problem as it happens at higher altitudes and more time to recover is available. It is hard to imagine a scenario where only one wing would be affected but it may be possible. The aircraft reaction would be very hard to suggest and would probably be different for different aircraft. Neither downdrafts nor updrafts will result in a stall condition by themselves. They will only result in changes to your vertical speed. (and sometime spill your coffee)
Making stall landings in crosswinds are definitely not recommended. Airspeed in excess of normal landing speeds are recommended for crosswinds and a combination of wing down and "kick the crab" techniques are usually used. I prefer the wing down technique unless conditions are severe enough to use both.
Dynamic stalls are much more complex than static or accelerated stalls. See the following link for more info. http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19810011501_1981011501.pdf
Accelerated stalls are usually a little more drastic in pitch changes than static stalls, but they are very similar.
Hope this helps answer your questions. Good luck.