Brent Regan wrote:
<<...According to Charlie he was instructing and the pilot was practicing accelerated stalls. On one attempt the pilot entered the stall uncoordinated that resulted in a very fast spin. >>
<<My advice is to practice stalls and avoid spins. Spins are not recoverable from altitudes where they are likely to happen but stalls can be IF the pilot's reactions are trained.>>
Charlie's student combined the two requisite ingredients to spin: stall + yaw. The airplane will not spin without both. "Stall" is a function of Angle of Attack (AOA) only - speed has nothing to do with it (remember the stall vs. bank angle charts from ground school?). Also, weight, c.g., accelerated airflow, etc., are factors. When the airplane approaches the critical AOA, you need to reduce AOA at the first sign (especially in the pattern) of stall: buffet, on board system, etc. Pushing is not what most of us are comfortable doing when we are low to the ground (eg., in the pattern). The untrained pilot's instinctive reaction to an unexpected nose-drop is to pull -- increasing AOA even further past AOAcrit.
Now look at "yaw." Most of the pilot's I have transitioned into high-performance airplanes start out by mis-judging the turn radius, which becomes most evident in the base-to-final turn (where altitude 'surplus' is definately low). One response to this overshoot condition is to use rudder to 'skid' the airplane and avoid increasing bank angle. This obviously causes yaw; the good news is that my transition students generally know better than to do this. Another response (what I see most commonly) is to increase bank angle and back pressure to pull the airplane around the corner. If you are not diligent with rudder use, it is common to be slightly uncoordinated here - and the increase in load factor (w/bank angle & back pressure) will cause AOA to increase - perhaps to AOAcrit = stall.
Here's the biggest threat I see in these airplanes: Pilot starts to overshoot final & increases bank angle/back pressure. Pilot encounters either "imminent" or "full" stall condition, RECOGNIZES it (good!), and pours the coals on (good). What the pilot does with the stick depends on one thing: TRAINING. Low to the ground, nose dropping, instinct says to pull (BAD). The dramatic increase in propellor effects almost guarantees a yaw condition; hence the low-altitude stall/spin entry. Oops.
The rudder requirement in the IV/P various dramatically at different power / airspeed combinations; this makes us exceptionally susceptible to being in a yaw condition unless we are extremely diligent with our rudder usage.
Oh, by the way, to see first-hand the effects all that 350hp has on 'wrapping up' the spin, go get an advanced spin course in a Pitts or Decathlon.
...since I am a relative new-comer, here's my introduction: Lancair check pilot (based in Texas), I teach unusual attitude/upset recovery in a Pitts and Decathlon, tailwheel transition in both, plus a Stearman, and own/fly/instruct in a Cessna 195. Eclectic mix, I know. I also do quite a bit of twin training, and fly fast jets for the AF Reserve...
Jim McIrvin
pilot195@rocketmail.com
210-275-7780
Lancair check pilot (flying 2 IV/Ps now)
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