Some points to ponder
Skylor is correct—it’s all about rudder coordination, which is why we put a slip/skid ball on our AOA indexer (visual display) and move the AOA tone left and right with the ball, so the pilot can hear when the rudder is not properly coordinated.
The video examples at the beginning of this thread are examples of a “skidding” departure, i.e., stalling the airplane while trying to “rudder” around the base turn. There is a bit of a an old wive’s tale that you can’t depart (lose control) in a “slipping” turn, but that’s not correct. While you have to force the airplane to react (unlike a skid, where it immediately snap rolls when the critical angle of attack is exceeded), it will eventually auto-rotate, but not until it’s provided lots of aerodynamic warning. Notice the ratchet effect prior to rolling over the top into a spin:
https://youtu.be/I6tBNnoaB6w.
If the airplane is properly coordinated, a stall may occur at very low altitude, and recovery is possible:
https://youtu.be/BPD5xk1wgOw. Obviously, the right answer is to go around. This was a controlled demonstration that illustrates the additional SA that accurate AOA cues provide when maneuvering.
As was pointed out, an airplane can stall at any airspeed in any attitude (and stall SPEED increases with G load). Ed is correct, it’s entirely possible to enter a steep spiral and increase airspeed and AOA simultaneously (all the way into an accelerated stall). Ed doesn’t bother to stall the airplane in his video, but I do in the second demonstration in this video:
https://youtu.be/PKWvCgQ-uzM. This occurs when the pilot has mis-managed what fighter pilots call the lift vector (where the lift is pointing) and the velocity vector (where the airplane is going, or the vertical component of the “flight path”). In this video, it’s easy to see the horizon, the standby airspeed indicator and listen to the angle of attack. If you aren’t familiar with our work, I clipped this video from a slightly longer maneuvering demonstration you can view here:
https://youtu.be/JxBLS8JL6Mo.
The “impossible turn" is not impossible, but it his highly dependent on many factors, not the least of which is aircraft performance. The ability to turn back is also highly dependent on ambient conditions, length of runway etc. The video of my turning back from 250’ AGL posted above is not a good example. At the time we shot that video, we had not yet conducted engine-off testing; so, we were not properly compensating for residual thrust (thanks again Skylor for calling us to task on that—huge input!). Turns out actual engine off glide angle is steeper than glide angle in IDLE. After conducting engine-off experiments at altitude, we determined that we could replicate actual engine-off performance in the RV-4 by applying flaps 40 with power at IDLE for low-altitude test. But things get even more aerodynamically complicated, because the RV-4 has such good climb performance, it actually continues to gain altitude AFTER engine failure as I transition to an on speed AOA condition for turnback. We are currently modeling this type of edge case for an iPhone app that integrates aircraft performance with ambient conditions to determine whether a turnback is practical under actual conditions during initial climb segment. Here are more representative turn backs:
https://youtu.be/aIvBnva1At8.
I'm not the smartest guy in the room. I've had the benefit of some good training and experience; and I have a good AOA system in my airplane, courtesy of a team of really talented folks that volunteer their time and ask nothing in return. John Boyd broke the code on energy maneuverability a long time ago, and my AOA system effectively allows me to hear energy cues real time. That's a tremendous amount of SA for a knuckle-dragger like me
. The military cracked the loss-of-control code over a half-century ago. Whether the airplane spins into the ground or spirals into the ground is a moot point. We changed the way we did business in the military by adapting AOA and incorporating Boyd's work into how we teach aircraft handling. We can do the same in GA/EAB or we can continue to suffer current mishap rates.
Fly safe,
Vac