Accelerated Stall Video

[brcase]

Based on some recent discussions of base to final Stall/Spins and Accelerated Stalls I created a video of an Accelerated Stall in a 172.

This was part of my investigation as to why it seems the spread of the stall warning and the actual stall seems so much wider than during an unaccelerated stall.

What I am learning is I thought I knew a lot about stalls and stall spin entries, I am learning there is a lot more I think I could learn. I have more questions and things I would like to explore than I had before.

My Basic take away is at least in the configuration tested, it was likely not possible to actually stall in an accelerated condition due to a turn. This is indicated by the fact that it stalled at the same airspeed as a when trying to do an unaccelerated stall. A G-meter would have been interesting, I suspect what happens is that when pulling back in the turn the aircraft airspeed decelerates so quickly that it reaches a 1G Stall Speed before wing actually stalls.
Testing with a more aft CG condition might change this result.
I am open to a better explanation as to why the Stall doesn't occur at a higher airspeed?

I also found it interesting how hard it was to actually Stall at 45 degrees. The airplane has severe overbanking tendency at that low speed before the stall requiring almost full opposite Aileron. A bit more right rudder would have helped this, but would not likely be a natural thing to do, but even holding that much aileron was not natural either. The more natural thing would be to let the nose drop and recover from the stall allowing the Ailerons to be come more effective.

Brian

 

[flyingron]

You're not in unaccelerated flight other than the turn. Speed doesn't control or define a stall. AOA does. The apparent stall speed difference occurs when you try to hold a level attitude through a turn while decreasing the speed. This can be a bit daunting in the 172, so most people demonstrating turning stalls yank it into the stall like you do.

 

[Clip4]

You are performing the maneuver too quickly and you have too much kinetic energy remaining.

 

[dtuuri]

After watching, I think if you had held your altitude it would not have stalled at all at that bank angle (+/-45°). You wouldn't have enough elevator available because in a steep bank the "boom effect" would decrease the down force on the tail, as would the change in relative wind from the turn tending to come more from above (EDIT: below) the tail than more from below (EDIT: above), i.e., the opposite of what you need to get a stall. So, in order to get a stall break, you needed to pull the nose up and get an assist from gravity when you ran out of elevator. That kind of screws up the whole definition of the maneuver — it was no longer an "accelerated stall", it was "something else".

EDIT: Diagram:

 

[dtuuri]

I'm surprised nobody argued with my theory above. Here's a recent example of an actual accelerated stall (video not yet released): TSCB Rockwell 690B 'Bird Dog' Fatal Crash Final Report - YouTube , so they CAN happen. Not all airplanes are designed the same, though.