PPRuNe Forums - View Single Post - South Africa - Aircraft Stalls as Skydivers Prepare to Jump
Old 4th Nov 2021, 17:48
  #22 (permalink)  
Join Date: Sep 2016
Location: USA
Posts: 720
Originally Posted by ehwatezedoing View Post
The pilot specifically said that the subsequent wing rocks were due to one engine spooling up more quickly than the other and you come up with this theory on your own!?
Pure pilot bashing....

I went very, very close to stall a Beech 18 one time during a jump run and for the exact same reason, way too many far back.
It's a strange feeling when you push your elevator all the way forward to its stop and the aircraft is doing the exact
Certainly a severe aft weight load can explain running out of forward elevator authority as in your anecdote... while that weight is still onboard. But not after that weight jumps out.

And while it's certainly possible that a faster spooling engine on one side can induce a yaw and in turn a roll (and a spin given high AOA) it's hard to imagine (putting it lightly) one side spooling up faster, then the other side, then the first one again, then the other again, a 4-time reversal.

The pilot may have told his story, but I would not take it as the definitive recounting of the events, given 1) the high misunderstanding of flight dynamics that many pilots have, and 2) the potentially warped perception of a stressed and overwhelmed experience like this. This isn't an attempt to trash talk this particular pilot, it's just human nature. And if the pilot didn't realize what he was doing during the maneuver, his recollection after is very likely to be similarly flawed.

To more reliably build a picture of the events, we have to take in the video and circumstantial evidence. And the circumstance of someone who doesn't regularly practice spins, is that it's very common for muscle memory (aft elevator to move the nose up and out of the ground) to overwhelm any reasoned notion of the proper thing to do with the elevator. Including after a recovery. Add on the tunnel visioned stress of suddenly finding yourself in a spin in a large multiengine airplane not certified for this maneuver, I think the likelihood of an improper response only increases.

And what we see in the video after the first recovery and a sudden normal acceleration (to the right in the frame) consistent with high AOA. And after that, a series of roll reversals (some with yaw) immediately one after the other, with sudden pitchups in between... again consistent with high AOA, with the pilot doing their best to control the thing with rudder. Just like the "falling leaf" exercise in basic trainers where the plane is held in a stall.

I think Pilot DAR above may be on to something with the pilot overdoing an attempt to level off before the slick airplane accelerates past its airspeed limit (especially the flap speed limit), but in that case why would the power be advanced at all?
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