Ignition Override,
You have correctly addressed a significant problem encountered in tests to the fully developed stall, that is, that (1) any assymetric thrust or slip is to be avoided at all cost, and (2) assymetric engine spool-up during recovery is to be avoided. Your quote -
when pulling both throttles back to where the bleeds are barely closed, about 52-55& N1, it is easy for one throttle to be set just a bit below what you want, and one engine can accelerate faster
If I may refer back to my earlier post, I think that these two items were covered -
During deliberate stall tests on jets, it’s a case of feet OFF the rudders, engine synch ON, Yaw Damper OFF – all to avoid any yaw moment.
All of that in the interests of avoiding assymetric thrust during the stall, PARTICULARLY the Engine Synch to ON. On aircraft without Engine synch, it was necessary to judiciously maintain the engine parameters equal, and
apply forward elevator, and only when the aircraft has responded with a pitch down, apply full Thrust.
During the recovery it is essential to FIRST unstall the aircraft before applying thrust. In so doing, the wings are at an AoA somewhat below the stall, and small thrust assymetry can be tolerated. Preventing engine stall is a secondary but important consideration.
Like 747FOCAL, I have seen the world upside down from B727, DC9 and other cockpits, I don't ever want to see it that way again. Even the best stall warning system does not 'know' the wing condition, and the worst I've seen was a test on a 'dog' aircraft with paint overspray on the upper wing surface, the full stall ocurred about 20 Kt above schedule, and before the stall warning activated. I think that this instance alone stands to justify such stall training as is possible for flight crews.
Regards,
Old Smokey