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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 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. apply forward elevator, and only when the aircraft has responded with a pitch down, apply full Thrust. 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 |
engine synchronizer question
Forgive me for being a decade or two behind the times, but the last synchronizer I can recall working on was a turboprop. What turbofan aircraft/engine configuration(s) offers or requires a synchronizer? What flight modes is it used in? Is it strictly used to avoid assymetric thrust, or to tune out noisy heterodyne beats?
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I'm sorry to step back down the thread here, but a question please to clear something up for my simple brain! I fly a variable geometry swept wing military jet (not a Flogger), and was a bit confused about Old Smokey's
Approach to stall ...where it’s RAPIDLY correct wing drop with roll control Just for information, when we get towards the stall, wings level unloading seems to do the trick. Actually did the 'trial' once when a little disorientated during a fight, and can confirm that technique does work to below HUD reading speed (50 kts). Avoided use of the rudder then too. Probably best to avoid that regime with passengers however! Finally, we have a hopeless, no visual simulator where I am at the moment, but I still think that there is benefit from going through the procedures required approaching the stall. Notwithstanding the valid comments about realism and simulator performance envelope, if nothing else, one can practice the cadence of the recovery. I really can't see there being too many negatives in that - and at least if you have to do it for real, it won't be for the first (and consequently perhaps last) time. Looking forward to the help! Psy |
Use of aileron - rudder
Psy-Clops and Old Smokey,
You both address the sensitive matter of controling bank during stall. It is so, that down moving aileron increases the angle of attack on that wing, thereby possibly exceeding stall aoa and aggravating the roll tendency. For this reason military training taught keeping the wings level by secondary effect of rudder. Although not at all a fan of rudder in flight on large aircraft (done to death on other threads) I have used this technique on air tests of the MD-80 series. If used sensitively it worked well. MDC once had a DC-9 invert on them during such a test, because one wing leading edge had been cleaned and the other one was covered in a layer of crushed flies. By the way, we went to full stall (but not to stick pusher, which was some percent beyond the stall) on these flights. FC. |
A quick reply - In transit.
What the last 2 respondants say is perfectly correct for an aircraft which only has aileron for roll control. For aircraft using aileron and roll spoilers, the spoiler is far more effective in roll control. Near the stall the spoiler dumps the lift on the rising wing more effectively than does the aileron, and, as a bonus, produces a little yaw in the direction desired. Regards, Old Smokey |
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