lmp Posted September 21, 2014 Posted September 21, 2014 Once every couple of flights this strange thing happens to me. I'm not sure if it's a bug or not. The aircraft becomes somewhat nose heavy after take off. It doesn't react to trim - I can see the trimmer button being pressed, but the neutral trim light doesn't go off. At this point, if I accelerate, the aircraft will get even more nose heavy (so the opposite to what you'd normally expect) to the point where I "run out of stick" trying to maintain altitude. The autopilot will recover from this just fine, even if I'm already in a steep dive, but as soon as I turn it off, I lose control again. Am I the only one experiencing this? Am I doing something wrong? I'll try to provide a track once this happens to me again.
ddhenda Posted September 21, 2014 Posted September 21, 2014 Once every couple of flights this strange thing happens to me. I'm not sure if it's a bug or not. The aircraft becomes somewhat nose heavy after take off. It doesn't react to trim - I can see the trimmer button being pressed, but the neutral trim light doesn't go off. At this point, if I accelerate, the aircraft will get even more nose heavy (so the opposite to what you'd normally expect) to the point where I "run out of stick" trying to maintain altitude. The autopilot will recover from this just fine, even if I'm already in a steep dive, but as soon as I turn it off, I lose control again. Am I the only one experiencing this? Am I doing something wrong? I'll try to provide a track once this happens to me again. did you turn on the trimm? Switch at the top row of RV panel
lmp Posted September 22, 2014 Author Posted September 22, 2014 It could be that I suppose. In that case I probably also missed the rest of the switches in that row. Could lack of trim or cone movement explain the nose getting heavier as I accelerate thing? I'll do some investigating after work. Thanks!
FishBike Posted September 24, 2014 Posted September 24, 2014 Could lack of trim or cone movement explain the nose getting heavier as I accelerate thing? I don't know about the MiG-21 specifically, but it's normal for transonic and supersonic aircraft to need significant nose-up trim as they accelerate up to and past Mach 1. There's even a name for this: Mach tuck.
Tango Posted September 24, 2014 Posted September 24, 2014 (edited) MiG-21 design is such that the trim condition change is "unremarkable" and passing the transsonic region, will actually require neutral trim to relieve what little force there is. What the -21 does have, is an actuator that changes the "arm" between the stick input and elevator deflection with change in Mach number, to neutralize the change in pitch sensitivity. Pure genius. Best regards, Tango. Edited September 24, 2014 by Tango
lmp Posted September 24, 2014 Author Posted September 24, 2014 Well, my problems stopped now that I'm paying attention to those switches, so it must have been it. Thanks for your comments.
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