riojax Posted April 2, 2023 Posted April 2, 2023 After a spin recovery, with clean air, good speed and AoA the cockpit still vibrate. flat1.trk
IvanK Posted April 2, 2023 Posted April 2, 2023 Watched the TRK. Looks like compressor stall to me, frozen RPM and very high JPT. 1
Bremspropeller Posted April 2, 2023 Posted April 2, 2023 (edited) One thing I've noticed and which seems to be reproduceable is that the stall only happens during the recovery and never during the departure / incipient spin. Going idle before starting any recovery action seems to not make any difference at all. Edited April 2, 2023 by Bremspropeller 1 So ein Feuerball, JUNGE!
riojax Posted April 3, 2023 Author Posted April 3, 2023 (edited) 10 hours ago, IvanK said: Watched the TRK. Looks like compressor stall to me, frozen RPM and very high JPT. Yes, I think the same, but in the track the throttle is very low... anyway I replayed it and tested (using the ESC menu -> Take control) to put the engine in idle and then it recovered, but took around 40 seconds in idle, good speed, low AoA, etc. I don't know too much the 9K-50 internals but I think that is too much time to recover the compression and combustion chamber pressure levels in this situation, also I think that is good to check the minimum throttle/fuel flow to recover the combustion chamber pressure in this engine. What do you think in your knowledge and experience? Edited April 3, 2023 by riojax 1
Solution IvanK Posted April 3, 2023 Solution Posted April 3, 2023 I can only speak from experience with the ATAR 9C5 from Which the 9K50 was derived. As to recovery time I guess it depends on exactly the severity of the stall and what you do Airspeed wise to recover. In reality you wouldn't sit there for 40 seconds hoping it was going to clear. I reckon I would have given it 10-15 seconds unless JPT was rising rapidly to the limit (750C) if no recovery Stop cock the engine whilst getting into the relight envelope and go for the relight. The ATAR9C5 had 3 basic types of Compressor stall or Surge. Momentary .. which was quick and cleared with no pilot intervention. A Partial surge that needed throttle to idle and increasing IAS 300-500K faster is better. The most extreme was the total surge.... required engine Shut down and relight. Mirage III bold face stated: If the stall is not cleared within 40 seconds or if the EGT(T4) exceeds 750C, or if the engine flames out : Throttle to Stop, Relight in the relight envelope. The Mirage F1 Emerg Checklist says: What I see in the TRK I would have interpreted as a Total surge. A really severe compressor stall can be most impressive with reverse flow flames out the intakes and even Blow in doors being blown clear out of the aeroplane. The only compressor stalls I ever experienced were relatively mild or partial (all caused by my over aggressive maneuvering) all cleared by selecting Idle and getting the aeroplane in balanced flight ASAP. 5
riojax Posted April 3, 2023 Author Posted April 3, 2023 1 hour ago, IvanK said: The ATAR9C5 had 3 basic types of Compressor stall or Surge. Momentary .. which was quick and cleared with no pilot intervention. A Partial surge that needed throttle to idle and increasing IAS 300-500K faster is better. The most extreme was the total surge.... required engine Shut down and relight. Mirage III bold face stated: If the stall is not cleared within 40 seconds or if the EGT(T4) exceeds 750C, or if the engine flames out : Throttle to Stop, Relight in the relight envelope. Ok, it seems reasonable then. Thank you a lot!
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