Pratt JT9D-7Q compressor stall question
I have a question for some engineers expert with the Pratt JT9D-7Q engine. Please if you're not an expert I don't need your "opinion."
Had an engine go into unrecoverable deep stall - low fluctuating EPR, spike in EGT, retarded power to idle and still would not recover, although EGT came down, but EPR continued to fluctuate. High 30s in altitude and .84 mach, very gentle level-off with little/no throttle movement. Shut the engine down and returned to the airport. Mx attributted the stall to a "clogged filter", however the filter never went into bypass as would be evidenced by an "icing" light.
Maintenance's expanation sounds like BS to me, but I'm a pilot and not an expert in JT9Ds.