Originally Posted by
RickNRoll
How could software cause that? Does the software patch just allow the engines to run harder so that a new failure mode has been exposed.
Educated guess is that they changed the stator vane scheduling in an effort to either optimize engine performance or get a little red line speed margin - if they got it wrong it can set up harmonics in the blades at certain rotor speeds.
Pratt has had that problem before - on the PW2000 they came out with some compressor tweaks as part of a performance improvement program. Turns out if you did derated climb, you could get a harmonic in (IIRC) the fifth stage compressor which could cause the blades to fail - interestingly it was only a problem with derated climb - full rated climb it was just fine.