Strange sound @ TOD, compressor stall?

[Daveman]

Out of FL240, eased the trim wheel down, pulled the pwr lvrs slowly back and heard strange, almost shudder noise. Not really a bang (tough to describe on a keyboard). I have no experience with a compressor stall but it was the first thing that came to mind. Other guy thought it was a fuselage noise.
It was 2 consecutive sounds.
Second and last leg no problems other than being a little unnerved when pulling back the power.
Garrett TFE 731-3-1G engines: no engine instrument abnormal indications.
Any thoughts. Thanks.

 

[English]

I've only had a compressor stall twice. Both times, it sounded like someone was hitting the side of the fuselage with a metal hammer. It was REALLY loud.

 

[banned username 2]

My GUESS is you might have a bad/sticking surge bleed valve which is causing a momentary spool mismatch which is resulting in a minor compressor surge due to the first spool decelerating slower than the second spool...

 

[enigma]

My GUESS is you might have a bad/sticking surge bleed valve which is causing a momentary spool mismatch which is resulting in a minor compressor surge due to the first spool decelerating slower than the second spool...

what he said!

enigma

 

[AnimalMother]

Or it could be the flux-capacitor is going bad.

 

[minitour]

Or it could be the flux-capacitor is going bad.

Great Scott, this is heavy, Doc!

 

[Gulfstream 200]

Or it could be the flux-capacitor is going bad.

or...your Garrett Grenade is about to blow.

I hope you have three of them out there...

 

[CL600Pilot]

My GUESS is you might have a bad/sticking surge bleed valve which is causing a momentary spool mismatch which is resulting in a minor compressor surge due to the first spool decelerating slower than the second spool...

We had the exact thing happen in a 600 Challenger with the Lycoming engines - started out as small noise - almost like something slid thru the cabin and lightly hit the partition - our mechs. told us it was probably the surge valve so we changed surge valves and it happen again a few weeks later - changed valves again and it happened again - changed valves again and then our 'bad surge valve' turned into a full fledged shake, rattle, and roll - locals coming out to see why there is a dump truck flying overhead - compressor stall at 400 feet above Grand Cayman. Turns out the 'coating' on the inside of the engine was beginning to flake off from improper install 20 years earlier causing changes in airflow patterns in the engine.

It more than likely is a surge valve but have it looked it - it may be something like we had that eventually developed into a serious compressor stall.

CL

PS - Our "plane captain" originally told us not to worry - it's just the wing bolt popping and all Challengers make that noise after 7,000 hours !(insert rolling eyes here)

 

[GravityHater]

can we assume all engine indications were nominal when this happened?

 

[banned username 2]

can we assume all engine indications were nominal when this happened?

Yes...

no engine instrument abnormal indications.

 

[U-I pilot]

Or it could be the flux-capacitor is going bad.

1 point 21 "jigga-wats"!!!!!!

 

[Daveman]

My GUESS is you might have a bad/sticking surge bleed valve which is causing a momentary spool mismatch which is resulting in a minor compressor surge due to the first spool decelerating slower than the second spool...

After looking in the books, sounds like this is the problem. Appreciate the input. Take care.

 

[dseagrav]

Thread hijack!

I was under the impression that a compressor stall was very damaging to the engine and was considered a very serious event. Is that true?

 

[banned username 2]

I was under the impression that a compressor stall was very damaging to the engine and was considered a very serious event. Is that true?

Yes, it is true if it is allowed to persist, a momentary compressor stall TYPICALLY won't cause any damage if it is rectified immediately... However if a compressor stall occurs, one should determine what the cause is because basically all modern jet engines are designed to never have a compressor stall if everything is working normally.

Basically a Compressor Stall will occur on acceleration and a Compressor Surge will occur on deceleration (what the gentleman who started this thread was most likely experiencing)...

Hope this helps!

 

[freightdogfred]

Depends also on the engine design....I've had numerous repeated stalls on a JT-3 (a low bypass fan engine) that would have torn a high bypass fan motor apart...

Pratt&Whitney=Thrust you can trust.

 

[banned username 2]

Depends also on the engine design....I've had numerous repeated stalls on a JT-3 (a low bypass fan engine) that would have torn a high bypass fan motor apart...

basically all modern jet engines are designed to never have a compressor stall if everything is working normally.

.....