Eng Stall v Surge; Is there a difference?

[Wander]

Hi all,
The title says it all really!
Is there a difference between an engine surge and stall?
Many thanks,
Wander.
:zzz:

[PPRuNeUser0172]

Not really, just diffferent types of surge.

Some will self clear by going to idle, some will require the engine to be shut down and re lit.

A surge is just a partial or full breakdown of airflow through the engine caused by an adverse pressure gradient, ingestion of hot gases or some other disruption to the airflow such as excessive side slip or high alpha.

[lomapaseo]

It all depends on your useage.

I've posted before on this subject.

A stall in a compressor is exactly the same as a stall on your wing (a localized breakdown in lift). A surge is unique to the engine which has a higher pressure contained behind the compressor which is stalling. Once the higher pressure overcomes the loss of pressure from a stalled stage than the air will reverse itself and come forward out of the inlet with a loud bang.

A localized temporary stall condition is much more common than an enveloping surge.

The stall is the begining while the surge is an ending

[PAXboy]

(Non-pilot speaking) If the stall/surge causes a loud bang, how easily would that be heard in the cabin?

I'm thinking of a time (some years ago) departing Kai Tak in a 744, when there was one HECK of a loud bang from the No3. I was sitting in Club by the window just in front of the starboard leading edge. The machine gave a bit of a shimmy, then I could hear the engine throttled back and slowly brought up again. It was one of the few times that I have being momentarily concerned on a flight. Not least as we had rotated only about ten seconds before and were heading out from '13' into the black night!! A beautiful flight from then on, of course. BA at it's best.

[grease7]

Oh you can easily hear that in the cabin. I have been in a hangar with doors closed and then in a portacabin office with doors closed. This while a 747 with jt9 engines doing a high power engine test run outside and then stalling at take-off setting. The bang is unbelieveable and not easily missed and if you are the groundcrew watching the engine outside is even more spectacular with flames coming out off the rear and front of the engine.
The jt9 and rb211 engines can survive such a big stall and continue after that. So what you said is a stall, a loud bang the engine going to idle to check parameters and then spinning up again.:ok:

[PAXboy]

Ah, jolly good. The 744 certainly met it's design imperatives! As we were starting a 14 hour sector to LHR, we must have been fairly heavy.

When I was on the flight deck in the middle of the night (it was 1991!) and I asked about the noise, they affected that nothing had happened and that they had heard and seen nothing. Sensible, as they would have no idea what the visitor was like and no point having the pax telling everyone about an 'engine failure'.

I was not worried for more than two seconds, as I heard the revs were under control but I am glad that I did not see any flames! But now I shall be prepared for them and looking out for a good display!! As ever, PPRuNe has the answers and reassurance. :ok:

--------------------
"I tell you, we are here on Earth to fart around, and don't let anybody tell you any different." Kurt Vonnegut, Jr.