A320 Packs ON T/O vs Compressor Stall

[bmbahia]

I just finished a research over the forum and couldn't find anything about this.

I was told that the use of the engine bleed on (packs on) in the A320 would likely minimize the possibility of a compressor stall during the take-off.
I'm skeptical about this affirmation and couldn't find anything that supports it, anywhere.
I read sometime ago that some 320 family operators states in their SOP that a packs off take-off is recommended. If this is correct, this operators would be more susceptible to compressor stalls.
Can anyone enlighten me on this one?

Thank You.

[lomapaseo]

it's a trade-off situation I believe.

Bleeding air at the higher operating line, can give you added margin below the surge/stall line but the price you pay is in effeciency which in the case of high power operation turns up as higher turbine inlet temp , TIT, EGT etc.

If you have plenty of EGT margin but a deteiorated surge/stall line then turning on the packs is fine.

I'm of course ignoring fuel burn since we are only talking short term effects here.

This kind of stuff lends itself to performance analysis by powerplant performance engineers (I'm not one) and is the basis for what is written in the various manuals. Be careful of listening to rumors

[yachtno1]

Does this apply to both the V2500 and the CFM Variants?:)

[PantLoad]

Compressor stalls during any regime of flight are not normal. If you're getting compressor stalls during takeoff (or during any other flight phase, for that matter), you've got serious engine problems. Worrying about whether or not to do a packs-on or packs-off takeoff (to avoid compressor stalls) is like deciding which bucket to use to bail out the Titanic.

There are three basic modes for takeoff with regard to bleed choices. First, you can do a packs-on takeoff, bleeding the engines. Second, you can do a packs-on takeoff, bleeding the APU. And last, you can do a packs-off takeoff.

There are pros and cons to each choice, but increasing engine stall margin is not one of the considerations. Your company's SOP, surely, addresses these considerations. For example, on hot days with tired engines, a no-engine-bleed takeoff using the maximum allowable flex might be advisable. This would maximize the EGT margin...whatever that margin might be.

To reiterate, if you're concerned about engine stalls, you should address this problem not with bleeds-off takeoffs, but with a tech log write-up.

PantLoad

[bmbahia]

Thank you for your replies. I still think that it won't enhance the safety margin if you take-off with packs on or off because of the compressor.
As PantLoad said, if you have any concern about a compressor stall, you shouldn't take-off.

Best Regards.:ok:

[Plastic Bug]

Um, I'm your basic idiot, but I thought that if you wanted to reduce your EGT margin, it was bleeds (packs, whatever) off. If you want to increase your STALL margin, it's Nacelle Anti-Ice on.

But I'm just an idiot.

PB

[PantLoad]

No, you are not an idiot!!! You are correct.

Please see Airbus FCOM 3.02.70, Page 5. You are correct.

PantLoad

[Clarence Oveur]

And now tell me why using nacelle anti-ice increases the stall margin, but using engine bleed doesn't?

[PantLoad]

Gentlemen,

I see the problem.

My writing is in need of help. My last paragraph should have stated:

To reiterate, if you're concerned about engine stalls, you should address this problem not with bleeds-on [Initially, I wrote "bleeds-off] takeoffs, but with a tech log write-up.

Please forgive me for this mistake. You guys are correct.

Sorry,

PantLoad

[A330AV8R]

Correct me if Im wrong here but If memory serves me right no where on Vol3 does it state especially on 3 . 02 . 70 P5 that using or not using Packs increases or decreases Compressor stall..... and Pant load was right , if your worrying about stalls then youve got a sick engine that needs a write up lest you want to throw your buddy whos taking over a burton !!

:E

[PantLoad]

Gentlemen, Gentlemen...

Yes, airfranz, you are also correct. 3.02.70 P5 does not address the pack issue. It DOES, however, suggest that employing wing and engine anti-ice will increase an engine's stall margin ["but will increase EGT accordingly"].

I respectfully suggest that we're all picking this issue apart unnecessarily. And, I apologise for causing the confusion and starting all of this because of my poor writing.

It's my fault...Sorry, Guys.

PantLoad