engine surge with EGT rising

[vopz]

this is a question about a procedure to follow :
in case of engine surge on B 737 NG we will have these parameters:

a) N1 and N2 fluctuate randomly.
b) Compressor stall noises are heard.
c) EGT rises to overheat conditions (over 800 DEG C) after a time of 1 to 2 minutes

so when we do the boxed items of the” ENGINE LIMIT SURGE AND STALL “check list ,we have to enter the flaps on the flaps speed schedule even when the EGT stay in the red band.

my question is :is it normal and logic to clean the airplane with the EGT in the amber band ?it's true that stall ceases when throttle is reduced but........

I would have preferred cutting off the engine then cleaning the airplane.

[SNS3Guppy]

As you're discussing raising flaps, you appear to be describing an engine problem on takeoff. Your first priority is always to fly the airplane. Protecting the engine is important, but not as important as flying and protecting the airplane.

If the engine has run to an overtemp condition during a stalled state (compressor stall), you're not going to be leaving it in an overtemperature condition for one or two minutes to see if it matches the description. However, you're going to fly the airplane first, which will include getting it cleaned up and flying your departure profile, before you tackle the engine problem.

[Intruder]

My perspective from a 4-engine airplane may be different, but...

If the problem is a surge/stall, and the problem may be resolved by simply reducing thrust on that engine, it may well be worth an attempt to pull back the thrust lever a bit to try to clear it. The result may well be an INCREASE in real available thrust if the stall clears.

Consider that the airplane is designed to fly from V1 with 1 engine completely failed. If you have even 50% thrust on the "bad" engine, you have significantly more than the minimum required for safe flight. The "fly the airplane" dictum may well include pulling back 1 thrust lever if circumstances favor it.

OTOH, if you have a written immediate-action procedure for the situation (our 747s do NOT!), you are obligated to follow the procedure unless you as PIC believe there is a safer alternative.

I've had the situation twice in recent history -- once just after takeoff and once at 600' on final. Both times the first action after positively identifying the engine was to pull back the thrust lever on that engine -- NOT to idle, but enough to clear the immediate stall.

[Ashling]

Once you've actioned the recall items if the surge does not clear or an exceedance is still indicated the checklist advises you to shut the engine down. As you allude to this stage is not recall so in accordance with Boeing procedures you would wait until the aircraft was clean until you did so. However if you were to decide that the symptoms were now more appropriate to severe damage you could then action those recall actions which would secure the engine.

You have to make a judgement about how badly damaged your engine is and whether you can wait to shut it down. Personaly if the EGT stayed above limits after the initial actions I'd action the severe damage damage checklist. Better to be safe.

[Intruder]

It is often feasible to prevent the temperature excedence in the first place by judicious reduction of thrust when the stall is first noticed. OTOH, if a GE CF6 engine stalls at all, it likely already has enough damage to warrant a rebuild (dunno 'bout the CFM56)...

[vopz]

yes i agree with you Ashling,Personaly if the EGT stayed above limits after the initial actions I'd action the severe damage damage checklist.but the broblem is that some crew are trainned to do the "engine limit surge /stall "check list ,and some others are trainned to do the "engine severe dammage or separation"check list.
believe me how badly if the crew (PF , PM) start a discussion at this height about what to do ,the engine limit..........or engine severe..........check list.
:ugh:

[lomapaseo]

yes i agree with you Ashling,Personaly if the EGT stayed above limits after the initial actions I'd action the severe damage damage checklist.but the broblem is that some crew are trainned to do the "engine limit surge /stall "check list ,and some others are trainned to do the "engine severe dammage or separation"check list.
believe me how badly if the crew (PF , PM) start a discussion at this height about what to do ,the engine limit..........or engine severe..........check list.


agree that there are differences in training sylabus regarding checklist action items.

I'm not a fan of interpretations of "severe" engine damage. The crew will never know for sure.

Typically the training configures the simulator to lose N1 and set a fire alarm to trigger a severe engine damage checklist and then adds in extra yaw for a seized engine.

However loss of N1 is quite common for just a loss of part of a fan blade on those machines that use speed pickups on the blade tips. Add to this that in actuality the fan never seizes until you drop down to landing air speeds.

Then there is the no-difference in drag between a seized fan engine and a still turning fan engine, since most of the drag is from the nacelle and a little from the compressor behind the fan.

The fire bell is the more significant symptom

Now back to the engine surge/stall. The good news is that many are recoverable by pulling back the throttle. However for those that have trashed the innards the EGT is never going down until you chop the fuel entirely. Even min idle fuel on a trashed engine will make a nice fire in the turbine.

[SNS3Guppy]

What damage may or may not have occured is subjective, and based on the nature of the problem, when it was discovered, and what was done and when it was done.

If the problem has occured during the early stages of the climbout, then that's not the time for troubleshooting. Someone else mentioned not having any immediate action, or memory items, for the 747. We do. Both for an engine stall and for a high EGT (which may or may not be related).

I don't believe the severe damage checklist is appropriate, as one is guessing as to what may have occured. One doesn't necessarily have any indication of severe damage, and even then one is guessing at hot section damage. If one intends to shut the engine down, then one can do so, but there won't necessarily be any indication or evidence of severe damage.

Retarding the thrust lever may well alleviate the condition, but more than likely if it's stalled with the temperature rising then a shutdown and restart is in order. If you're still bringing up the flaps the PNF and FE can work it out (or in the case of the 737, the PNF), but the first priority is always flying the airplane. We repeat this over and over and it ought to be a given, but time after time when an annunciator illuminates, a bell goes off, or an abnormal condition is viewed, I've witnessed pilots switch from flying the airplane and attempt to begin working on the problem. It happens, so it bears repeating again. Fly the airplane.

If you're at 3,000' in a noise abatement procedure and retracting flaps, then you've got time to address the problem. If you're at 800' flying the special engine-out procedure, then perhaps waiting to get cleaned up is a more appropriate choice.

More than once I've seen an overanxious crewmember attempt to shut down the wrong engine, even though it's a confirmed call that should involve more than one person in the process. Remember that the most dangerous component in the airplane is the pilot, and that fast hands kill. Don't be in too big a hurry to touch that engine. Save it if you can, but your first priority is always flying the airplane.

[Ashling]

A fire is far from the only symptom of severe damage.

From Mr Boeings 737NG checklist.

Engine Fire, Severe Damage or Seperation

Condition: Fire is detected in the related engine; severe damage which may be associated with airframe vibration and/or abnormal engine indications has occurred; or the engine has seperated.

I'm not saying it is svere damage but if you leave the engine outside of its limits without doing anything it may well turn into it and that is the problem with the surge limit stall checklist as the engine shutdown bit is non recall and therefore would be left until the aircraft is cleaned up which may take some considerable time especially if an engine out procedure needs to be flown. Its going to very uncomfortable sitting there with an engine red lined but doing nothing more than disconnecting the autothrottle and retarding the thrust lever for several minutes. Sure Boeing allows the Captain to do the shutdown non standard from recall but I know of several people who have been criticised for this as it was non recall.

Therefore, immediately after take off, to my mind it is better to go down the severe damage route if the IAs for the surge limit stall do not work. The engine needs to be shutdown if the surge does not clear and its redlined and the severe damage checklist is recall so can be done monitored and confirmed. You know your engine is secure and as there is no fire you do not have to discharge a bottle and so the whole process is reversable if required. Just as you cannot prove the engine is severly damaged from the flight deck you cannot prove it isn't or about to become so.

We all agree low level is not the place to mess around and you should focus on the flying. So secure the engine and do just that.

[wileydog3]

Didn't fly the NGs but our old stall/surge checklist didn't require shutting down the engine IF pulling back the thrust lever solved the stall/surge problem. IF, however, the engine continues belching and coughing then we went to the engine shutdown checklist.

But from reading about the stall/surge events, it can be a very exciting moment with a fair amount of vibration making it appear much worse than it actually is. Either way, at my old house we always cleaned up on takeoff before beginning any engine failure/fire/severe damage checklist. You have enough thrust with the remaining engine to fly.. so no rush.

[lomapaseo]

I agree that there is a lot of good advice in this thread about flying the aircraft first.

It was really a wake up call in the crew response to the UAL B747 out of SFO-AKL a few years back.

We took a hard look at severe engine failures and the preponderance of evidence was that quick shutdowns would have saved nothing. On the other hand the evidence showed quite a few over eager shutdowns for even benign engine annomalies that resulted in accidents.

you decide we can second guess you later :)

[SNS3Guppy]

Severe engine damage...why run a checklist based on what might be? Or what it might become, or what it isn't?

If you have high EGT, do you not have a checklist for that? We do. Same for an engine stall or surge.

Certainly an engine stall can produce severe damage, or be part of a chain that leads there, but if it's simply a stalled engine with rising EGT, you're not there yet. One might say that it's best to run the engine separation checklist...after all a high EGT might become a fire that might cause enough damage to cause enough imbalance that the engine separates...

But that hasn't happened yet, and selecting a checklist for what hasn't happened yet isn't appropriate. I see your reasoning...that checklist covers everything, so why not use it, right? Because it's the wrong checklist.

[Ashling]

Chaps

The checklist is the same for fire and for seperation hence fire, severe damage or seperation checklist.

SN3 the NG does not have a high egt checklist its covered by the surge limit stall checklist.

I agree that normaly haveing carried out the IAs for a surge/stall you would normaly progress to the shutdown checklist if said IAs were unsuccessfull. As the shutdown checklist is non recall you have to get your QRH out and action it. That is Boeings procedure and that of my airline. So if you have a surge post V1 you would fly to safe alt were you would confirm the failure, say 400' and carry out the IAs monitored or confirmed. Say the surge does not clear and still gives 800 degrees fluctuateing N1 and N2 and compressor stall noises as described in the scenario. You would now fly your engine failure procedure, which may take some time, after the final turn of that procedure and above accell alt you would clean up and engage an autopilot then call for the QRH reference items. All the time you are doing this, which may be several minutes, you are cooking your engine.

In my view the engine surge limit stall checklist is poorly written for an event immediately after take off for the reason given above. The engine shutdown bit of the checklist should be a recall item, imho, but sadly it is not. So if you follow the checklist you have to wait to action the shutdown it if the event occurs on take off. If you leave it for several minutes you will have a severely damaged engine. Sure Boeing allow you to action any checklist by recall if you think it is necessary but people can be and are criticised for this in the sim.

So if I have an engine with a redline egt, spouting flame makeing loud banging noises with N1 N2 fluctuating and not responding to the surge limit IA's I am shutting it down. Not leaveing it in that state for several minutes. If TRE's in the sim do not like me actioning the rest of the surge limit stall checklist from memory then I will call it severe damage and shut it down by the recall action.

My priority is to fly the aircraft so I'll secure the engine and do just that. In my view too much time is spent trying to diagnose engine problems low down which can only detract from flying the aircraft especially as many engine failure procedures involve turns low down and you want both crew focused on getting that right.