N1 - 0, N2 - 0 (737 argument with an instructor)

[emirares787]

Hello, dear colleagues

Some month ago I had flew with a simulator session on B737CL as a first officer.
Everything went well and at some point I had an Engine Malfunction after V1. Seemed like an engine failure, I reacted very well and kept the aircraft on runway heading. Approaching to 800ft AGL I was told by the first officer that we have an engine failure. But, before making a decision on the actions I need to take, I studied the engine indications. So that is what I am sure of: N1 indicated 0, N2 indicated 0. I have been trained that this indicated an Engine Severe Damage, which made me call for a memory drill of the appropriate checklist.



But after that, I was interrupted by the instructor – stating that he gave me a simple engine failure. My argument about N1 and N2 indications being at point ZERO did not suit him, as it is not stated in any Boeing 737 Manual.

We did not find any agreement at that point. Please guys, any advices on the topic – except for the basic knowledge and some obvious facts.



Best regards!

[Beakor]

These are the conditions from the 737 QRH for Severe Damage.

Condition: One or more of these occur:
•Engine fire warning
•Airframe vibrations with abnormal engine indications
•Engine separation.

You had abnormal engine indications but if this was not accompanied by airframe vibrations then it doesn’t meet the condition for Severe Damage. Practically I think this is only possible in a simulator. In the aircraft, the chances of both spools stopped with no airframe vibration is virtually impossible. A signal failure to both indicators may do this but then you may not lose thrust. So, in my opinion, your instructor is technically correct but it’s not a likely scenario for real. Sounds like that sim puts N1 and N2 to zero when Engine Flameout is selected.

[Capt Scribble]

If you are at flying speed, the N1 must have some rotation unless it is seized (on the ramp the fan turns in the wind). Different airframe, but still jet technology, Airbus would suggest treating no rotation as damage.

[Check Airman]

If you are at flying speed, the N1 must have some rotation unless it is seized (on the ramp the fan turns in the wind). Different airframe, but still jet technology, Airbus would suggest treating no rotation as damage.

I tend to agree with this. It’d at least be windmilling. The simulator is just that- a simulator. It’s not perfect. Sometimes you just have to nod and smile.

[tdracer]

Capt. and Check have said, it'd be pretty much impossible to have zero rotational speed on both rotors without severe engine damage. It could be an indication problem, but there are multiple independent data paths involved for rotor speed that would all have to be failed for that to happen - again, very, very unlikely without severe engine damage (or even separation).

[lomapaseo]

Yes a loss of engine rpm to zero is either loss of signal or locked rotors. Locked rotors are extremely rare. in-flight (too much wind and the broken pieces loosen up) Both rotors being locked in flight is way outside the data base experience but I uppose it could happen

Airframe vibration associated with loss of thrust and any other any engine symptom is time to wake up and follow the FCOM,

The simulators you are typically trained on cannot reliably replicate these combination so a typical training syllabus often simulates something akin to multiple engine symptoms to the point of training you to go deeper into decision making.

Real life events that progress in the powerplant beyond the first seconds following a severe engine failure are indeed rare

[Mach E Avelli]

IT seems that your simulator is slightly unrealistic and your instructor is not making due allowance for this.
If all rotation came to a sudden stop, some vibration (probably a lot of vibration) would precede it.
Once completely seized, the vibration could then cease.
Further, as it seized there would probably be a spike in EGT.
It is better when in doubt to run the worst case checklist. That is the Severe Damage checklist. The engine is buggered anyway, so what more harm could you do?
Also consider that fire detection and EGT systems are not infallible. You could have a fire or severe over temp which is not obvious. When in doubt do the full drill.
Straight flameouts at takeoff are less likely, and would suggest either a fuel problem (at this stage this would probably be unknown) or environmental (which would be fairly obvious). Healthy engines don’t suddenly stop with no residual rotation.

[PantLoad]

Years ago, during take off right about at V1, had the left engine N2 seize. Thought the left wing was coming off. Whole airplane shook like crazy. First flight of the day; early morning departure. Woke us up for sure.

This was only for a few seconds. Once the N2 was completely stopped, all the violence stopped.

Our SOP at the time was to execute the “Engine Fire, Severe Damage, Separation” checklist. Since we never got an actual fire indication, we stopped the checklist just shy of discharging a fire bottle.

Can’t remember what actual N1 and N2 RPMs are at take off thrust, but it’s a lot. (Maybe 14,500 RPM....dunno?)
For such mass to come to a complete stop in a matter of seconds, it’s a violent experience. I know this; it actually happened to me.

Fly safe,

PantLoad

[back to Boeing]

I’d treat zero N1 and zero N2 as severe damage if there is an associated swing (otherwise it’s a failed indication in my book). And doing the severe damage separation memory items is not unsafe if an engine is failing/ has failed. I am not a TRE or a TRI or a trainer in any respect but I personally think the instructor was wrong to stop the simulator at that point. Have a discussion in the debrief by all means but not during the exercise.

[mikeygd]

Were you one of two first officers, or in command? Or am I pointing out the obvious?

[KayPam]

Airbus says that the following list allows to suspect engine damage :
Rapid increase of EGT above the red line
Important mismatch of the rotor speeds, or no rotation
Significant increase of aircraft vibrations, or buffeting, or both
Hydraulic system loss
Repeated or not controllable engine stalls

The manual states that two or more are required, but in every sim i ever did in an airbus (two different countries, a dozen of instructors from 6 different airlines), no rotation on either N1 or N2 was engine damage.

[ImbracableCrunk]

10 years in CL and we were taught no rotation = severe damage.

[Mr Good Cat]

These are the conditions from the 737 QRH for Severe Damage.

Condition: One or more of these occur:
•Engine fire warning
•Airframe vibrations with abnormal engine indications
•Engine separation.

You had abnormal engine indications but if this was not accompanied by airframe vibrations then it doesn’t meet the condition for Severe Damage. Practically I think this is only possible in a simulator. In the aircraft, the chances of both spools stopped with no airframe vibration is virtually impossible. A signal failure to both indicators may do this but then you may not lose thrust. So, in my opinion, your instructor is technically correct but it’s not a likely scenario for real. Sounds like that sim puts N1 and N2 to zero when Engine Flameout is selected.

To the letter of the law, this ^^^

It’s quite rightly been pointed out that the likelihood of having no airframe vibration if you have both rotors locked is probably nil.

However, you do exactly what it says on the tin (i.e. don’t do severe damage without airframe vibration) and you’ll have something to stand by in court. The correct checklist would obviously be Surge/Limit/Stall which will lead you into a shutdown for this condition anyway. In a real incident, a sneaky lawyer might find some reason to ping the blame on you for a subsequent problem by showing you don’t know the manuals for your engine situation. Anything done outside them must able to be justified in court. Sucks, because I think we all know that two locked rotors must be severe damage. I think in the sim I would let this play and raise it as a talking point. If it was handled safely then the box has been ticked for engine-out handling.

[tdracer]

Are we talking a full motion simulator? If it's a fixed simulator, it would be pretty hard to simulate airframe vibration...

[Rt Hon Jim Hacker MP]

What was his point? I don't know the 737, but the only difference is pulling/pushing the fire handle on any Boeing or Airbus I've flown. In the highly unlikely event that you need to restart the thing, it's reversible anyway.

A sim is a good procedure trainer but any instructor or examiner needs to point out that a lot of it is "best guess" anyway. Next time you get a sim TCAS RA, watch what the intruder does. It follows you. Would that happen in the real world?

[By George]

I am currently working as a 737 Sim Instructor. We teach no rotation equals severe damage. On the instructors panel, selecting this function simulates no N1 and no N2 with no vibration. The only difference to a straight failure being a distinct 'pop' during the actual failure itself. If the candidates treat it as a simple failure to be tackled at the end of the fourth segment, it programs a fire before they reach this point. The Civil Aviation authority we work under treat no rotation as severe damage and expect shutdown in the second segment.

I have had a failure of this nature in real life, although it was a JT8D. It sounded like a bucket of bolts spinning around with initial vibration but once it seized, no vibration at all. There are limitations to even modern simulators and despite the, 'Just like the real thing' sing song they are not and never will be.

[FlightDetent]

Possible cause:

The instructor actioned a simple failure on his controls - and thus were right, while at the same time
The student saw N1 = 0 and evaluated severe damage - which is what needs to be done on the real aircraft.

[ZFT]

I am currently working as a 737 Sim Instructor. We teach no rotation equals severe damage. On the instructors panel, selecting this function simulates no N1 and no N2 with no vibration. The only difference to a straight failure being a distinct 'pop' during the actual failure itself. If the candidates treat it as a simple failure to be tackled at the end of the fourth segment, it programs a fire before they reach this point. The Civil Aviation authority we work under treat no rotation as severe damage and expect shutdown in the second segment.

I have had a failure of this nature in real life, although it was a JT8D. It sounded like a bucket of bolts spinning around with initial vibration but once it seized, no vibration at all. There are limitations to even modern simulators and despite the, 'Just like the real thing' sing song they are not and never will be.I’m posting from a decaying memory here (and I know someone will correct me if wrong!) but I recall that there is a difference with approach/attitude from the airframe manufacturers (and hence data providers and these days often the source of the software model) with issues such as “Severe Engine Malfunctions” and “Engine response to Volcanic Ash encounters”.

Whilst Airbus and others suppliers support these types of malfunctions with vibrations, sometimes quite severe or erratic engine indications and or shutdowns being experienced, Boeing tends to take a different approach and has stated that there is no or insufficient data for them to provide the model.

The TDMs of course are obligated to only meet approved data.

[emirares787]

In fact what I wrote is a bit confusing. We were 2 first officers training in one session.

[Centaurus]

In the simulator I operate (B737-300 Category D Full Flight), a flame out initiated on the instructor panel gives instant loss of thrust and a yaw and roll in the direction of the "dead" engine. The N1 and N2 decay until eventually the N2 and N1 show low numbers but continue to rotate slowly under influence of forward speed. There is no vibration. The follow up checklists do not require the crew to pull the fire handles.
There is an item on the instructor panel annotated "Engine Seizure." When actuated, there is instant loud engine noise associated with the engine running down and seizing. At the same time there is the expected yaw and roll towards the seized engine. There is severe vibration which is absolutly unmistakeable physically as well showing up on the relevant vibration indicator. .

In this simulator the N1 will quickly fall to zero caused by the failure of the drive shaft from the accessories gear box, while the N2 will run down more slowly. It is the zero reading on the N1 that is a characteristic of a seized rotor. That, and the severe vibration on that engine that would trigger the Severe Damage checklist rather than a mere engine flameout checklist.

Be careful here if the vibration indicators are EFIS type and not analogue. The needle on the EFIS dial is very small. Beyond a certain vibration limit that needle vanishes off screen. I believe that was one of the problems associated with the Boeing 737-400 crash at East Midlands where mis-identification of the failed engine occurred. In this event the EFIS vibration indicator needle disappeared off screen because it had registered a high reading beyond the capability of the vibration system and thus showed no reading at all on the gauge. It is wise therefore to look for corroborative evidence of severe damage or otherwise rather than rely solely on one source of information

See: https://en.wikipedia.org/wiki/Kegworth_air_disaster

One extract from that report stated:"The vibration indicators were smaller than on the previous versions of the 737 in which the pilots had the majority of their experience. The dials on the two vibration gauges (one for each engine) were small and the LED needle went around the outside of the dial as opposed to the inside of the dial as in the previous 737 series aircraft. The pilots had received no simulator training on the new model, as no simulator for the 737-400 existed in the UK at that time. At the time, vibration indicators were known for being unreliable[3]:69–70 (and normally ignored by pilots), but unknown to the pilots, this was one of the first aircraft to have a very accurate vibration readout."

Post No 2 says it all. If your simulator has the N1 and N2 gauges falling to zero readings simultaneously when on the instructor panel the instructor has selected a simple flameout engine failure, this would suggest the simulator fidelity fails to meet that of a Level D category full flight simulator. Your instructor should be aware of this. If your simulator is a no motion operation then there will be no vibration present. This should have been briefed by the instructor concerned.

Be aware that pedantic simulator instructors exist and you could court retribution if you attempt to argue with these type of characters. A fact of life in simulator training. The QRH/FCOM are your friends when it comes to differences of technical opinion.

[Mr Good Cat]

Be aware that pedantic simulator instructors exist and you could court retribution if you attempt to argue with these type of characters. A fact of life in simulator training. The QRH/FCOM are your friends when it comes to differences of technical opinion.

And the QRH/FCOM does say that severe damage is Abnormal Indications WITH <airframe> vibration. So hard to argue with that call.

As usual in aviation though, we tend to miss the big picture. It’s obvious the correct QRH will lead into an engine shutdown anyway. So the goal of safely handling an engine failure will be achieved. Providing you didn’t flip the plane upside down of course.

[Papa_Golf]

No N1 or N2 rotation is damage, period. If it's a "simple" flame out N1 would be still spinning.

[FullWings]

I think in these kind of situations, you just have to nod, pretend to write something down, then do your own research later.

A simple risk/benefit analysis of pulling the fire handle (or not) with a possibly severely damaged engine and accessories tends to lean towards doing it. If it isn’t shot to bits and some time later you really need it back, the procedure is completely reversible. On the other hand, if it is badly broken and still connected to hydraulics, fuel, pneumatics and electrics, there is a chance this may lead to further significant problems, like loss of hydraulic systems, smoke/fumes in the air con or even fire in the nacelle (or a combination of these). Which would you rather be dealing with while flying around on one engine?

Another point is that with increasing severity, there is also an increasing likelihood of high energy bits taking out some/all of the warning systems. A while ago one of our jets had an uncontained failure (on the ground, luckily) which punched holes in the aircraft and set it on fire but there weren’t any immediate warnings...

[Papa_Golf]

I think in these kind of situations, you just have to nod, pretend to write something down, then do your own research later.


"Oh I see Captain, thank you Captain. Very useful input. I'll look into that."

[FlyingStone]

I think in these kind of situations, you just have to nod, pretend to write something down, then do your own research later.

This, with a very refined OIC technique, is the best advice.

[sonicbum]

"Oh I see Captain, thank you Captain. Very useful input. I'll look into that."

If that happens, the instructor needs to be taken out training and be retrained or do something else.

You must NEVER leave a training session with question marks popping over your head unless there are some evident contradictions within the documentation or some wording is poorly chosen by the manufacturer/operator. In that case the instructor MUST come back at the earliest stage with an answer to the trainees after consultation with technical pilot or CFI, HT, or anybody who can answer the question.

Worst thing to see in training is people getting out of sim sessions with uncertainties and the inability of the instructor to clearly explain WHY something works the way it does.

[FullWings]

I understand that but at the end of the day, most people are trying to get signed up for another six months with the minimum of drama and an extended argumentative debrief is probably not high on their wish-list. There are normally friendly trainers or Standards pilots who can explain/educate in a non-jeopardy environment, plus provide appropriate feedback if necessary.

After 4hrs inside an unreliable box on legs, it’s the last thing you need. I agree about leaving unsure but as long as you clear it up before you go flying again, confidence can return...

[sonicbum]

I understand that but at the end of the day, most people are trying to get signed up for another six months with the minimum of drama and an extended argumentative debrief is probably not high on their wish-list. There are normally friendly trainers or Standards pilots who can explain/educate in a non-jeopardy environment, plus provide appropriate feedback if necessary.

After 4hrs inside an unreliable box on legs, it’s the last thing you need. I agree about leaving unsure but as long as you clear it up before you go flying again, confidence can return...

You are absolutely right. The problem lies always within the organization and not the trainees in this kind of context.
There are unfortunately too many instructors and examiners in the wrong position and often this has nothing to do with their knowledge or skills, it has to do with the attitude or their ability to be good "educators".

[alf5071h]

This event is an example of a hazard of misapplication - misunderstanding the concept of SOPs; an extreme SOP culture where all events are expected to follow the rules. Life is far from that perfection; training should concentrate more on process, understanding, thinking about an appropriate course of action, opposed to placing events into neat training boxes to be ticked off.

Also a reminder of how the industry forgets, mislays knowledge, most of which applies today but is put aside because of rarity of events; a weakness from improving safety standards.

From many years ago, and dusted off in the 90s for the PSM+ICR studies, a long lost example of Engine Malfunction Analysis - for crew.
https://www.dropbox.com/s/f18gotbmjs24ciw/Engine%20malfunction%20analysis.pdf?dl=0

PSM+ICR page 2 https://www.skybrary.aero/bookshelf/books/1623.pdf
'The simulator propulsion system malfunction models in many cases are inaccurate and/or do not have key cues of vibration and/or noise. There is also no robust process that ensures the quality and realism of simulator propulsion system malfunction models or that the malfunctions which are used in the training process are those most frequently encountered in service or those most commonly leading to inappropriate crew response. This shortfall leads, in some cases, to negative training.

While current training programs concentrate appropriately on pilot handling of engine failure (single engine loss of thrust and resulting thrust asymmetry) at the most critical point in flight, they do not address the malfunction characteristics (auditory and vibratory cues) most likely to result in inappropriate response.

The changing pilot population, coupled with reduced exposure to in-service events from increased propulsion system reliability, is resulting in large numbers of flight crews who have little or no prior experience with actual propulsion system failures.'

[FullWings]

Absolutely Alf.

I remember when I converted onto the 737-200 (wow!) back in the mists of time, when combative Instrument Ratings were a thing, it was almost expected that you’d have run the drills before the gear had fully locked up. Okay, a little bit in jest but not much. No time for analysis, mutual decision making, flightpath assured and all that modern rubbish!

This perpetuated the slavish following of SOPs, IMO, as that was the way to impress the instructor. Watch those hands dance over the levers! See how quick and confident I am! Luckily, being an average kind of pilot, I managed to survive without too much mental trauma but some were not so lucky.

I recall doing a 2-day sim with a captain I’d flown with before on the line - really nice chap and competent operator; not a “rules” guy at all. One of items was a “LOFT” exercise, run by the co-pilot in real time, with various scenarios for the instructor to choose from: due to lack of time, we got a confirmed bomb threat. OK, said I, there’s a familiar airfield right in front of us on a ~3deg approach, let’s go for it at Vmo and do as much of the QRH as we can on the way in. I found the capt. somewhat evasive and continually trying to slow down (not a bad thing in itself) but also determined to do all the checklists right to the bitter end, even if it meant going into the hold. I managed to persuade him that time was of the essence (tick tock tick tock) and through constant intervention managed to get the aircraft on the ground and everyone off pretty swiftly.

In the debrief afterwards, the trainer asked the capt. if he thought I was pushing a bit hard during the approach, and he replied that no, he’d have done exactly the same thing IN REAL LIFE. Unsurprisingly, the rather observant trainer caught that one immediately and asked why it should be any different to the sim? The capt. then described how as a junior F/O many years ago he’d been shouted at by a trainer and told that he would never get a command and shouldn’t be flying at all. His crime? Missing one item off an unimportant checklist. Since then he’d had a pathological fear of simulators, to the point where he had difficulty sleeping during the week before and was physically sick in the car park before each session. He could only survive by doing what was printed on the checklists: no more, no less. He then broke down in tears.

The trainer and I both looked at each other and mouthed a silent “F...”.

Nowadays we’re all nice people(?) and there are peer support groups, industrial psychologists, free mental health care, etc. Back then? Not so much and the expectation was more biased to “man up and deal with it”. Still makes my blood boil how some people were permanently scarred by completely avoidable incidents.

[PantLoad]

So beautifully said!


Fly safe,

PantLoad

[Luke258]

Ive experienced the very same thing once. Made me Pass my check only partially. Really annoying...

[sonicbum]

Absolutely Alf.

I remember when I converted onto the 737-200 (wow!) back in the mists of time, when combative Instrument Ratings were a thing, it was almost expected that you’d have run the drills before the gear had fully locked up. Okay, a little bit in jest but not much. No time for analysis, mutual decision making, flightpath assured and all that modern rubbish!

This perpetuated the slavish following of SOPs, IMO, as that was the way to impress the instructor. Watch those hands dance over the levers! See how quick and confident I am! Luckily, being an average kind of pilot, I managed to survive without too much mental trauma but some were not so lucky.

I recall doing a 2-day sim with a captain I’d flown with before on the line - really nice chap and competent operator; not a “rules” guy at all. One of items was a “LOFT” exercise, run by the co-pilot in real time, with various scenarios for the instructor to choose from: due to lack of time, we got a confirmed bomb threat. OK, said I, there’s a familiar airfield right in front of us on a ~3deg approach, let’s go for it at Vmo and do as much of the QRH as we can on the way in. I found the capt. somewhat evasive and continually trying to slow down (not a bad thing in itself) but also determined to do all the checklists right to the bitter end, even if it meant going into the hold. I managed to persuade him that time was of the essence (tick tock tick tock) and through constant intervention managed to get the aircraft on the ground and everyone off pretty swiftly.

In the debrief afterwards, the trainer asked the capt. if he thought I was pushing a bit hard during the approach, and he replied that no, he’d have done exactly the same thing IN REAL LIFE. Unsurprisingly, the rather observant trainer caught that one immediately and asked why it should be any different to the sim? The capt. then described how as a junior F/O many years ago he’d been shouted at by a trainer and told that he would never get a command and shouldn’t be flying at all. His crime? Missing one item off an unimportant checklist. Since then he’d had a pathological fear of simulators, to the point where he had difficulty sleeping during the week before and was physically sick in the car park before each session. He could only survive by doing what was printed on the checklists: no more, no less. He then broke down in tears.

The trainer and I both looked at each other and mouthed a silent “F...”.

Nowadays we’re all nice people(?) and there are peer support groups, industrial psychologists, free mental health care, etc. Back then? Not so much and the expectation was more biased to “man up and deal with it”. Still makes my blood boil how some people were permanently scarred by completely avoidable incidents.

Great story, thanks for sharing ! That is a perfect example of how bad trainers can affect people’s professional activity and life in general.

[alf5071h]

FullWings :ok:
Instructors and management should read the section on continuous learning; page 4….
RPET The Resilient Performance Enhancement Toolkit 1. Erik Hollnagel, PDF Free Download (http://docplayer.net/186804890-Rpet-the-resilient-performance-enhancement-toolkit-1-erik-hollnagel-2019.html)

Related:- 'Deviant airline pilots: why we need them'.
https://jeroenwolbers.files.wordpress.com/2017/01/egos-2017-short-paper-passenier-et-al-deviant-airline-pilots.pdf

[a1anx]

Has any one experienced the C of G being moved during a SIM detail or having it put so far aft as to make the 'a/c' virtually unflyable?

I've witnessed this and had it done to me and wonder if it's possible to have a digital record of key parameters throughout the detail to discourage trainers from playing tricks.........they're NOT all saints :)

[classic200]

As a Flight Engineer for many years with over 11000 hours and many sim sessions I have seen a lot of engine problems, and N1 - 0, N2 - 0, is a engine severe damage / separation checklist, your instructor is wrong!

[Beakor]

A tip I give people for the sim in case this should occur, (Engine failure, no vibration, all spools stopped):

If you’ve done the Severe Damage memory actions and the sim instructor questions it, tell them you felt airframe vibration. It’s impossible for the instructor to prove that you didn’t (especially if the other pilot backs you up) and you’ve then met the conditions for Severe Damage. It should then turn into a discussion if the instructor feels like pushing it.

As I said earlier, this situation is a sim only gamesmanship issue. In the real jet, if both spools suddenly stopped there would most definitely be vibration. Severe Damage would be the correct and obvious action.

[Denti]

It's been a while, but in the airlines i flew the 737 every engine failure after take off (V1 cuts) was treated as severe damage, and the engine fire or severe damage or separation checklist was done (call: Engine fire, take action). Yes, for a simple flame out as well. Made things a lot easier as there was no differentiation, just one set of memory items and checklist to do. In cruise that would have been handled differently though.

And yes, no N1 and/or N2 was always seen as sign for severe damage. The newer level D sims had actually very noticeable airframe shudder for a seizure, you would notice that immediately.

[RetiredBA/BY]

We really have some problems these, days, abysmal instructors, seriously lacking in basic airmanship. Zero N1 and N2 tells me the engine is knackered, period.
The Boeing checklist is called for, “ engine fire, severe damage or seperation. “
Carry out the drill and do an engine out approach, not least because no N1 , N2 suggests to me the engine is not producing thrust, if, infact, its still on the wing!

Trying to second guess the cause of the problem is counterproductive. Assume the engine is dead and concentrate on the single engine procedure.

Simples.

Put the jet safely on the ground and THEN make further detailed analysis of the engine problem.
, so perhaps you should ask your instructor exactly what he meant by “engine failure”,

The 737 flies perfectly well on one.

( and yes I was a trainer, trained by Boeing on the 73 with 8000 hours on the type)

[clvf88]

We really have some problems these, days, abysmal instructors, seriously lacking in basic airmanship. Zero N1 or N2 tells me the engine is knackered, period.
The Boeing checklist is called for, “ engine fire, severe damage or seperation. “
Carry out the drill and do an engine out approach, not least because no N1 , N2 suggests to me the engine is not producing thrust, if, infact, its still on the wing!

Trying to second guess the cause of the problem is counterproductive. Assume the engine is dead and concentrate on the single engine procedure.

Simples.

Put the jet safely on the ground and THEN make further detailed analysis of the engine problem.
, so perhaps you should ask your instructor exactly what he meant by “engine failure”,

The 737 flies perfectly well on one.

( and yes I was a trainer, trained by Boeing on the 73 with 8000 hours on the type)

:ok: Ex 73 - absolutely agree.

[Roj approved]

Totally agree with everything previously written, unless the instructor briefed something different, it is a Severe Damage situation.

In the company I work at, a few years ago they introduced a "feedback" channel where these incidences could be anonymously reported to the training department. they are also available to be read un edited by the pilot group. There is also the opportunity to comment on the feedback, so if it has happened to more than one crew, the others can add their weigh to it.

This has had a very positive effect in curbing the Rouge Instructor/Check captain behaviour.

[Mach E Avelli]

It is incumbent on instructors and examiners to avoid negative training, or training in such a way that crews make assumptions simply because they are in a simulator. If the simulator has some non-realistic failure scenarios it's better not to go there. There are usually enough other failures in even quite basic simulators to test crew decision making.
A good examiner will work around simulator deficiencies in creative ways. For example, to reinforce that it is severe damage, and knowing that when the engine runs down vibration ceases (if that is what is in that particular simulator's tiny brain), introduce vibration preceding the actual engine 'failure' for long enough for the crew to recognise there is a serious problem. Or trigger fire warning before, simultaneous with, or soon after the failure. Then it's cut & dried what you expect them to do; no excuses for the wrong drill.
If you intend them to action a simple flame-out, at least create conditions that would be conducive to such an event, such as a contaminated runway and icing, or a fuel leak.
But back to the OP - as everyone here agrees, no rotation = severe damage.

[Avinthenews]

What’s more important Flying the aircraft or diagnosing the aircraft?

This length of this thread is exactly what Boeing is trying to avoid. Crews going heads down diagnosing what’s over and above the failure.

Fly the aircraft.

If vibration is distracting the crew from flying then take steps to stop the vibration.

and continue to

Fly the aircraft.

It’s been seen time after time crews diagnosing the problem, is it, is it not and next the aircraft is descending or not following the SID or being late to fly the engine out SID because the aircraft is no longer being flown accurately.

Worst case diagnose incorrectly and start messing with a good engine!

That last ones easy in the sim you programme simple indication faults on the good engine, zeros would be good and everyone gets sucked in diagnosing!

And no ones flying!

”So why did you get that GPWS warning?”

ahh because we were discussing wether it was severe or not.....

[Centaurus]

So that is what I am sure of: N1 indicated 0, N2 indicated 0. I have been trained that this indicated an Engine Severe Damage, which made me call for a memory drill of the appropriate checklist.

Assuming the sim was on motion and therefore the motion is felt through the whole cabin. Suddenly N1 and N2 run to zero and aircraft yaws and rolls to the failed side. Is it a flameout or a severe damage event? Was there airframe vibration? If the answer was Yes then severe damage and use the appropriate non-normal QRH checklist.

If there was no vibration but N1 and N2 went to zero, then it is a basic engine flameout since there was a yaw and roll. The fact that N1 and N2 both went to zero could be an aberration in the fidelity of the simulator or a deliberate ploy by the instructor to test the pilot's diagnostic knowledge. The presence or absence of airframe vibration is the key to the actions to be taken.

The OP never mentioned anything about airframe vibration yet he did mention the simultaneous falling to zero reading of the N1 and N2. Nor did he mention anything about vibration indicator readings. .

In other words, he failed to include all the relevant items that could have assisted responders to this thread to make a meaningful assessment of the state of the failed engine. For example, did the cunning instructor select a staight forward engine failure (flameout) and simultaneously select a failure of the N1 and N2 instrument indications?

if indeed he did, could that scenario actually happen in real life? Answer: Almost certainly not.

On the face of it, and going by what the OP described, it seems the instructor may have introduced three totally unrelated non-normals at the same time. That was unfair and poor instructor technique.

With the cockpit indications provided by the instructor, coupled by the assumed absence of airframe vibration, the pilot under test should have diagnosed the fault as engine failure - not severe damage. This suggests the instructor was correct even though he used a sleight of hand by failing the N1 and N2 gauges simultaneously with the flameout.

[clvf88]

Assuming the sim was on motion and therefore the motion is felt through the whole cabin. Suddenly N1 and N2 run to zero and aircraft yaws and rolls to the failed side. Is it a flameout or a severe damage event? Was there airframe vibration? If the answer was Yes then severe damage and use the appropriate non-normal QRH checklist.

If there was no vibration but N1 and N2 went to zero, then it is a basic engine flameout since there was a yaw and roll. The fact that N1 and N2 both went to zero could be an aberration in the fidelity of the simulator or a deliberate ploy by the instructor to test the pilot's diagnostic knowledge. The presence or absence of airframe vibration is the key to the actions to be taken.

The OP never mentioned anything about airframe vibration yet he did mention the simultaneous falling to zero reading of the N1 and N2. Nor did he mention anything about vibration indicator readings. .

In other words, he failed to include all the relevant items that could have assisted responders to this thread to make a meaningful assessment of the state of the failed engine. For example, did the cunning instructor select a staight forward engine failure (flameout) and simultaneously select a failure of the N1 and N2 instrument indications?

if indeed he did, could that scenario actually happen in real life? Answer: Almost certainly not.

On the face of it, and going by what the OP described, it seems the instructor may have introduced three totally unrelated non-normals at the same time. That was unfair and poor instructor technique.

With the cockpit indications provided by the instructor, coupled by the assumed absence of airframe vibration, the pilot under test should have diagnosed the fault as engine failure - not severe damage. This suggests the instructor was correct even though he used a sleight of hand by failing the N1 and N2 gauges simultaneously with the flameout.

Sorry mate but thats a load of rubbish :ugh: Have a read of the comments above. No rotation = severe damage. And if we must keep harping on about vibration, the checklist refers to airframe vibration so the engine vibration isn't hugely relevent.

[sonicbum]

If there was no vibration but N1 and N2 went to zero, then it is a basic engine flameout since there was a yaw and roll.

Can You explain us how a coaxial concentric multi shaft turbofan engine can read N1/N2 ZERO without mechanical damage ?

Thanks.

[sheppey]

But, before making a decision on the actions I need to take, I studied the engine indications. So that is what I am sure of: N1 indicated 0, N2 indicated 0. I have been trained that this indicated an Engine Severe Damage, which made me call for a memory drill of the appropriate checklist.
The OP description of what he looked at in deciding the action to take is too simplified. As Centaurus noted there was no mention by the OP of any other engine parameters. The whole subject under discussion is not worth arguing about until the OP provides more detail on what else he saw other than the readings of two gauges, the N1 and N2.

Having had long experience at simulator training involving hundreds of engine non-normals including engine seizures, I cannot recall ever selecting on the instructor panel a deliberate engine seizure without the first indication to the flight crew being significant airframe vibration. Of course the seizure will eventually cause the N1 and N2 to fall to zero as the seizure takes effect. But without amplification by the OP of any other engine indications to back up his opinion the non-normal was a seizure, the discussion goes around in circles.

In the example given by the OP he seems to rely solely on the readings of two instruments N1 and N2 as proof of an engine seizure. The instructor disagreed and said it was an engine failure. After all, it was the instructor who "arranged" the the event so we should assume he knows which button he selected on his own panel.

Sorry mate but thats a load of rubbish
An interesting and informative thread spoilt by a rude remark civf88

[alf5071h]

As with all situations it is the context which frames our judgement. Context is often limited in simulation, and furthermore by instructor application.

Time / duration of events add different meaning. A flameout can result in zero rotation, but takes time; quicker at low airspeed and/or with combinations of fan rotation but core stopped.
A fast, violent stop will be dominated by dissipation of energy. Engine vibration might not be as significant as potentially more disturbing and misleading aircraft vibration.
There may be no turbine vibs - because the component has departed the aircraft, but the noise and airframe vibration could be interpreted as an alternative scenario, e.g. stalling, depressurisation; thus attention could be on stall avoidance or not over-stressing - first fly the aircraft.

Alternatively a flame out could be unnoticed until the oil pressure light comes on, both engines being at idle during a fast descent which maintains rotation; each type and situation has unique characteristics, as does human reaction - pilot and instructor - who's point of view.

Consider the objectives of training; safety. Awareness and actions (SOPs) are never perfect, but the outcome should be sufficiently safe, … and always an opportunity to learn, both crew and instructor.

[sonicbum]

The OP description of what he looked at in deciding the action to take is too simplified. As Centaurus noted there was no mention by the OP of any other engine parameters. The whole subject under discussion is not worth arguing about until the OP provides more detail on what else he saw other than the readings of two gauges, the N1 and N2.

Having had long experience at simulator training involving hundreds of engine non-normals including engine seizures, I cannot recall ever selecting on the instructor panel a deliberate engine seizure without the first indication to the flight crew being significant airframe vibration. Of course the seizure will eventually cause the N1 and N2 to fall to zero as the seizure takes effect. But without amplification by the OP of any other engine indications to back up his opinion the non-normal was a seizure, the discussion goes around in circles.

In the example given by the OP he seems to rely solely on the readings of two instruments N1 and N2 as proof of an engine seizure. The instructor disagreed and said it was an engine failure. After all, it was the instructor who "arranged" the the event so we should assume he knows which button he selected on his own panel.


An interesting and informative thread spoilt by a rude remark civf88

CFM engine - N2 Accessory Drive Lost. No vibrations (in the sim), N2 runs to zero due to the radial drive shaft rupture.

[lomapaseo]

The analysis going on in this thread really concerns me. The simulator session regarding engine failure symptoms should not be ad-hoc. Follow the FCOM. At least that can be changed to recognize important new techniques, As some have said Fly the Aircraft First. Don't try and interpret beyond what you are trained unless you run out of options in flying the aircraft.
If there is general agreement that the FCOM has missed something important, let the experts fix it.

[sheppey]

No vibrations (in the sim),
That is correct. In the full flight level D simulators I am familiar with, the actuation of the "Engine Seizure" selection starts the process with an instant very strong shaking of the simulator plus a loud noise of the engine winding down in RPM. When the seizure is complete, the vibration and noise level ceases. This is a CMF56 engine. On the same simulator a failure of the auxilliary gear box shaft exhibits the same charatacteristics as you describe.i.e N2 runs to zero and the engine flames out. This is not by defintion Severe Damage

[sonicbum]

This is not by defintion Severe Damage

This failure is a function of the radial drive shaft rupture.
If You think a high bypass turbofan engine flying at 140+ kt can go from 90+ % N1 or N2 to ZERO in a matter of a few seconds without damage then I guess we are not on the same page, but it is always good to discuss and learn more.

[amc890]

What’s more important Flying the aircraft or diagnosing the aircraft?

This length of this thread is exactly what Boeing is trying to avoid. Crews going heads down diagnosing what’s over and above the failure.

Fly the aircraft.

If vibration is distracting the crew from flying then take steps to stop the vibration.

and continue to

Fly the aircraft.

It’s been seen time after time crews diagnosing the problem, is it, is it not and next the aircraft is descending or not following the SID or being late to fly the engine out SID because the aircraft is no longer being flown accurately.

Worst case diagnose incorrectly and start messing with a good engine!

That last ones easy in the sim you programme simple indication faults on the good engine, zeros would be good and everyone gets sucked in diagnosing!

And no ones flying!

”So why did you get that GPWS warning?”

ahh because we were discussing wether it was severe or not.....
Exactly on point. Some people are way over thinking this. Whatever happened to just follow the manufacturers checklist to the letter.

[clvf88]

An interesting and informative thread spoilt by a rude remark civf88
An interesting and informative thread (I use that loosely) which had come to a valid consensus. Only for someone who had not bothered reading any of it to start repeating the same points which had been successfully argued against above.

A simultaneous N1 / N2 instrument failure :ugh:

[FullWings]

Ladies! Please!

In the rush to find a “wrong” answer, is it possible that both diagnoses have some merit and there is not 100% certainty because of lack of detail? Faced with a completely seized engine on both rotors, it’s not going to run again until it’s left the repair shop, so there is no harm whatsoever in doing the Severe checklist. Being pedantic you could argue that it was just a rundown(!) without vibration so it just needs securing.

Both are points of view and both could be “right” but, in real life, what would you do if an engine failed (and you know this because of the yaw and loss of performance) and even though there is no vibration N1 & N2 have gone to zero over a short time interval? Would you really go “oh yes, definitely fine, let’s start it back up later”? I think I’d be checking under the wing to see how much of it was left...

[sheppey]

But after that, I was interrupted by the instructor – stating that he gave me a simple engine failure.

Well there you are then. What's all the hue and fuss about?

Regardlees what the N1 and N2 readings were (either instantaneously or some time later), if we are to believe the OP username Emirares787 when he writes that the instructor told him he had given him a simple engine faillure, then readers of this saga must accept the instructor did just that. Even the copilot diagnosed an engine failure. The PF obviously disagreed with the copilot assessment. Fine - that is his privilege.

[Mach E Avelli]

QUOTE.....in real life, what would you do if an engine failed (and you know this because of the yaw and loss of performance) and even though there is no vibration N1 & N2 have gone to zero over a short time interval? Would you really go “oh yes, definitely fine, let’s start it back up later”? I think I’d be checking under the wing to see how much of it was left...[/QUOTE]

Precisely! Pod mounted engines have been known to completely depart the wing. That would certainly cause the N1 & N2 gauges to be somewhat confused. Of course in the real machine there would be all sorts of other unpleasant cues, but older simulators will lack these. The OP mentions this was a B737 Classic sim, so it would not be 'state of the art'.
Centaurus/Sheppey may have been exposed to so much simulator he is only looking at it from the perspective of an instructor panel with a limited portfolio of failure modes. That's for the instructor to work around, not the candidate. Neither should the candidate be expected to read the instructor's mind to determine what is required; however it is certainly part of the instructor's job to look at what cues are being presented in the candidate's seat, and whether the actions taken are reasonable - not what buttons have been pressed on the IOS !
When doubt exists, a pilot under check should never be pinged for doing a worst case checklist.

Save the cheaper options for discussion during line checks.

[sonicbum]

Centaurus/Sheppey may have been exposed to so much simulator he is only looking at it from the perspective of an instructor panel with a limited portfolio of failure modes. That's for the instructor to work around, not the candidate.

I believe it's actually quite the opposite.
When You have spent decades in the sim You have a very wide view of the spectrum plus You probably have done TONS of snag clearances in the SIM.
Anyway I agree there is not much left for discussion, it was very interesting so far with different point of view and lots of food for thoughts !

[FullWings]

When doubt exists, a pilot under check should never be pinged for doing a worst case checklist.
And that is the nub of it and why this thread exists at all.

There is a tendency to drift towards the unquestioning following of SOPs and that there is only one way (my way) of dealing with an issue that gives a positive outcome. There are very, very few circumstances that require immediate action with no real time to think about it first (high-speed RTO comes to mind). Although an engine failure seems like a simple thing with clearly defined actions as a result, even this is not as straightforward as it seems.

One of our training documents is a 40-page interactive book covering some of the engine failure possibilities and ways to deal with them. OK, you say, but to keep things simple, the manufacturers have distilled all that into a few choices that are simple to action in a time of high workload. Absolutely true, I say, but you can still end up in a cul-de-sac if you rush in blindly without due mental process. Imagine you go through a flock of birds after takeoff (does happen) and there are a few pops but the engines are still running. Shortly after that you notice the EGTs are high on both and then there is a fire warning on one engine. SOPs say to shut it down and fire the bottle but is that wise *right now*, especially as it is still producing thrust? What are we going to do if we get a fire warning on the remaining engine?

I’m sure everyone reading this would pause and reassess the situation, should it happen to them, but if you continually beat people over the head to follow SOPs no matter of any indication to the contrary, it might lead to a sub-optimal outcome. The fate of the French Concorde was sealed when a running engine was shut down due to a fire warning, leaving not enough thrust to stay airborne. Yes, it was probably going to crash anyway but that action made it a certainty.

[Flyerman11]

If you're unsure if it was a "simple" flameout or a severe damage, then treat it as severe damage.

It's best to land with a good engine shutdown than to try and re-start an engine with severe damage.

IMHO 0 N1 is a good sign of a seized engine. N2 may slowly wind down to 0 at low airspeeds, but N1 should always be rotating simply by windmilling.

[Mach E Avelli]

And that is the nub of it and why this thread exists at all.

There is a tendency to drift towards the unquestioning following of SOPs and that there is only one way (my way) of dealing with an issue that gives a positive outcome. There are very, very few circumstances that require immediate action with no real time to think about it first (high-speed RTO comes to mind). Although an engine failure seems like a simple thing with clearly defined actions as a result, even this is not as straightforward as it seems.

One of our training documents is a 40-page interactive book covering some of the engine failure possibilities and ways to deal with them. OK, you say, but to keep things simple, the manufacturers have distilled all that into a few choices that are simple to action in a time of high workload. Absolutely true, I say, but you can still end up in a cul-de-sac if you rush in blindly without due mental process. Imagine you go through a flock of birds after takeoff (does happen) and there are a few pops but the engines are still running. Shortly after that you notice the EGTs are high on both and then there is a fire warning on one engine. SOPs say to shut it down and fire the bottle but is that wise *right now*, especially as it is still producing thrust? What are we going to do if we get a fire warning on the remaining engine?

I’m sure everyone reading this would pause and reassess the situation, should it happen to them, but if you continually beat people over the head to follow SOPs no matter of any indication to the contrary, it might lead to a sub-optimal outcome. The fate of the French Concorde was sealed when a running engine was shut down due to a fire warning, leaving not enough thrust to stay airborne. Yes, it was probably going to crash anyway but that action made it a certainty.

Fullwings you speak my language!
At the risk of thread drift, there is a problem arising in some training 'cultures' which I think stems from being too anxious to pitch every procedure at some primitive pilot (the lowest common denominator) who has somehow infiltrated the system and is waiting to screw up.
We see policies written that forbid pilots to ever reset a circuit breaker unless it is specifically called up in the QRH. No more making one reset if you would like to have the system, but instead write it up for the engineers to reset and too bad if you are at a non-engineering port. No more attempting one recycle of some 'sticky' valve - write it up and ground the operation pending an engineer hitting it with a rubber hammer.
As for running an engine beyond its 5 minute limit if it's really needed to ensure adequate performance, or making a spit-arse turn to a reciprocal runway and landing overweight with an uncontained fire and not completing the full checklist - heaven forbid it should ever be suggested, let alone practiced in the simulator.

The result of this mentality is we have carefully scripted simulator checks where everything is rehearsed well before the event. I have actually had candidates ask me for the exact test sequences, approaches, route etc 14 days in advance of a simple Instrument Rating renewal. They arc up when I reply with a copy of the official test form and delay notification of the route until 24 hours in advance. Yet their masters often hit them with short notice roster changes or off-schedule charters and they cash their pay cheques cheerfully enough.
In some jurisdictions it seems gone are the days of non-jeopardy LOFT exercises where crews were encouraged to step outside their comfort zone. Now, it's all about ticking the boxes on the form.

[Centaurus]

The result of this mentality is we have carefully scripted simulator checks where everything is rehearsed well before the event

It may be an Australian thing to cover once's backside in event a CASA audit.

In another era I did some contract simulator training on the 737NG with the then SAS Flight Academy at Arlanda airport in Sweden. Instructors were encouraged to use their experience within reason and time permitting to add the occasional non-jeopardy exercise. By chance I was training two experienced former Israeli pilots for their type rating on the 737NG. Both were 747 captains who had bid down to fly the new 737NG rather than spend a life in long haul.

Both had flown Mirage fighter bombers on war operations with the Israeli Air Force. They certainly knew how to fly. Midway through the type rating we were ahead of schedule and I asked if they would like to practice a tight low level circuit to see how quickly they could get on the ground given a terrorist event on board. After all, these threats were not unknown in their part of the world.

From lift-off, into a close-in circuit to stopping after touchdown, started with five minutes. With further practice both pilots were able to takeoff and land the 737 in under two minutes from lift off. Under these emergency conditions there was no time for checklists or the niceties of TEM and CRM. They both flew superbly and were so impressed with this exercise and its applicability to a war zone operation, their airline El Al Israeli Airline introduced this low level tight circuit into the training syllabus. .

[FullWings]

The result of this mentality is we have carefully scripted simulator checks where everything is rehearsed well before the event. I have actually had candidates ask me for the exact test sequences, approaches, route etc 14 days in advance of a simple Instrument Rating renewal. They arc up when I reply with a copy of the official test form and delay notification of the route until 24 hours in advance. Yet their masters often hit them with short notice roster changes or off-schedule charters and they cash their pay cheques cheerfully enough.
In some jurisdictions it seems gone are the days of non-jeopardy LOFT exercises where crews were encouraged to step outside their comfort zone. Now, it's all about ticking the boxes on the form.
We have gone down the ATQP route and almost everyone I speak with much prefers it. In the old days you almost had to get hold of the instructor's notes as it was assumed that you were in possession of them anyway! IMO it led to a rather false atmosphere with crews sitting there waiting for the EVENT then responding far too quickly with a pre-prepared plan.

Now, the trainer (within practical limits of time, databases, etc.) can let the detail progress according to the decisions made by the crew and can alter things as it is no longer running on rails. The focus has changed from being +/- X kts and +/- Y ft to “how was the situation managed?”, “did they use all the available information to come to a decision?”, “was the decision making process effective?” and things of that nature.

Of course we still do traditional failures, malfunctions, handling, etc. but that’s more “train to competence” so on a assessment detail the soft skills are much more under the microscope, as they have greater influence on bringing a flight to a successful conclusion than being able to do an inverted night asymmetric NDB on a partial panel...

[Check Airman]

As for running an engine beyond its 5 minute limit if it's really needed to ensure adequate performance, or making a spit-arse turn to a reciprocal runway and landing overweight with an uncontained fire and not completing the full checklist - heaven forbid it should ever be suggested, let alone practiced in the simulator.

Funny you should mention this. I recently did engine out training event where I opted to ignore our non-normal SOP for power and flap settings in light of the high terrain and elevation. The instructor had no objection to the decision.

There are still good instructors out there. Ones who can read a checklist, and still remember how to fly an aircraft. Give me one of those guys any day.

[lomapaseo]

I guess somebody has to practice a severe engine ,damage check list of some sort but in all my memory I can't think of one event where both rotors seized or even where a non fire shutdown without A/C vibes saved the day.

Way too many old wives tales about "why" relative to loss of n1 and n2 not associated with a departed engine.

Don't get me wrong, I'm all for pilot training about when to fly and when to read a checklist but let's not outthink the causal details.

[Checkboard]

in which case that is major damage or the engine has departed the aircraft completely
If the engine has departed the airframe, the LAST thing you will notice would be the N2 indication. :)

I've flown a separation in the sim a few times - it's an interesting exercise as the loss of weight on one side means you are applying opposite airleron to rudder. Of course - that's the sim. In the real world the engine tends to depart under thrust - so goes forward, then up and over - in the process taking the leading edge dvices with it so you lose weight, but also lift....

[lomapaseo]

If the engine has departed the airframe, the LAST thing you will notice would be the N2 indication. :)

I've flown a separation in the sim a few times - it's an interesting exercise as the loss of weight on one side means you are applying opposite airleron to rudder. Of course - that's the sim. In the real world the engine tends to depart under thrust - so goes forward, then up and over - in the process taking the leading edge dvices with it so you lose weight, but also lift....


Don't forget it also goes 90 degrees to the right or left depending on which way the rotors are turning.

[megan]

in the process taking the leading edge dvices with it so you lose weight, but also liftThe trouble with the DC-10 at Chicago was that it relied on hydraulic pressure to keep the leading edge devices deployed, once the hydraulics lost pressure due damage incurred they retracted. It was said it wouldn't happen on a Boeing as the devices are mechanically latched (I don't know if that is indeed a fact, but was a reason given at the time). If that is indeed the case I'd assume damage would be limited to those devices impacted by debris and the loss of lift being minimal.

[tdracer]

The trouble with the DC-10 at Chicago was that it relied on hydraulic pressure to keep the leading edge devices deployed, once the hydraulics lost pressure due damage incurred they retracted. It was said it wouldn't happen on a Boeing as the devices are mechanically latched (I don't know if that is indeed a fact, but was a reason given at the time). If that is indeed the case I'd assume damage would be limited to those devices impacted by debris and the loss of lift being minimal.
That's correct, although not via mechanical latches. On Puget Sound Boeings, the flaps/slats are moved via jack screws - not by direct hydraulic pressure as was the case on the DC-10. Jack screws can't really be back-driven, so loss of hydraulics means they'll stay where they are.

[lomapaseo]

The trouble with the DC-10 at Chicago was that it relied on hydraulic pressure to keep the leading edge devices deployed, once the hydraulics lost pressure due damage incurred they retracted. It was said it wouldn't happen on a Boeing as the devices are mechanically latched (I don't know if that is indeed a fact, but was a reason given at the time). If that is indeed the case I'd assume damage would be limited to those devices impacted by debris and the loss of lift being minimal.

Don't forget that it's not just loss of lift but roll recovery as well. Some planes can be managed well at speed, but when you slow down to land you have got your hands full.

[Centaurus]

In the real world the engine tends to depart under thrust - so goes forward, then up and over - in the process taking the leading edge dvices with it so you lose weight, but also lift....

https://en.wikipedia.org/wiki/American_Airlines_Flight_191