Defining Severe Engine Damage re QRH actions
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Defining Severe Engine Damage re QRH actions
Recently an engine manufacturer published a bulletin which defined severe damage assessment in terms of QRH actions. It may have been part of an Airbus document published by the flight safety department of a major airline but I am unsure.
Broadly, the document defined severe damage if significant vibration is noticed during the engine operation/failure. In the case of the Boeing 737 for example, the QRH drill is to shut down the engine and pull the fire fire switch. It is not necessary to fire a bottle unless there are indications of engine fire. One of the engine instrument indications or a turbine seizure (Severe Damage) is the N2 indicating zero.
The flight safety bulletin quotes the manufacturer that the cue for using the Severe Damage checklist is if significant engine vibration is present.
One of the engine non-normals available in some simulators is Accessory Gear Box Shaft Failure. In effect this causes a flame-out due lack of fuel to the burners. There is no vibration present (simulator) although the N2 indicates zero the same indication also being seen with a turbine seizure.
Opinons are sought as to whether an Auxilliary Drive Shaft failure is by defintiion, a Severe Damage Checklist QRH action or not. The B737 FCOM, QRH or FCTM do not amplify this particular event and it is left to the crew to decide the appropriate QRH drill. This gives rise to personal opinions and we all know about personal opinions in a simulator.
Clearly, if significant vibration does not exist then presumably severe damage is not present even though the engine has flamed out because of the auxilliary drive shaft failure. Opinions welcomed of course but preferably back up with published data. Thanks in advance
Broadly, the document defined severe damage if significant vibration is noticed during the engine operation/failure. In the case of the Boeing 737 for example, the QRH drill is to shut down the engine and pull the fire fire switch. It is not necessary to fire a bottle unless there are indications of engine fire. One of the engine instrument indications or a turbine seizure (Severe Damage) is the N2 indicating zero.
The flight safety bulletin quotes the manufacturer that the cue for using the Severe Damage checklist is if significant engine vibration is present.
One of the engine non-normals available in some simulators is Accessory Gear Box Shaft Failure. In effect this causes a flame-out due lack of fuel to the burners. There is no vibration present (simulator) although the N2 indicates zero the same indication also being seen with a turbine seizure.
Opinons are sought as to whether an Auxilliary Drive Shaft failure is by defintiion, a Severe Damage Checklist QRH action or not. The B737 FCOM, QRH or FCTM do not amplify this particular event and it is left to the crew to decide the appropriate QRH drill. This gives rise to personal opinions and we all know about personal opinions in a simulator.
Clearly, if significant vibration does not exist then presumably severe damage is not present even though the engine has flamed out because of the auxilliary drive shaft failure. Opinions welcomed of course but preferably back up with published data. Thanks in advance
Last edited by Tee Emm; 21st Nov 2010 at 02:49.
Umm, an engine manufacturer can tell you what a severe engine failure is.
It's up to the aircraft manufacturer to tell you the pro and cons of how to treat the symptoms using aircraft instruments and controls.
So what do they recommend about a silent gear box failure where all that happens is the EGT drops to nil, the generators and hydraulics go dead the N2 may or may not go to zero (no signal??) but the N1 drops to windmill.
IMO if your actions might aggravate a failure condition then it ought to be specifically covered in the manuals.
So consider what can go wrong when you answer
It's up to the aircraft manufacturer to tell you the pro and cons of how to treat the symptoms using aircraft instruments and controls.
So what do they recommend about a silent gear box failure where all that happens is the EGT drops to nil, the generators and hydraulics go dead the N2 may or may not go to zero (no signal??) but the N1 drops to windmill.
IMO if your actions might aggravate a failure condition then it ought to be specifically covered in the manuals.
So consider what can go wrong when you answer
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Foe the 737 at least, there is no need for the crew to pontificate over this one. No vibration then it doesnt meet the QRH conditions for severe damage, but it does meet the conditions engine limit, surge or stall. This is clear and unambiguous in the QRH.
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So, Sciolistes, you would happily leave the Eng Start Lever in idle?
Whenever in doubt about theseverity of an engine problem, treat is as a severe engine damage! You can never go wrong that way.
This thread sounds like some people are more training how to fly the simulator then how to fly a real live aeroplane in conditions and cicumstances that are never exactly like the simulator.
Whenever in doubt about theseverity of an engine problem, treat is as a severe engine damage! You can never go wrong that way.
This thread sounds like some people are more training how to fly the simulator then how to fly a real live aeroplane in conditions and cicumstances that are never exactly like the simulator.
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So, Sciolistes, you would happily leave the Eng Start Lever in idle
Back to the OQ - while I cannot offer any 'published data' I fully agree with Sciolistes - maybe I am being dim, but I cannot see the problem.
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If the engine has failed, then one doesn't really care that it failed for a fuel pump failure or of the accessory drive shaft has failed; it's simply failed. Unless there's a sign severe damage, there's no reason to treat the engine for severe damage.
That the engine has been damaged internally in a severe way isn't relevant; the actual damage that has occurred isn't important; how it affects crew operation is what's important.
The severe damage checklist is a ballpark catch-all for a big, immediate problem. On our checklist, it's called the Engine Fire/Severe Damage/Separation checklist; it's for handling multiple contingencies, and the only immediate action item on the list is the same for all three possibilities: maintain control of the airplane. The items which follow involve control of the airplane issues, then fire issues, then system issues (hydraulic, electrical, etc).
The actual cause of the severe damage isn't so important as what to do about it. If you've got a real problem that doesn't fit any particular other definition and it's vibrating, then it's severe damage.
If the accessory drive has failed and the engine has flamed out, then one has an Inflight Engine Failure/Shutdown checklist, instead. (Our procedures also call for this checklist in the event of vibration).
If a specific failure is identified that matches any one of the other procedures, then use that. If you've got a real problem without a specific definition, you've got the severe damage checklist.
That the engine has been damaged internally in a severe way isn't relevant; the actual damage that has occurred isn't important; how it affects crew operation is what's important.
The severe damage checklist is a ballpark catch-all for a big, immediate problem. On our checklist, it's called the Engine Fire/Severe Damage/Separation checklist; it's for handling multiple contingencies, and the only immediate action item on the list is the same for all three possibilities: maintain control of the airplane. The items which follow involve control of the airplane issues, then fire issues, then system issues (hydraulic, electrical, etc).
The actual cause of the severe damage isn't so important as what to do about it. If you've got a real problem that doesn't fit any particular other definition and it's vibrating, then it's severe damage.
If the accessory drive has failed and the engine has flamed out, then one has an Inflight Engine Failure/Shutdown checklist, instead. (Our procedures also call for this checklist in the event of vibration).
If a specific failure is identified that matches any one of the other procedures, then use that. If you've got a real problem without a specific definition, you've got the severe damage checklist.
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BOAC,
I`m on a different type now, so no QRH for grabs....
If my memory serves me well, the recall items for engine limit were: A/T disengage and Thrust lever retard until engine indications within limits.
If this is correct, that would mean that the fuel would still be pumping (at least until the NNC has been completed).
If an engine fails during T/O or climb, there is, almost by definition, something seriously wrong. Imagine a firehose spraying a stream of jetfuel on the hot parts......
So, apart from doing the simulatortricks we all learn to recognise, in real life I would easily opt for the severe damage procedure whenever there is the smallest doubt about the state of affairs with the engine.
I`m on a different type now, so no QRH for grabs....
If my memory serves me well, the recall items for engine limit were: A/T disengage and Thrust lever retard until engine indications within limits.
If this is correct, that would mean that the fuel would still be pumping (at least until the NNC has been completed).
If an engine fails during T/O or climb, there is, almost by definition, something seriously wrong. Imagine a firehose spraying a stream of jetfuel on the hot parts......
So, apart from doing the simulatortricks we all learn to recognise, in real life I would easily opt for the severe damage procedure whenever there is the smallest doubt about the state of affairs with the engine.
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No, you have, as you say, described 'Engine Limit' there. The QRH for that directs you to close the start lever if the engine does not behave. I'm not sure why Sciolistes leapt off down the 'engine limit, surge or stall' route. Nothing to do with 'Accessory Drive Failure'.
For the failure described by Tee Emm - 'run down' - it will direct you to close the start lever.
For the failure described by Tee Emm - 'run down' - it will direct you to close the start lever.
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Look at the conditions in the QRH. Engine limit surge or stall is the appropriate non normal as N2 is low. The objective quoted in the QRH is recover normal engine operation or shutdown the engine if recovery is not possible. So the recall will direct you to close the thrust lever. Once you are cleaned and stable you can do the reference items, which in this case would lead you to shut down the engine.
You'll discover the cause when you're back on the ground a day later.
You'll discover the cause when you're back on the ground a day later.
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I cannot recall ever hearing of the cited hardware fault (accessory gearbox dying...) in flight, unless caused by some considerable external event (I recall one hit by a thrown fan blade from the opposite engine...)
However, I know a test crew who attempted to start a preserved engine, and when it finally lit off, a tailpipe fire (preservative oil) ensued. The throttle jock panicked, re-engaged the starter during coastdown, and was unable to restart the engine.
Upon hitting the starter, N2 took off pretty quickly, oil pressure indicated OK, but fuel flow remained very low, no EGT, no N1, ...
We found the "tower shaft" was sheared from the starter impact torque - a very clean break. The starter would turn the gearbox, pumps, etc. BUT no drive available to the core engine! I rewrote the engine fault isolation book to cover this event.
However, I know a test crew who attempted to start a preserved engine, and when it finally lit off, a tailpipe fire (preservative oil) ensued. The throttle jock panicked, re-engaged the starter during coastdown, and was unable to restart the engine.
Upon hitting the starter, N2 took off pretty quickly, oil pressure indicated OK, but fuel flow remained very low, no EGT, no N1, ...
We found the "tower shaft" was sheared from the starter impact torque - a very clean break. The starter would turn the gearbox, pumps, etc. BUT no drive available to the core engine! I rewrote the engine fault isolation book to cover this event.
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Engine limit surge or stall is the appropriate non normal as N2 is low.
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This is a SLOW post..
N2 degredation unless faulty indication will be rapidly followed by egt/n1 etc abnormal indication. This is a common sence formula for a failed engine or indicator. I do not understand why this is in question.
If gearbox drive shaft fails.
You loose all accesorys including pmg in FADEC engines, older engines well better to have thrust when needed.
N2 degredation unless faulty indication will be rapidly followed by egt/n1 etc abnormal indication. This is a common sence formula for a failed engine or indicator. I do not understand why this is in question.
If gearbox drive shaft fails.
You loose all accesorys including pmg in FADEC engines, older engines well better to have thrust when needed.
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grounded27:
You lose all accessories including the HP fuel pump. Instant flameout. 
If gearbox drive shaft fails.
You loose all accesorys including pmg in FADEC engines, older engines well better to have thrust when needed.
You loose all accesorys including pmg in FADEC engines, older engines well better to have thrust when needed.
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I think we're all agreed that it not severe damage. I don't think you can classify it as a flameout either, as something else has gone wrong given the engine indications.
So you neitber need to jump onto an extended recall that has you closing start levers and messing with engine fire switches. Niether do you want to wait until clean and stable before doing anything. Hence the engine limit, surge or stall checklist. Minimal recall to reduce thrust until indications remain within limits or the thrust lever has closed, then shut down the engine at your lesuire later.
Making the appropriate choice is all about understanding the precise wording of the condition statements and the objective (if stated). This is something not fully appreciated by some pilots, they only memorise the actions and thus occasionally fail to correctly select the most appropriate checklist.
It would be entirely innappropriate to start jumping to conclusions about shaft failure or whatever. Such troubleshooting is only appropriate if you have multiple failures crossing checklists or there isn't an appropriate unanunciated checklist available.
So you neitber need to jump onto an extended recall that has you closing start levers and messing with engine fire switches. Niether do you want to wait until clean and stable before doing anything. Hence the engine limit, surge or stall checklist. Minimal recall to reduce thrust until indications remain within limits or the thrust lever has closed, then shut down the engine at your lesuire later.
Making the appropriate choice is all about understanding the precise wording of the condition statements and the objective (if stated). This is something not fully appreciated by some pilots, they only memorise the actions and thus occasionally fail to correctly select the most appropriate checklist.
It would be entirely innappropriate to start jumping to conclusions about shaft failure or whatever. Such troubleshooting is only appropriate if you have multiple failures crossing checklists or there isn't an appropriate unanunciated checklist available.
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t would be entirely innappropriate to start jumping to conclusions about shaft failure or whatever.
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Tried it in the simulator today. Aux drive shaft failure at 90 pecent N1. The engine simply flames out with no fuss and bother. The N2 falls instantly to zero indication. The vibration is less than that during take off. Normal load shedding occurs. Clearly no severe damage indications.
Guys, it is exactly the other way around. You have real life. And then there are the simulators that trie to simulate as accurately as possible, but still SIMULATE, what will happen so we can train that.
There is no value whatsoever in the behaviour of a simulator extrapolated to real life. I even think it is dangerous to assume there is.
In real life, chances are very good that things will go just that little bit differently.
See what happened with Qantas recently. I don`t think that scenario was programmed in the simulator. Real life always bites you in the butt if you don`t expect it.
BOAC
If the engine MFG has data that shows what will happen
If the engine MFG has provided that data to the simulator MFG
If the simulator MFG has encoded that into the software
If the smulator MFG has provided that software or data to all operators (sponsors) of that version of the simulator
If the sponsors have updated the code
Seat 0A
Right on. Seems to be the first part of "aviate navigate communicate"
For the past 10 years, I have been controlling the software on several Level D simulators. We try really hard to get it correct, but without hard data to support it, there is a lot of SWAG going on. Case in point is something as easy as EGPWS callouts. I have had 3 different check airmen for a single customer swear what they were, and they were all different. Go figure.
I would suggest that the simulator is probably spot on for a simple aux drive shaft failure?
If the engine MFG has provided that data to the simulator MFG
If the simulator MFG has encoded that into the software
If the smulator MFG has provided that software or data to all operators (sponsors) of that version of the simulator
If the sponsors have updated the code
Seat 0A
Guys, it is exactly the other way around. You have real life. And then there are the simulators that trie to simulate as accurately as possible, but still SIMULATE, what will happen so we can train that.
For the past 10 years, I have been controlling the software on several Level D simulators. We try really hard to get it correct, but without hard data to support it, there is a lot of SWAG going on. Case in point is something as easy as EGPWS callouts. I have had 3 different check airmen for a single customer swear what they were, and they were all different. Go figure.
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I find it a bit worriesome to see how people seem to think that the behaviour of the simulator with a programmed failure of somekind is somehow a valid indication to forecast how an actual airplane will behave in real life.