EGT OVERLIMIT at T/O: continue flight?
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Here's a more interesting question: what do you do if your aircraft has no EGT gauge? The airplane I'm on only has a "Jet Pipe Overheat" aural and EICAS messages. The only action item in response is to back off the thrust a little and, if that doesn't help, shut the SOB down. But at no time am I aware what the EGT actually is.
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Now THAT raises an interesting question (or three):
1) Is this an FAA certified aircraft? Under what interpretation of the rules is this proper instrumentation for a critical engine parameter?
2) On what basis is the engine maintained? Hard time or cycles? On-condition?
Is trend monitoring part of an FDR of some sort?
3) How many aircraft use this kind of Go/No Go instrumentation for EGT/TPT?
1) Is this an FAA certified aircraft? Under what interpretation of the rules is this proper instrumentation for a critical engine parameter?
2) On what basis is the engine maintained? Hard time or cycles? On-condition?
Is trend monitoring part of an FDR of some sort?
3) How many aircraft use this kind of Go/No Go instrumentation for EGT/TPT?
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Originally Posted by barit1
2) On what basis is the engine maintained? Hard time or cycles? On-condition?
Is trend monitoring part of an FDR of some sort?
Originally Posted by barit1
3) How many aircraft use this kind of Go/No Go instrumentation for EGT/TPT?
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ITT, EGT, TPT, TIT... It doesn't really matter to the pilot which one the engine mfgr determines is the critical or monitored one. It only matters that a temperature limit is established, and procedures are established to deal with exceedences.
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In fact on many engines "EGT" is a misnomer, because the thermocouples are between the HPT & LPT, therefore properly should be called ITT. (I know GE engines are like this)
Old habits die hard...
Old habits die hard...
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i concur with barit1,
over 20 years test cell testing of mainly cfm56-3c1's shows the extent of thermal growth of the rotating group which of course is predominantly the high pressure turbine disc creates around a 20 deg c egt reduction upon a second transient accel to temp rated take off.
was oboard an aircraft around ten years ago and the pilot took the 737-400 to take off within about 40 sec's of acheiving min idle...i felt like yelling at him, lol.
more importantly, if the engine in question is only running at 22k (3b2 rating) she's getting pretty tired and the decision makers should stop penny pinching and get it off.
have only recently stumbled upon this site and as stated above, 20 years testing, 30 years in the game until a year ago, thoroughly enjoyed it and have no intention of turning my brain off.....i took great pleasure in exhaustive study to gain a complete understanding of the cfm56-3 main engine control and other engine systems and am more than happy to offer input if required.
safe flying to all, cell dude.
over 20 years test cell testing of mainly cfm56-3c1's shows the extent of thermal growth of the rotating group which of course is predominantly the high pressure turbine disc creates around a 20 deg c egt reduction upon a second transient accel to temp rated take off.
was oboard an aircraft around ten years ago and the pilot took the 737-400 to take off within about 40 sec's of acheiving min idle...i felt like yelling at him, lol.
more importantly, if the engine in question is only running at 22k (3b2 rating) she's getting pretty tired and the decision makers should stop penny pinching and get it off.
have only recently stumbled upon this site and as stated above, 20 years testing, 30 years in the game until a year ago, thoroughly enjoyed it and have no intention of turning my brain off.....i took great pleasure in exhaustive study to gain a complete understanding of the cfm56-3 main engine control and other engine systems and am more than happy to offer input if required.
safe flying to all, cell dude.
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Hiya
Hiya Cell Dude
Give me a hand with Barit!..gets over enthusiastic at times!
Please read the A380 engine thread. If you have any idea what happened to the Qantas incident please post up.
Regards
Give me a hand with Barit!..gets over enthusiastic at times!
Please read the A380 engine thread. If you have any idea what happened to the Qantas incident please post up.
Regards
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...Not necessarily a need for immediate shutdown and turn back.
...It should be covered under "alternate operations" in your QRH. Typically, it requires immediate thrust reduction to return EGT to within normal operating limits and to make a log entry of observed over temperature and duration.
"If EGT can be returned to normal, continue operation provided that there is no evidence of damage and all other engine parameters are normal."
"If EGT can be returned to normal, continue operation provided that there is no evidence of damage and all other engine parameters are normal."
Psychophysiological entity
Those of us that came from props via things like Darts, nursed old tired engines as a matter of course . . . almost daily.
I found it amazing just how much one could come back on EGT with no noticeable reduction in observable performance. EPR gauges were favored by the inexperienced crews as they seemed to be giving an absolute statement of results. And of course, the feedback into the pilot's brains, was instant-ish.
Different world then though. (most of our energy was converted into noise.
I found it amazing just how much one could come back on EGT with no noticeable reduction in observable performance. EPR gauges were favored by the inexperienced crews as they seemed to be giving an absolute statement of results. And of course, the feedback into the pilot's brains, was instant-ish.
Different world then though. (most of our energy was converted into noise.
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I'll concur with GlueBall - in fact if there's any indication of a "weak sister" engine, this should be a briefing item.
My background tells me that EGT (ITT...) overtemp should not be addressed until first thrust reduction (unless accompanied by fire warning, of course). After all, the OEM establishes the temp limit based on long-term engine health, and NOT as an immediate safety-critical issue.
However, today - considering that most aircraft are overpowered - there's nothing lost by retarding EGT back within limits, PROVIDED that other duties aren't neglected.
My background tells me that EGT (ITT...) overtemp should not be addressed until first thrust reduction (unless accompanied by fire warning, of course). After all, the OEM establishes the temp limit based on long-term engine health, and NOT as an immediate safety-critical issue.
However, today - considering that most aircraft are overpowered - there's nothing lost by retarding EGT back within limits, PROVIDED that other duties aren't neglected.
From a safety standpoint ( single flight, not maintenance after you land)
excessive EGT is a symptom and not a cause of possible power loss.
excessive TIT is not only a symptom but a probable cause of power loss.
Yes there could be a link between the two but that is for the consideration of the folks that write the manuals for the crew. The problem with ignoring overlimits EGT at high power is that TIT could be affected as well (albeit not instrumeted) and that the damage to the High turbne blade tips will worsen the inflight problem if the engine is not throttled back to reduce EGT.
Of course EGT may be caused by internal damage (not just wear) and as such if you don't throttle back the damage will likely escalate and force a shutdown.
In my memory bank the only problem I can recall with excessive EGT (without other overt engine symptoms) was an event where it took an hour or two to finally shuck some blades and that was in the high pressure turbine.
On the other hand there have been several accidents where engine failures preciptated excessive EGT (pegged meters), not corrected and only molten metal was left in the turbine.
follow your manuals as they cover the important stuff, the rest we can opinion on PPrune
excessive EGT is a symptom and not a cause of possible power loss.
excessive TIT is not only a symptom but a probable cause of power loss.
Yes there could be a link between the two but that is for the consideration of the folks that write the manuals for the crew. The problem with ignoring overlimits EGT at high power is that TIT could be affected as well (albeit not instrumeted) and that the damage to the High turbne blade tips will worsen the inflight problem if the engine is not throttled back to reduce EGT.
Of course EGT may be caused by internal damage (not just wear) and as such if you don't throttle back the damage will likely escalate and force a shutdown.
In my memory bank the only problem I can recall with excessive EGT (without other overt engine symptoms) was an event where it took an hour or two to finally shuck some blades and that was in the high pressure turbine.
On the other hand there have been several accidents where engine failures preciptated excessive EGT (pegged meters), not corrected and only molten metal was left in the turbine.
follow your manuals as they cover the important stuff, the rest we can opinion on PPrune
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1) Use basic airmanship at first to avoid the over temp in the first place.
If you know that you are about to make a full thrust takeoff with high ambient temperatures, be prepared. Keep an eye on the engines (as you always should anyway) during the takeoff roll and be prepared to reduce a couple of percent. Most commonly one of the engines will be more critical for various reasons (different number of cycles, wear, maintenance etc.).
Furthermore be especially alert at rotation and initial climb out because of change of airflow into the engine. Select climb thrust earlier than normal if environment allows for it.
My company flies regularly to hot and high places, and this is company sanctioned procedure. Before going into a discussion about compromised take off performance, bear in mind that we are not taking about a 10% reduction on both engines at the start of the take off roll but maybe 1 or 2 percent on one engine before lift off.
2) If that was unsuccessful (with the above method the overshoot should in any case only be few degrees), follow the QRH afterwards and make actions accordingly. For the e.g. 737 it doesn't mention anything about landing at nearest suitable airport, if the engine subsequently stays within limits. Hence, you can continue.
If you know that you are about to make a full thrust takeoff with high ambient temperatures, be prepared. Keep an eye on the engines (as you always should anyway) during the takeoff roll and be prepared to reduce a couple of percent. Most commonly one of the engines will be more critical for various reasons (different number of cycles, wear, maintenance etc.).
Furthermore be especially alert at rotation and initial climb out because of change of airflow into the engine. Select climb thrust earlier than normal if environment allows for it.
My company flies regularly to hot and high places, and this is company sanctioned procedure. Before going into a discussion about compromised take off performance, bear in mind that we are not taking about a 10% reduction on both engines at the start of the take off roll but maybe 1 or 2 percent on one engine before lift off.
2) If that was unsuccessful (with the above method the overshoot should in any case only be few degrees), follow the QRH afterwards and make actions accordingly. For the e.g. 737 it doesn't mention anything about landing at nearest suitable airport, if the engine subsequently stays within limits. Hence, you can continue.
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lomapaseo;
Why would thrust be affected if that is what you set (by setting an EPR or N1) to see an EGT exceedance?
regards,
HN39
excessive TIT is not only a symptom but a probable cause of power loss.
regards,
HN39
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All the jet engines I've flown had an engine warm up time - 3 minutes.
If they thought 4 minutes, or 5, or 6, was critical they would have made that the limit.
Same time limt for cool down. Sometimes the 3 minute cooldown was allowed to be reduced if X degrees and Y degrees were not exceeded on approach/reverse.
If they thought 4 minutes, or 5, or 6, was critical they would have made that the limit.
Same time limt for cool down. Sometimes the 3 minute cooldown was allowed to be reduced if X degrees and Y degrees were not exceeded on approach/reverse.
Hazelnuts
Your point is valid. Thrust would not be affected until the engine finally ran down due to loss of pumping of the High compressor.
What would probably happen is that high turbine efficiency would go to hell and the TIT keep going up trying to maintain thrust. To me that is a cascading failure mode.. I view that as a lot more serious than just an EGT rise without other symptoms.
lomapaseo;
Quote:
excessive TIT is not only a symptom but a probable cause of power loss.
Quote:
excessive TIT is not only a symptom but a probable cause of power loss.
Why would thrust be affected if that is what you set (by setting an EPR or N1) to see an EGT exceedance?
regards,
HN39
regards,
HN39
What would probably happen is that high turbine efficiency would go to hell and the TIT keep going up trying to maintain thrust. To me that is a cascading failure mode.. I view that as a lot more serious than just an EGT rise without other symptoms.
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on A320 which has CFM56-5 it's a inhibited warning till lift-off, so then the first action is taken at 400 ft, no RTO is considered.
on 737 we started the limit/surge/stall checklist at 400ft as well.
on 737 we started the limit/surge/stall checklist at 400ft as well.
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Kosmo,
We fly in a hot environment and have seen a few overheats from time to time. A difference of +/- 2% is within limits for the setting of takeoff thrust but I never liked the idea of messing about with thust at that stage. If it predictably overheats then as as far as I am concerned there is a problem that needs sorting and I would rather the company spends the necessary wonga to rectify the prolem or take the aircraft off the line.
True, but how much and how long would be a consideration. The Boeing AFM contians a bit more info. Regardless, if no engineering down route I would defo return.
We fly in a hot environment and have seen a few overheats from time to time. A difference of +/- 2% is within limits for the setting of takeoff thrust but I never liked the idea of messing about with thust at that stage. If it predictably overheats then as as far as I am concerned there is a problem that needs sorting and I would rather the company spends the necessary wonga to rectify the prolem or take the aircraft off the line.
For the e.g. 737 it doesn't mention anything about landing at nearest suitable airport, if the engine subsequently stays within limits. Hence, you can continue.
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Two thoughts:
1) The obvious: Turn off A/C packs (or run them from the APU) to gain EGT margin.
2) If the aircraft is enroute back to main base, and no further hot-day, rated-thrust takeoffs are anticipated before that, it does seem reasonable to press on, so long as the engine remains more-or-less normal.
I'd think it less wise to dispatch from main base in that condition, though. The engine won't heal itself.
1) The obvious: Turn off A/C packs (or run them from the APU) to gain EGT margin.
2) If the aircraft is enroute back to main base, and no further hot-day, rated-thrust takeoffs are anticipated before that, it does seem reasonable to press on, so long as the engine remains more-or-less normal.
I'd think it less wise to dispatch from main base in that condition, though. The engine won't heal itself.
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The Boeing QRH is pretty clear about this. If the EGT is the only parameter out of the normal ranges and it occurs in conditions where it may have been expected, hot high conditions for example then:
EGT Exceedence On Takeoff
This condition is most likely to occur when using a high takeoff thrust setting particularly when operating from hot/high airfields, and/or when experiencing a temperature inversion.
In the event of an EGT exceedence during takeoff the engine is reliable for continued operation provided:
• EGT is the only engine parameter outside limits.
• No other abnormal engine indications exist e.g. vibration, spool speed, fuel flow.
• EGT returns to the normal range after thrust reduction.
This advice also applies if such an exceedence occurs on both engines during takeoff and in the case of ETOPs operations.
Do not retard the thrust lever in an attempt to control the exceedence until airborne, the aircraft is climbing normally and a safe takeoff flight path is assured.
At a suitable altitude as soon as possible after the gear is selected up, retard the thrust lever on the affected engines until the exceedence is within limits. Whilst the subsequent maintenance action depends on the amplitude and duration of the exceedence, the recommended flight crew action does not. All maintenance actions are assumed to be carried out after completion of the scheduled flight.
I hope this direct quote from the Boeing QRH helps to clear up some of the arguments!
Jazzy
EGT Exceedence On Takeoff
This condition is most likely to occur when using a high takeoff thrust setting particularly when operating from hot/high airfields, and/or when experiencing a temperature inversion.
In the event of an EGT exceedence during takeoff the engine is reliable for continued operation provided:
• EGT is the only engine parameter outside limits.
• No other abnormal engine indications exist e.g. vibration, spool speed, fuel flow.
• EGT returns to the normal range after thrust reduction.
This advice also applies if such an exceedence occurs on both engines during takeoff and in the case of ETOPs operations.
Do not retard the thrust lever in an attempt to control the exceedence until airborne, the aircraft is climbing normally and a safe takeoff flight path is assured.
At a suitable altitude as soon as possible after the gear is selected up, retard the thrust lever on the affected engines until the exceedence is within limits. Whilst the subsequent maintenance action depends on the amplitude and duration of the exceedence, the recommended flight crew action does not. All maintenance actions are assumed to be carried out after completion of the scheduled flight.
I hope this direct quote from the Boeing QRH helps to clear up some of the arguments!
Jazzy