737NG overheat
In one B737 Classic simulator I flew, actuation of the fire warning switch on the simulator instructor panel would cause an immediate overheat warning light (with appropriate Master Caution/Overheat lights on). Approximately five seconds later the fire warning switch actuated. This was useful to the pilot as even a few seconds early warning of an engine fire was helpful.
Yet another 737 Classic simulator was wired up so that the same actuation of an engine fire warning on the instructor panel instantly produced a fire switch illumination.
The difference in philosophy between the two simulators is quite significant. In the case of the first simulator in order for the simulator instructor to "arrange" a fire warning close to V1, it meant the overheat light would come on several seconds earlier than the selected fire warning thus alerting the crew. The Boeing advice is to reject below 80 knots and continue if an overheat warning occurs after 80 knots.
On the other hand, a rejected take off up to VI is advised for a fire warning. So, in the first simulator, the crew are faced with a period of uncertainty - especially if they (rightly or wrongly) assume in that particular simulator that the overheat warning will be followed by a fire warning. By rejecting the take off below V1 if the overheat light illuminates, there is less chance of running off the end of the runway if the take off performance is runway limiting.
I would be interested to know the applicable philosophy in other B737 Classics. In other words in the real thing (engine fire) would you always get an overheat warning first? If that is a correct statement, then is the second simulator mentioned above, where a fire warning actuation is not preceded by an overheat indication, indicative of faulty fidelity?
Yet another 737 Classic simulator was wired up so that the same actuation of an engine fire warning on the instructor panel instantly produced a fire switch illumination.
The difference in philosophy between the two simulators is quite significant. In the case of the first simulator in order for the simulator instructor to "arrange" a fire warning close to V1, it meant the overheat light would come on several seconds earlier than the selected fire warning thus alerting the crew. The Boeing advice is to reject below 80 knots and continue if an overheat warning occurs after 80 knots.
On the other hand, a rejected take off up to VI is advised for a fire warning. So, in the first simulator, the crew are faced with a period of uncertainty - especially if they (rightly or wrongly) assume in that particular simulator that the overheat warning will be followed by a fire warning. By rejecting the take off below V1 if the overheat light illuminates, there is less chance of running off the end of the runway if the take off performance is runway limiting.
I would be interested to know the applicable philosophy in other B737 Classics. In other words in the real thing (engine fire) would you always get an overheat warning first? If that is a correct statement, then is the second simulator mentioned above, where a fire warning actuation is not preceded by an overheat indication, indicative of faulty fidelity?
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Cosmo Kramer, you wrote
and
I wrote:
You know what the word "by" means?
Maybe you should process info before shouting about nonsense,hopefully not an accurate insight into your managing of a flightdeck...
It uses the word core but the tubing is still outside of the core, essentially measuring the temp in the shroud adjacent to the core.
Fire/overheat have nothing to do with the temperature of the engine core. What a load of nonsense.
sensor is by the engine core.,on the high pressure turbine case
Maybe you should process info before shouting about nonsense,hopefully not an accurate insight into your managing of a flightdeck...
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For clarification, the fire detection loops do activate both the overheat and fire warnings, just with differing temperature thresholds. None of the detectors are inside the engines - they are around them. They detect heat build up inside the nacelle, not inside the exhaust or turbine, and so have no relationship with engine DU indications. An overheat warning can be triggered by a bleed air leak, as suggested, but also a core leak (combustion gasses leaking between combustion, turbine and exhaust stages) or a small fire. It is a very serious condition.
I take the comment about further effects including structural integrity of the pylon, too. While one might anticipate a bleed duct warning instead, that may or may not happen - a turbine leak could end up going all sorts of places, especially once things start burning or melting away. Even if the pylon was unaffected, the structural integrity of the nacelle could be affected.
I take the comment about further effects including structural integrity of the pylon, too. While one might anticipate a bleed duct warning instead, that may or may not happen - a turbine leak could end up going all sorts of places, especially once things start burning or melting away. Even if the pylon was unaffected, the structural integrity of the nacelle could be affected.
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An overheat warning is for overheat of the engine shroud, not the engine core
Rest i agree.
Just because the loops are located near, but outside, the core, doesn't mean that anything going on in the core is being monitored.
In the engine core there is both heat and fire, and you don't really want to put either out, unless parked at the gate.
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My objection here, is that people seem to mix 3 things together: Engine fire, severe damage and engine separation - just because it is the same same steps that are necessary (hence same checklist) to bring the situation under control.
"Hey man, you got to idle that engine if you got an overheat, otherwise it may lead to fire and then you'll get severe damage and your engine might fall off" - might seem like a logical train of thoughts. And probably could happen: Overheat of gearbox leads to fire, fire ruptures oil supply to the engine, bearings fail, causing severe internal engine damage, high vibrations cause engine mount to fail, engine separates. But for this to happen the flight crew would have to sit on their hands for several minutes (maybe 10s of minutes for all the things to develop), hence a very unlikely scenario.
Fact is you can have a overheat fire, without severe damage. Or you can have severe damage with out a fire. Or the engine might separate with out either.
An engine mount can fail without previous warning.
A fire in the cowling can take place due to a fluid leak.
An overheat condition can take place because of a bleed leak
A severe damage can be caused by a bird.
Etc.
The point is, to THINK about the situation, before reacting. In simulator we are taught drills - predetermined responses to predetermined situations. Which is not bad at all, because it's good to have a set of responses ingrained in your backbone.
But it is still useful, to think, and know what is going on. I.e. an engine (cowling) fire can burn for quite sometime before action is required. This is useful to know if you depart with critical terrain. The side with a cowl fire still has an perfectly good (internally) engine. It might make your life easier, to let it burn for 1-2 mins, and use the thrust to gain altitude, before attending to the cowl fire.
Is a false statement, if I understand it the way it comes over. I.e. "reducing the thrust causes the core temperature to decrease and hence the overheat condition may disappear". Again, the temperature inside the core, is not being monitored by the overheat/fire detector loops. It might be a good idea to idle the engine for other reasons (like a bleed leak).
Is a false statement. First, it won't go overheat -> severe damage. Considering the light came on off, it would probably either be an indication fault or the temperature had barely risen to trigger the overheat condition, hence still a way to go before the fire loops would trigger, as they have a higher threshold.
Just because the simulator is programmed to: overheat condition x 15 secs = engine fire. It doesn't mean it will happen like this in the aircraft.
An overheat flicking on/off like in the original posters scenario, might not require an immediate engine shutdown. The poster thought about the situation and monitored it, without acting - in the end the indication disappeared. All good and well.
In short, I think the original poster did a good job. Probably getting the aircraft to it's destination, without making a big drama.
N1 Limit, did you get information for your maintenance afterwards, as to what triggered the overheat condition?
"Hey man, you got to idle that engine if you got an overheat, otherwise it may lead to fire and then you'll get severe damage and your engine might fall off" - might seem like a logical train of thoughts. And probably could happen: Overheat of gearbox leads to fire, fire ruptures oil supply to the engine, bearings fail, causing severe internal engine damage, high vibrations cause engine mount to fail, engine separates. But for this to happen the flight crew would have to sit on their hands for several minutes (maybe 10s of minutes for all the things to develop), hence a very unlikely scenario.
Fact is you can have a overheat fire, without severe damage. Or you can have severe damage with out a fire. Or the engine might separate with out either.
An engine mount can fail without previous warning.
A fire in the cowling can take place due to a fluid leak.
An overheat condition can take place because of a bleed leak
A severe damage can be caused by a bird.
Etc.
The point is, to THINK about the situation, before reacting. In simulator we are taught drills - predetermined responses to predetermined situations. Which is not bad at all, because it's good to have a set of responses ingrained in your backbone.
But it is still useful, to think, and know what is going on. I.e. an engine (cowling) fire can burn for quite sometime before action is required. This is useful to know if you depart with critical terrain. The side with a cowl fire still has an perfectly good (internally) engine. It might make your life easier, to let it burn for 1-2 mins, and use the thrust to gain altitude, before attending to the cowl fire.
On the NG,the sensors for overheat and Fire are located about the Fan and the engine Core...so quite a good idea to idle the engine..
Follow the qrh next time. Is better to shutdown an engine because a false alarm and not to have a severe damage thinking that is a false alarm.
Just because the simulator is programmed to: overheat condition x 15 secs = engine fire. It doesn't mean it will happen like this in the aircraft.
An overheat flicking on/off like in the original posters scenario, might not require an immediate engine shutdown. The poster thought about the situation and monitored it, without acting - in the end the indication disappeared. All good and well.
In short, I think the original poster did a good job. Probably getting the aircraft to it's destination, without making a big drama.
N1 Limit, did you get information for your maintenance afterwards, as to what triggered the overheat condition?
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AMM:
Purpose
The overheat and fire detector senses high temperatures in the engine compartment -
Location
Three sections of the detector are mounted around the fan case (the accessory compartment) and one section is mounted on the high pressure turbine case (core compartment).
Never did i say any temp sensors were INSIDE the core.
Considering not idling the engine as DIRECTED by the QRH is a poor advice and reminds me of this note in the QRH:
It should be noted that, in determining the safest course of action, troubleshooting, i.e., taking steps beyond published non-normal checklist steps, may cause further loss of system function or system failure. Troubleshooting should only be considered when completion of the published non-normal checklist results in an unacceptable situation.
QRH actions for overheat:
1 Autothrottle(ifengaged)...........Disengage
2 Thrustlever
(affected engine) . . . . . . Confirm . . . . . . . Close
3 If the ENG OVERHEAT light stays illuminated:
►►Go to the ENGINE FIRE or Engine Severe Damage or Separation checklist
I told the OP that idling was a good idea,ie a better idea than running the engine at high thrust because he believed his normal engine parameters (EGT)was normal therefore an overheat was disregarded.
True,but the sensors are strategically place around the core as it is considered a fire hazard area,to monitor heat/fire temp due to leaks.
Purpose
The overheat and fire detector senses high temperatures in the engine compartment -
Location
Three sections of the detector are mounted around the fan case (the accessory compartment) and one section is mounted on the high pressure turbine case (core compartment).
Never did i say any temp sensors were INSIDE the core.
Considering not idling the engine as DIRECTED by the QRH is a poor advice and reminds me of this note in the QRH:
It should be noted that, in determining the safest course of action, troubleshooting, i.e., taking steps beyond published non-normal checklist steps, may cause further loss of system function or system failure. Troubleshooting should only be considered when completion of the published non-normal checklist results in an unacceptable situation.
QRH actions for overheat:
1 Autothrottle(ifengaged)...........Disengage
2 Thrustlever
(affected engine) . . . . . . Confirm . . . . . . . Close
3 If the ENG OVERHEAT light stays illuminated:
►►Go to the ENGINE FIRE or Engine Severe Damage or Separation checklist
Is a false statement, if I understand it the way it comes over. I.e. "reducing the thrust causes the core temperature to decrease and hence the overheat condition may disappear". Again, the temperature inside the core, is not being monitored by the overheat/fire detector loops. It might be a good idea to idle the engine for other reasons (like a bleed leak).
Just because the loops are located near, but outside, the core, doesn't mean that anything going on in the core is being monitored.
In the engine core there is both heat and fire, and you don't really want to put either out, unless parked at the gate.
In the engine core there is both heat and fire, and you don't really want to put either out, unless parked at the gate.
Last edited by de facto; 3rd Mar 2014 at 17:41.
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Ok, then it sounds like we basically we agree
Except, the original poster didn't have a persistent overheat condition, but a flickering light. In any problem relating to the engine, I would say that looking at the engine parameters is common sense. I have no idea if a core leak would cause abnormal engine parameters? Most likely, it would certainly not produce a flickering overheat indication, but rather directly a fire warning.
Hence, with a flicking indication and everything else looking good, I think the original poster solved the problem in a reasonable manner.
Except, the original poster didn't have a persistent overheat condition, but a flickering light. In any problem relating to the engine, I would say that looking at the engine parameters is common sense. I have no idea if a core leak would cause abnormal engine parameters? Most likely, it would certainly not produce a flickering overheat indication, but rather directly a fire warning.
Hence, with a flicking indication and everything else looking good, I think the original poster solved the problem in a reasonable manner.
