wheel-well fire??
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wheel-well fire??
Boeing have stressed that the B737 wheel-well fire indication is from an overheat sensor. If the source of the heat is from the undercarriage then when this is lowered the source of the heat has been removed from the sensor and the indication may extinguish. It does NOT mean the fire has gone out.
If such a warning is received on departure, and after the gear has been lowered the indication extinguishes, what will you do?
I've asked various crews and the discussion is very circular. "I'd go to a hold and follow the company procedure for assessing the situation and consider the options and then action the chosen one." I explained this could take >10 mins longer remaining in the air. "I'd rip it round and land ASAP." But what if it was an NPA and for a VNAV/LNAV approach the plates need finding and the FMC programmed? If it is an ILS at a familiar airfield, then it is much easier and only a Vref and the chart is required. The rest can be flown without FMC.
What would you do if it was VMC? Just a Vref and rip it round? What about NITS & PA to pax? Some yes, some not bothered.
Guys had experienced this in the sim as a Landing Gear QRH systems item. Fire warning out, exercise finished, sim re-set and move on. But what would you do in real life?
I've only had it happen once and that was at medium level on climb out en-route. Must be a false warning, but when there's doubt there is no doubt. Then the indication went out with gear lowered. CAVOK and return to familiar engineering base. No drama: it was known wiring problem, but not to me. One friend had one on stand after landing = evac. Who's to say he was right or wrong.
So, back to question in a scenario where it might well be an honest warning. I expect 20 pilots 20 opinions, so let's hear them.
If such a warning is received on departure, and after the gear has been lowered the indication extinguishes, what will you do?
I've asked various crews and the discussion is very circular. "I'd go to a hold and follow the company procedure for assessing the situation and consider the options and then action the chosen one." I explained this could take >10 mins longer remaining in the air. "I'd rip it round and land ASAP." But what if it was an NPA and for a VNAV/LNAV approach the plates need finding and the FMC programmed? If it is an ILS at a familiar airfield, then it is much easier and only a Vref and the chart is required. The rest can be flown without FMC.
What would you do if it was VMC? Just a Vref and rip it round? What about NITS & PA to pax? Some yes, some not bothered.
Guys had experienced this in the sim as a Landing Gear QRH systems item. Fire warning out, exercise finished, sim re-set and move on. But what would you do in real life?
I've only had it happen once and that was at medium level on climb out en-route. Must be a false warning, but when there's doubt there is no doubt. Then the indication went out with gear lowered. CAVOK and return to familiar engineering base. No drama: it was known wiring problem, but not to me. One friend had one on stand after landing = evac. Who's to say he was right or wrong.
So, back to question in a scenario where it might well be an honest warning. I expect 20 pilots 20 opinions, so let's hear them.
I would be deeply uncomfortable doing anything other than a fairly rapid return after any sort of fire indication, especially in an area where all my hydraulics, flap motors &c are located.
The weather and the approach would be the main variables. Hopefully it's either a home base or we've conducted an approach there 45 minutes or so ago so we are reasonably familiar with what to expect so not much to set up.
The main worry for me could potentially be stopping distance and what's hanging off the end of my gear struts. Of course I still only occupy the right seat but that is the position I would advocate!
The weather and the approach would be the main variables. Hopefully it's either a home base or we've conducted an approach there 45 minutes or so ago so we are reasonably familiar with what to expect so not much to set up.
The main worry for me could potentially be stopping distance and what's hanging off the end of my gear struts. Of course I still only occupy the right seat but that is the position I would advocate!
A follow up to the post by perantau
Swissair Flight 306 (Caravelle) airborne for 8 minutes Swissair Flight 306 - Ask.com Encyclopedia
Nigeria Airways Flight 2120 (DC-8) airborne for 10 minutes Nigeria Airways Flight 2120 - Ask.com Encyclopedia
Mexicana Flight 940 (727) airborne for 15 minutes Mexicana Flight 940 - Ask.com Encyclopedia
If it's for real you don't have much time seems to be the lesson to take away.
Swissair Flight 306 (Caravelle) airborne for 8 minutes Swissair Flight 306 - Ask.com Encyclopedia
Nigeria Airways Flight 2120 (DC-8) airborne for 10 minutes Nigeria Airways Flight 2120 - Ask.com Encyclopedia
Mexicana Flight 940 (727) airborne for 15 minutes Mexicana Flight 940 - Ask.com Encyclopedia
If it's for real you don't have much time seems to be the lesson to take away.
Last edited by megan; 27th Apr 2015 at 01:28.
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Typically a nuisance warning, but perhaps not.
Scenario: post-departure, wheel well fire warning. Gear down, light extinguishes. Land at nearest suitable is the guidance. Why would one do anything different?
I understand that an inop wheel well fire detection is not a MMEL item in the UK. Can anyone comment on this? Is the EASA/JAA the same?
I understand that an inop wheel well fire detection is not a MMEL item in the UK. Can anyone comment on this? Is the EASA/JAA the same?
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Scenario: post-departure, wheel well fire warning. Gear down, light extinguishes. Land at nearest suitable is the guidance. Why would one do anything different?
There are difference of opinions about "land at nearest suitable" and "land ASAP."
I agree guys, but the point is being missed. There are airlines who have extensive TEM procedures and other problem solving sequences. There is much cockpit conferencing to satisfy the never ending CRM; there have procedures in place to ensure there's no rushing into the first choice, but examine ALL the options. NITS & PA etc. It takes forever. This discussion is about the dangerous, IMHO, cosy feeling that as the fire indication has extinguished then all is OK and you can go to a HOLD and follow all those various procedures which are fine for some scenarios, but not all. In the sim this is what is taught. Obviously, if any fire warning remains lit then land ASAP is the name of the game. This is a grey area, but I feel it is not stressed enough in the sim: hence my curiosity about other's opinions. As there is a wide spectrum of 'what you would do on the spot', but it is not necessarily what sim training advocates, then here needs to be some clarification from the training department as to what is acceptable so there is not a flight deck dispute as the raw F/O demands full procedure while grey-haired fox whats to land ASAP. In Swissair MD-11 I think it was the other way round, interestingly.
In 30 years of training I was never subjected to an inextinguishable engine fire in the air. It was only used to cause a pax evac. Cabin fire? yes, but so far from a landing option that there was time. I have given the engine scenario as an instructor, and the reactions were very mixed and disappointing. They varied from a speedy and well managed return with minimum fuss, to rabbits in headlights what to do confusion. The rules said one thing, but survival said another. Agh!
As has been discussed on the 'Airbus handling improvement' thread it is about using the simulator to its full potential for positive and constructive training, not ticking boxes.
There are difference of opinions about "land at nearest suitable" and "land ASAP."
I agree guys, but the point is being missed. There are airlines who have extensive TEM procedures and other problem solving sequences. There is much cockpit conferencing to satisfy the never ending CRM; there have procedures in place to ensure there's no rushing into the first choice, but examine ALL the options. NITS & PA etc. It takes forever. This discussion is about the dangerous, IMHO, cosy feeling that as the fire indication has extinguished then all is OK and you can go to a HOLD and follow all those various procedures which are fine for some scenarios, but not all. In the sim this is what is taught. Obviously, if any fire warning remains lit then land ASAP is the name of the game. This is a grey area, but I feel it is not stressed enough in the sim: hence my curiosity about other's opinions. As there is a wide spectrum of 'what you would do on the spot', but it is not necessarily what sim training advocates, then here needs to be some clarification from the training department as to what is acceptable so there is not a flight deck dispute as the raw F/O demands full procedure while grey-haired fox whats to land ASAP. In Swissair MD-11 I think it was the other way round, interestingly.
In 30 years of training I was never subjected to an inextinguishable engine fire in the air. It was only used to cause a pax evac. Cabin fire? yes, but so far from a landing option that there was time. I have given the engine scenario as an instructor, and the reactions were very mixed and disappointing. They varied from a speedy and well managed return with minimum fuss, to rabbits in headlights what to do confusion. The rules said one thing, but survival said another. Agh!
As has been discussed on the 'Airbus handling improvement' thread it is about using the simulator to its full potential for positive and constructive training, not ticking boxes.
Last edited by RAT 5; 27th Apr 2015 at 10:20.
RAT 5, I don't know who you work for, but that sounds a lot like some issues at my airline. We have a structured decision model, the the NITS PA framework. The training department have started realising that they were training robots to follow their sequence almost no matter what the failure.
They are now trying to emphasise that the key issue is making the decision, and that one does not have to go through a full set of drills all the time. However, this is shall we say taking time to trickle down to all the trainers.
The fundamental problem with a very rigid approach to SOPs as practiced by the major LoCos is that everything in the manuals is treated as a diktat, and has led to checking that is biased towards making sure everyone is "following the script."
They are now trying to emphasise that the key issue is making the decision, and that one does not have to go through a full set of drills all the time. However, this is shall we say taking time to trickle down to all the trainers.
The fundamental problem with a very rigid approach to SOPs as practiced by the major LoCos is that everything in the manuals is treated as a diktat, and has led to checking that is biased towards making sure everyone is "following the script."
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Warning lights - a scenario
What if the warning light went out because the wire burnt through?
Yes I know "Matilda told such awful lies it made one gasp and stretch one's eyes..."
So... let's say a known occurrence occurs and CRM is followed and the consensus is that it is that microswitch again and an edict says we'll do it "shortly". So... wheels down, wheels up, light goes out. Dam' microswitch. Except it wasn't. All perish.
Yes I know "Matilda told such awful lies it made one gasp and stretch one's eyes..."
So... let's say a known occurrence occurs and CRM is followed and the consensus is that it is that microswitch again and an edict says we'll do it "shortly". So... wheels down, wheels up, light goes out. Dam' microswitch. Except it wasn't. All perish.
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You land it a nearest suitable airport,,its in the NNC...
If the fire indication remains on,do the same....a NITS is essential without the need to blabla for an hour and fly into a holding that is miles away...
A slighly extended downwind to do all is plenty enough in that scenario..
If the fire indication remains on,do the same....a NITS is essential without the need to blabla for an hour and fly into a holding that is miles away...
A slighly extended downwind to do all is plenty enough in that scenario..
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To throw a spanner in the light goes out scenario:
If the overheat detection was due to a fire on the wheel assembly, when it is lowered the heat source is removed from the detection loop, thus extinguishes, but will the fire be out on the extended undercarriage?
Answer to OP: return to land ASAP as fire/overheat situation may not be resolved, leave cabin crew in seats, position to 10nm final should give ample time for all checks to be completed and company models to be satisfied
If the overheat detection was due to a fire on the wheel assembly, when it is lowered the heat source is removed from the detection loop, thus extinguishes, but will the fire be out on the extended undercarriage?
Answer to OP: return to land ASAP as fire/overheat situation may not be resolved, leave cabin crew in seats, position to 10nm final should give ample time for all checks to be completed and company models to be satisfied
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There are difference of opinions about "land at nearest suitable" and "land ASAP."
On the 737 and, I believe the 57 and 67, wheel well fire detectors are single loop. The engines and APU utilize more reliable dual loops. I've been told Airbus tends not to have wheel well loops at all, relying on brake temp sensors instead.
It is ironic to think that following TEM procedures would increase the hazard, RAT 5! I can think of alternate CRM scenario with your silver haired gent saying: "Ignore it sprog, I've seen it xx times in my career and they all turned out to be duds."
If the overheat detection was due to a fire on the wheel assembly, when it is lowered the heat source is removed from the detection loop, thus extinguishes, but will the fire be out on the extended undercarriage?
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Some aircraft are equipped with brake temperature sensors - one for each set of brakes (wheel), while others have overheat sensing loops in the wheel well. Some aircraft, like Boeing wide-bodies, have both. On narrow-bodied Boeing aircraft, brake temp sensors are typically customer options, however I understand the A320 series comes with them out of the box.
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is the fire/overheat sensors BOTH in the wheel and wheelwell ?
Hence my question, if the light goes out can you be ASSURED any possible fire on the assembly is out?
Granted it is hanging in the rushing air and likely to be blown out as a result...
IMHO, wheel well fire warning light out thus can refer only to the fact that the HEAT SOURCE HAS BEEN REMOVED from the proximity of the single loop. It does not mean the (possible fire) heat source is EXTINGUISHED.
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It may be of use to the discussion to know the (exponentially) primary generators of heat in the wheel wells, by sheer mass and heat sink/radiation qualities, are the main wheel brake assemblies. Only a fuel leak would have more potential energy in this area of the aircraft.
Halon will not put out a magnesium fire and due to wheel wells being poorly closed compartments, the concentration levels needed for fire suppression would be difficult to sustain - the bottles would need to be very large. Halon also reacts poorly with hot metal, including that hot set of steel brake rotors and disks that most likely was the heat source for initiating the fire/overheat condition in the first place.
So, going back to the principal source of the heat, air, and lots of it is the best way to cool the brake assemblies. Gear down = happy feet.
would having Halon bottles in the wheelwell help extinguish the fire/overheat condition?
So, going back to the principal source of the heat, air, and lots of it is the best way to cool the brake assemblies. Gear down = happy feet.
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So, going back to the principal source of the heat, air, and lots of it is the best way to cool the brake assemblies. Gear down = happy feet.
The wheel well contains hydraulic pipes and wiring. There have been problems with wiring insulation breaking down and sparking. There have been minute hydraulic leaks with a very fine spray. Put the 2 together and you might get a fire that will extinguish with airflow and then perhaps re-ignite. There's lots of oil & grease residue too. So the hot brake, or hydraulic fluid dripping on hot brake, may not be the only cause of a fire. What is the flash temp of hydraulic fluid? Could a brake get so hot on departure as to ignite it, or grease?
The wheel well contains hydraulic pipes and wiring. There have been problems with wiring insulation breaking down and sparking. There have been minute hydraulic leaks with a very fine spray. Put the 2 together and you might get a fire that will extinguish with airflow and then perhaps re-ignite. There's lots of oil & grease residue too. So the hot brake, or hydraulic fluid dripping on hot brake, may not be the only cause of a fire. What is the flash temp of hydraulic fluid? Could a brake get so hot on departure as to ignite it, or grease?
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I believe type IV hydraulic fluid's flash point is around 3-400 degrees F, RAT 5. I also think grease is in such limited quantities (bearings/joints) to preclude it being the cause of a serious fire - tires are more likely suspects in comparison.
Quite true. Gives even better reason for leaving the gear down, yes?
MD-80 AUX HYD pump wiring comes to mind!
There have been minute hydraulic leaks with a very fine spray. Put the 2 together and you might get a fire that will extinguish with airflow and then perhaps re-ignite.
There have been problems with wiring insulation breaking down and sparking. There have been minute hydraulic leaks with a very fine spray.
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With no final opinion, and listening to arguments on both sides, I am going to play the devil's advocate......
If we have an engine fire after a heavy takeoff from a short, slippery runway and the fire warning remains after blowing the bottles, the procedure is to land ASAP.
What do you do if the engine fire light goes out after blowing the bottles. Frequently, take the time to dump fuel then land. But you might say...hey, I can inspect the engine to ensure that the fire has extinguished. Not necessarily on a freighter or with tail mounted engines. Do you still dump fuel and then land? Seems to happen that way.
Why then, is it any different for a wheelwell fire compared to an engine fire. In fact, if the wheelwell fire light has been out for 20 minutes, doesn't Boeing say that the gear can be retracted for performance reasons. Why.....because it was hot brakes, not a wheelwell fire and the brakes have now cooled.
But some say...dual fire sensors are in engine/APU versus a single sensor in the wheelwell, therefore the extinguishing of the fire warning for the engine/APU is more reliable than for the gear. But the dual sensors are intertwined with each other aren't they. If they are, a fire is going not going to burn one and leave the other one OK. So is it any more reliable or really just more redundancy for dispatch purposes.
Mexicana and Swissair were tire explosions, not wheelwell fires. Nationair was a landing gear fire in which the gear remained retracted. If you have an actual fire in your wheelwell, you will know soon. On the Nationair flight, within a very short time period, they had multiple secondary failures. Plus, they had other indications of a blown tire on almost the entire takeoff roll indicating that it was not just a brake overheat.
So if you had a wheelwell fire indication(which will likely be a certain time period after being airborne as the brakes take time before reaching max temp), drop the gear and typically turn around to go back to the departure airport and if there have been no further anomalies since the fire light extinguished 5 minutes ago, how likely is it that you still have or ever had a fire? Not very likely.
With those still fairly warm brakes now landing on a short runway when overweight, you might have trouble getting stopped if you automatically just return and land right away. Which would make you look rather silly to write off an aircraft due to a hot brake(which by the way will not help your stopping capability much).
If we have an engine fire after a heavy takeoff from a short, slippery runway and the fire warning remains after blowing the bottles, the procedure is to land ASAP.
What do you do if the engine fire light goes out after blowing the bottles. Frequently, take the time to dump fuel then land. But you might say...hey, I can inspect the engine to ensure that the fire has extinguished. Not necessarily on a freighter or with tail mounted engines. Do you still dump fuel and then land? Seems to happen that way.
Why then, is it any different for a wheelwell fire compared to an engine fire. In fact, if the wheelwell fire light has been out for 20 minutes, doesn't Boeing say that the gear can be retracted for performance reasons. Why.....because it was hot brakes, not a wheelwell fire and the brakes have now cooled.
But some say...dual fire sensors are in engine/APU versus a single sensor in the wheelwell, therefore the extinguishing of the fire warning for the engine/APU is more reliable than for the gear. But the dual sensors are intertwined with each other aren't they. If they are, a fire is going not going to burn one and leave the other one OK. So is it any more reliable or really just more redundancy for dispatch purposes.
Mexicana and Swissair were tire explosions, not wheelwell fires. Nationair was a landing gear fire in which the gear remained retracted. If you have an actual fire in your wheelwell, you will know soon. On the Nationair flight, within a very short time period, they had multiple secondary failures. Plus, they had other indications of a blown tire on almost the entire takeoff roll indicating that it was not just a brake overheat.
So if you had a wheelwell fire indication(which will likely be a certain time period after being airborne as the brakes take time before reaching max temp), drop the gear and typically turn around to go back to the departure airport and if there have been no further anomalies since the fire light extinguished 5 minutes ago, how likely is it that you still have or ever had a fire? Not very likely.
With those still fairly warm brakes now landing on a short runway when overweight, you might have trouble getting stopped if you automatically just return and land right away. Which would make you look rather silly to write off an aircraft due to a hot brake(which by the way will not help your stopping capability much).
Last edited by JammedStab; 7th Jun 2015 at 02:37.