777 fuel leak
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Good info you guys placed here.
I have been flying all sorts of 777 for the past ten years and to be honest, never gave too much thought on fuel leaks.
What Boeing tries to do is to give us some sort of guidance for possible failures and as they state in their manuals, they cannot write a checklist for everything. The crew judgment, after consulting engineering and other sources, is still the best option for unexpected and not-checklist-covered events. The crew must avail of the technical information provided by the experts on ground; however, it is up to the commander to decide the best course of action. IMHO, the guy who landed against company recommendation, did the right thing. The folks on the ground are not under pressure, they have the books in front of them, the coffee is ready, and everything seems to be all right.
I have been flying all sorts of 777 for the past ten years and to be honest, never gave too much thought on fuel leaks.
What Boeing tries to do is to give us some sort of guidance for possible failures and as they state in their manuals, they cannot write a checklist for everything. The crew judgment, after consulting engineering and other sources, is still the best option for unexpected and not-checklist-covered events. The crew must avail of the technical information provided by the experts on ground; however, it is up to the commander to decide the best course of action. IMHO, the guy who landed against company recommendation, did the right thing. The folks on the ground are not under pressure, they have the books in front of them, the coffee is ready, and everything seems to be all right.
Per Ardua ad Astraeus
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Jack - the point of getting out of your seat would be to hopefully ELIMINATE the engine leak (not PROVE the tank leak) as if it is significant you will have a good chance of seeing it (even at night, when there is nearly always some background light - I speak from a few years of flying visual identifications on unlit targets. Only once out of many was I unable to see something). Of course, if you are in a Tristar or...............
'Max fuel imbalance' would be determined by controllability rather than manufacturers' limits if fuel quantity becomes a life-threatening issue.
'Max fuel imbalance' would be determined by controllability rather than manufacturers' limits if fuel quantity becomes a life-threatening issue.
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B777 fuel leak
787cruiser, if you are referring to the incident a few years ago on a pacific rim carrier I think it was not punishment per se ( for the PIC ) but delays in the findings caused by power play between the line operations and maintenance divisions against the safety division. This led to the extended grounding of the PIC casting aspersions that the company had found fault in his decision. The line operations division which ran the dispatch department and maintenance division were trying to cover their asses; the safety division did not know how to deal with issue when the PIC was clearly right but the other divisions called for his head. The issue was left hanging with the PIC finally cleared to fly without any resolution except for the Boeing letter reminding crew to stick to QRH/ECL procedures and that the fuel leak checklist assumes leak from strut to engine.
Out of interest what would be the max fuel imbalance allowed and still maintain controlability, when running both engines from the same tank?
"The primary purpose of fuel balance limitations on Boeing aircraft is for structural life of the airframe and not for controllability limitations."
"Lateral control is not significantly affected when operating with fuel beyond normal balance limits."
"The primary purpose for fuel balance alerts are to inform the crew that imbalances beyond the current state may result in increased trim drag and higher fuel consumption."
I had the chance to see fuel dump on the B777 myself(enroute diversion trying to save 1 pax's life),that's visible!! But engine fuel leak would be alot harder to spot.Smaller in volume and possibly somewhere below the big engine.
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The 777 checklist is only entitled FUEL LEAK.
We are considering very different cases with regard to an Engine Fuel leak and a fuel leak elsewhere (tank, line, pump etc).
The checklist actually assumes an ENGINE fuel leak, but sadly doesn't state that in either the Electronic checklist (ECL) or in the paper QRH.
Sadly in the case of a fuel leak not in the engine, blindly following the checklist may lead to problems.
It advises to shut the engine on the affected side down in the assumption that that will stop the leak.
It then advises that normal fuel balancing can be actioned. Not a great idea if shutting the engine down didn't solve the problem. You will now be in the position of pumping useable fuel from the good tank across to the other side and overboard. oops!
So there you are, mid atlantic, engine shut down, leaking fuel out of both tanks!! Doh!!
Consider the Airbus that managed to glide into the Azores. They were lucky...
PS TOP TIP - When the Fuel Imbalance message is displayed after an engine failure don;t just assume its due to an engine being shut down. Do make a positove immediate check as to whether you have developed a leak (a la Concorde). A quick look of Calculated vs Totaliser on progress page 2 gives a quick confidence check.
happy flying.
Rgds,
SR
We are considering very different cases with regard to an Engine Fuel leak and a fuel leak elsewhere (tank, line, pump etc).
The checklist actually assumes an ENGINE fuel leak, but sadly doesn't state that in either the Electronic checklist (ECL) or in the paper QRH.
Sadly in the case of a fuel leak not in the engine, blindly following the checklist may lead to problems.
It advises to shut the engine on the affected side down in the assumption that that will stop the leak.
It then advises that normal fuel balancing can be actioned. Not a great idea if shutting the engine down didn't solve the problem. You will now be in the position of pumping useable fuel from the good tank across to the other side and overboard. oops!
So there you are, mid atlantic, engine shut down, leaking fuel out of both tanks!! Doh!!
Consider the Airbus that managed to glide into the Azores. They were lucky...
PS TOP TIP - When the Fuel Imbalance message is displayed after an engine failure don;t just assume its due to an engine being shut down. Do make a positove immediate check as to whether you have developed a leak (a la Concorde). A quick look of Calculated vs Totaliser on progress page 2 gives a quick confidence check.
happy flying.
Rgds,
SR
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Hi Sink Rate,
Thank you for your well considered post. The fore-mentioned former colleague of mine indeed made these considerations during the incident. He deduced that there was indeed a fuel leak ( in spite of the fact that some B777 totaliser do behave wildly at times with fuel differences between calculated and sensed going as high as 6000lbs to 7000lbs ). However the leak rate was far below that ballpark figure of 1000lbs per 30 minutes, and there were no unusual fuel flow/fuel used indications. Even the maintenance control with real time engine data monitoring was fooled by the fluctuating totaliser readings, low leak rate and normal engine/fuel parameters. He realised that shutting down an engine during ETOPS operations would bring about more operational and safety issues especially that most of the available suitable airports and diversionary routes on that particular night had thunderstorm activities which could prove fatal in case of lightning strike should he still be leaking fuel in spite of engine shutdown. Like someone indicated, the engine could be restarted but during the time needed to positively ascertained that it was not an engine leak, the aircraft would have to be drifted down to cloud laden lower levels which he wanted to avoid. In his case it indeed turned out to be a small engine fuel leak; and the despatch and maintenance guys were all out to cover their embarassment. The safety guys were initially not happy that he did not follow Boeing procedures to shut down the engine...the safety dept was dominated by B744 guys who knew next to nothing about the intricacies of real life ETOPS operations.
As I had indicated earlier, the Boeing fuel leak checklist has pitfalls exactly as you alluded to...normal fuel balancing after the engine shutdown. I there is indeed a tank fuel leak and the engine shutdown without the crew being any wiser, it can be disastrous.
I was initially not aware of this fact, but that particular captain pointed out to me that he was well aware of the fact that the fuel leak checklist did cover other fuel leaks as well a engine fuel leak with the provision that visual confirmation being vital. The portion of the checklist dealing with engine fuel leak is generally misinterpreted by most crew memebers. He maintained that if there are procedural steps following a statement in the checklist, those procedural steps WILL HAVE AN INDENT immediately below that statement. This was something he tried enlightening the safety dept, but the B744 aces over there just laughed it off as a despaerate line pilot clutching at straws to prove his point! I learnt something old but highly forgotten.
Thank you for your well considered post. The fore-mentioned former colleague of mine indeed made these considerations during the incident. He deduced that there was indeed a fuel leak ( in spite of the fact that some B777 totaliser do behave wildly at times with fuel differences between calculated and sensed going as high as 6000lbs to 7000lbs ). However the leak rate was far below that ballpark figure of 1000lbs per 30 minutes, and there were no unusual fuel flow/fuel used indications. Even the maintenance control with real time engine data monitoring was fooled by the fluctuating totaliser readings, low leak rate and normal engine/fuel parameters. He realised that shutting down an engine during ETOPS operations would bring about more operational and safety issues especially that most of the available suitable airports and diversionary routes on that particular night had thunderstorm activities which could prove fatal in case of lightning strike should he still be leaking fuel in spite of engine shutdown. Like someone indicated, the engine could be restarted but during the time needed to positively ascertained that it was not an engine leak, the aircraft would have to be drifted down to cloud laden lower levels which he wanted to avoid. In his case it indeed turned out to be a small engine fuel leak; and the despatch and maintenance guys were all out to cover their embarassment. The safety guys were initially not happy that he did not follow Boeing procedures to shut down the engine...the safety dept was dominated by B744 guys who knew next to nothing about the intricacies of real life ETOPS operations.
As I had indicated earlier, the Boeing fuel leak checklist has pitfalls exactly as you alluded to...normal fuel balancing after the engine shutdown. I there is indeed a tank fuel leak and the engine shutdown without the crew being any wiser, it can be disastrous.
I was initially not aware of this fact, but that particular captain pointed out to me that he was well aware of the fact that the fuel leak checklist did cover other fuel leaks as well a engine fuel leak with the provision that visual confirmation being vital. The portion of the checklist dealing with engine fuel leak is generally misinterpreted by most crew memebers. He maintained that if there are procedural steps following a statement in the checklist, those procedural steps WILL HAVE AN INDENT immediately below that statement. This was something he tried enlightening the safety dept, but the B744 aces over there just laughed it off as a despaerate line pilot clutching at straws to prove his point! I learnt something old but highly forgotten.
Last edited by 787cruiser; 10th Sep 2007 at 23:07.
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good info
Correct me if I'm wrong
Does the checklist not allude to the fact that correct normal fuel management procedures are used post shutdown....i.e remaining fuel can be used for the operating engine..?
Hence (assuming an engine leak)...the way I read the CL
You would use from the "live engine" tank til FUEL IMBAL displays then balance from the high tank (assuming no tank leak)
If it was a tank leak I don't believe the CL infers you balance from the good side to the leaking tank
Cheers
Does the checklist not allude to the fact that correct normal fuel management procedures are used post shutdown....i.e remaining fuel can be used for the operating engine..?
Hence (assuming an engine leak)...the way I read the CL
You would use from the "live engine" tank til FUEL IMBAL displays then balance from the high tank (assuming no tank leak)
If it was a tank leak I don't believe the CL infers you balance from the good side to the leaking tank
Cheers
Last edited by jack744; 11th Sep 2007 at 00:49.
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Jack, you are right...what Sink Rate alluded to was " blindly " following the checklist and thereafter " blindly " ( highly unlikely, but does happen ) crossfeeding in " normal fuel management ". It is certainly hoped that this will not happen but in a stressful situation coupled with rapid loss rate and unreliable totaliser/fqi one cannot discount such possibility.
Mind you, I have seen 3000+ flight hours F/Os with ATP who are made cruise captains fouled up fuel management in this fashion in the simulator LOFT with fuel leak/engine leak problems!
Mind you, I have seen 3000+ flight hours F/Os with ATP who are made cruise captains fouled up fuel management in this fashion in the simulator LOFT with fuel leak/engine leak problems!
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The checklist in itself doesn't differentiate between what type of leak you are dealing with (which IMHO it should).
It thus STATES in no uncertain terms that once the engine is shut down normal fuel management (ie balancing) can be accomplished.
In the cold light of day we have had the chance to think about it and common sense prevails that in the event of a tank leak then cross feeding would probably be unwise.
Having seen a tank fuel leak about 50 times now (in the simulator at least) I could tell you 50 different ways that line crews might handle it, some better, some worse.
What is apparant though is a reluctance to stray away from a checkilst even when it goes against common sense.
Its all about the big picture....
It thus STATES in no uncertain terms that once the engine is shut down normal fuel management (ie balancing) can be accomplished.
In the cold light of day we have had the chance to think about it and common sense prevails that in the event of a tank leak then cross feeding would probably be unwise.
Having seen a tank fuel leak about 50 times now (in the simulator at least) I could tell you 50 different ways that line crews might handle it, some better, some worse.
What is apparant though is a reluctance to stray away from a checkilst even when it goes against common sense.
Its all about the big picture....
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787cruiser, Sink Rate, Jack, etc. I believe Boeing has changed the fuel leak checklist several times after the incident mentioned by 787cruiser. The present checklist DOES NOT mention ENGINE FUEL LEAK after the condition of imbalance of 1000lbs per 30 minutes or more after initiating the checklist procedure. Billabongbill, I believe that was the incident of mentioned. Kudos to the PIC who had the guts to defy the know - alls from dispatch and maintenance who had all the time to scrutinise the real time data at leisure in the comfort of their snug offices on the ground, and still erred in their assessment! I had flown many times with the skipper of that flight and found him to be a consummate B777 operator. Sadly, he came from the backwaters of SEAsia and the powers that be deemed fit to let him sweat while they quibble over who to blame!
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Right woody, had an observation flight with that skipper many years ago in & out of ORD and SFO. Pretty proficient and knowledgeable chap.
I understand that the dispatch and maintenance insisted that he return to home base when he exercised his command authority to make a precautionary diversion, and he countermanded that too. The company blokes must have been mighty pissed to be refused thrice!! Small wonder they decided to make him sweat before clearing him.
I understand that the dispatch and maintenance insisted that he return to home base when he exercised his command authority to make a precautionary diversion, and he countermanded that too. The company blokes must have been mighty pissed to be refused thrice!! Small wonder they decided to make him sweat before clearing him.
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160 kts & BuzzBox,
Our 767 Sim training indicates no controllability problems (1 wing tank empty/1 wing tank full) (confirming Boeing's view).
In fact, with the engine shut down as per the checklist, all the control inputs are generally neutral (due to the heavy wing compensating for the yaw! tank on the good side FULL).
Perhaps JSA, MFC, LER, JOC, or JME could shed light on this subject on behalf of Boeing ( or perhaps anonymously!!!)
GSV
Our 767 Sim training indicates no controllability problems (1 wing tank empty/1 wing tank full) (confirming Boeing's view).
In fact, with the engine shut down as per the checklist, all the control inputs are generally neutral (due to the heavy wing compensating for the yaw! tank on the good side FULL).
Perhaps JSA, MFC, LER, JOC, or JME could shed light on this subject on behalf of Boeing ( or perhaps anonymously!!!)
GSV
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With respect to the command authority vice despatch, management etc can't help but think of a quote from either Len Morgan or Ernie Gann
Career flying is an uptight, stressful occupation. Laymen have little conception of the pressures under which a professional works. His work is regulated to the point of absurdity by non flying management and federal officials who pretend to understand flying better than he does. He carries a thick book of rules so confusing even its authors cant explain them. In effect, a committee of deskbound experts ride with him on every trip, instructing, admonishing, warning, watching until theres a problem.Then all fingers are pointed at him.
Career flying is an uptight, stressful occupation. Laymen have little conception of the pressures under which a professional works. His work is regulated to the point of absurdity by non flying management and federal officials who pretend to understand flying better than he does. He carries a thick book of rules so confusing even its authors cant explain them. In effect, a committee of deskbound experts ride with him on every trip, instructing, admonishing, warning, watching until theres a problem.Then all fingers are pointed at him.
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Fuel Leak B777
I know this is an old thread but Boeing still haven't changed the checklist.
In my humble opinion the only way to determine if it is an engine leak or a tank leak is to pull the fire handle after shutting down the engine. This closes the pylon valve. If the leak continues then it is a tank leak. If it stops it is an engine leak.
It is my understanding that certification requirements define an engine leak as being between the pylon valve and the engine.
Clearly if it is a tank leak the engine may as well be restarted. Boeings checklist is very poor in this regard. It will save the day inall cases but can result in unnecessary single engine operations.
Some will argue you dont need to pull the fire handle and that once the engine is shut down continued leakage is a tank leak. This is not correct as there is still stuff between the fuel cuttoff valve and the pylon valve that could be leaking.
In my humble opinion the only way to determine if it is an engine leak or a tank leak is to pull the fire handle after shutting down the engine. This closes the pylon valve. If the leak continues then it is a tank leak. If it stops it is an engine leak.
It is my understanding that certification requirements define an engine leak as being between the pylon valve and the engine.
Clearly if it is a tank leak the engine may as well be restarted. Boeings checklist is very poor in this regard. It will save the day inall cases but can result in unnecessary single engine operations.
Some will argue you dont need to pull the fire handle and that once the engine is shut down continued leakage is a tank leak. This is not correct as there is still stuff between the fuel cuttoff valve and the pylon valve that could be leaking.
The book say:
"FUEL CONTROL Switch
RUN (AUTOSTART ON)
Opens the spar fuel valve
arms the engine fuel valve (the EEC opens the valve when required)
arms the selected ignitors(s) (the EEC turns the ignitors on when
required).
RUN (AUTOSTART OFF)
opens the spar fuel valve
opens the engine fuel valve
turns ignitors on.
CUTOFF
closes the fuel valves
removes ignitor power
unlocks the engine fire switch."
B777 fuel control switch actually control the spar valve as well as the engine fuel valve. Thus, not required to pull the fire handle.Of course, fire handle will also do the job of the fuel control switch.
If the centre tank has fuel and either wing tank loses fuel profusely, it is likely to be a tank leak as engine fuel leak would deplete centre tank fuel instead of wing tank fuel.
Have a look at the fuel schematic, notice how near are the spar valves to the engines? Personally, spray observed downstream of the engine pylon can be treated as engine fuel leak as closing the spar valve (by fuel control switch or fire handle) would stop the leak. But tank or pipe line leak upstream of the spar valve have no way to plug it. Also, very hard to pin point the actual leak location.Thus, a land ASAP may be a best option if unable to make destination. Don't forget fuel gauge error can appear to be fuel leak too. Leak downstream of fuel metering unit can cause a reduction of thrust even with thrust level at full forward.Fuel flow would be normal. Shutting it down would stop the leak.
Had a actual wing tank crack some time back in a B737 on a 2hrs flight over water. Captured the leak rate for 30mins then projected the total lost.Proceeded to destination with 700kgs lesser than planned. Saw the ground crew jumping like frog-on-a-hot-wok while docking in as the right wing was dripping.
"FUEL CONTROL Switch
RUN (AUTOSTART ON)
Opens the spar fuel valve
arms the engine fuel valve (the EEC opens the valve when required)
arms the selected ignitors(s) (the EEC turns the ignitors on when
required).
RUN (AUTOSTART OFF)
opens the spar fuel valve
opens the engine fuel valve
turns ignitors on.
CUTOFF
closes the fuel valves
removes ignitor power
unlocks the engine fire switch."
B777 fuel control switch actually control the spar valve as well as the engine fuel valve. Thus, not required to pull the fire handle.Of course, fire handle will also do the job of the fuel control switch.
If the centre tank has fuel and either wing tank loses fuel profusely, it is likely to be a tank leak as engine fuel leak would deplete centre tank fuel instead of wing tank fuel.
Have a look at the fuel schematic, notice how near are the spar valves to the engines? Personally, spray observed downstream of the engine pylon can be treated as engine fuel leak as closing the spar valve (by fuel control switch or fire handle) would stop the leak. But tank or pipe line leak upstream of the spar valve have no way to plug it. Also, very hard to pin point the actual leak location.Thus, a land ASAP may be a best option if unable to make destination. Don't forget fuel gauge error can appear to be fuel leak too. Leak downstream of fuel metering unit can cause a reduction of thrust even with thrust level at full forward.Fuel flow would be normal. Shutting it down would stop the leak.
Had a actual wing tank crack some time back in a B737 on a 2hrs flight over water. Captured the leak rate for 30mins then projected the total lost.Proceeded to destination with 700kgs lesser than planned. Saw the ground crew jumping like frog-on-a-hot-wok while docking in as the right wing was dripping.
