Qantas Plane Flew on Empty Fuel Tank
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Anything to do with the 3% check? It can lead you into trouble if previous errors arent accounted for? I am sure Jaba can tell us all how it should work, with all his experience and all
What are you on about...... I am not claiming to be a Boeing fuel system expert at all...... if you read the ATSB report you may have noticed that those words were lifted directly from it
.I just found that an interesting point that the ATSB felt that had a change in procedure not been implimented, the crew may have had a higher chance of spotting an error. Maybe you thought I was having a swipe at the crew personally, and I am certainly not!
In hindsight you may agree your sarcastic remark was out of line!
J
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The B747 300 has 5 main tanks and four reserve tanks. Unless all indicators are working accurately it is impossible to tell exactly where all the fuel is late in the flight.
By the end of the flight the system is configured tank to engine but even then the fuel in the outboard reserves is not drained into the outboard main tanks until 20 mins before TOD, again reducing the chance of the FE spotting a problem.
It is therefore not unusual to end up with a low tank quantity after a long flight but normally the FE has a fair idea which tank indicator(s) are slightly out and pads the fuel in those tanks. If the operator, as reported changed the requirement to stick check the tanks, then it seems to me that the change removed a chance to identify an inaccurate indicator which would have allowed the FE to pad the final balance prior to landing.
I must admit I was surprised that no water drain appears to have been carried out. I often used the presence of water in a sample as a way to identify a suspect indication.But again there appears to be a recent change in procedure from my experience when fuel was water drained prior to each T/O even if fuel was not uplifted
Basically the old system worked on the Classic and the changes seem to be only put in place to standardise the procedures with other types in the fleet.
Having identified a problem ie no fuel in a tank/engine combination that the crew had no earlier warning and an airport right in front of them,I see it as perfectly reasonable to land on 3 engines. Pilots who fly with only 2 engines don't seem to realise how well the 747 manages on 3.
If they had been further out I'm sure they would have manifolded the engine and restarted it and monitored the quantities and fuel flows.
And yes with the exception of transferring fuel from reserves into mains, the Classic B747 has no way of transferring fuel between tanks in flight. On the ground it can be done on the mains by using the fuel dump system.
Overall I can't see that the crew did anything wrong. They just followed procedures and checklists as written and got the aircraft on the ground safely as they were paid to do.
Wunwing
By the end of the flight the system is configured tank to engine but even then the fuel in the outboard reserves is not drained into the outboard main tanks until 20 mins before TOD, again reducing the chance of the FE spotting a problem.
It is therefore not unusual to end up with a low tank quantity after a long flight but normally the FE has a fair idea which tank indicator(s) are slightly out and pads the fuel in those tanks. If the operator, as reported changed the requirement to stick check the tanks, then it seems to me that the change removed a chance to identify an inaccurate indicator which would have allowed the FE to pad the final balance prior to landing.
I must admit I was surprised that no water drain appears to have been carried out. I often used the presence of water in a sample as a way to identify a suspect indication.But again there appears to be a recent change in procedure from my experience when fuel was water drained prior to each T/O even if fuel was not uplifted
Basically the old system worked on the Classic and the changes seem to be only put in place to standardise the procedures with other types in the fleet.
Having identified a problem ie no fuel in a tank/engine combination that the crew had no earlier warning and an airport right in front of them,I see it as perfectly reasonable to land on 3 engines. Pilots who fly with only 2 engines don't seem to realise how well the 747 manages on 3.
If they had been further out I'm sure they would have manifolded the engine and restarted it and monitored the quantities and fuel flows.
And yes with the exception of transferring fuel from reserves into mains, the Classic B747 has no way of transferring fuel between tanks in flight. On the ground it can be done on the mains by using the fuel dump system.
Overall I can't see that the crew did anything wrong. They just followed procedures and checklists as written and got the aircraft on the ground safely as they were paid to do.
Wunwing
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Aircraft departs A with say 100tonne on board
Arrives B with say 25 tonne having burnt 75 tonne as planned
Next sector requires 100 tonne
Refueller requested to add 75 tonne and following refuelling crew crosschecks fuel remaining, fuel added and fuel onboard which equals (should equal) 100 tonne
If fuel requested, fuel loaded and fuel required crosscheck then trip should be OK
Aircraft departs and during flight crew monitors fuel burn off/ completes fuel howgosit log (including monitoring individual engine fuel flows)
Any discrepancy will immediately show and proper analysis should resolve and indicate where the problem most probably is i.e. whether it is a fuel leak or indication problem, etc.
Feeding the engine from another tank would be a highly preferred option prior to shutting an engine down even on a 4 engine aircraft and, one would think, sound in-flight and analysis procedures should have guided a competent crew to this decision.
DK
Arrives B with say 25 tonne having burnt 75 tonne as planned
Next sector requires 100 tonne
Refueller requested to add 75 tonne and following refuelling crew crosschecks fuel remaining, fuel added and fuel onboard which equals (should equal) 100 tonne
If fuel requested, fuel loaded and fuel required crosscheck then trip should be OK
Aircraft departs and during flight crew monitors fuel burn off/ completes fuel howgosit log (including monitoring individual engine fuel flows)
Any discrepancy will immediately show and proper analysis should resolve and indicate where the problem most probably is i.e. whether it is a fuel leak or indication problem, etc.
Feeding the engine from another tank would be a highly preferred option prior to shutting an engine down even on a 4 engine aircraft and, one would think, sound in-flight and analysis procedures should have guided a competent crew to this decision.
DK
Last edited by Dark Knight; 2nd Jul 2008 at 12:19.
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DK. It's not as simple as that. With all those tanks and various fuel configs during the flight, the indicators jump around a bit as fuel quty transitions from one probe to the next in the tank. There is also stratas of fuel density that the compensator system picks up.
I'm not sure of current limits but a tolerance of up to 10% in a tank was also allowed within the other confines of 3% etc. The end result is at low qutys it is quite normal after a long flight to not know exactly where all the fuel is down to the last 1000 kgs. Hence my comments about it being good to know which tanks had a water content on the last drain.
I note that the aircraft was on a ferry flight which means that it was not far above zero fuel weight on arrival MEL. With a max T/O weight of about 380,000 kgs and a ZFW of about 230,000kgs the aircraft was approx 150,000kgs below max T/O weight which means on 3 engines it would fly rather well.
Since the fuel flow system only looks at fuel down from the strut there could have easily been a leak between the tank and the transmitter. Why stuff around in that situation, just land. In another situation yes I may have treated it differently.
Wunwing
I'm not sure of current limits but a tolerance of up to 10% in a tank was also allowed within the other confines of 3% etc. The end result is at low qutys it is quite normal after a long flight to not know exactly where all the fuel is down to the last 1000 kgs. Hence my comments about it being good to know which tanks had a water content on the last drain.
I note that the aircraft was on a ferry flight which means that it was not far above zero fuel weight on arrival MEL. With a max T/O weight of about 380,000 kgs and a ZFW of about 230,000kgs the aircraft was approx 150,000kgs below max T/O weight which means on 3 engines it would fly rather well.
Since the fuel flow system only looks at fuel down from the strut there could have easily been a leak between the tank and the transmitter. Why stuff around in that situation, just land. In another situation yes I may have treated it differently.
Wunwing
Any discrepancy will immediately show and proper analysis should resolve and indicate where the problem most probably is i.e. whether it is a fuel leak or indication problem, etc.
I have been caught by this once. Thinking we were going to land with what we wanted, on taxi in, one of the low fuel lights came on. Got the Engos to dip the tank - sure enough, it was way down on the indicated quantity and had flown for many sectors like that. Only when you "press the point" to minimum fuel will you find the error...unless you dip the tanks prior to each departure (which, it seems, QF decided to stop doing on the Classics) or after arrival.
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Wunwing, you must be flying a different brand of Boeing; always found the fuel systems to be highly reliable but then it was with well maintained aircraft.
Also had a sound idea of fuel status and if fuel down the strut did not equate to what was in, or should be in the tank, then it would be rapidly evident something was amiss able to be defined as where the problem is.
It is also what in-flight fuel management is all about; knowing what is going on, where it is going and how much there should be.
Your paragraph about various fuel configs, fuel densities, etc. is twaddle and balderdash.
DK
Also had a sound idea of fuel status and if fuel down the strut did not equate to what was in, or should be in the tank, then it would be rapidly evident something was amiss able to be defined as where the problem is.
It is also what in-flight fuel management is all about; knowing what is going on, where it is going and how much there should be.
Your paragraph about various fuel configs, fuel densities, etc. is twaddle and balderdash.
DK
Last edited by Dark Knight; 2nd Jul 2008 at 12:21. Reason: spelling, syntax
professional crews do not shut down a perfectly good engine unless it can absolutely be shown there is a major need to do so
From the ATSB report ..... After completing the appropriate ‘non-normal’ checklist items, the crew shut down the number-3 engine
I guessing one of the checklists that would have been of some interest would be the Fuel Leak checklist, which a previous poster has already mentioned!
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DK, there is no implied criticism of the crew in the ATSB report. One would surmise that after the engine failed at TOD then a fuel leak may have been one of the scenarios discussed. Better to keep the crossfeeds closed in this case, descend and land on three rather than pump your remaining fuel overboard.
Sounds like the crew did a good job to me.
Sounds like the crew did a good job to me.
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DK
I think the aircraft concerned has been fitted with digital indicators, which are not as accurate instantaneously as the old electro mechanical types.
Over a period of say 15 minutes, they are fine and eventually resolve the indications to a more accurate reading than the old indicators, but at TOD with a suspected fuel leak, or even a slight chance of a leak, I certainly wouldn't trust them for an instantaneous decision.
Wunwing
I think the aircraft concerned has been fitted with digital indicators, which are not as accurate instantaneously as the old electro mechanical types.
Over a period of say 15 minutes, they are fine and eventually resolve the indications to a more accurate reading than the old indicators, but at TOD with a suspected fuel leak, or even a slight chance of a leak, I certainly wouldn't trust them for an instantaneous decision.
Wunwing
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Someone must be flying a different brand of Boeing; always found the fuel systems to be highly reliable but then it was with well maintained aircraft and sound procedures.
If the aircraft concerned
then why are there not procedures in place to ensure correct fuel loads are loaded and carried?
If this is correct `
then; why is this allowed to persist and why are there not procedures in place to ensure correct fuel is carried, uplifted and burnt?
How can a crew possibly know what fuel is on board of this previous statement is correct?
How can a fuel tolerance of 3%
and ensure a crew know what fuel is where or consumed?
Where & when (how often) are fuel tank drips done?
Once upon a time they were done very regularly if not once daily and certainly on request.
If the problem started at an earlier time somewhere there has to be a time when fuel ordered, fuel loaded and fuel on board did not tally; why was it not picked up?
DK
If the aircraft concerned
has been fitted with digital indicators, which are not as accurate instantaneously as the old electro mechanical types and this is a known fault
If this is correct `
With all those tanks and various fuel configs during the flight, the indicators jump around a bit as fuel quty transitions from one probe to the next in the tank. There is also stratas of fuel density that the compensator system picks up.
I'm not sure of current limits but a tolerance of up to 10% in a tank was also allowed within the other confines of 3% etc. The end result is at low qutys it is quite normal after a long flight to not know exactly where all the fuel is down to the last 1000 kgs. Hence my comments about it being good to know which tanks had a water content on the last drain’
How can a crew possibly know what fuel is on board of this previous statement is correct?
How can a fuel tolerance of 3%
suddenly be converted to 10% within other confines, etc
Where & when (how often) are fuel tank drips done?
Once upon a time they were done very regularly if not once daily and certainly on request.
If the problem started at an earlier time somewhere there has to be a time when fuel ordered, fuel loaded and fuel on board did not tally; why was it not picked up?
DK
Last edited by Dark Knight; 2nd Jul 2008 at 12:22.
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DK, a quick search of your posts reveals your attitudes to QF pilots. You weren't there, you don't know what went on or why the crew did what they did.
They landed safely and nowhere in the official reports or the QF investigation is any blame levelled at the crew. Try again with something more concrete next time.
They landed safely and nowhere in the official reports or the QF investigation is any blame levelled at the crew. Try again with something more concrete next time.
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Firstly I don't work for QF so I am not an apologist for them.
I do have about 15,000 hours as an FE on all models of the B747 Classic so I have some idea of what was going on.
What I don't find in the ATSB report is any comment that the aircraft was under fueled so I think it can be assumed that the fuel was on board, hence my earlier comments that it is difficult at an INSTANTANEOUS point in time to know exactly what quty is in a specific tank. We have to remember that the design of the FQI system goes back to the 1960s and is basically unchanged .
All that has been altered is replacing the old indicators with new ones which are LCDs.
I also suspect that human factors came into it in as much as there was probably a seat change on the panel at about TOD, when the FE returned from rest, so he wouldn't have the advantage of knowing the indication trends.
Finally QF have been a very large operator B747 Classics since 1971. Going back through the ATSB site there appears very few fuel problems over 37 years. So even after the procedure changes, it is hard to say they had a major problem. In this case, the crew appear to be following a fuel leak checklist and shut down an engine and that is the only reason that the ATSB got involved .
Wunwing
I do have about 15,000 hours as an FE on all models of the B747 Classic so I have some idea of what was going on.
What I don't find in the ATSB report is any comment that the aircraft was under fueled so I think it can be assumed that the fuel was on board, hence my earlier comments that it is difficult at an INSTANTANEOUS point in time to know exactly what quty is in a specific tank. We have to remember that the design of the FQI system goes back to the 1960s and is basically unchanged .
All that has been altered is replacing the old indicators with new ones which are LCDs.
I also suspect that human factors came into it in as much as there was probably a seat change on the panel at about TOD, when the FE returned from rest, so he wouldn't have the advantage of knowing the indication trends.
Finally QF have been a very large operator B747 Classics since 1971. Going back through the ATSB site there appears very few fuel problems over 37 years. So even after the procedure changes, it is hard to say they had a major problem. In this case, the crew appear to be following a fuel leak checklist and shut down an engine and that is the only reason that the ATSB got involved .
Wunwing
