Continental Pilots Say Jets Flying On Fumes
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my understanding is that at full tanks the Boeing (modern, since 1980s) have a slight negative fuel guage error at full tanks totalizer, but have ZERO fuel guage error at zero fuel totalizer. The fuel tank gauge error is related to the total fuel on board.
Not to belabour the obvious, but I doubt there are many operators worldwide (that pay for their fuel!) not emphasizing, pressuring? their pilots to take any more than minimum fuel.
A twist on this though is a recent memo praising one of our finest for removing a substantial quantity of the planned fuel load after deciding he/she did not 'need that much'
It was emphasized how much money this saved..
I don't really think we need to encourage this !
A twist on this though is a recent memo praising one of our finest for removing a substantial quantity of the planned fuel load after deciding he/she did not 'need that much'
It was emphasized how much money this saved..
I don't really think we need to encourage this !
Last edited by stilton; 28th Nov 2007 at 04:32.
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Accuracy of FQIS
In response to the question on FQIS accuracy.
I believe the minimum designed accuracy of fuel quantity indication systems is 5%. However most modern systems are accurate to 3%. Some systems also have error indications that will advise you if the system is gauging to an accuracy of less than 3%.
In practice geater accuracies are hard to achieve as the "accuracy" of the fuel is only around 1% (as its properties vary a lot).
FQIS systems are on condition. There may be a serviceability check in major servicings, but mostly the maintenance processes will rely on pilot-reported problems. There is no accuracy limits for maintenance in terms of percentages; but there will be limits in the standard tests. based on mass indications.
In practice modern systems are very robust and the digital systems will remove the inputs from suspect probes. The older summing systems do carry errors though, and often maintenance crews calibrate out the errors, which is not really how the system should work.
The best way to maintain accuracy of capacitance systems is to drain the water regularly, and for pilots to report accurately any percieved errors and fluctuations.
It isn't easy to work on the systems, particularly when in-tank maintenance is required. Too often, to avoid the cost, simple measures like replacing the indicator (repeatedly) is carried out to keep the plane flying.
It's not all doom though. As the errors are %-based, the system normally gets more accurate as you burn fuel (1% of 5000kgs vs 1% of 20,000kgs). Unless fuel draining isn't carried out regularly, whereby fungus can form on the probe causing it to overead.
I believe the minimum designed accuracy of fuel quantity indication systems is 5%. However most modern systems are accurate to 3%. Some systems also have error indications that will advise you if the system is gauging to an accuracy of less than 3%.
In practice geater accuracies are hard to achieve as the "accuracy" of the fuel is only around 1% (as its properties vary a lot).
FQIS systems are on condition. There may be a serviceability check in major servicings, but mostly the maintenance processes will rely on pilot-reported problems. There is no accuracy limits for maintenance in terms of percentages; but there will be limits in the standard tests. based on mass indications.
In practice modern systems are very robust and the digital systems will remove the inputs from suspect probes. The older summing systems do carry errors though, and often maintenance crews calibrate out the errors, which is not really how the system should work.
The best way to maintain accuracy of capacitance systems is to drain the water regularly, and for pilots to report accurately any percieved errors and fluctuations.
It isn't easy to work on the systems, particularly when in-tank maintenance is required. Too often, to avoid the cost, simple measures like replacing the indicator (repeatedly) is carried out to keep the plane flying.
It's not all doom though. As the errors are %-based, the system normally gets more accurate as you burn fuel (1% of 5000kgs vs 1% of 20,000kgs). Unless fuel draining isn't carried out regularly, whereby fungus can form on the probe causing it to overead.
Two years ago, for the first time, some people in my company decided that the Dispatch Release fuel could be reduced by 200 pounds, without a new release or amendment.
I wonder which management "suit(s)" pocketed a cash bonus for that slight operating cost reduction idea? Many of their cost-savings were later somewhat nullified when the Upper Mgmt "Team"
were given about $300,000,000 worth of free corporate stock.
This Release Fuel policy change only happened because of high fuel prices-there can be no other possible reason. Sure, our APU burns about that much when we sit on the ground about 45 minutes after fueling.
If our Dispatch Supervisors ever had the sole authority to determine the maximum fuel we could carry (which they never will: with all due respect, they are not in the c0ckpit with us), it would be like the HMOs here telling doctors whether your required medical procedure can be paid for, or should something much less effective be prescribed for your major medical condition...
I wonder which management "suit(s)" pocketed a cash bonus for that slight operating cost reduction idea? Many of their cost-savings were later somewhat nullified when the Upper Mgmt "Team"
were given about $300,000,000 worth of free corporate stock.This Release Fuel policy change only happened because of high fuel prices-there can be no other possible reason. Sure, our APU burns about that much when we sit on the ground about 45 minutes after fueling.
If our Dispatch Supervisors ever had the sole authority to determine the maximum fuel we could carry (which they never will: with all due respect, they are not in the c0ckpit with us), it would be like the HMOs
here telling doctors whether your required medical procedure can be paid for, or should something much less effective be prescribed for your major medical condition...
Join Date: Oct 2003
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I'm in the process of starting an airline ... (nothing special, actually just a small GA operation), however AC commanders will ALWAYS be encouraged to err on the side of safety. For us it will be the cashflow cost of an uplift (rather than the fuel/mass penalty) that will be the greatest problem ....
However ......
Departure delay after start-up (common for GA types at Intl airports) followed by stronger headwinds than forecast, followed by a hold at destination, followed by a weather go-around, followed by further holding, coupled with fuel guage/totaliser error, followed by a serene silence on the next app, followed by an impact between AC and small planet ..... End of my business.
Therefore .......
Dont skimp on the fuel.
OK, so a small GA operation will not have the same commercial considerations as the big guys, and nor will the fuel planning have such an impact on the bottom line.
But .......
I question if my operation would have the same corporate attitude to fuel uplift if I were not a pilot. I think not!!!
However ......
Departure delay after start-up (common for GA types at Intl airports) followed by stronger headwinds than forecast, followed by a hold at destination, followed by a weather go-around, followed by further holding, coupled with fuel guage/totaliser error, followed by a serene silence on the next app, followed by an impact between AC and small planet ..... End of my business.
Therefore .......
Dont skimp on the fuel.
OK, so a small GA operation will not have the same commercial considerations as the big guys, and nor will the fuel planning have such an impact on the bottom line.
But .......
I question if my operation would have the same corporate attitude to fuel uplift if I were not a pilot. I think not!!!
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Could be completely wrong here...
I might be missing the point here (wouldnt be the first time either) but why is there a pressure to uplift less fuel for a leg, if the fuel you don't use will only be used for the next leg?
I realise this might seem too simplistic but surely if you lift say 15% more than you need and don't use it, it doesn't go anywhere, it simply gets integrated into the next leg calculation and used there, hence that leg will have less of an uplift than it normally would. Since its all from the same company coffers, surley it all evens out? This would cater for the holds, unforseen headwinds etc which would and will happen anyways. Just means you wouldn't have to divert and upset all your pax. Again sorry if I'm missing the point here.
The only time you have too much fuel is when you're fire.
I realise this might seem too simplistic but surely if you lift say 15% more than you need and don't use it, it doesn't go anywhere, it simply gets integrated into the next leg calculation and used there, hence that leg will have less of an uplift than it normally would. Since its all from the same company coffers, surley it all evens out? This would cater for the holds, unforseen headwinds etc which would and will happen anyways. Just means you wouldn't have to divert and upset all your pax. Again sorry if I'm missing the point here.
The only time you have too much fuel is when you're fire.
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Pacific Baron
The bottom line is that any weight, & that includes fuel, costs money, & that means fuel, to carry it from point of departure to point of destination. The problem is, that as a commander, sometimes the decision to put on extra fuel creates the problem that you were hoping to avoid. i.e. the more fuel you put on, the heavier you are, the lower the altitude the are able to maintain relative to other traffic. END RESULT. you have created your own worst nightmare> FOOD FOR THOUGHT!!!!!!!!!!!!!!!!!!!!!!
EXPERIENCE cannot be bought!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
EXPERIENCE cannot be bought!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
