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Usenet Posted 22 years ago
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Dipstick, dripstick and the Metric System
The Gimli Glider is the name given to a famous incident in aviation history, on July 23, 1983, when a Boeing 767, Air Canada Flight 143, ran out of fuel at 40,000 feet over northern Canada and had to glide to a landing at a former airbase at Gimli, Manitoba.
The story starts in a somewhat amusing fashion, an argument over metric conversion. Normally a 767 is fueled almost completely automatically using a device known as the Fuel Quantity Information System Processor, which runs all of the internal pumps and reports to the pilots on the status of the fuel load. However Flight 143's FQIS was not working properly, a problem later traced to a bad solder joint in the capacitance gauges in the fuel tanks. The fuel load was instead measured with a dripstick, a sort of dipstick for planes, giving the total volume of fuel in the tanks.
The problem occurred when it became time to calculate how much fuel was needed for the trip from Montreal to Edmonton. The calculations were based not on volume, but weight, so the measurements had to be converted. The 767 measured fuel in kilograms, whereas all of the other manuals and planes in the Air Canada fleet used pounds. Looking in their notes for the conversion they used the factor of 1.77 pounds/liter, but a plane measured in kg should have used .8 kg/liter instead. After using the 1.77 figure they punched in 20,400 to the computer, indicating kg, and the computer said there was enough fuel. In fact they had only 9144 kg onboard, definitely not enough for their flight to Edmonton.
http://en.wikipedia.org/wiki/Gimli Glider
The story starts in a somewhat amusing fashion, an argument over metric conversion. Normally a 767 is fueled almost completely automatically using a device known as the Fuel Quantity Information System Processor, which runs all of the internal pumps and reports to the pilots on the status of the fuel load. However Flight 143's FQIS was not working properly, a problem later traced to a bad solder joint in the capacitance gauges in the fuel tanks. The fuel load was instead measured with a dripstick, a sort of dipstick for planes, giving the total volume of fuel in the tanks.
The problem occurred when it became time to calculate how much fuel was needed for the trip from Montreal to Edmonton. The calculations were based not on volume, but weight, so the measurements had to be converted. The 767 measured fuel in kilograms, whereas all of the other manuals and planes in the Air Canada fleet used pounds. Looking in their notes for the conversion they used the factor of 1.77 pounds/liter, but a plane measured in kg should have used .8 kg/liter instead. After using the 1.77 figure they punched in 20,400 to the computer, indicating kg, and the computer said there was enough fuel. In fact they had only 9144 kg onboard, definitely not enough for their flight to Edmonton.
http://en.wikipedia.org/wiki/Gimli Glider
Top answer
[/nq] There's the crux of the problem. I wonder whose bright idea it was to be different. At the very least, such a decision should have been accompanied by big warning labels.
- [/nq] There's the crux of the problem.
- I wonder whose bright idea it was to be different.
- At the very least, such a decision should have been accompanied by big warning labels.
- 77 pounds/liter, but a plane measured in kg ...
- there was enough fuel.
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189 Answers
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[nq:1]The 767 measured fuel in kilograms, whereas all of the other manuals and planes in the Air Canada fleet used pounds.[/nq]
There's the crux of the problem. I wonder whose bright idea it was to be different. At the very least, such a decision should have been accompanied by big warning labels.
[nq:1]Looking in their notes for the conversion they used the factor of 1.77 pounds/liter, bu
There's the crux of the problem. I wonder whose bright idea it was to be different. At the very least, such a decision should have been accompanied by big warning labels.
[nq:1]Looking in their notes for the conversion they used the factor of 1.77 pounds/liter, bu
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Of course not, the computer just read it as 1.77
But the use of all those formulae with (pound) and (US gallon) or (BTU) in them is a curiosity that is limited mostly to the US. Instead of inventing ways to live with the mess
it makes more sense to get rid of it once and for all,
Jan
But the use of all those formulae with (pound) and (US gallon) or (BTU) in them is a curiosity that is limited mostly to the US. Instead of inventing ways to live with the mess
it makes more sense to get rid of it once and for all,
Jan
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[nq:2]The lack of explicit units in computation has been one ... obvious conversion automatically and told them they needed more fuel.[/nq]
[nq:1]Of course not, the computer just read it as 1.77 But the use of all those formulae with (pound) and ... inventing ways to live with the mess it makes more sense to get rid of it once and for all,[/nq]
First off, that doesn't solve the problem of
[nq:1]Of course not, the computer just read it as 1.77 But the use of all those formulae with (pound) and ... inventing ways to live with the mess it makes more sense to get rid of it once and for all,[/nq]
First off, that doesn't solve the problem of
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The problem seems to have arised in a more convoluted way: after mesuring the volume using a dripstick, the pilots converted it manually to pounds. Then, they punched in the result: 20400 pounds; they knew that they were punching pounds in the computer, but they did not know (or forgot) that the plane computer required kilos. Anyway, it seems odd that an experimented tripulation did not rea
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The problem seems to have arisen in a more convoluted way: after mesuring the volume using a dripstick, the pilots converted it manually to pounds. Then, they punched in the result: 20400 pounds; they knew that they were punching pounds in the computer, but they did not know (or forgot) that the plane computer required kilos. Anyway, it seems odd that an experimented tripulation did not rea
00
The problem seems to have arisen in a more convoluted way: after mesuring the volume using a dripstick, the pilots converted it manually to pounds. Then, they punched in the result: 20400 pounds; they knew that they were punching pounds in the computer, but they did not know (or forgot) that the plane computer required kilos. Anyway, it seems odd that an experienced tripulation did not real
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[nq:2]Of course not, the computer just read it as 1.77 ... sense to get rid of it once and for all,[/nq]
[nq:1]First off, that doesn't solve the problem of specifying bare numbers. The exact same problem can (and, I'm pretty sure, ... conversion factor is "neater" has no bearing on the problem. The computer still gets it wrong, in potentially disastrous ways.[/nq]
In principle no, but in p
[nq:1]First off, that doesn't solve the problem of specifying bare numbers. The exact same problem can (and, I'm pretty sure, ... conversion factor is "neater" has no bearing on the problem. The computer still gets it wrong, in potentially disastrous ways.[/nq]
In principle no, but in p
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Javi Poziyo:
Evan Kirshenbaum:
[nq:2]There's the crux of the problem. I wonder whose bright idea it was to be different.[/nq]
What else were they supposed to do, convert the entire fleet overnight?
[nq:2]At the very least, such a decision should have been accompanied by big warning labels.[/nq]
In retrospect, that looks like a good idea.
[nq:2]The lack of explicit unit
Evan Kirshenbaum:
[nq:2]There's the crux of the problem. I wonder whose bright idea it was to be different.[/nq]
What else were they supposed to do, convert the entire fleet overnight?
[nq:2]At the very least, such a decision should have been accompanied by big warning labels.[/nq]
In retrospect, that looks like a good idea.
[nq:2]The lack of explicit unit
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[nq:1]The Gimli Glider is the name given to a famous incident in aviation history, on July 23, 1983, when a ... at 40,000 feet over northern Canada and had to glide to a landing at a former airbase at Gimli, Manitoba.[/nq]
Turned into a TV Movie in 1995 and, coincidentally, shown on UK terrestrial a few afternoons ago:
Turned into a TV Movie in 1995 and, coincidentally, shown on UK terrestrial a few afternoons ago:
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[nq:1]The tanks then had to be fueled to a known quantity, which was measured by volume. However, the mass of the fuel is what really matters, and since the density varies by temperature, a conversion is required.[/nq]
We had a related discussion here on that in relation to cars. You buy fuel by volume (litre or gallon)
but what matters is of course energy, hence mass.
Some claimed tha
We had a related discussion here on that in relation to cars. You buy fuel by volume (litre or gallon)
but what matters is of course energy, hence mass.
Some claimed tha
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