Is this a good way to burn off extra fuel
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Is this a good way to burn off extra fuel
Widebody jet, 30 degrees C, full takeoff thrust required, max taxi weight but due to a runway change, the planned taxi routing runway is shorter than expected.
500 kg need to be burned before takeoff is legal. No problem, just ride the brakes with a higher than normal thrust setting. A parallel taxiway is available where we could stop and burn off fuel but when questioned, the captain says he has done this before. The other crewmembers don't seem concerned either when I ask about checking the brake temps. Saw one of them at 2 units a couple of minutes before takeoff.
Do I worry too much about this? Are carbon brakes so good that it is not an issue? Or is it poor airmanship?
500 kg need to be burned before takeoff is legal. No problem, just ride the brakes with a higher than normal thrust setting. A parallel taxiway is available where we could stop and burn off fuel but when questioned, the captain says he has done this before. The other crewmembers don't seem concerned either when I ask about checking the brake temps. Saw one of them at 2 units a couple of minutes before takeoff.
Do I worry too much about this? Are carbon brakes so good that it is not an issue? Or is it poor airmanship?
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Never flown a widebody, so out of ignorance, I'll ask what the size of the plane has to do with it.
You said the brake temps were at 2 units. What's the maximum for takeoff? If there's still a good margin left, I don't see a problem. What would you have done?
You said the brake temps were at 2 units. What's the maximum for takeoff? If there's still a good margin left, I don't see a problem. What would you have done?
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What would you have done?
How many years widebody experience do you have?
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That is intentional abuse of the brakes, in my opinion. If this pilot shows you he has no feeling for mechanical systems, I'd wonder what else he doesn't understand about stress on the aircraft.
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JammedStab..... its a bad idea....
https://en.wikipedia.org/wiki/Nigeri...ys_Flight_2120
IIRC, The report cites the long taxi with excessive braking as one of the causes.
https://en.wikipedia.org/wiki/Nigeri...ys_Flight_2120
IIRC, The report cites the long taxi with excessive braking as one of the causes.
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The prevailing wisdom from the east side of the Atlantic seems to be that it was a bad idea. It's done from time to time on the western edge. Seems like there were 3 options:
1. Ride the brakes during taxi
2. Pull over somewhere with the power above idle
3. Pull over somewhere with the power at idle
1 & 2 will result in higher brake temps. The OP said 2 units. What's the maximum for takeoff? If it's 10, I hope it shouldn't be a problem.
Options 3 would keep the brakes cool, but may not have been feasible due to some time constraint.
1. Ride the brakes during taxi
2. Pull over somewhere with the power above idle
3. Pull over somewhere with the power at idle
1 & 2 will result in higher brake temps. The OP said 2 units. What's the maximum for takeoff? If it's 10, I hope it shouldn't be a problem.
Options 3 would keep the brakes cool, but may not have been feasible due to some time constraint.
Is that correct?A widebody has to burn of 500kg of fuel before take off? So worldwide there are tons of fuel wasted,surely there must be a better way!What is the average burn from push back to take of with taxying and awaiting take of clearance?Passenger question!!!
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The max takeoff weight is determined by the most limiting of about a dozen different factors, and the fuel loaded onto the plane is determined such that you are at your planned takeoff weight when you reach the end of the runway.
But sometimes things change after you push back from the gate (in this thread's first poster's case, they went to a shorter runway than planned) and you have to get rid of some of that weight, which you wouldn't have loaded onto the plane in the first place had you known how things were gonna go.
Edit: oops, I just re-read the first post and that's not what happened. But it just as easily could have.
Reminds me of the time I had to burn off the most fuel... In a short haul airplane on a short flight, MTOW was that flight was limited by max landing weight at the destination. Due to a rerouting for storm passage that drastically cut the flight plan distance, we had to lose 2000 pounds... which was a quarter of our fuel load! I wonder what the record is, percentage-wise. Maybe we hold it?
But sometimes things change after you push back from the gate (in this thread's first poster's case, they went to a shorter runway than planned) and you have to get rid of some of that weight, which you wouldn't have loaded onto the plane in the first place had you known how things were gonna go.
Edit: oops, I just re-read the first post and that's not what happened. But it just as easily could have.
Reminds me of the time I had to burn off the most fuel... In a short haul airplane on a short flight, MTOW was that flight was limited by max landing weight at the destination. Due to a rerouting for storm passage that drastically cut the flight plan distance, we had to lose 2000 pounds... which was a quarter of our fuel load! I wonder what the record is, percentage-wise. Maybe we hold it?
Last edited by Vessbot; 21st Aug 2017 at 00:43.
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@Check Airman
holding with whatever thrust set will NOT heat up the brakes.
you need friction + movement to create heat in the brakes. no movement = no heat.
so your option 2 will not result in higher brake temperatures.
still a long taxi might also raise brake temps, probably not as much as taxiing with higher thrust but still the question is how much fuel had to be burned off.
holding with whatever thrust set will NOT heat up the brakes.
you need friction + movement to create heat in the brakes. no movement = no heat.
so your option 2 will not result in higher brake temperatures.
still a long taxi might also raise brake temps, probably not as much as taxiing with higher thrust but still the question is how much fuel had to be burned off.
Using the standard weights for pax, and seeing how much unweighed carry on they bring on board, I wonder how accurate the weights used for performance calcs actually are. 500kg for a fully loaded 747 represents a bit over 1kg per passenger after all.
Lowly turboprop driver here.
On any type I have come across yet, fuel usage on ground has been a function only of engine power over time. Nothing else. Taxi speed, distance etc. seem to have only a minuscule or no effect at all, and seeing that OAT, pressure, wind etc. are a given when on the ground and cannot be influenced, IŽd disregard their influence as well.
So the option to just sit somewhere out of the way, with the parking brake set and therefore not even having to ask the question whether the brakes will be abnormally heated or not, and increase engine power a little bit to a prudent value seems to have much merit. Also, if not already in use, starting the APU might speed up the desired reduction of fuel on board.
IŽd therefore respectfully suggest asking ATC to hold in a quiet taxiway, the runway bypass or something like this (airfield dependent), obtain the approval to increase power to a setting e. g. for a crossbleed start, and just wait there until the MTOW is achieved.
If allowed in the company and not already done, is the use of alternate passenger weights an option?
Here is another accident that was caused by taxiing around while riding the brakes: a Swissair Caravelle that was taxied up and down the runway with high power settings in order to clear the fog, then took off and suffered a fire in the main wheel bay.
On any type I have come across yet, fuel usage on ground has been a function only of engine power over time. Nothing else. Taxi speed, distance etc. seem to have only a minuscule or no effect at all, and seeing that OAT, pressure, wind etc. are a given when on the ground and cannot be influenced, IŽd disregard their influence as well.
So the option to just sit somewhere out of the way, with the parking brake set and therefore not even having to ask the question whether the brakes will be abnormally heated or not, and increase engine power a little bit to a prudent value seems to have much merit. Also, if not already in use, starting the APU might speed up the desired reduction of fuel on board.
IŽd therefore respectfully suggest asking ATC to hold in a quiet taxiway, the runway bypass or something like this (airfield dependent), obtain the approval to increase power to a setting e. g. for a crossbleed start, and just wait there until the MTOW is achieved.
If allowed in the company and not already done, is the use of alternate passenger weights an option?
Here is another accident that was caused by taxiing around while riding the brakes: a Swissair Caravelle that was taxied up and down the runway with high power settings in order to clear the fog, then took off and suffered a fire in the main wheel bay.
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First of all, your fuel summation unit is often less accurate than 500 kg., especially on ground. Do not waste fuel. If you have to leave the gate with max. Ramp fuel, this also means you are dispatching with min. Flight plan fuel for your flight...
Secondly, some here do need to get into the books more and get an understanding on how carbon brakes work.
You will NOT overheat brakes when you are stationery and add thrust. You need FRICTION for brakes to heat up. Prolonged taxi is therefore more harmful than holding with thrust.
From all options, the best is to just ask to hold for a couple of minutes and burn the bloody 500 kg. If you insist. But do understand that ALL values on your loadsheet are estimates, and NOT absolute numbers, as is the onboard fuel displayed.
Ps. On B744, you need to look into the brake cooling schedule if your brakes temps. Are over 2 units. Nothing in the books on what the max. Brake units are for take-off but you do have to realize this. On Widebody, brake temp. Does rise very quickly.
Secondly, some here do need to get into the books more and get an understanding on how carbon brakes work.
You will NOT overheat brakes when you are stationery and add thrust. You need FRICTION for brakes to heat up. Prolonged taxi is therefore more harmful than holding with thrust.
From all options, the best is to just ask to hold for a couple of minutes and burn the bloody 500 kg. If you insist. But do understand that ALL values on your loadsheet are estimates, and NOT absolute numbers, as is the onboard fuel displayed.
Ps. On B744, you need to look into the brake cooling schedule if your brakes temps. Are over 2 units. Nothing in the books on what the max. Brake units are for take-off but you do have to realize this. On Widebody, brake temp. Does rise very quickly.
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Using the standard weights for pax, and seeing how much unweighed carry on they bring on board, I wonder how accurate the weights used for performance calcs actually are. 500kg for a fully loaded 747 represents a bit over 1kg per passenger after all.
Thanks Megan. I wonder how many out there would really do this, or just get on with it. Performance calculation is a dark art, not a precise science. It could be embarrassing if later on in the flight you needed that fuel. But cooking the brakes seems not a sensible idea.
Thanks Megan. I wonder how many out there would really do this, or just get on with it. Performance calculation is a dark art, not a precise science. It could be embarrassing if later on in the flight you needed that fuel. But cooking the brakes seems not a sensible idea.
If you are illegally overweight and have a totally unrelated incident which brings this to the attention of your regulating authority you may expect to have the book thrown at you.
The paperwork, and recorded data, must be legal.
Riding the brakes to burn off fuel? I had to check the date
The paperwork, and recorded data, must be legal.
Riding the brakes to burn off fuel? I had to check the date
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Widebody jet, 30 degrees C, full takeoff thrust required, max taxi weight but due to a runway change, the planned taxi routing runway is shorter than expected.
500 kg need to be burned before takeoff is legal. No problem, just ride the brakes with a higher than normal thrust setting. A parallel taxiway is available where we could stop and burn off fuel but when questioned, the captain says he has done this before. The other crewmembers don't seem concerned either when I ask about checking the brake temps. Saw one of them at 2 units a couple of minutes before takeoff.
Do I worry too much about this? Are carbon brakes so good that it is not an issue? Or is it poor airmanship?
500 kg need to be burned before takeoff is legal. No problem, just ride the brakes with a higher than normal thrust setting. A parallel taxiway is available where we could stop and burn off fuel but when questioned, the captain says he has done this before. The other crewmembers don't seem concerned either when I ask about checking the brake temps. Saw one of them at 2 units a couple of minutes before takeoff.
Do I worry too much about this? Are carbon brakes so good that it is not an issue? Or is it poor airmanship?
I remember a BA 747-136 at Muscat that was much delayed, departing around 10am local.
Between getting the airfield data and start up the oat had gone up by about 10 degrees C.
He requested to sit on the end of the runway and burn off several tons of fuel. As he did this he kicked up a massive sand storm behind, but also the temp rose further and more fuel had to be burnt. It took about 20 mins to get down to RTOW. I think he refiled to tech stop on the way to London.
Between getting the airfield data and start up the oat had gone up by about 10 degrees C.
He requested to sit on the end of the runway and burn off several tons of fuel. As he did this he kicked up a massive sand storm behind, but also the temp rose further and more fuel had to be burnt. It took about 20 mins to get down to RTOW. I think he refiled to tech stop on the way to London.
If it's the latter our SOP allow to assume a 50% burn off of contingency fuel, means increased trip fuel....