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Is this a good way to burn off extra fuel

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Is this a good way to burn off extra fuel

Old 20th Aug 2017, 15:08
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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?
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Old 20th Aug 2017, 16:37
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How many years widebody experience does he have? How many years widebody experience do you have?
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Old 20th Aug 2017, 17:07
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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?
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Old 20th Aug 2017, 21:42
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That is a TERRIBLE habit! Find a place to sit and burn it off.
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Old 20th Aug 2017, 21:59
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What would you have done?
I'd have asked to go to a quiet corner and then burn off the fuel. Look after your brakes, you never know when you might need them, especially at max weight.

How many years widebody experience do you have?
33 years
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Old 20th Aug 2017, 22:17
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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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Old 20th Aug 2017, 23:44
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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.
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Old 21st Aug 2017, 00:13
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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.
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Old 21st Aug 2017, 00:23
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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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Old 21st Aug 2017, 00:31
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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?

Last edited by Vessbot; 21st Aug 2017 at 00:43.
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Old 21st Aug 2017, 00:48
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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.
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Old 21st Aug 2017, 01:49
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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.
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Old 21st Aug 2017, 03:30
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Ask Atc where you can park and run up the
thrust.

Burn off the fuel.

Depart.
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Old 21st Aug 2017, 06:13
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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.
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Old 21st Aug 2017, 07:11
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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.
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Old 21st Aug 2017, 09:20
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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.
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Old 21st Aug 2017, 09:42
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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
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Old 21st Aug 2017, 10:21
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Originally Posted by JammedStab
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?
Take the parallel taxiway, set the parking brake, turn on the APU and wait. How long will it take to burn off 500kg of fuel on a widebody on the ground ? 30 min ? Well that's it not much you can do. Once you get to destination Your Cpt will write a nice report explaining what happened and eventually it will just be a lesson learnt for all. On the other hand pushing with non standard practices while increasing the threats (hot brakes) is something that could easily end up in the wrong way if Murphy decides to have a look at your flight on that specific day.
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Old 21st Aug 2017, 10:36
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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.
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Old 21st Aug 2017, 10:54
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Originally Posted by JammedStab
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.
Well IMHO it depends WHY is TOW limited. Structural? Performance? Landing weight?

If it's the latter our SOP allow to assume a 50% burn off of contingency fuel, means increased trip fuel....
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