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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 28th Aug 2017, 20:48
  #81 (permalink)  
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Once again...I work for an airline where an exceedance is taken very seriously including exceeding a max taxi weight(they had a big letter about it once) or the max takeoff weight. So no need to tell me about how the performance won't be affected. I don't care. I care about not being demoted.

So...is this a good way to burn off excess fuel?.....Which has been answered straight from the FCTM and now from FAA world as well.

Thanks
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Old 29th Aug 2017, 03:28
  #82 (permalink)  
 
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ACCURATE WEIGHT?

When I was a line Captain on (big jet) with xxxx, I used to carry an extra 2000 kgs more than the CFP/NFP required to cater for known extra BURN on the regular 9 hour flight.All line pilots knew this, and did this, because we knew that inspite of best intentions at this very professional outfit, the ZFW was always understated, mainly from the Nigerian PAX who carried massive amounts of cabin bags.
When the fleet CP harrassed me about this practice, I told him if you look at the FMC target thrust in cruise, it is much lower that ACTUAL THRUST, meaning we are heavier than we think.To work out how much heavier, just keep increasing the ZFW number on your performance page until the ACTUAL THRUST and the TARGET THRUST are the same.The result is scary.All your V speeds are thus too low for take off and landing.

Funny thing was, the same CP had an engine failure at 500 feet agl from the same airport on the same route and couldnt climb away, in fact his bigjet started to descend!!! Eventually he managed it, but upon landing a re-weigh indicated they were 6000 kgs over the stated ZFW, so I have to take most of the comments posted here with a large pinch of salt.....Pete.
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Old 29th Aug 2017, 10:51
  #83 (permalink)  

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I agree, Pete, there are so many inaccuracies involved the only way you could know for sure is weigh the aircraft at the departure holding point. All those outraged types on here saying they would never take off overweight may already have done that on many occasions without knowing it!

Having said that, read your ops manuals, don't break any rules and never ride carbon brakes.
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Old 29th Aug 2017, 13:21
  #84 (permalink)  
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Originally Posted by overstress
don't break any rules and never ride carbon brakes.
The question is....why not. Is there a particular reason for this type of brake not to, or is it for the same reason as steel brakes?
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Old 29th Aug 2017, 14:56
  #85 (permalink)  
 
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To be pedantic and not condone any dubious practices, but....

Many on here say it is illegal, not a good idea, etc. to take off overweight. What they really mean it is not a good idea etc. to take off with a load sheet showing you are overweight.

The two are not the same. If you can alter the load sheet, sensibly, you can solve the latter scenario. If you want to ensure the former you'd better be prepared to cancel your slot time, expect to use discretion after having checked all the pax & bag actual weights, incur the wrath of CP for all of the above. Anyone who takes off at load sheet'd MRTOW is taking a blind but legal leap of faith.
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Old 1st Sep 2017, 15:26
  #86 (permalink)  

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awair, all very well, but if your company ops manual says you can disregard unburned taxi fuel, (as mine does) then that's what I will continue to do. I can hardly be committing a wrong if the manual says you can do it.
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Old 2nd Sep 2017, 00:18
  #87 (permalink)  
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Ops manuals are typically approved by the governing authority. Could you please tell us which country you work in so we are aware of what country approves this.

Will we get an answer?
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Old 2nd Sep 2017, 07:51
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Originally Posted by JammedStab
The question is....why not. Is there a particular reason for this type of brake not to, or is it for the same reason as steel brakes?
Why not! - there is no approved procedure to ride carbon brakes or steel brakes - do they react differently YES!.

Now if this pilot is riding brakes for an extended period he is going into an area of brake use that has no data and thus the usefulness of the brakes is now un-known, in what we now know is not an empty aircraft but an over weight one for this flight.

Friction creates heat - over time heat is transferred further and further and other items can get hot, possibly to hot if the heat period is very long. Think something melting or boiling!

Aircraft are tested to procedures max braking no reverse, consecutive braking and other tests and from this limits are obtained - there is no test for riding brakes, so the parameters of this use are un-known in future performance. So no braking performance can be planed or expected.

* Carbon brakes work best and have good wear characteristics at an optimum temp that is quite high, and no doubt designed to fit the normal braking requirements of the aircraft type. Below this temp they have a much faster wear rate and if the temp get too high they become warped.

I think we can all agree that in aircraft, the brakes are solely designed for stopping an aircraft and not designed for stopping an aircraft accelerating.

We could always use a touch of flap to trim the aircraft - but that is un-known data and that is why the elevator is trimmed.
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Old 2nd Sep 2017, 09:18
  #89 (permalink)  
 
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Originally Posted by overstress
awair, all very well, but if your company ops manual says you can disregard unburned taxi fuel, (as mine does) then that's what I will continue to do. I can hardly be committing a wrong if the manual says you can do it.
Good, so let's say your structural MTOW is 300t and your Max Ramp Weight is 302t (random figures). You're well packed today, long flight so no MLW issues and you pushback at 302T. Your loadsheet has a 2t taxi fuel. ATC now changes runway in use to a runway that is just less than 2 min taxi from your current position. Happy days ! Setup, no problems with performances (long big runways sea level no obstacles lovely temperature etc..) quick rebrief and off we go, we've saved 30-45 min taxi and we are about to takeoff at 301t (1t above your MTOW). So your Company manual says you can disregard unburned taxi fuel, hence who cares ? We're super legal, let's exceed a limitation. You happily takeoff and a few hours later people working in your flight safety office get a nice red flag on the OFDM and call you for tea and biscuits. From there you learn to read the manuals, read the SOP and also "think" about what you are doing.
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Old 2nd Sep 2017, 09:52
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Setup, no problems with performances (long big runways sea level no obstacles lovely temperature etc..)
How do you check the performance in this case? Most tools will not allow entering weight above MTOW as even the AFM doesn't have data to support it.
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Old 2nd Sep 2017, 09:56
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Originally Posted by sonicbum
Good, so let's say your structural MTOW is 300t and your Max Ramp Weight is 302t (random figures). You're well packed today, long flight so no MLW issues and you pushback at 302T. Your loadsheet has a 2t taxi fuel. ATC now changes runway in use to a runway that is just less than 2 min taxi from your current position. Happy days ! Setup, no problems with performances (long big runways sea level no obstacles lovely temperature etc..) quick rebrief and off we go, we've saved 30-45 min taxi and we are about to takeoff at 301t (1t above your MTOW). So your Company manual says you can disregard unburned taxi fuel, hence who cares ? We're super legal, let's exceed a limitation. You happily takeoff and a few hours later people working in your flight safety office get a nice red flag on the OFDM and call you for tea and biscuits. From there you learn to read the manuals, read the SOP and also "think" about what you are doing.
If your approved company manual says you can do 20% over any weight or even fly inverted .

Trust me it is legal and approved - they have given details and data to have it approved ( by what ever means inc rough weights of pax and carry on) by a governing body.
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Old 2nd Sep 2017, 10:24
  #92 (permalink)  
 
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Band a Lot,

I am pretty sure that You have given a wrong interpretation to some wording of your ops manual. If you are aware of being overweight by looking at your fmc or whatever other system shows your current GW it is your responsibility to do something about it (hopefully not by riding the brakes please). The load sheet is a plan of how your aircraft is loaded prior to start your flight and how, based on the expected flight plan data, it is going to evolve. Should figures significantly change because of any change such as a reclearance you still have to ensure you are complying with the aircraft and performance limitations.
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Old 2nd Sep 2017, 14:49
  #93 (permalink)  
 
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Every Ops manual I've worked with has used standard pax weights; all approved. Standard baggage weights as well. You have to be kidding if you think theses are realistic. Approved? Yes. Accurate? No. You go figure. So messing about for 500kgs on a large jet. It's all about paperwork not reality, surely.
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Old 2nd Sep 2017, 15:04
  #94 (permalink)  
 
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RAT5 you are missing the OP point I believe. There is no doubt that as standard weights are used, the 300t or whatever weight your load sheet shows you for departure will most likely be different that the actual current weight of the airplane. You don't know by how much, you would need a scale, but industry standards are built in such a way that you will be covered. What we are talking about here is the fact that if you know that you are currently overweight because if you are supposed to burn a certain amount of taxi fuel as per your load sheet and you actually burn much less, then you know you are overweight, it is simple maths and the load sheet has nothing to to with it as it will still show the correct figures. Taking off above MTOW be it structural or regulated is simply not legal.
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Old 2nd Sep 2017, 15:22
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Given many of us may here be quoting from the same book but I'm another one whose company ops manual quite clearly states that there is no requirement to ensure all taxi fuel is burned prior to commencement of the take off roll provided any possible weight exceedence is "considered minor" (not defined).

I haven't quoted the two line rule verbatim apart from the two words in quotes but nevertheless the policy is clearly worded and as far as I see not really open to being misunderstood or misconstrued. Now how the company squares that statement with the requirements likes of EASA, and the numbers Boeing and Airbus publish I will leave for further discussion.......
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Old 2nd Sep 2017, 15:45
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What I've learned is that there's nothing that isn't open to being misunderstood or misconstrued, no matter how simple. Never underestimate the ability of a lazy or inattentive pilot to understand something as the direct opposite of what it says. Or, when given an inch of discretion, to take a mile instead.
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Old 3rd Sep 2017, 06:35
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If a aircraft manufacturer states that the MTOW is 225,000 kg in it manual.

and a Regulator (FAA/CAA/CASA) states that a flight shall not be planned to take-off above MTOW.

And the Regulator has approved the company operations manual to plan a flight.

The Regulator will over rule the manufacturer in every country.

So if approved, that unused but planned taxi fuel weight need not be deemed excessive then that aircraft can legally fly above the manufactures listed limit - in this case it can take off at 225,500kg.

Key word/s are planned & deemed excessive - excessive should be described in the company approved manual.
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Old 3rd Sep 2017, 07:15
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Taking off overweight... A big no no in most airliners including the one I fly. With QAR data, we would be called by the safety department immediately. And in the other hand it's a common acceptable praticse in other small airlines. No need to mention any countries; I can not recall any colleagues who had flown in Africa who never took off overweight. Surely any aircraft can do it. We all know that. And noone will question you as long as everything is normal. But then if something bad happens, good luck to explain to the authorities why you accept to take off overweight. I guess it's a question of knowing and accepting the risks... A bit like driving slightly over the speed limit.
it's kinda annoying when people say: " if this happens or that happens... blablabla." Well if you lose one wing, guess what you will surely die. But sometimes, we have to relax, assess the risks going with flying and do what you have to do. Having saying that, I'm not saying we should take off overweight. Especially when it's due to extra fuel, it does not hurt anyone except the environment to wait few minutes on a taxiway to burn that extra fuel.
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Old 3rd Sep 2017, 07:24
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Originally Posted by Band a Lot
Why not! - there is no approved procedure to ride carbon brakes or steel brakes - do they react differently YES!....Friction creates heat ....* Carbon brakes work best and have good wear characteristics at an optimum temp that is quite high, and no doubt designed to fit the normal braking requirements of the aircraft type. Below this temp they have a much faster wear rate and if the temp get too high they become warped....I think we can all agree that in aircraft, the brakes are solely designed for stopping an aircraft and not designed for stopping an aircraft accelerating....
Actually, the brakes only stop the wheels/tires. It's the tire contacts with the runway surface that stops the aircraft. You can estimate the amount of heat energy that would need to be rejected by using up 1100 lbs (500 kg) of jet fuel, assuming the LHV of jet fuel is approx 18,500 Btu/lb.
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Old 3rd Sep 2017, 09:24
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The brake is attached to the rim, not the tire!

So the tyre can slip (very rare) or the tyre can skid - anti skid will assist here if not effected by excessive heat.


Now is this with cold brakes or hot ones?

I can work out what "x" weight aircraft will need for braking distance on "un-used " or first brake application, possibly a 0 temp indication.

But at a 2 indication, how does that effect my brake performance at MTO? or shall I wait for a zero reading before takeoff?


P.S. the tires will be pre heated by riding brakes of a extended period.
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