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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 23rd Aug 2017, 06:24
  #41 (permalink)  
 
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Originally Posted by Bull at a Gate
Seriously? You think that brake temperatures increase significantly when the wheels aren't turning?
No, that misconception was demolished about 30 posts back ...
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Old 23rd Aug 2017, 12:46
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While I don't necessarily advocate taking off deliberately overweight...

I've seen people getting excited seeing a couple of kg's over MTOW on the a/c's weight display and doing some weird stuff, riding the brakes included. (BTW, has anyone mentioned additional FOD risk due to increased thrust during taxi?)

Now, the airplane's weight display (at least on the type I fly) calculates the gross weight by adding actual fuel weight to the ZFW entered into the MCDU. This displayed gross weight goes up and down as the fuel is sloshing around during taxi and its accuracy is limited. I think when legalities are concerned, the Loadsheet should be the basis of determining the TOW.

On one such occasion I have seen the CA burning the fuel during taxi. Then, when we stopped at the HP the ECAM weight indication stabilized and we ended up showing 2000lbs below MTOW...
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Old 23rd Aug 2017, 14:24
  #43 (permalink)  
 
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One other thing...

The take-off run itself, from brake release until rotation can consume almost 500 kg. On a widebody. So if pure performance allows it ( performance calculations can be capped of by structural limits, but the pure performance is higher) , you will still be legal when rotating 😆...Not that I recommend this obviously..
Once again: the loadsheet is the legal documentation. That one HAS to be correct. The actual taxi routing etc. can vary.
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Old 23rd Aug 2017, 17:05
  #44 (permalink)  
 
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This threat has gone from maybe "what" to something much worse. The original post was about being 500 kg to heavy for the assigned runway. Now how to you kill 500kg, not do a re-dispatch or cruise at a lower level and fly at a higher cruise, to be legal for departing on the assigned runway. I'd never recommend riding the brakes on taxi out, who wants to abort with possible overheated brakes. 500kg or just over a 1000 pounds is nothing. On a wide body 500kg is maybe an extra ten seconds at a higher power setting prior to brake release. Next time you roll down the runway note the fuel burn and you will have your answer.
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Old 23rd Aug 2017, 20:59
  #45 (permalink)  
 
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How to lose 500kgs on the load sheet = tippex.

Last edited by RAT 5; 24th Aug 2017 at 17:10.
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Old 24th Aug 2017, 16:10
  #46 (permalink)  
 
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Looks kind'a awkward on an ACARS loadsheet...


Long time ago, in the mid-late 1980's after a very heavy DC-8 take-off somewhere in the Middle East, and barely making it (normal), the Captain tore the loadsheet into 3 pieces, passed on part to me and another to the F/E: "eat it!!!"

But then again we had some extremeists like the one that had 3 suitcases removed as he considered us overweight
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Old 24th Aug 2017, 16:28
  #47 (permalink)  
 
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Legally there is no way to takeoff with that extra weight. Just park some where or go back and come back. Yes the temperatures may rise RTOW will further reduce but you are not expected to keep schedule by doing something stupid or illegal.
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Old 26th Aug 2017, 21:07
  #48 (permalink)  

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So you have dispatched below max ramp weight but you have used less than your flt plan taxy fuel taxying out? And you are worried you may be over MTOW? How do you know the accuracy of the ZFW anyway? Performance has margins, ignore the 'excess' taxy fuel and go, provided any exceedance is considered minor. (According to an Ops Manual near me).

It is NOT a requirement to burn all your taxi fuel before getting airborne, therefore you will be within your calculated performance criteria.
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Old 26th Aug 2017, 22:39
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IIRC in EASALand, OEW weighing and calculations have a 1% margin of error. On any widebody that is quite a bit. Also, using standard pax and bag weights is far from being always accurate.
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Old 27th Aug 2017, 00:50
  #50 (permalink)  
 
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1) This pilot should be made to pay for all brake packs out of his salary. What a idiot for wasting money, and as implied before increasing rick due heat.

2) Was it actually required to burn the fuel? I assume the flight plan was correct, just the estimated taxi time changed on this 30 degree day.

3) Max Take Off weights are common, when lined up on runway the temp is 2 degrees higher than planned - is a recalc carried out to see if more fuel needs to be burned before opening up the throttles?
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Old 27th Aug 2017, 02:12
  #51 (permalink)  
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Thanks for the replies. For those advocating that it is no big deal to takeoff a little bit overweight....I have done plenty of that in the old days and am well aware that there is likely to be little real world consequence.

But I now work for a company where a minor exceedence a limitation is a huge deal with serious consequences. So, the limits will be respected as things are closely monitored on these advanced aircraft. No need to discuss further.

As for the aircraft, the limit was max structural weight(I'm sure most figured that out as I stated we were at our max taxi weight). But we must have been close to runway limits at no derate or ATM was allowed.

There have been some accidents caused by excessive use of brakes prior to takeoff but those were steel brake. What about carbon brakes which supposedly like some heat.

I am not aware of any maximum brake unit heat prior to takeoff but I was also concerned that peak heat would happen after takeoff and we might end up having to extend the gear if we got a brake temp warning. Are these realistic concerns? 4 hours after takeoff when I returned from my crew rest, there was still some heat indicated on the brakes. That being said, I have noticed in the past that it does take a while for them to get down to zero.
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Old 27th Aug 2017, 02:45
  #52 (permalink)  
 
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Originally Posted by overstress
So you have dispatched below max ramp weight but you have used less than your flt plan taxy fuel taxying out? And you are worried you may be over MTOW? How do you know the accuracy of the ZFW anyway? Performance has margins, ignore the 'excess' taxy fuel and go, provided any exceedance is considered minor. (According to an Ops Manual near me).

It is NOT a requirement to burn all your taxi fuel before getting airborne, therefore you will be within your calculated performance criteria.
Not sure where you fly, but in the companies I've flown for, it clearly states that the indicated weight at the start of the takeoff roll must not be more than the applicable maximum.

Which country issued the ops manual you're looking at?
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Old 27th Aug 2017, 02:48
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At least submit an ASAP or the equivalent safety reporting system at your airline. The company really should do an engineering assessment of this practice so an official policy can be developed and appropriate guidance made available to line crews. Since it's already known that most wear on carbon brakes occurs before they come up to operating temperature, excessive use of cold brakes will cause excessive wear. Besides, who wants smoking hot brakes tucked away in their wheel wells anyway?
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Old 27th Aug 2017, 02:48
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Originally Posted by Band a Lot
1) This pilot should be made to pay for all brake packs out of his salary. What a idiot for wasting money, and as implied before increasing rick due heat.

2) Was it actually required to burn the fuel? I assume the flight plan was correct, just the estimated taxi time changed on this 30 degree day.

3) Max Take Off weights are common, when lined up on runway the temp is 2 degrees higher than planned - is a recalc carried out to see if more fuel needs to be burned before opening up the throttles?
Point 1 was just unnecessary.
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Old 27th Aug 2017, 02:51
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@Jammed Stab

I'm unaware of your type, but assuming you were at 2 out of 10 units, I wouldn't be overly concerned with degradation of stopping performance, or brake cooling after takeoff.

I'm sure the engineers took those things into account when they determined the maximum temperature for takeoff. 8 out of 10 units would be a different matter though.
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Old 27th Aug 2017, 02:54
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Originally Posted by Band a Lot
1) This pilot should be made to pay for all brake packs out of his salary. What a idiot for wasting money, and as implied before increasing rick due heat.

2) Was it actually required to burn the fuel? I assume the flight plan was correct, just the estimated taxi time changed on this 30 degree day.

3) Max Take Off weights are common, when lined up on runway the temp is 2 degrees higher than planned - is a recalc carried out to see if more fuel needs to be burned before opening up the throttles?
3) Our system allows us to send for new numbers when the temperature changes significantly. The performance paperwork that comes with the dispatch release covers a temperature range, and the associated max weights, so that information is readily available to the crew.
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Old 27th Aug 2017, 02:56
  #57 (permalink)  
 
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Originally Posted by westhawk
At least submit an ASAP or the equivalent safety reporting system at your airline. The company really should do an engineering assessment of this practice so an official policy can be developed and appropriate guidance made available to line crews. Since it's already known that most wear on carbon brakes occurs before they come up to operating temperature, excessive use of cold brakes will cause excessive wear. Besides, who wants smoking hot brakes tucked away in their wheel wells anyway?
Who said anything about smoking hot brakes?
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Old 27th Aug 2017, 04:00
  #58 (permalink)  
 
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Who said anything about smoking hot brakes?
I did! (sarcastically) But there is little doubt that the brakes will be some amount hotter after takeoff than they would have been without riding them on the taxi to the runway.

To me, the idea of riding the brakes with the thrust levers pushed up so as to burn off additional fuel seems unreasonable. I would be much more supportive of just taking a short delay to burn the extra fuel while stopped. While it might have very little effect upon actual aircraft performance, taking off when you know you are above the calculated limiting weight is practically indefensible from a regulatory viewpoint. In my experience, small amounts over various limits sometimes go "unnoticed" for this reason. Most of the time it doesn't make any difference, but once in awhile...
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Old 27th Aug 2017, 04:17
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Check Airman - show me 1 procedure for "Riding Brakes" in any manufactures manuals.

Any anyone intentionally caused excessive wear on anything - they should pay for it.

Hire a car and do a bunch of burnouts - expect to pay for it! The invoice will read something like " tires - excessive wear on rear (could be front).

regarding 3) So lets say temp range is 10-15C and it clicks over to 16C as you were about to go - what is your procedure? Not asking if information is readily available or not.
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Old 27th Aug 2017, 06:58
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Digressing from the original post,
BAND A LOT - to answer your query point 3 is clearly stated in 'pilot guide to takeoff safety' of the FAA website pg 25/45 last para. How a pilots fulfills his responsibility of complying with last minute temp calculations is upto the pilot. I am sure there are many more legal documents putting the responsibility on the pilot to ensure compliance with last min temp/wind etc changes.

As far as the original post is concerned it has happened plenty of times where taxi fuel is catered for in greater quantities and RTOW (tow off weight) was restricted structurally & sometimes otherwise. Safest bet would be to hold with parking brake set.

I do not know about the brake energy consequences in a carbon brake so can't comment more than that.
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