Old 11th Nov 2019, 08:02
  #20 (permalink)  
fdr
 
Join Date: Jun 2001
Location: 3rd Rock, #29B
Posts: 679
Originally Posted by DaveReidUK View Post
The stats come from Eurocontrol, that well-known collection of fake news purveyors. They even provide a simple diagram to help those who can't get their head around the issue:


EUROCONTROL - Fuel Tankering Economic Benefits and Environmental Impact

Yup,

Tankering gets done in one direction normally, there is an economic benefit that outweighs the additional cost of carriage. The effect of weight is indicated in the Breguet range formula, but in general, adding extra fuel over long ranges will cost considerably in the amount of fuel that remains from that on arrival. Somewhere around ~ 4% of the excess fuel will be burnt per hour of flight. EU land tracks the data of flights into and out of their space, it helps keep the grins on la Vache qui rit. So the data exists to make some assumptions, if one bothers getting the data. Only part of the routes that exist justify any tankering due to differentials on fuel costs justifying the wear/tear and extra fuel burns, and that is logically only in one direction on each of those routes. For long haul, say 12 hour or longer flights, extra fuel is a double edged sword, the burn itself takes out some 40%+ of the economic benefit, and may alter the ability to achieve any reasonable cruise altitude, which has a potential to adversely affect the total fuel burn for the whole flight, once stuck down, it can be a PITA to get back up again on many routes.

We operate efficiently over the course of the flight, to arrive and get slotted into a holding patten as after 12 to 16 hours of suggestion that we are comin', we still snarl up with the flights that took off 45 minutes before... long haul tend to be heavier than the short haul as the way of things, and we get to spend time in the stack. Before that, we also have the pleasure of waiting for coordination, and then pushing back, starting donks, and finding out we are #26 in the queue. If that doesn't give enough annoyance, we also get the vertical path for coordination that drops the aircraft out of optimal path some 250nm from destination, and we get to fumigate the mid atmosphere with soot and CO2 while wasting time and obviously the fuel to turn to noise, soot, and CO2. My favourite arrival has a mandatory crossing height 90nm from destination at 9,000'.

Worrying about fuel burn from tankering is low down on the efficiency issues totem we have in the industry.

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