Fuel burn estimates

[proteus6]

Would you guys answer a quick question around fuel burn?
How good are your fuel burn estimates, are they within 10% of fuel used?, does it vary between aircraft within the fleet?- are there good aircraft and not so good aircraft within your fleet?
thanks

[Green Guard]

same question we can ask: "what about your car ? "

[Denti]

Fuel burn estimates are within less than 1% of used fuel for our operation, individual performance adjustments are made for each aircraft depending how long it has been since the last fuselage and engine wash and of course individual characteristics.

[Boslandew]

GG

We could do but he's asking about your aircraft.

[proteus6]

thanks Denti, that's the sort of answer I was looking for, I am supprised that you are as close as 1%, what is the differance between the best and worst aircraft (like for like) are they within 5% fuel burn of each other?

[framer]

We have 14 737's and they all seem the same. As with Denti we have individual
Adjustments and if the uploaded winds are accurate the burns are amazingly accurate. I would guess within 1 or 2% but I haven't checked specifically to work out a %.

[Denti]

To be honest i can't really say how the worst and the best aircraft factor against each other, we have over 50 737s right now, mixed between 700s and 800s, aged between 14 years old and delivered last week. With engines mixed around the whole fleet, both -7B and BE variants. So there are bound to be some differences, however they are taken care of at the planning stage and the difference between planned fuel burn and real fuel burn is negligible.

I can't comment on our airbus fleets (yet) as i do not fly them, however from what i hear it is the same there. The flight planning system (LIDO) together with up to date forecasted winds and performance data is incredibly accurate.

[misd-agin]

Individual a/c's performance is tracked and flight plans adjusted for better, or worse, than standard fuel burn.

Yes, there are 'good' and 'bad' a/c. Time since engine wash, new vs. old engines, drag from damage, are some of the variables.

My last year's fuel burn was approximately 99.5% of expected. Underburned by approx. 0.5% per flight. Standard performance for the fleet.

[framer]

Misd-agin,
Is that a private aircraft or does your airline provide individual data/ feedback?

[lederhosen]

One area we have a problem is when the actual weight is significantly different from the estimated weight that flight plan fuel burn is based on. I had a good example of this a couple of days ago with an ethnic flight where the official zero fuel weight provided five minutes before departure was within a few kilo of max, but only 500 kilo over estimated. The fuel burn was 400 kg over flight plan with some short cuts and a straight in arrival so how accurate the reported figure was is open to conjecture as the actual weight should only have incurred 150 kg penalty.

I had allowed for this eventuality based on previous experience. But it does beg the question how realistic the zero fuel weights are at times. Bucket and spade flights with lots of children almost always use less fuel. Ethnic flights outside school holidays mainly use more. Looking historically over a long enough period the estimated and actual burn should be the same thing. But on individual flights local knowledge is required, which after all is what we are paid for.

[BOAC]

Not too sure what an 'ethnic' flight is, Leder, but in Astraeus we had sets of pax weights for different flights eg African, where rolled up carpets etc (but no chicken:)) seemed to appear as 'hand baggage' with monotonous regularity.

[Skyjob]

LIDO, Jeppesen and many more offer the airlines ways to optimise predicted fuel burns. But each comes with its own limitations and so forth.

Most importantly, is how good and dedicated your operations staff is to maintain and use correctly all the figures provided, including route restrictions (intermediate level off altitudes), which can be great discrepancy creators.

Here are some of the common but not always incorporated items for accuracy:
* Individual airframe corrections versus a new aircraft
* Accurate route profiling, vertically
* Optimising lateral routings
* Inclusion of runway specific fuel burns for a single SID STAR
* Operational information for higher/lower levels fuel/time penalties/gains
* Accurate use of statistical taxi times runway specific if needed

In terms of accuracy: ~50 kgs each sector, <1% :ok: on both of todays ~2:30h flights which were predicted with LIDO, using the correct registration, incorrect FL for 1st route (as not tankering as much as LIDO suggested thus operating lighter and able to climb taking advantage of additional tailwind), correct runway usage, etc...

[flyboyike]

We just take a SWAG.

[Desert185]

BOAC
Not too sure what an 'ethnic' flight is, Leder, but in Astraeus we had sets of pax weights for different flights eg African, where rolled up carpets etc (but no chicken) seemed to appear as 'hand baggage' with monotonous regularity.

I remember a particular Hadj flight from Jeddah to Tehran in a 727-200 that resulted in much more runway being used and the fuel burn being off a bit. :mad: Thanks to the regional practice of "bakhshish" we had a few more personal items loaded and carried onboard than planned. :=

[flyboyike]

Is bakhsish usually consumed with babaganoush?

[Natstrackalpha]

for flyboyike (is it pronounced Ike or icky?)



def: bakhshish as in buckshi