daguerreotype

747 v3 ERF trip fuel calculation

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Hello,

With reference to the previous thread named "747-v3 Fuel consumption problem" ,

I would like to work on the fuel consumption. I fly only with the 747-400ERF. I have good estimations of TRIP FUEL on short and medium haul but not on long hauls so far. Therefore I'd like your input.

Following the report of bad estimation of flight fuel in the above thread I tried to have a better estimation, trying a long haul flight to Australia without any weather (standard stetting in P3D).

-(FPL-IDENT-IS -1B744/H -SDFHIRGWY/EB2 -OMDB1304 -M084F370 ANVIX L223 TARDI N629 GIDAN P570 EMURU M300 IGAMA P895 BIKOK M641 CM N640 ELATI N509 PD T21 LEC J141 PKS A576 KADOM W713 AKMIR W113 ODALE -YSSY1404 YSCB -PBN/A1B1C1D1 )

6359 nm, Estimated Elapsed Time  1258 (LRC FL370)

With zero winds, I would take :
TRIP FUEL : 118, 700 tons  (261 500 lbs) of fuel (only for the trip fuel) by adding a margin to the regressed fuel value calculated from FCOM tables

Usually my regressed or interpolated way to compute the trip fuel have proven efficient, and they also have with short and medium haul in this 744.

Having problems with y predictions I decided to see what other suggested. From simBrief I have :

TRIP SYD 132,4 tons. for the 74F M085 FL370. (<- why significantly higher than FCOM figures ?)

On the test flight with default weather in P3D I had to divert to WOOMERA because I was going LOW FUEL and was unable to reach YSSY. I had 144t in total at take off in OMDB. I will have to retrieve the exact landing fuel figure from my sim computer but I expended all that fuel to get to Woomera, and that's significantly higher than even simBrief trip fuel value to YSSY. I accept approximations when I do my fuel calculations (because we are in simulation) but only provided they are reasonably reliable.

So what you'd you use for TRIP FUEL and what would be your source ?
Thanks in advance.

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Hi Mr Rodgers,

In the figure, blue values are straight from the FCOM long range table. But yes, I don't exclude the option that for short haul my own linear regression might be acceptable enough while it might be suboptimal for long haul. That's why I ask for a methodology from other people. Or a ground ops suite from PMDG.
So let's forget any tool and have a look at the FCOM tables for LRC for instance. Here I don't use any tool. For PW4056 6500 nm => about 111 tons of trip fuel required. To me it would not be a problem to assume +/- 10% to retain 122 tons as trip fuel to cover engine type discrepancy as a simplification. That's less than what I take, far less than what SimBrief says, and even far less than what seems to be really required in the sim.

 

Anyone has a value, so I can calibrate ?

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There is no one value, and attempting to bias the fuel burn is prone to gross errors because it is a dynamic problem.  Dynamic in that the fuel burn changes as you burn fuel and a few other factors.  Any the best estimate of actual fuel burn is many measurements taken over a sample period of at least 10 min., and even then you'll find the standard deviation often exceeds 3% and you are not able to get the desired level of statistical confidence.  I played with this problem for a week and threw my hands up in  surrender.

The best I have found that is available to the non-commercial market is PFPX, which has a dedicated forum full of users and contributors one of which has developed tables for the newer variants including the ERF.  One needs the tables by Boeing or Operators that are very hard to come by, and not available in the license that PMDG has with Boeing.

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I use Simbrief for my flight planning and fuel estimation and I've not yet had any problems with 747v3.

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8 hours ago, daguerreotype said:

 

So what you'd you use for TRIP FUEL and what would be your source ?
Thanks in advance.

 

well here's the numbers from PFPX for that route. i have not flown the ERF much yet so i can't comment to it's accuracy, but it is very accurate with the 400,400ER, and 400F flights i have done. i couldn't get it to make a plan for ZFW much above 525000, at 550000 it was overweight. also did one at 400000. you can see there is a huge difference in consumption at the different weights. these predict for about 30000 on landing, which might be sort of low contingency-wise.. this planning also takes step climbs into account, neither of these flights could reach FL370 at this weight until a bit later in the trip. perhaps those variables are the type of thing that is not working in your calculations..

===================================

ZFW: 525000  M0.84

               FUEL    CORR    ENDUR
TRIP         319357  ........  13:41 
CONT 5%       15968  ........  00:51
ALTN YSRI      5729  ........  00:12
FINAL RESV     9302  ........  00:30
MIN T/O      350356  ........  15:14   
EXTRA             0  ........  00:00     
TAXI           1500  ........  00:15       
RELEASE      351856  ........  15:29   

starts at FL310

=============================

ZFW: 400000   M0.84

               FUEL    CORR    ENDUR
TRIP         251814  ........  13:49 
CONT 5%       12591  ........  00:50
ALTN YSRI      5293  ........  00:11
FINAL RESV     7517  ........  00:30
MIN T/O      277215  ........  15:21      
EXTRA             0  ........  00:00     
TAXI           1500  ........  00:15       
RELEASE      278715  ........  15:36     
                                           
starts at FL350

================================

LRC was similar, at 321000 trip fuel for ZFW 525000, 13:32 flight time

with current weather, the numbers look a bit closer to yours

0.84 ZFW 525000    TRIP fuel 304502, 12:48 flight time

 

good luck,-andy crosby

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Dan, thank you for the answer. I'd better avoid the Payware PFPX if I can succeed in tweaking my tools, since for routing I don't need it. I understand it has tables however. But I'm sure we can find something with an acceptable and conservative  approximation only from the Long Range Cruise Enroute Fuel and Time pages from a "generic" 747, like the 747-400/PW4056.

Thank you Kevin, for your report of the use of simBrief.
 

And Andy, thanks for your input and for saying "good luck". Your numbers from PFPX will indeed help me to find a better and conservative calculation. With a segmentation of the route per step climb and weights I guess.

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7 hours ago, daguerreotype said:

 

And Andy, thanks for your input and for saying "good luck". Your numbers from PFPX will indeed help me to find a better and conservative calculation. With a segmentation of the route per step climb and weights I guess.

just to follow up on this, i tested the flight numbers from PFPX by flying it. with real world weather i got a fuel remaining prediction of 30.2 and at the gate in YSSY i ended up with 35.6  .. not bad! i did use time accel for a lot of the overwater cruise but it was still 4-5 hours or so total, so there was probably a bit of change to the wind but not as much as if it was a full 13 hours. i also flew a slightly different profile than PFPX calculated, doing a step climb a bit earlier than planned, to get a little more breathing room over a big storm that was brewing over the water between india and sri lanka.. anyway i think those values seem pretty close..

cheers,-andy crosby

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Thanks. I have made a new revision of my calculations and therefore will test them in the near futur.

MAXIMUM	ZFW	277150
ESTIMA.	ZFW	262440
ACTUAL	ZFW	. . .
		KG
--------- --------- --------- --------- --------- --------- ---------		
TRIP	131433	289762
CONT	6572	14488
ALTN 	315	693
FINAL	8000	17637
ADDNL	0	0
TRING	. . .	. . .
PLN TOF	146319	322580
EXTRA	3000	6614
TOF	149319	329194
TAXI	400	882
BLOCK	149719	330076
	KG	LBS

 

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Hi,

Here is the data I use in Simbrief and it works well with GE engines

Aircraft/ Cruise Profile: M85; Fuel Factor: M06

Optional Entries/ Altitude: FL340 (good average for wind estimates)

Selections/ Cont fuel: 3%; Reserves: 30 min

Happy flying

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