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AIRIFR

747 performance

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Hello,

 

I am having issue with fuel on this KSFO-YSSY.

 

The total distance of flight is 6536nm, the AWC for today was -4, my planned FL is 380.

ZFW 475,128lbs.

 

With all those, I estimated TFOB 321000lbs for a PLW of 499,128lbs.

 

But entering the data in FMC, shows 0.0 fuel at YSSY. ??

 

I used the cruise planning chart in PMDG 747X operating manual as always but on this flight it shows 0.0

 

And that was even before entering the winds in RTE DATA/DES FORECAST.

 

 

 

I double checked figures etc but still came up with same fuel load for the conditions.

 

Anyone having same problem when using the figures on PMDG cruise planning charts?

 

 

Thank you.

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Welcome to AVSIM!

 

What is the alternate distance of this flight? Did you follow the entire fuel planning schematic in the PMDG B747 AOM?

 

Assuming an alternate distance of 30 NM, I calculate total fuel required to be 370600 lb and initial cruising altitude to be FL360 using an Excel fuel calculator I created based primarily on PMDG and UVA recommendations. However, it is optimized for short-haul flights, so results for long-haul flights may be less accurate.

 

For my purposes, I adjusted the following fuel definitions to be more dynamic.

Minimum landing fuel = alternate fuel + fuel for 45 min cruise

Contingency fuel = 4500 lb + 5% flight duration × 18000 lb/h

Taxi fuel = fuel for 20 min cruise at 40% power

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based mainly on PMDG and UVA recommendations.

 

Thank you ;)

 

 

What recommendations?

 

 

I thought those PMDG charts were accurate, it looks like not then..

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What recommendations?

 

 

I thought those PMDG charts were accurate, it looks like not then..

The PMDG performance tables should be quite accurate (though there are a few obvious errors). I supplement the PMDG recommendations with a few of United Virtual Airlines's, which are described in this document.

 

Ultimately, the most accurate FSX flight planning method will probably be via the upcoming PFPX utility, which precisely analyzes and adjusts output based on wind data.

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I think the charts give you your "trip fuel" number. To that you need to add minimum landing fuel/alternate fuel/contingency fuel.

 

If you only load the trip fuel amount to the aircraft, it will arrive with almost zero fuel on board.

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I think the charts give you your "trip fuel" number. To that you need to add minimum landing fuel/alternate fuel/contingency fuel.

 

If you only load the trip fuel amount to the aircraft, it will arrive with almost zero fuel on board.

 

This is with minimum landing fuel... and if you dont need alternate/contingency fuel why add it, my flight today no alternate/contigency fuel.

 

 

 

And the charts give you everything, not just trip.

 

If you read again my original post

 

Thank you

 

The PMDG performance tables should be quite accurate (though there are a few obvious errors). ...PFPX utility, which precisely analyzes and adjusts output based on wind data.

 

I thought too Pmdg charts accurate, and they account for winds aloft too.

 

Maybe it is the way PMDG 747-400 is modeled into FSX (and FS9?), not quite accurate, especially on 6000+ nm flight.

 

Hopefully 747v2 will change all that :)

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This is with minimum landing fuel... and if you dont need alternate/contingency fuel why add it, my flight today no alternate/contigency fuel.

 

 

 

And the charts give you everything, not just trip.

 

If you read again my original post

 

Thank you

 

i did read your original post ! and no the chart gives you TRIP fuel

 

6536 nm at FL380 = 283,300 lbs fuel from the chart.

 

Add burnout correction ...say 13.5 hours x 940 lbs/hr x 2.5 = 31,700 lbs

 

So total TRIP fuel is 315,000.

 

To that you need to add your minimum landing fuel.

 

If the chart gave you total fuel to board, what do you make of the bottom left number for 400nm at FL410 ? 34,000 lbs for a climb to FL410, fly 400 nm, land and taxi and still have 24,000 lbs in the tanks ?

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what do you make of the bottom left number for 400nm at FL410 ? 34,000 lbs for a climb to FL410, fly 400 nm, land and taxi and still have 24,000 lbs in the tanks ?

 

I think you're confused about that chart.

The chart does provide for alternate and contigency but not same place than cruise planning.

 

And minimum fuel is added already.

 

Thank you

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It is you who is confused about the chart. It gives TRIP fuel required. You need to add minimum landing fuel to that figure (plus alternate+ contingency if you wish) to get your TFOB amount that you need to load the plane with.

 

That is why your FMC is telling you that you will have no fuel left on arrival at YSSY.

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It is you who is confused about the chart. It gives TRIP fuel required. You need to add minimum landing fuel to that figure (plus alternate+ contingency if you wish) to get your TFOB amount that you need to load the plane with.

 

That is why your FMC is telling you that you will have no fuel left on arrival at YSSY.

 

Landing fuel is included already, already said that ;), so either it is bug in my FSX or some else...

 

 

And " what do you make of the bottom left number for 400nm at FL410 ? 34,000 lbs for a climb to FL410, fly 400 nm, land and taxi and still have 24,000 lbs in the tanks ?""

 

34,000lbs is just that for climb,cruise,descent..provided you follow speed schedules and PLW is 475,000lbs, ;)

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Landing fuel is included already, already said that ;), so either it is bug in my FSX or some else...

 

Landing fuel is included where? You are loading the plane with 321,000 lbs of fuel. The trip fuel I calculate to be 315,000 lbs. So you are only boarding 6,000 lbs of landing fuel.

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Landing fuel is included where? You are loading the plane with 321,000 lbs of fuel. The trip fuel I calculate to be 315,000 lbs. So you are only boarding 6,000 lbs of landing fuel.

 

 

315,000 was YOUR calculation...

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315,000 was YOUR calculation...

 

Yes, and in trying to help you I gave you my working out logic in my post above. If you want help with this why not provide your working out of the fuel required. I think perhaps you are not adding the fuel burnout correction.

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Yes, and in trying to help you I gave you my working out logic in my post above. If you want help with this why not provide your working out of the fuel required. I think perhaps you are not adding the fuel burnout correction.

 

Yeah cool, I know, I did add everything, trust me, it is not my first flight in the PMDG 747 and using those charts.

it could be a that I mixed up some figures and gave me this result, but thanks for helping out, we know we're talking about the same stuff here.

 

My return flight if this happens again, I will know there's definately some wrong.

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If your issue persists, consider posting your calculations so we can compare ours and identify any errors.

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Yeah will do,

 

How about you guys? What about your remaining fuel at landing, same as planned or different like me?, as per PMDG charts Im talking, NOT with any other tool.

 

It could be that the winds aloft information Im getting is not accurate hence wrong planning, if winds aloft info is wrong obviously this gonna false all the calculations lol.

 

Where/how do you guys get your avg winds aloft for your flights?

 

 

Im thinking of something now, Im gonna try a different method for winds aloft, for my next flight and see the outcome, Ill let you know.

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I mainly fly short-haul European flights. I usually calculate reserves to be between 21000 and 25000 lb. I believe I usually land with 25000–40000 lb (depending on the flight).

 

I currently use Jeppesen and NOAA winds aloft data. Perhaps there are more accurate methods, but these sources seem reliable.

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I usually land with 25000–40000 lb of fuel (depending on the flight).

 

Thanks for the info!

 

For the flights where you land with 40000lbs and you had planned 21-25, if winds aloft/your planning etc accurate, why land with extra 19-15000lbs? Does this mean if charts accurate that then it could be the modeling of the 747-400X not as accurate?

 

I try to understand those fuel remaining differences, too much/low, with everything else (winds aloft, planning etc..) being accurate.

Maybe 2-3000 difference ok but not 15-19000.

 

Could be PMDG/FSX limitation to reproduce accurately flight characteristics?

 

Hopefully the new 747v2 will bring better accuracy.

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