747 Fuel Issue

[Guest SwissMD11]

Hey Guys,I have a problem with the fuel on the PMDG 747. For Example : I had started my flight from LHR-MRU with 32.5 (according to the FMC) of fuel remaining at MRU. That time the optimum altitude shown by the FMC was FL298 so I set my cruising altitude to FL290 and using ICAO rules, I step climbed to FL330 when the FMC told me I was ready. The EFOB at MRU increased a little. And some time after that, my EFOB at MRU started decreasing very slowly. I thought that it would be no problem so I left the PC and when I came back , it showed that the EFOB at MRU would be 9.9 ?? SO, I tried some things like descending to the optimum altitude and reducing the speed to Mach .80. They helped for a while but the EFOB started decreasing again slowly. I don't know why this happening ?? I have the latest SP installed.BTW, my Cost Index was 50.

[craig_read 43]

Hi,Fuel planning is often a difficult subject for a lot of people with these more complicated FS aircraft. Using your step climb profiles etc and the data available within the manuals it is possible to quite accurately work out your fuel burn. But I don't see any mention of wind in your post. Having a large headwind on route will effectively increase the distance you have to fly.. At the gate, and with no wind data, the FMC will be unable to accurately predict your fuel burn on route. The FMC constantly updates its predictions, and as a consequence of a headwind the fuel at arrival will decrease as the flight progresses...What I would do in your position is find out what the average wind component is expected to be for your flight, and work out what extra distance that means for your plan.. Flight Plan Distance + Headwind Distance Added = Total DistanceWinds can get quite significant at altitude, in fact it means a flight time difference in some cases of well over an hour.. Trade winds mean it's quicker in some cases to fly one way than it is the other.. These factors all make a difference to the fuel required, and of course the fuel you're carrying makes a difference to your cruise altitudes too.. It's all very interconnected.Using that modified distance work out the fuel burn and fill the aircraft as appropriate. There is the option to enter wind data into the FMC, this will help with the calcs.Not sure if that's given you anymore information than you already had.CheersCraig

[Guest SwissMD11]

>What I would do in your position is find out what the average>wind component is expected to be for your flight, and work out>what extra distance that means for your plan.. >>Flight Plan Distance + Headwind Distance Added = Total>DistanceSorry to sound stupid but how do I find out the Average Wind Component ?>There is the option to enter>wind data into the FMC, this will help with the calcs.Do I enter the Winds on the ACT DES FORECAST page ?Thanks Alot. :D

[craig_read 43]

If you have a packages FSBuild and ASX or AS6, these packages will actually calculate the average wind component for you. If you know the winds on your various legs then you can work it out but that's really going into quite a lot of depth, working out wind components based on wind speed and bearing against your bearing etc.What I suggest is, that you take a look at FSBuild and ASX or AS6 and use them to collect the required wind data and calculate the average component. Failing that AS6 and ASX have detailed weather predictions for the whole flight with winds aloft data included within them. The winds data is entered into the route pages as data, the descent forcast page does take wind information but this is for the descent profile at the end of the flight..I am sorry I can't be more specific.. but I hope that steers you in the right direction..CheersCraig

[Shmiffy 0]

Hi SwissMD11. Firstly, if you could use your real name in your post, it would make me feel a little more like i am talking to a person rather than an aircraft ;)Right then, Fuel...There really is not a great deal to add to what Craig has already said. But for the purposes of a procedural approach to it, i will let you in on the way that i do it. 1. Choose your flight, and find a flight plan (i try and find that day's real world FP, as that would have been planned based on the most economic route for the airline, using their million dollar super computers, what i dont have access to!)2. Input the flightplan into your planning software of choice. I use Flight Operations Centre or FSBuild. FS Build is linked to my Activesky setup for R/W WX, whereas FOC is linked to a real world WX Server that the airlines use. 3. Use your Flight Planning software to generate the Paper Flight Plan (or the Communications Flight Plan as BA would call it). 4. Once you have an FS9/X Plan, and a B744/X (in my case) plan, input the plan to Activesky 6.5/X5. Calculate the winds for your first flight alt (for me today it was FL300 on my trip that i am currently flying from EGLL to KSFO at 3 Tonnes short of MTOW).6. With your FMC open. Go to the Page and then or this will bring you to your route winds page. At this stage, i have filled the aircraft with my calculated ammount of fuel and the reserve in the PERF page is 0.7. Input your winds to the Right LSK's as (my next waypoint) {6820N) <252/037> and so on for that altitude. Then recalc the winds for your step climb alt's and input them at the appropriate LSK's.8. Rinse and repeat as necessary. 9. I usually plan to have 14.0 remaining on arrival prior to starting the APU. If i need to add or remove some fuel prior to completing the rest of the FMC formalities, i do. 10. I then set my Reserve to about 12, depending on the destination. Today it is 10, as i have a many and varied choice of diverts in North America, and Fuel Critical would be unlikeley to cause any serious concern unless i was looking at arrival at SFO with about 8T or less.I should thank Steve Bell (G-CIVA) for teaching me that simple method, among many other things 744 related, and getting me flying at sensible altitudes and sensible fuel bills. Enjoy :-hahPaul SmithEditor - Focus MagazineBritish Airways Virtual