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Rising EFOB for arrival....

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Hi all, this problem is starting to annoy me...The problem is that as soon as I start taxiing, and then take-off, on the PROG page, the EFOB for arrival rises steadily the entire flight. I take-off and it's around 8.0 or so, and by the time I've landed it's all the way up at 16-20.0. This was happening with the POSKY air file, but now I switched to the defualt 767 PIC air file and it's doing the same thing...There is also no tail wind during the flights this has happened either...BTW...What's the reserve fuel amount for a 767-300?Thanks,Tim

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The same happens for me. Yet, I think the answer is very simple. Like any computer, it depends on input in order to calculate results.So, with the above in mind here goes the explanation. When you take off, you have a high power setting, and thus the computer uses the current FF to make its calculations, as you reach cruise, the FF is reduced, thus the EFOB calculation result is increased. As you step climb, or fuel is burned and the AC becomes lighter, the computation is changed once again and more is added to the EFOB. Once you reach TOC, power is reduced and you will note a new computational result for your EFOB. It would be very difficult to give you a more exact number for EFOB, there simply are too many variable to take into consideration. Keep the above in mind when you use the information displayed.Is this what you were looking for?Regards,Jay

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Not exactly.The FMS doesn't use current fuel flow nor enroute fuel flow to calculate the EFOB. The real FMS uses the CI (or MCP Crz), FL, ISA temp dev, wind and planned step climbs to determine the fuel burn. All it really does is it checks a database.The reason your EFOB is higher than predicted is because the new airfile uses less fuel than the FMS accounts for and thus you always have more fuel on board as you pass waypoints than predicted. The FMS then updates the EFOB calculation. This is a limitation of FS2002.Hope this helped,Mark

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Thanks, for your post, very informative. Yet, what new airfile are you referring to, or is this simply the FS2K2 airfile?

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This may or may not be somewhat related to the FMC fuel calculations versus the totalizer / actual fuel on board.I have done some burn testing. On short routes, 1.5 hours or less, the fuel burn is highly accurate compared to real world tables that I have. My regular CYOW-CYYZ flight burns about 8-9000lb real world, same on the PIC. Longer flights, not so accurate...the PIC for FS2k2 is not burning enough at the higher altitudes.This is in contrast to the FS2000 PIC which burned higher amounts of fuel at the lower altitudes which required the pilot to take on about 3-6000lbs extra fuel to compensate. It now seems the PIC-2k2 burns the right amount at lower altitudes, but is a little lean above FL310 or thereabouts.Caveat's...The real world figures I have are for an Air Canada 767-300er with PW engines. For the temps, gross weight, speed, and altitude I was testing, I should have been burning about 4400-4500 lbs/hr/engine, the PIC was burning approx 4100 lbs/hr/eng. If the GE engines are that much more efficient than the Pratt's, I suggest every airline in the world would use them...so I have to assume the GE and PW fule burns are close. The difference of 3-400 lbs/hr/engine can add up to thousands of pounds (5-6000lbs) on a 7 hour pond hop.I do not know if this accounts for the mismatch between the FMC calculations and the FOB actual, I always seem to have a discrepancy on the longer flights...but it is IMHO a very minor inconsistency that I am happy to live with. I wonder if there is a person with burn data for the GE's who can show me I am wrong?? The numbers I have show the PIC burns too little up high. Anyone who knows me on this forum or on VATSIM knows I am the biggest PIC fan there is, so let it be known I am not bashing this marvel of PC simualtion!!!!Rob.

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By the new airfile I mean the airfile that came with the latest 767PIC patch for FS2002.

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Guest HPSOV

I dont have the GE manuals with me at the moment, but can check the FF figures for you later if you wish. I do know however that the fuel burn difference between our GE and RR powered 767-300's is 900kg (2000lb) on Sydney-Melbourne (1 hour) sector. This is a huge difference given the near identical power outputs of the engine. Our RR engines are currently undergiong a modification which will reduce their fuel burn and cruise EGT by reducing their internal mass aroud 100kg.

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Wow - that is a big difference.Look forward to seeing the GE numbers.Thanks HPRob.

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