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CTBlankenship

PMDG 737 800 NGX Fuel Burn Rates (CI of 50 and 500)

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PMDG737NGXCostIndexFuelPPHCalculations.j

I don't know if this is the correct forum to place this in but here goes.

I didn't want to drop 50 EU on PFPX so I took the time to observe fuel burn rates for the PMDG 737-800 NGX on a couple of cross country flights from KLAX to KATL (I also used SimBrief and found their fuel calculations to be off). 

How you use it is first make sure your PERF INIT Cost Index is set to 30.  Next, take the length of your trip and divide it by ground speed for the altitude you will be flying to get the number of hours for the trip.  Next, multiply the number of hours by the fuel burn rate for that altitude.  This should give you the total amount of fuel needed to make the flight.  Next, add the base amount of fuel required for ground ops, unusable fuel, a 30 minute hold time and a 45 minute reserve and this is the total fuel load to put into the plane. 

These figures were arrived at by clearing all weather thereby removing all effects on the plane by wind.  So, I look at ASN and determine the winds aloft for the altitude and direction of flight and make some adjustments for head winds (ignoring tail winds as these ground speed numbers are on the high side a tad).  This method usually comes up within +/- 500 lbs. at the time of arrival.

Try it out and let me know how close you get to correct fuel load.

Then again ... this works pretty good too (LOL) ... http://fuelplanner.com/ ... except it does not take into account effects of altitude.

It is interesting to see the difference the CI number is to airplane performance and how powerful it is ...

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Did you run the trials and get the number for the table Charles?  That's a lot of work, I've done it several time but in larger planes the weight becomes a major factor too and it takes hours to do something like this.

If I'm doing a quick trip in the NGX I'll just use the FMS to come up with a fuel load that leaves me about 4000 lbs at destination. That works pretty good too.  If you're going to fly the NGX on ETOPS routes then the PFPX investment is worth it.


Dan Downs KCRP

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Yes ... I set the flight up from LAX to ATL and then set the altitude (with the two different CIs) and let the plane motor on for an hour and then recorded the fuel burn.  I cleared the weather so the Ground Speeds are high ... which can be problematic as this shortens the hours of the flight and thusly can reduce the calculated amount of fuel but it doesn't throw things off in too bad.

No, I don't run ETOPS ... when I begin doing that I'll consider PFPX ... but not now.

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