# Robert or anyone? Need fuel burn formula so I can update fuel planner

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Hello! I bought the 800/900 and took a look at the fuel burn tables. I see that there are several cells in the table that are empty, in the lower right corner of the table. In other words, there is no fuel burn data for longer flights at higher altitudes. Why is that? I thought that maybe those longer flights were simply out of the range of the aircraft, but there IS data for those longer flights at lower flight levels. Wouldn't the higher flight levels make for more efficient fuel consumption? I'm confused about this.At any rate, the missing data is going to make it tricky for me to update the fuel planner program. I'll have to have it pop up an error if those combinations of distance and flight level are selected by the user. :(Ideally, I would have a formula that could be used to calculate the approximate fuel burn for a flight of any distance at any cruise altitude. That way the user could enter any distance from 50 miles on up to the max range of the aircraft, and any flight level from FL180 on up to max cruise.Does such a formula exist that would be accurate for the PMDG aircraft in FS? Thanks in advance to Robert or any other member of the PMDG crew, or anyone on the forums, that might be able to offer some guidance here.

Hey,You could probably make equations to find values for the missing entries by using the existing values as a trend model, they may not be accurate to the model though. You'd have to work out a different formula for each aircraft and each flight level (four in total) then use them to find all the solutions (34 solutions). Not exactly user friendly as an all in one equation but it would probably be sufficient enough if you only need the missing numbers from the charts.I could give it a go if I can find my old math books :)CheersDavid

There was a link in this forum to a complete 737 flight manual which has 800/900 charts. They inlcude fuel burn up to FL410 (ISA fuel burn lbs/hr/engine). My ISP won't allow such a large zip to be sent. Perhaps someone else can?Jim Harnes

>There was a link in this forum to a complete 737 flight>manual which has 800/900 charts. They inlcude fuel burn up to>FL410 (ISA fuel burn lbs/hr/engine). My ISP won't allow such>a large zip to be sent. Perhaps someone else can?>>Jim Harnes let me check my manual... and if I've got the charts I'll extract them and ship just the charts.

Jim,Are you talking about the CO AOM? If you've got a page number I can post the pages.If Tim is going to send the charts that's fine. I'd still like to know how close my calculations were though :)CheersDavidP.s Apart from a couple of the missing values in the 900 sheet, there is really no point in adding these values to the load planner is there?. E.g. at FL330 with a distance of 4000nm the chart gives a fuel load estimate of 54,600lbs (and that's before all the 'extras' needed). The max fuel load of the NG's is 46,036lbs

David,Yes, it's the COA AOM. The 800 charts start in Normal Ops, two engine long range cruise, Sec 5 page 60 and the 900 charts start on page 62.Would be nice to know how accurate we can be!!Jim Harnes

Hey Jim,How do you work out the estimated fuel load using those charts? Also, any ideas why the -600 was left out of that manual?I'll post the pages here tomorrow, I take only the two pages will be needed?CheersDavid

David,Ross was talking about only the 800/900, so presume that's the data he needs. As the 600 isn't in the AOM, perhaps it isn't in COA's fleet. Don't really know. As to how to use the charts, they give fuel usage per hour for long range cruise only, e.g., for the 900 at FL410 it's 2185 lbs/hr=4370 lbs/hr for cruise. Then there are adjustments for non-standard conditions and additions for APU usage, taxi, holding, alternate, FAA required reserve, etc, etc. Thank goodness Ross has all this captured in his program!! Otherwise, we'd all spend too much time with fuel charts and calculators!!Jim Harnes

Actually I'll need to be able to come up with a reliable forumula for all 4 variants, if I'm going to modify the program to calculate the fuel burn instead of taking it from the tables in the PMDG manual, as it does now.

>There was a link in this forum to a complete 737 flight>manual >Jim Harnes I did a search but did not find this manual.Can you give me please the link?Hans

Hey Hans,Send a mail to Mark Wickens at m.wickens@rhodium-consulting.com asking about it. He'll send you a link to where you can download it.The original post is [a href=http://forums.avsim.net/dcboard.php?az=show_topic&forum=136&topic_id=42152&mesg_id=42152&listing_type=search]here[/a].CheersDavid

Ross,I forgot to say; If you want the numbers I worked out let me know (they haven't been tested in FS, I'm not keen on 3800NM flights :)).CheersDavid

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