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Kevin Meyers
Posts: 1492
Joined: Mon Mar 24, 2008 10:07 pm
Location: Pacific Palisades, CA

Fuel Calculations

Tue Dec 02, 2008 5:40 pm

I'm looking for a better way than guessing to determine how much fuel to put in my aircraft when I fly on Vatsim. This being for both x-plane when I fly my props, and FS9 when I fly the jets.
Does anyone know of a good free program that calculates fuel, or better yet some mathematical equation?
-Kevin Meyers
ZLA_KC
Graduate of ZLA Pilot Certification Program

Eric Newman
Posts: 25
Joined: Fri Sep 12, 2008 12:57 pm

Tue Dec 02, 2008 6:54 pm

How do you do it now?

I just use the good ol' calculator, POH and pencil and paper
Its pretty accurate.

Kevin Meyers
Posts: 1492
Joined: Mon Mar 24, 2008 10:07 pm
Location: Pacific Palisades, CA

Tue Dec 02, 2008 7:08 pm

i dont really do any calculations right now...just throw a percentage in there that sounds about right and go
-Kevin Meyers
ZLA_KC
Graduate of ZLA Pilot Certification Program

User avatar
Wayne Conrad
Posts: 1494
Joined: Thu Dec 14, 2006 11:24 am
Location: Phoenix, Aridzona

Tue Dec 02, 2008 7:26 pm

For the bug smasher, determine the fuel flow in pounds per hour (X-Plane does everything in pounds). Do that by telling X-Plane to display fuel flow with the plane at your "usual" cruise altitude, cruise speed, leaning appropriately, and seeing what the fuel flow is. Divide by trip distance to get fuel needed. Add legally required reserve fuel (30 minutes if VFR day, 45 minutes otherwise). Add takeoff/climb fuel. Add "Oh oh" fuel.

A crude estimate of climb fuel can be made by noting the fuel flow at takeoff, noting the average climb rate you get during climb (e.g., if you get 1500 fpm at takeoff from sea-level but only 700 fpm at 8,000 feet, then figure an average climb rate of 1,100 fpm. So, climbing to 8000 feet from sea level will take you roughly 7.5 minutes; multiply by your takeoff fuel flow).

Or you can get more sophisticated and do the flight testing to make a time/distance/fuel-to-altitude chart. It only takes an afternoon.

"Oh oh" fuel is fuel for weather diversions, holds, & etc., so that these things do not eat into your lawful reserve fuel. How much "Oh oh" fuel you add depends upon the nearness of available alternate airports, the badness of the weather, etc. Flying in Socal on a good weather day? You might not feel the need for much, with plenty of airports around. Flying in Alaska where the airports are far apart and the weather changes quickly? Fill the tanks to the brim!

Kevin Meyers
Posts: 1492
Joined: Mon Mar 24, 2008 10:07 pm
Location: Pacific Palisades, CA

Tue Dec 02, 2008 7:36 pm

sounds good, ill try that out, thanks Wayne!
-Kevin Meyers
ZLA_KC
Graduate of ZLA Pilot Certification Program

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