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Fuel calculator help please.......

Pro Member Trainee
Pulp1 Trainee

I am trying to add a new aircraft to the fuel calculator the only problem is how do I find out what the miles per gallon is for the said aircraft which is an Airbus A310-300?.

Thanks for any help.
🙂

Pro Member Chief Captain
CRJCapt Chief Captain

Pulp1 wrote:

I am trying to add a new aircraft to the fuel calculator the only problem is how do I find out what the miles per gallon is for the said aircraft which is an Airbus A310-300?.
Thanks for any help.
🙂

You have to determine the rate of fuel burn(cruise) in gallons, per hour. The value is normally shown in pounds on the fuel flow gauge(s). You can covert pounds to gallons by dividing pounds by 6.7.
Example:5000 lbs would equal 746 gallons.

Once you have this figure, divide it by the true airspeed(TAS) of the aircraft. TAS= ground speed, in zero wind conditions.
Example: 746 gal. /450 knots=1.66 MPG

Note: This is not the real procedure and could only be somewhat accurate at one altitude with zero wind.

Pro Member Trainee
n9xv Trainee

NMPG = (Groundspeed * Lbs-per-Gal) / PPH

or,

NMPG = Groundspeed / GPH

Where,

GPH = PPH / Lbs-per-Gal

This is true at any given altitude & FF rate.

Pro Member First Officer
lionlicker First Officer

Hi Pulp1

Here is a method to detirmine the fuel consumption of any sim aircraft.

A prerequisite is to calculate your TAS correctly.

You cannot trust the console TAS readouts on many of the sim aircraft (especially some of the add-ons), so here is a more accurate way.

You'll need a calculator that has sin and cos function on it (most standard calculators have sin and cosine)

When you conduct performance trials on your selected aircraft, your best friends are the GPS and the [shift Z] red text info at the top of your screen.

This example will give you fuel consumption in lbs/Nm.

1) Detirmine (E) the amount of fuel burnt in exactly 60 seconds. At a common cruise flight level - and in consistent wind conditions - pause the sim and use [Alt A F] record the lbs of fuel in tanks - then unpause and fly for exactly 60 seconds - then pause and [Alt A F] and record the amount of fuel remaining. Use subtraction to quantify the lbs/min.
E= lbs/min

2) Leave the sim on pause while you calculate the TAS.
A=magnetic direction wind is coming from (from red text top of screen)
B=velocity of wind in knots (from red text top of screen)
C=magnetic direction of ground track (top middle on GPS)
D=velocity of ground track in knots (lower left on GPS)

TAS = the square root of the following : -
(sinA*B + sinC*D)^2 + (cosA*B + cosC*D)^2

3) Detirmine (F)= TAS / 60 = the amount of air (Nm) that you flew through in the last 60 seconds
F=TAS/60

4) And finally you get your lbs/Nm from E / F.
lbs/Nm = E/F

If you want a result in gallons/Nm, just substitute gallons for lbs in the above steps.

When you plan your flights you need to account for winds aloft, as the above only represents the amount of fuel burnt when you fly through 1 Nm of air.

Here are some results for:-
Cessna Skyhawk C172 SP : 0.42 lbs/Nm
Beechcraft Baron 58 : 0.71 lbs/Nm
Lockheed Vega : 1.05 lbs/Nm
Learjet Bombardier 45 : 2.15 lbs/Nm
Douglas DC-3 : 4.1 lbs/Nm
Bombardier CRJ 700 : 10.05 lbs/Nm
Boeing 737.800 : 20.1 lbs/Nm
Airbus A321 : 23.7 lbs/Nm
Boeing 747.400 : 52 lbs/Nm

. . . . - see if you come up with the same results ???

Obviously aircraft payload will vary the the results - so it make sense to conduct your trials when the aircraft is about 60% fuel and 80% payload (or something like that?)

Pro Member Trainee
n9xv Trainee

We can only get the same results if we have all the variables in lionlicker's example (magnetic course, wind direction & speed, and groundspeed).

True airspeed will not tell you anything about gas mileage. Its groundspeed that you want to indicate the "meaningfull" progress over the ground at a given fuel flow rate etc.

If your flying at 250-KTAS directly against the jet stream (which we'll say is moving at a humble 200-Kts) at 40,000-ft, and your fuel flow at cruise is let's say 15-GPH.

then,

1 - your groundspeed is only 50-Kts.

2- your NMPG (Nautical Miles Per Gallon) found as
Groundspeed / GPH, is only 3.33.

the point,

The airplane flies great as the air rushes by at some 250-Kts. Only problem is - you are'nt really going anywhere, at least not in an efficient economical kind of way. Groundspeed is the variable that indicates something meaningful about the flight whether in terms of fuel economy or flight time etc.

Pro Member First Officer
lionlicker First Officer

n9xv you are missing something vital here.

People need a benchmark figure so they can calculate how much fuel to put into their plane before T.O.

So obviously it would represent how much fuel the plane uses in no wind conditions, and then they can take into account wind conditions.

I still stand by the figures I provided in my last post, and I still stand by the method I use to detirmine them. They are correct. And the need to correctly calculate TAS is definetely a prerequisite if you want to find out the consumption of a given sim aircraft.

No doubt we all have different units of measure (miles per gallon - - - or pounds per mile --- whatever )- - - but the principle is the same.

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