Fuel Calculation

[Steve Waite]

Proper fuel monitoring takes careful flying.

From the briefing I’ve shown the aircraft flight parameters configuration.

Aircraft Configuration Notes:

Cruise Altitude: 7000 ft
Cruise Airspeed: 155 Knots

Ascent Airspeed: 130 Knots
Descent Airspeed: 155 Knots

Ascent Rate: 700 fpm
Ascent Rate Above 4000 ft: 500 fpm
Descent Rate: 1500 fpm

The flight is built from the parameters you choose.

During the flight: I will try and maintain average ascent airspeed of 130 Knots.
Below 4000ft: I will try and maintain average ascent rate of 700fpm,
Above 4000ft: I will try and maintain average ascent rate of 500fpm.
When I reach cruise altitude of 7000ft, I will level off, and try and maintain average cruise airspeed of 155 Knots.
I will descend at 1500fpm, and 155 Knots.
I will use the shortest path out of, and in to the airports, with respect to how ATC usually guides the flight.
I will adhere to the aircraft landing speeds.

I have to do that because these are the settings in Aircraft Parameters, and also to measure the fuel usage correctly, with respect to the distance travelled.

[Steve Waite]

The fuel load for the flight was calculated with zero Taxi and Reserve. Flying straight from the runway.

After the flight the assessment said my average range during the flight was 953 Nm

In the parameters the aircraft was already set for 750Nm approximate range, so I changed it to 950Nm

So if I fly the exact route again, in the exact same conditions, I should still get 950Nm range or so.

I can now set my reserve and taxi & manouvres times.

[Steve Waite]

I regenerated the same flight again with the new range setting, but without adding taxi and reserve, I got less fuel in the tanks for the same route. I flew the route, and this time I had a couple of gallons left when I landed. Thus proving the accuracy of the fuel calculation!

Now in the aircraft parameters section, I have the "real" performance data for the Simulated aircraft. These are the values that count.

Regards;
Steve

[Steve Waite]

Ideal Flight uses a generic algorithm to determine the starting set of parameters for each plane. That is to say, a set of values is chosen for each aircraft that are most likely to work, but may not be very close to the actual performance of the aircraft.

As you see in the thread here, you need to fly the aircraft and record the results to determine the real parameters. That is part of the fun of IF!

Please remember to check the parameters carefully whenever you install a new aircraft.

[jscharpf]

"Do the flight and see how much fuel you use. With Ideal flight, you record what your plane "actually does" IF does not dictate the fuel"

I love this feature! It really makes you do your homework. I actually enjoyed going to the Cirrus website and looking up the specs from my eaglesoft SR22G. I found that for whatever reason I can fly much more economically, and I plan on adjusting my settings to this.

[Steve Waite]

"Do the flight and see how much fuel you use. With Ideal flight, you record what your plane "actually does" IF does not dictate the fuel"

I love this feature! It really makes you do your homework. I actually enjoyed going to the Cirrus website and looking up the specs from my eaglesoft SR22G. I found that for whatever reason I can fly much more economically, and I plan on adjusting my settings to this.

Yes, the simulated aircraft may show a different range to that of the specs for a real one.
You only need to change the cruise altitude, rate of climb, or cruise speed a little, to get differences you can see.

Remember too, in Ideal Flight you have winds aloft, all the time. You can turn winds off for a test cruise fuel report. When settled into a cruise at your rated speed and alt, with a known load, pull down the addon menu and choose the IF Fuel report, this gives you an excellant base figure.

Steve

[Andayle]

Hi all,

Sorry to dig up and old post but my very small problem is very much related to this. I only really fly 2 aircraft, the Aerosoft Airbus X and the PMDG 737NGX. The Airbus I have managed to nail down the fuel figures quiet nicely but am having a real problem getting the fuel prediction for the 737 to be adequate.

Does anyone else have the PMDG 737NGX and wouldn't mind sharing their performance figures from IF?

Really love this gem of a program, not had any faults at all with the actual flying and this is the last little niggle I have found. Keep up the great work Steve. This has gone on my must have FSX addons and will be recommended to friends.

[Steve Waite]

Hi,
Check the assessment at the bottom, look at the fuel reports for your ngx flights. There should be an emerging value for Range, but it always depends on a great deal of factors. So one flight may produce a different range because you flew against the wind, or with a larger load. The weather in IF produces changes in humidity, pressure, and temperature affecting the performance, and also depending on where you go. I would try repeating a route; if you fly exactly the same each time, you will use the same amount of fuel, else something else is affecting the fuel use. Although you fly at N1 rather than fpm during the climb, it makes no difference as long as you fly the same with the same throtle and so on.
I did a lot of testing with the 737, but was ages ago, I'll have a play. The bottom line is that the fuel use should be repeatable, and with that mechanism the fuel is calculated. Always ensure you have thought about and tuned the Range value in Flight Parameters.
regards
Steve