by Steve Waite » Tue May 18, 2021 9:04 am
A bit more about Ideal Flight and the fuel approximation...
We must consider that we can use Ideal Flight with any aircraft past, present or future. That requires a special way of thinking about fuel use. Since Ideal Flight doesn't know how much fuel we need for any aircraft and does not replace the official fuel calculator method for each individual aircraft, which can vary a lot depending on aircraft type, engine type, airframe drag, weight and so on. The differences are almost infinite. So, what can Ideal Flight do for us?
We can tell Ideal Flight the aircraft approximate Range. This requires knowing how fast we cruise and how long we ascend and descend.
For example, if we fly a route and use 200 gallons in 2 hours, we are using approximately 100 gallons an hour on average.
So, if our aircraft can carry 400 gallons, we have on average 4 hours flight time. Our Range time is 4 hours approximately.
If we fly at 200 knots our Range distance is 200 times 4 equals 800 nautical miles approximately.
Ideal Flight considers how much time we are in ascent and descent, and that leaves our distance portion at cruise speed.
Therefore, we must apply values into the flight parameters page, ascent rates, cruise speed, range, ascent speed, approach speed, final speed, taxi time.
Then using the Range and the other parameters, Ideal Flight calculates the approximate fuel.
Once we have the Range value, the fuel amount can then be increased with the taxi time, holding time and reserve time.
In practice, we usually ascend and descend and approach and land at the same speeds, so we generally only enter those values once for each aircraft. Also, we generally take the same payloads, and the aircraft drag remains the same at the same altitudes. In effect, the Range comes out approximately the same for most flights.
After a few flights, we find out that the Range parameter is approximately the same each time and the fuel estimate is close to what we use on the flight. If we fly the same flight twice, we should be using approximately the same fuel each time. With winds in our favour, we use less fuel and with wind against us, we use more fuel. The Ideal Flight calculation takes the wind vector on the aircraft into account as it does the cruise distance portion.
We can find the approximate range during the flight by using the Fuel Report from the in-sim menu. After the flight, we get a range value in the assessment. We can also check in the flight log for the output from using the Fuel Report menu item in a stable flight condition.
We must fly the aircraft the same way each flight, according to the parameters we chose, to find the range for that type of flight. Ideal Flight adjusts for the length of the cruise portion and the wind vector on the aircraft.
This way makes it easy to approximate the fuel quantity we might need for a particular route. On the Flight Generator page, we can input whatever fuel we need or leave it in automatic which uses our Range and other flight parameters.
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