Fuel Calculations

[Ant1981]

Why, when FSX Navlog tells you how much fuel you'll use, do you actually use alot more? How am I going to know what I need if the Navlog can't even do it?

[NikeHerk67]

Why, when FSX Navlog tells you how much fuel you'll use, do you actually use alot more? How am I going to know what I need if the Navlog can't even do it?

Perhaps, like driving an automobile, you're trying to get good mileage by using DRAG STRIP techniques. :)
Very important in flying are the take-off, climb rate, cruise altitude, MACH rates, decent and landing speeds. These are some things that you can try to improve on to conserve fuel. I'd suggest flying the same route a few tims and trying to improve each time. Most of the time flight simulator pilots, especially new ones, use way too much throtte for everything.

Edit:
Oh yes and too much fuel as well.......plan your fuel for enought to make it from point A to point B and to point C if necessary plus some extra on top of that in case you're put into a holding pattern or for Go-Around of two.

[deepsea345]

as a rule of the thumb for me i add an additional half to my fuel for short flights

i.e. 1,000 gallons (calculated by FSX) + 500 gallons (half) = 1,500 gallons


and twice the fuel for long-distance flights into heavy airports (and therefore long taxiing and holding patterns)

i.e. 7,000 gallons (cal. by FSX) times 2 = 14,000 gallons

so far this has worked for me:D but im pretty sure this is not how it works in real life:o

[Tim_A]

The nav log has no idea what power setting you are going to use. I don't know where its figure comes from, but it's only a guideline. To be accurate you will need to refer to the POH for the aircraft. It will give fuel consumption figures for a whole range of power settings, in cruise, climb and descent, and at different altitudes & temperatures.

[Ant1981]

Do the standard aircraft come with the POH? I'm betting if they do, some of my add on ones don't. I'll need to be studying this then, as to get to FL320 or about, at a V/S of +1800 I need about or appear to need about 80-90% N1.

[Tim_A]

You may well need to dig around to find one. Since you said elsewhere you are flying a VC10, I had a poke about, and came up with this: http://www.vc10.net/Technical/perf_manual_index.html

[Ant1981]

Thanks Tim, I'll check it out :)

[lnuss]

You might take note, too, that aircraft in FS don't necessarily match their real life counterparts in fuel burn, though some come mighty close. The best thing is, for each model, to find the burn rate for your specific aircraft by doing your own tests -- fill the tanks, then takeoff and climb to cruise altitude, then check fuel remaining and time of the climb. Refill at altitude (menus, of course), then fly at cruise power setting for 15 min, half an hour, or whatever, then check fuel burned against time. Do the same for descent from cruise altitude to landing.

Once you do this, you'll have precise figures for that aircraft in each typical stage of flight at the power settings you tend to use.

We tend to do this in real life, too (if we fly the same individual aircraft regularly), in spite of the manufacturer-supplied information, since aircraft vary a little from one to another, even of what should be identical aircraft. Even after that, we typically add something of a cushion for unexpected events, in addition to the reserve fuel we need to try to keep after landing. Of course we obviously can't refuel at altitude, but we can still compare consumption with handbook figures and adjust accordingly.

[tatest]

I find out how much fuel the modeled aircraft uses by flight testing. Much of my simulated flying is flight testing, mostly cruise tests and slow flight performance; that's because I've collected quite a few freeware models, and most are poorly documented.

For some models, the cruise performance approximates what the (FS9, in my case) Nav Log suggests; most often, I use less fuel, probably because the log is assuming higher power settings. Other models, I've found the flight planner is so far off the performance of the model, the information is not at all useful, consumption as low as 30% or as high as 300% of what the flight planner suggests; suggested cruise speeds as much as 50% higher than what the model can do.

As for the simulated model matching what is in the POH or training manuals, sometimes the models do, sometimes they don't. I've found a few models (FS8 conversions) that burn fuel at 1/2 to 1/5 the rate they should, and a few that use as much as 50% too much. How well a model approximates real world performance can determine whether I keep it or can it, something learned only by flight testing, and researching the real world information.

[pensguy]

I ran out of fuel flying into a strong headwind. Left the airport with reserves, and ran out about 3/4 of the way. If I am making a long flight, I usually leave it on 100%. It's not like I am trying to save an airline money.....

[skylab]

The only time you have too much fuel is when you're on fire.

Fill it up!

And.....don't forget to check the oil.

[InsyleM]

The only time you have too much fuel is when you're on fire.

Fill it up!

And.....don't forget to check the oil.

or if your overweight to takeoff or land