C172 low fuel warning error

  • Hello,

    I found out that the low fuel warning in the C172 never illuminates so I've played around with the settings in the TMD file and had to change the logic condition from 0.01892705 to 16.01892705 to finally see the warning below average 5 gallons.

    Just wanted to let you know.

    Code
                <[logic_greater][LeftFuelLow][]
                    <[string8][Input0][16.01892705]>  //<[string8][Input0][0.01892705]>
                    <[string8][Input1][LeftFuelTank.Output]>
                >

    Also, I have a question for Jan Jet-Pack (IPACS) : is there a way to calculate a random value for the fuel fill level?

    Code
                // 26 Gal avgas with 0.780 kg per l avgas
                <[fuel_tank][LeftFuelTank][]
                    <[float64][MaximumQuantity][76.768]>
                    <[float64][FillLevel][0.22]> --> random formula with result between say 0.30 and 0.80
                    <[string8][InputPressure][LeftWingFuelLine.Output]>
                    <[string8][AddFlow][LeftWingFuelLine.AddFlow]>
                >

    Best, Sylvain

  • Hello,

    I found out that the low fuel warning in the C172 never illuminates so I've played around with the settings in the TMD file and had to change the logic condition from 0.01892705 to 16.01892705 to finally see the warning below average 5 gallons.

    Just wanted to let you know.

    Code
                <[logic_greater][LeftFuelLow][]
                    <[string8][Input0][16.01892705]>  //<[string8][Input0][0.01892705]>
                    <[string8][Input1][LeftFuelTank.Output]>
                >

    Also, I have a question for Jan Jet-Pack (IPACS) : is there a way to calculate a random value for the fuel fill level?

    Code
                // 26 Gal avgas with 0.780 kg per l avgas
                <[fuel_tank][LeftFuelTank][]
                    <[float64][MaximumQuantity][76.768]>
                    <[float64][FillLevel][0.22]> --> random formula with result between say 0.30 and 0.80
                    <[string8][InputPressure][LeftWingFuelLine.Output]>
                    <[string8][AddFlow][LeftWingFuelLine.AddFlow]>
                >

    This is interesting. I haven't looked closely - does the C172 record fuel usage? And is it reasonably accurate? Also I guess it would be possible to manually edit the C172 TSC file and modify <[float64][FillLevel][0.22]> before launching FS2. This might be done using perestain 's Pilot Journey mission generator which already edits main.mcf.

    I doubt the aircraft would plummet to the ground if fuel hit 0 but for Pilot Journey it would be interesting to incorporate a penalty for triggering the low fuel light.

  • It's only visual indeed and weight and balance never change. Fuel usage isn't simulated (yet).

    ..but it does go down? At a sensible rate from your experience?

  • Fuel used is not a physical property of the aircraft, that is why there is no fuel used per default. If you look into the a320.tmd you will find an integral that sums up the fuel flow over time to give you the fuel used. With the fuel flow being in kg/s and the time being in seconds this gives you fuel used in kg (which we can only do because of the SI units! otherwise we would spend all computing power on unit conversions)

    Not sure if this is relevant but here is a quote from Jetpack in the Starfighter posts

    Steve

  • ..but it does go down? At a sensible rate from your experience?

    Looks more like a countdown timer to me. It has no relation to anything you do. Right now the 'visual fuelflow' is more some sort of gimmick. As said before, once it hits zero the times stops but you simpy keep flying. There also is no change in weight which is why you can so easily skip a part of flight using the Location screen: your weight at arrival will be the same as your take off weight anyway.

  • Looks more like a countdown timer to me. It has no relation to anything you do. Right now the 'visual fuelflow' is more some sort of gimmick. As said before, once it hits zero the times stops but you simpy keep flying. There also is no change in weight which is why you can so easily skip a part of flight using the Location screen: your weight at arrival will be the same as your take off weight anyway.

    thanks for the clarification.

  • To clear up a few things here...

    - The fuel flow in the Cessna (and Learjet and A320) is physically simulated, that means yes, the fuel decreases over time, depending on how much is actually consumed by the engines. We also simulate fuel pressure on the fuel lines, fuel valves and fuel pumps. When you look at the A320 fuel ecam page and turn off the fuel pumps you can see some drastic changes.

    - Fuel mass currently stays constant, so no change in weight and balance as of today.

    - Engines currently don't cut out when the tanks are empty, which was implemented as a safety precaution because the code for the fuel tanks was quite new at the time. We have to simulate the engine actually sucking in fuel and then starving off when no fuel flow is received. But with a little bit of faking it should totally be possible to cut the engine when fuel tanks are empty. But we don't want to fake that, so the engine just continues running.

    - The mentioned posting of mine with the "fuel used" value, well that is just the value on the display, that is running a simulation of the fuel flow and then calculating the fuel used from that, this is similar to what real airliners do. They can measure the fuel level directly but have to do all kinds of tricks to account for pitch attitude, temperature and pressure changes. So actually integrating the fuel flow is still done in modern airliners as far as I know. But again, this is just a display value, such value won't impact the engines or weight even if we are at a point where we simulate weight loss...

    Now to the initial question... :)

    Hello,

    I found out that the low fuel warning in the C172 never illuminates so I've played around with the settings in the TMD file and had to change the logic condition from 0.01892705 to 16.01892705 to finally see the warning below average 5 gallons.

    Just wanted to let you know.

    Code
                <[logic_greater][LeftFuelLow][]
                    <[string8][Input0][16.01892705]>  //<[string8][Input0][0.01892705]>
                    <[string8][Input1][LeftFuelTank.Output]>
                >

    Also, I have a question for Jan Jet-Pack (IPACS) : is there a way to calculate a random value for the fuel fill level?

    Code
                // 26 Gal avgas with 0.780 kg per l avgas
                <[fuel_tank][LeftFuelTank][]
                    <[float64][MaximumQuantity][76.768]>
                    <[float64][FillLevel][0.22]> --> random formula with result between say 0.30 and 0.80
                    <[string8][InputPressure][LeftWingFuelLine.Output]>
                    <[string8][AddFlow][LeftWingFuelLine.AddFlow]>
                >

    I think I meant to use the fuel tank fill level, not the actual fuel quantity. Right now the logic_greater is comparing 1.8% to the fuel quantity in kg, that can't work! :D So you're change is correct here, it should trigger either when reaching 16kg (roughly 5gallons) or it should trigger at 1.8% fill level.

    Randomizing the fill level is currently not possible. The tmd would be the wrong place for that. This would be added when we implement weight and balance for all aircraft and then you might see a menu option to randomize payload and or fuel.

  • Looks more like a countdown timer to me. It has no relation to anything you do. Right now the 'visual fuelflow' is more some sort of gimmick. As said before, once it hits zero the times stops but you simpy keep flying. There also is no change in weight which is why you can so easily skip a part of flight using the Location screen: your weight at arrival will be the same as your take off weight anyway.

    This is not correct, its not just a countdown, we actually simulate fuel flow and fuel pressure on the each of the fuel lines and also simulate fuel valves, etc.. (see my post above)

  • This is not correct, its not just a countdown, we actually simulate fuel flow and fuel pressure on the each of the fuel lines and also simulate fuel valves, etc.. (see my post above)

    Great. So no mass reduction and no engine cut out but for perestain 's pilot journey it would be fit for purpose to stick a fuel level into the tsc before launching fs2 and there could be a penalty for the fuel low light coming on e.g. Emergency landing/recovery/repair.

  • Great. So no mass reduction and no engine cut out but for perestain 's pilot journey it would be fit for purpose to stick a fuel level into the tsc before launching fs2 and there could be a penalty for the fuel low light coming on e.g. Emergency landing/recovery/repair.

    Yes you can just change the fill level in the tmd file (tsc is for scenery only) and if you are really brave you then manually pull the mixture out and try to glide it in. But the cessna doesn't actually glide all that well, so yeah. good luck with that LOL

  • My memory is getting more suspect every day, but I think I do see the low fuel warning in the Learjet every now and then.

    Even though the fuel used or remaining fuel as seen on the gauges may not be correct, having an indication of using fuel is a lot better than no movement whatsoever.

    One day we will have these basic features and can calculate W & B and perform some fuel management in these planes. Until then . . .

    Thanks Jan for your detailed responses.

    Regards,

    Ray

  • This is not correct, its not just a countdown, we actually simulate fuel flow and fuel pressure on the each of the fuel lines and also simulate fuel valves, etc.. (see my post above)

    I happily stand corrected. ;) Looking forward to the change of fuel mass and engines cutting off because that'll have an impact on your flying.