• Which the release of FS2020 we see an explosition of activity on the forun and of course we are very happy to see this. But having all questions about FS2020 in one forum becomes a bit messy. So therefore we would like to ask you all to use the following guidelines when posting your questions:

    • Tag FS2020 specific questions with the MSFS2020 tag.
    • Questions about making 3D assets can be posted in the 3D asset design forum. Either post them in the subforum of the modelling tool you use or in the general forum if they are general.
    • Questions about aircraft design can be posted in the Aircraft design forum
    • Questions about airport design can be posted in the FS2020 airport design forum. Once airport development tools have been updated for FS2020 you can post tool speciifc questions in the subforums of those tools as well of course.
    • Questions about terrain design can be posted in the FS2020 terrain design forum.
    • Questions about SimConnect can be posted in the SimConnect forum.

    Any other question that is not specific to an aspect of development or tool can be posted in the General chat forum.

    By following these guidelines we make sure that the forums remain easy to read for everybody and also that the right people can find your post to answer it.

Flight Plan Estimated Fuel Flow

R

Richie35

Messages
47
Country
us-california
Hi again,
Can any one relate how the estimated fuel requirements are derived in the FS flight planner. It seems that the estimate on my model is at about 6 gph (36 pph) as displayed in the and that is a bit too high. I know fuel consumption varies with throttle setting and altitude. The (A::ESTIMATED FUEL FLOW, pounds per hour) displays the above data. Is there any way to correct that flight plan value. I have used the bestpowerspecificfuelconsumption setting in the aircraft.cfg to obtain the correct fuel flow as close as possible as defined in the manufacturers' POH.
Thanks for any guidance but note this is not a critical problem as I can produce a chart for fuel consumption at various altitudes.

Richie
 
My best guess is that it is estimating your takeoff, climb, and descent/approach throttle setting from some canned profile. Profiles are always different between types and manufacturers. In my aircraft for example, takeoff thrust is around 85% and climb thrust is around 80%. I don't see how FS would know that and it probably assumes 100% for takeoff and some other number for climb. 95%? Who knows. It could also have your cruise speed wrong. It uses the value in the config file which in reality changes with altitude and winds.


Here's an easy solution. Try making a gauge that scales that variable and see if that's accurate. I'm only guessing, I've never played with those variables.

Code: 
<String>%(

(C:fs9gps:FlightPlanWaypointRemainingTotalDistance,nmiles)  
(A:ESTIMATED CRUISE SPEED,knots) / 
(A:ESTIMATED FUEL FLOW,gallons) *
[COLOR="DarkRed"]<!--insert your own scalar below-->[/COLOR]
0.50 *

)%!5d!</String>



The formula above is:

remaining distance divided into cruise speed times estimated fuel flow times your scalar.
 
JX,
Thanks for your reply and advice. I checked a flight plan using clear weather data and the speed was calculated at the cruise speed (104) from takeoff to landing. The time, I guess was calculated from distance divided by time. So that still remains the question, "where does the core program derive the fuel consumption?" Is it from the engine perimeters in the aircraft.cfg or .air file?
The (A:RECIP ENG FUEL FLOW:1, pounds per hour) displays 36 pph which is consistant with the calculation of fuel required in the flight plan.
The code you listed has me some what confused as I interpet it as a gauge and how does that change the above fuel flow? How does that change the value in the sim other than display?

Richie
 
JX,
I stand corrected in my last message. the Fuel flow ref should be (A:ESTIMATED FUEL FLOW,pounds per hour).
Richie
 
Yea I was suggesting a gauge. You can't change the calculation in the nav log. FS get's the 36 from the airfile. As I was saying before I suspect it has a preset 'profile' that it uses to come up with that average. It doesn't have aircraft specific performance tables nor does it know what the settings are in each phase of flight. It is using generic info.
 
JX,
I have a test gauge that accomplishes what you have suggested and monitors most of the engine perimeters. I was wondering what the source data was derived from and you confirmed that information so I will have to leave that part alone. The actual fuel consumption in the model matches the manufacturers' data. Thanks for you time and effort. I cannot find a section in the .air file that eludes to the fuel consumption so i adjusted the bestpowerspecificfuelconsumption= line in the [piston engine] section of the aircraft.cfg file and that works quite well.

Regards,
Richie
 
or you could try the cruise_speed entry. The problem with tweaking the fuel consumption line is that affects in flight characteristics. If the navlog is the problem, but the inflight performance is right, I would suggest not altering in flight performance.
 
JX,
Thanks for your comments and that is my intent to not mess with this any more, so therefore I will leave it as is.

Richie
 
You must log in or register to reply here.
Back
Top