Weird fuel flow behavior?



  • The fuel flow behavior seems off even after v0.5.1. The mixture setting only seems to have an effect on fuel flow readings in a very narrow range of the mixture lever (around 50%) near the cruise setting , above that narrow range I can go to full rich and the fuel flow pretty much stays the same.



  • I agree; I was just about to post something similar!
    This problem was introduced in v0.5.0

    It now behaves like the other standard MS GA planes.

    Prior to v0.5.0 the Arrow's fuel flow would go well up into the cruise range on full flow and you could adjust it easily all they way down to cutt off



  • The Mixture control on this aircraft is not used for setting Fuel Flow... It should be set using the EGT gauge to Full Rich (Takeoff), Peak EGT (Best Economy Cruise), or Peak EGT -100F (Best Power Cruise). The throttle should then be set to the desired MP and Fuel Flow for 55%, 65%, or 75% power per the cruise performance charts in the POH...



  • The mixture lever controls fuel flow. The throttle controls air flow. Together they determine the mixture. There is indeed a problem with fuel flow. It appears to be artificially limited in version 0.5.0. Problem was also present in version 0.1.0.

    There's been a lot of work done over the past few versions on power. This could very well be a sort of compromise that allows you to get the fuel flow you need for a given power setting, but not necessarily the fuel flow you want.

    For example you can get enough fuel flow to generate 75% power at 6,000 ft. But you can't achieve a fuel flow of 16 gallons per hour at 6,000 ft at 25 squared on mp/rpm. That's a perfectly reasonable fuel flow if you are in a climb on a hot day and wanted to keep the cylinders cool. At 6,000 ft, you can get a maximum of 12 gallons per hour in v0.5.0 which is artificially low.

    It's noticeable, but it really doesn't limit the performance you can get out of the aircraft.



  • Thanks for the heads up everyone
    I’m now googling how complex engines work and starting to understand the basics



  • @BernieV said in Weird fuel flow behavior?:

    At 6,000 ft, you can get a maximum of 12 gallons per hour in v0.5.0 which is artificially low.

    Don't have the time to test it now, but did you check your OAT when trying that?
    According to the ODM charts, there is no way to reach best 75% power cruise setup at 6000ft if OAT is above ~8°C.

    I don't know how the actual fuel flow behaves (I too would think that the mixture lever should impact it over the whole range), but at least the valid cruise settings are limited to the numbers in the POH.

    I couldn't reach 75% best power cruise setup at 8000ft today since the OAT was around 10°C, so the max fuel flow I got was the 65% best power cruise level at 11.4GPH.