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Could someone provide some guidance on how the attached 912ULS performance graph (fig 4) should be interpreted? For example, to find Fuel Consumption, it seems far too simple to enter the graph at the bottom with RPM and move vertically until intersecting the MAP from the left axis and then reading off FF on the right side axis? If it is that simple, then the result is at odds with fig 5.2, Fuel Consumption.  At 75% power, fuel consumption from fig 4 is approximately 27 L/HR vs 18.5 L/HR from fig 5.2. Both images are from the performance section of the Rotax 912 Operators Manual. What am I missing? 

 

11053_1_IMG_8349.png (You do not have access to download this file.)
11053_1_IMG_8351.png (You do not have access to download this file.)
  • Re: 912ULS Fuel Consumption Data

    by » 9 hours ago


    Hi James,

    Neither documents consumption figures come close to my actual fuel consumption.

    At 5000 rpm / 25" MAP I am seeing a fairly consistent  4.25 L/hr (98RON ULP).

    The 14.25 L/hr is the average consumption derived from actual (refuelling volume) fuel used / Hobbs hours flown.

    😈


  • Re: 912ULS Fuel Consumption Data

    by » 7 hours ago


    Thanks Sean. I am planning at around 25 L/hr which appears to be what I am getting. The Dynon FF indication is similar. That’s what I am finding confusing. The Rotax data appears contradictory. 


  • Re: 912ULS Fuel Consumption Data

    by » 5 hours ago


    What sort of aircraft?

    Seems to my uneducated mind, that the draggier the aircraft, the higher the L/hr, at say Cruise 75% power.

    My Dynon fuel flow, in Cruise, never indicates  below 17L/hr. Given my average fuel consumption, this cant be correct.

    FYI the Fuel Used/Remaining function is spot on.😈

     


  • Re: 912ULS Fuel Consumption Data

    by » 5 hours ago


    CTLS @ 75% power.

    I would have thought that drag would only affect TAS ie 75% power would incur a particular fuel flow and the airframe would dictate the resulting TAS? 


  • Re: 912ULS Fuel Consumption Data

    by » 5 hours ago


    I would thing so to BUT how is it my Sonex/912ULS/Airmaster CS, cruises at 5000 rpm (75% power?) & delivers a consistent 14.25 L/hr (average for flight),  @ 130 knots True?

    My last aircraft, ATEC Zephyr/912ULS, econamy Cruise, 100 knots indicated, 5200 rpm for 13 +L/hr (single pilot, no MAP gauge)?

    Seems that aerodynamic design comes into the L/hr

    😈


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