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A random thought;

Every carburettor Rotax 9 mechanical fuel pump  orientation that I have seen has the in/out spigot's facing approximately 45 degrees up and back (away from the prop). This then forces the fuel lines in/out to be located over the engine and subject to heat soak, with the potential for fuel vaporisation/fuel lock  facing roughly 45 degrees up & back (away from the prop).

Looking at the outside of the pump, it seem that it may lend itself to rotating the casing from which the spigots emerge. IF this be the case there would be greater options for routing the fuel lines to the pump and from the pump to the carburettors 

Question

1. Can the pump outer casing be rotated (after removing the screws)?

2. If the above is negative - can the pump be purchased with the spigots facing in a different direction eg 45 degrees down and back?

  • Re: Fuel Pump Orientation

    by » 3 months ago


    Don't tell me I have found the one topic that has never before been discussed and /or I am the first to speculate about alternative fuel line routing.


  • Re: Fuel Pump Orientation

    by » 3 months ago


    Physically it could be rotated, butttt in most cases the in and out fittings and hose wouldn’t fit the big majority of the planes because it would contact the cowling. Then the drain fitting that works with gravity would be facing up. 
    Then if you could rotate only the pump outer housing the pump fittings and hose would push back into the engine. 
    Having enough room for fittings and hose would be your enemy.


    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell


  • Re: Fuel Pump Orientation

    by » 3 months ago


    Hadn't thought about the drain fitting - definite problem there.

    As for the rest - having the option to purchase a pump, with the spigot's in the orientation that would best suit your application would , to my mind, be a definite plus plus.

    In my new aircraft (as with the old) there would be no cowling contact issues. The fuel hoses could  be routed under the engine, thus reducing the potential for fuel vaporisation. Shure the muffler is still a source of heat but having a much lower mass, than the the engine itself, should cool quicker and anyhow some thoughtful heat shielding/insulation would mitigate this as a heat source.


  • Re: Fuel Pump Orientation

    by » 3 months ago


    Roger FYI  - the drain fitting is on the main casting,  not on the outer housing that has the in/out spigots.

     

    So I return to my origional question - is the outer housing rotatable???


  • Re: Fuel Pump Orientation

    by » 3 months ago


    Theoretically, the fuel pump housing can be rotated, however, Rotax states the fuel pump cover can't be opened. SB 912-063R1 states the following: The fuel pump cover must not be opened for inspection. Check security markings (witness paint) (Page 10 of the SB) https://legacy.rotaxowner.com/si_tb_info/serviceb/sb-912-063.pdf

     

    We don't know what kind of ill effect this would have on the fuel pump/fuel pressure as we have never tested this. Thousands of aircraft fly around with the fuel pump orientated in the original postion and with the fuel lines routed above the engine with no issues. If you are worried about vapor lock and heat soak, take a look at this article as it may have some good information for you - https://www.rotax-owner.com/en/flightsafety/476-ai476

    Fuel pumps come from the Rotax factory with the inlet and outlet in only one position.  


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