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912iS fuel system

in 912iS Technical Questions 11 years ago
The rotax installation manual for the 912iS describes 2 fuel filters, 1 between the header tank and the pumps, and one between the pumps and the injection rail.
What are the type and model of these filters? and, do you need access to these filter from bellow for draining?

thanks
Ofer

  • Re: 912iS fuel system

    by » 11 years ago

    Hi Ofer,

    Metal filters in this case are best because of pressure within the system after the pumps and the possibility of alcohol fuels which do affect some plastic filters. They should be in a place where you can remove them if you want to replace them, but most metal filters are re-usable and should be in a place where they can be opened and inspected at the annual. Cost may be around $40- $75 each depending on type and brand. Type and brand may be more up to you depending on what country you live in and or where you order. It may look something like this, but not limited to:

    http://www.aircraft-spruce.com/catalog/appages/micron10.php

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

    Thank you said by: Stanislav Zubar
      
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  • Re: 912iS fuel system

    by » 11 years ago

    The installation manual requires:
    - 50-67 micron filter before the pumps. This should also be a gascolator/water trap. Andair has a 62 micron gascolator part number GAS375-MF-62M
    - 8-12 micron fine filter after the pumps. The Bosch 0450905021 is ideal as it is metal and has lots of filter material so plugging up is less likely.
    It is NOT practical to wash a 8-12 micron filter, the weave is much too fine so any attempt to wash it will only contaminate it more. throw out the filter and replace it with a new one.
    Rob
      
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  • Re: 912iS fuel system

    by » 10 years ago

    Hi Rob, thank you for your advice on fuel filters. I am building a Zenith CH750 with a 912 iS engine which is currently being converted to the Sport model by the Australian Agent.

    I am currently installing the fuel pipework which came with my firewall forward kit. So far all is good and the "tips" in the amendment pages to the 912 iS install manual seem to exactly match the design of my firewall forward kit.

    One Question however. Rotax appended a note to the fuel system which says that the main and backup fuel pumps must never be operated together because their flow volume will, overload the fuel pressure regulator and the "A" alternator can't handle the current draw and that the ECU will flag a "fail" somewhere.

    Does this mean that I can't test the backup pump during my takeoff checks? Does it mean I must not switch on the backup pump during takeoff and landing?

    If this is the case then some wiring changes are in order.
      
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  • Re: 912iS fuel system

    by » 10 years ago



    One Question however. Rotax appended a note to the fuel system which says that the main and backup fuel pumps must never be operated together because their flow volume will, overload the fuel pressure regulator and the "A" alternator can't handle the current draw and that the ECU will flag a "fail" somewhere.

    Does this mean that I can't test the backup pump during my takeoff checks? Does it mean I must not switch on the backup pump during takeoff and landing?



    Geoffrey, Your information about the fuel pressure regulator & alternator concerned me so much I spent some time checking out the manuals to see if I had missed something. Do you have a reference chapter where this information can be found?

    I did find the following which I hope helps, but I would be interested if the manuals do suggest that both fuel pumps are not to be run simultaneously.

    In the Installation manual,http://www.flyrotax.com/portaldata/5/dokus/d05879.pdf section 73-00-00 page 2 there is a notice about parallel fuel pumps (but connecting the fuel pumps in parallel is not a recommended configuration) so this notice is probably a bit misleading.

    I checked out the operators manual http://www.flyrotax.com/portaldata/5/dokus/d05875.pdf & I can't find anything about not switching on both fuel pumps together, in fact the operators manual page 3-12 under "Holding Point Control" there is a procedure to run both fuel pumps simultaneously.
      
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  • Re: 912iS fuel system

    by » 10 years ago

    I think the Installation Manual may need another revision to add more clarification here.
    Not sure why a parallel pump system is mentioned when the engine is supplied with a pump pack that has a series(check valve)system already configured?? Why would anyone do that?
    I asked Rotax for some clarification about running the pumps and the answer is:
    - you can run with both pumps ON all the time. It is advisable to do this.
    -You can turn the aux pump off in cruise if you really want to.
    -Both pumps ON for takeoff and landing.
    -If you operate with both pumps ON all the time, make sure you cycle/test them during your run-up in case you have a fault.
      
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