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Good morning, two weeks ago went for a 45 minute flight in a 2009 LSA with a 100 horsepower Rotax. After deciding to go flying again and after a 5 to 10 minute delayed taxi, we took off and experienced a loss of power and vibration as the plane just started to become airborne. Aborted takeoff, did 4 to 5 runups getting the temperatures of the engine quite high (just hitting redlines, cyl 285F). We took off and experienced a second loss of power, again at rotation speed. This time maintained power through two losses of power and vibrations and aborted takeoff.

Notes:

Tanks were sumped and clear of water prior to first 45 minute flight and after.

MoGas has been solely used in the airplane for last 22 hours. (TTAFE 134 hrs)

Discussion has been possible vapor lock, no return system on fuel. (all metal air frame low wing, sport cruiser)

Five year hose replacement was done at 88 hours and possible chards in carburetors. Very emphatically I was told you will find debris in carburetor from hose kit.

Plan right now is to remove carburetors and rebuild using local aviation Rotax mechanics.

Any help you can offer will be appreciated. Plane is currently in Santa Monica.
  • Re: Loss of Power on Takeoff

    by » 11 years ago


    Hi Brain,

    They most likely don't need a rebuild. Just pull the bowls first and take a look inside. If you had a banjo bolt on the cross over balance tube I would remove those and look inside the fitting. Sport Cruiser if I remember right has no banjo bolt, but has extra rubber fuel line and no recirculation line. Carb debris can show up any time after a hose change. It could be 5 hrs. or 50 hrs. My guess at this point is rubber debris. If you find black particles make sure it's rubber hose and not the floats flaking. I would also like to know what fuel hose was used.
    Call me if you have any questions. I have been working with this around the US.

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


  • Re: Loss of Power on Takeoff

    by » 11 years ago


    Hi Brian

    It could possibly be rubber particles from the hoses, but they very rarely make it into the float chamber.

    They usually get held up at the inlet banjo on the carb as they can be too big to get past this point and the needle valve.

    They can temporarily block the inlet on one carb, or more permanently restrict the fuel flow which becomes evident when you have held the engine on full power for a short while and the fuel demand is higher than the fuel flow rate due to the restriction.

    I would suggest removing the float hinge and needle valve and inlet banjo and blowing out the carb inlet from inside-out.

    If you are using compressed air, remove the carb tops and diaphragms as well as they can be disturbed.

    It could also be vapour lock and would suggest fitting a return line to help prevent this.

    Cheers Mark

  • Re: Loss of Power on Takeoff

    by » 11 years ago


    This is what I found in the float bowls after approx. 50-60 hrs. TSN.
    This was enough to get sucked into the bottom of the jet and cause reduction in RPM and engine roughness. Also, this happened at full throttle on take off after gaining altitude.
    Normal landing ensued.

    Another 912 leaving Lancaster, PA was not so fortunate and landed in the corn off the end of the runway doing damage to the landing gear.

    Rich
    CarbbowlCo-pilotside.Lookslikefiberfromahose.JPG (You do not have access to download this file.)
    Closeupoffibermaterialfromfloatbowl.JPG (You do not have access to download this file.)
    TwoaluminumsliversandsmallpieceoflookslikerubberPilotsidefloatbowl.JPG (You do not have access to download this file.)

  • Re: Loss of Power on Takeoff

    by » 11 years ago


    Hi Rich

    Is it possible these are pieces of float material. I cannot see how something that big could possibly get past the needle valve.

    If there is aluminium in there as well, it has probably been in there since manufacture.

    Mark

  • Re: Loss of Power on Takeoff

    by » 11 years ago


    Mark.

    It's not float material. Both the aluminum slivers and hose debris were probably there since new.
    If you look at the bottom guide pin in the float bowl, you'll see dissolved rubber at the pin base. Look closely.

    I think the piece of rubber laid at the bottom of the bowl until the ethanol (10%) fuel dissolved the rubber. When the rubber dissolved exposing the fiber, it was light enough to get sucked up into the jet at WOT, Partially blocking the fuel flow.

    It took 50-60 hrs. TTSN of flight time before the problem occured.

    Rich

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