I recently purchased an experimental with a new 915is. I did two transition flights then on my first solo I noticed an audible, hi-pitched whine coming from the engine when it was at full power on takeoff & climbout. When I reduced power it went away. The noise was loud enough to get my attention so I elected to land. Nothing was found on post flight. It sounded like it could've been the turbo or fuel pump(s).

Next few flights I experienced the same noise but continued flying near the airfield to see if I could troubleshoot. Same circumstance - noise only present on high power settings. At one point it was making a 'pulsating' whine similar to an oscillating pump. Interestingly enough I could not duplicate any of these noises when ground testing at full power; only when airborne.  Also, I haven't had any abnormal engine indications during any of the events and I've been using UL 91 octane.  OATs were all in the 70's so no reason to expect vapor lock or pump cavitation.

Today I was ground running the engine with no headset. After starting the engine on pump #1, I turned on pump #2. When it came on it was making a noise similar to what I've been hearing, albeit nowhere near as loud. So my gut tells me it is indeed the pump.  

So my question is, how loud is a fuel pump supposed to be before I should be concerned? The reason I'm concerned now is I do not remember hearing this noise during my transition training, however I accept I might've been too busy learning the airplane and perhaps just didn't notice. But now that I'm solo I'm hearing everything. Any ideas?


Tucson, AZ (KTUS)

  • Re: Whining Engine Noise at Takeoff

    by » 5 weeks ago


    Sounds like we have a common issue. See my post below, "fuel pump light'. 

    Wish Rotax would jump in and shed some light on this topic.


    Steve G.

  • Re: Whining Engine Noise at Takeoff

    by » 4 weeks ago

    Hi Chris

    Check your engine serial and pump serial number.  Look to see if it may be affected by any service bulletins.  

    go to flyrotax.com and download the bullitians


    39501_2_915 fuel pumps.jpg (You do not have access to download this file.)

  • Re: Whining Engine Noise at Takeoff

    by » 4 weeks ago

    Thanks guys, I checked the serial numbers and it doesn't look like my pumps fall under any current service bulletins so I'm continuing to troubleshoot.  My next step will be to run the engine with Avgas and see if that changes anything.  I recall reading about switching fuels in a 912is that was having similar issues so we'll see.

    Steve - I've been running both pumps from startup to shutdown so I haven't noticed if there was much difference running each pump in flight.



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