acw

My Feedback: (1)

I have an Ultra Bandit EVO with a full bypass. The plane has around 15 flights now and is performing well. One strange thing is a low pitch flutter like sound which is only present when I apply about 1/3 power and more. This appears to come from the pipe or the turbine itself.

Any idea regarding what this is and if any fix is possible?

BarracudaHockey

My Feedback: (11)

We had an Hummingbird with an 85 making that sort of noise and it turned out to be a broken blade on the turbine compressor wheel

camss69

My Feedback: (46)

There’s a guy at my club that had one making that noise as well. He switched from diesel to Kero and it mysteriously went away. There’s at least one more I’m aware of that also makes that noise. Both different brands of turbines and both have made it since new, and both different size engines.

I would like to know the actual cause as well.

scoeroo

My Feedback: (9)

Possible combustion harmonic at part throttle ..... hence disappears at higher throttle

Dave Wilshere

What tailpipe on turbine to tailpipe tube gap?

acw

My Feedback: (1)

Good question. It is about 26mm. Looks like the turbine is a little far... Moving the turbine closer to pipe would require some work. Do you have experience indicating this could be the issue?

Dave Wilshere

This fully ducted.? If so 26mm is about right.

acw

My Feedback: (1)

Yeah, it is a full bypass. There is a 25x8mm hole on top of the turbine which is covered with aluminum tape. I start to wonder it this could be vibrating...

Dave Wilshere

Try flying it with the bypass top off for one flight.
It won’t be your hole/tape.