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Re: Engine Vibration

PostPosted: Sat Sep 05, 2015 5:48 am
by Jack L
John,

Rotax specifically states to use a propeller with a Mass Moment Of Inertia (MMOI) that is below 5800 kgcmcu or premature gearbox failure will occur. Other causes to premature failure include low idle speeds, improper oil, exceeding oil change intervals and I am sure there are others.

The only propeller manufacturer that I know who posts MMOI is Sensenich, there could be others but I haven't seen it. I am now running a 74.8" Kiev and sent Kiev an email prior to installation requesting the MMOI, they responded with 4700 kgcmcu.

Search MMOI in this forum and you will find links to an EAA video and other information on the subject.

Re: Engine Vibration

PostPosted: Sat Sep 05, 2015 9:22 pm
by User GDS
My gearbox vibrations began after around 300 hours in service.

I have not performed the test myself, but I believe that the 72" warp drive propeller with tapered tips is below the MMOI standard. The unverified story is that the propeller is too heavy if it has squared tips, but just makes it under if it has tapered tips. I have always used Shell Sport plus 4 oil, Rotax oil filters and performed service at 50 hour intervals. I think where I'm different than the average Rotax user is in the number of power cycles I put it through. I am 10 minutes from the desert and I fly down there and do 5 to 10 take offs and landings per hour. It's kinda like having the plane in flight school duty.

Re: Engine Vibration

PostPosted: Mon Sep 07, 2015 8:24 pm
by Johnny C!
Thanks!

John


Jack L wrote:John,

Rotax specifically states to use a propeller with a Mass Moment Of Inertia (MMOI) that is below 5800 kgcmcu or premature gearbox failure will occur. Other causes to premature failure include low idle speeds, improper oil, exceeding oil change intervals and I am sure there are others.

The only propeller manufacturer that I know who posts MMOI is Sensenich, there could be others but I haven't seen it. I am now running a 74.8" Kiev and sent Kiev an email prior to installation requesting the MMOI, they responded with 4700 kgcmcu.

Search MMOI in this forum and you will find links to an EAA video and other information on the subject.