Vibration on 912ULS
in General Tech Discussion
9 years ago
Greetings to all, I am new to this forum but not new to Rotax engines. I had an RV12 and now fly a Highlander with a 912ULS. The engine has 320 hours of what I would describe as extreme duty, averaging 4-5 off-airport landings (and full power cycles) per hour.
I have a vibration issue that started some time ago and has been getting worse. The vibration is not ordinarily present on ground run ups but begins after flying for about 5 minutes (after engine is fully warmed up?) It is very noticeable between 3000 and 5400 rpm and is worse is I yaw the plane back and forth. If I pull power and go below 3000rpm, the vibration stops, even if I maintain airspeed. At around 5400rpm, I can turn the vibration off and on by changing rpm. IOW, at 5390, vibration, at 5420, no vibration.
Gearbox situation: I sent the gearbox out and it was re-shimmed and they adjusted the clutch. No change in vibration issue.
Propeller situation: I have a three blade warp drive that I have used since first flight, it has been checked for consistent pitch and dynamically balanced. I recently installed a Prince propeller, had it dynamically balanced, and have exactly the same vibration problem as with the warp drive.
Engine Maintenance: I do 50 hour oil and filter changes and follow the current Rotax maintenance manual inspection checklist very carefully. At around 100 hours I found a small metal chip on the magnetic plug, nothing but the normal amount of dust since then. Carbs were balanced and checked for float buoyancy at the annual C.I., April, 2015. There are no mods to the engine, I use nothing but the recommended spark plugs, oil, filters.
I push the engine pretty hard but take good care of it. Any ideas would be appreciated.
Thanks, Gary
Big Bear Lake, CA
I have a vibration issue that started some time ago and has been getting worse. The vibration is not ordinarily present on ground run ups but begins after flying for about 5 minutes (after engine is fully warmed up?) It is very noticeable between 3000 and 5400 rpm and is worse is I yaw the plane back and forth. If I pull power and go below 3000rpm, the vibration stops, even if I maintain airspeed. At around 5400rpm, I can turn the vibration off and on by changing rpm. IOW, at 5390, vibration, at 5420, no vibration.
Gearbox situation: I sent the gearbox out and it was re-shimmed and they adjusted the clutch. No change in vibration issue.
Propeller situation: I have a three blade warp drive that I have used since first flight, it has been checked for consistent pitch and dynamically balanced. I recently installed a Prince propeller, had it dynamically balanced, and have exactly the same vibration problem as with the warp drive.
Engine Maintenance: I do 50 hour oil and filter changes and follow the current Rotax maintenance manual inspection checklist very carefully. At around 100 hours I found a small metal chip on the magnetic plug, nothing but the normal amount of dust since then. Carbs were balanced and checked for float buoyancy at the annual C.I., April, 2015. There are no mods to the engine, I use nothing but the recommended spark plugs, oil, filters.
I push the engine pretty hard but take good care of it. Any ideas would be appreciated.
Thanks, Gary
Big Bear Lake, CA
