Rv12iS gearbox chatter

[rcarsey]

I have about 390 hours on the engine now.. Within the past month, I've noticed a vibration in certain situations. Initially, I believed it was on unbalanced front tire which was rotating in the wind.. But after rebalancing it (only 1/4oz off), I am faced with a more expensive problem.

The vibration seems to happen when I throttle back, for instance, before I begin a descent. If I advance the throttle a bit again, the vibration seems to (immediately) go away. In stable air, at a fixed throttle setting, it does not seem to happen.

From what I've read, almost all gearboxes (especially with 100LL use) need servicing at the 600hr inspection. Ok, mine is a bit.. 30% earlier.

Assuming this is the actual problem, two questions:

1. Is the aircraft safe to operate? The vibrations aren't shaking the plane, but I can feel it in my feet. I don't want to continue operation if its going to cause damage to other parts . The last oil change 50 hours ago showed NO debris.

2. Is this a problem I want/can fix on my own? I don't mind spending some $ on specialized tools, especially if this will be happening again down the road. And if so, which gears/item #s will I want to buy before I start disassembling it (assuming I can still continue to fly it between now and the time I get parts).

[Bob Y]

Probably a good question for the Rotax Owner forum, if you’re a member. You could ask Lockwood, but they’ll likely suggest pulling the gearbox and sending it to them, but probably worth asking anyway.

[philcam]

Rob,

I assume your prop is balanced?

[Piper J3]

With 100LL.... perhaps check overload clutch per Rotax maintenance manual with fish-scale spring. Lead contamination is tough on the gearbox. Gears spin lead against walls of gear case and clutch plate friction surfaces get slippery.

I have early SN RV-12 and my 912ULS has >800TT operated on 93E10 with no gearbox problems. Some of the early gearboxes had improper heat-treat, but apparently I got a good one.

Also, I'm using Mobil1 Racing 4T Full Synthetic Motorcycle Oil 10W-40 exclusively....

[Taltruda]

Sounds like you use 100LL, isn’t the oil change interval more frequent than 50 hours? I thought it was like 25 with 100LL..

[henrysamson]

It used to be 25 hours but is now 50.

Henry

[Dvalcik]

Rob, I would call Lockwood and talk to them. I had mine done at 600 hours even though there were some signs of wear we went ahead and replaced the needed parts.

[funflying]

Great to see your post Dave. I haven’t noted any issues but am just over 600 hours and plan to send my gearbox for service. I’ve been told by a Rotax mechanic that following the maintenance schedule on my 912 it will operate great throughout the TBO period.
I wondered how some of the higher time RV12’s followed suggested maintenance schedules.

[RFSchaller]

Mine has 1280 hrs. Almost all on no lead auto gas. No gearbox issues. Mine is an ELSA, and I did not pull the gearbox for the 600 hour check. My reasoning was that this check primarily looks at the overload clutch breakaway torque on the dogs, and that is a prop strike protection. I go with plan A: no prop strikes. I do the breakaway torque check at annual that basically checks the spring pack force. It has always been in spec since first flight in 2012.

I always appreciate respectful comments that might challenge my position.

[mcems]

I have 1200 hours on mine also using all no lead gas. I did not do the 600 hour rebuild. I also check the specs at annual time Its always within the numbers in the manual.

Brad Stiefvater
Salem SD