First Annual.

[rosslr]

G'day Doug,

good to hear from you. How come you are flying with Scotty - whats wrong with your plane?? Hope it is all good.

As for the gearbox - for me the vibration was the only symptom - nothing showing up in the filter or the magnetic plug - apart from black fine coating of sludgy type material - nothing I would consider excessive for the first 200hrs of the engine. The vibration was just a gradual thing and not excessive - but before I had it sent for inspection and subsequent repair I could notice it on climb, in cruise and when revs were reduced on decent.

I have had discussions with Airmaster who are doubtful of the the contribution of the 75" blades tot he problem but are happy to work with me to trial new blades. I have had the prop re balanced and it is really smooth now - I plan to see if it happens again and to look at the cases of others with this problem on the 912is sport - I understand that the gearbox is different to the one on the 912uls.

Anyway, good to hear from you Doug and still looking forward to you arriving down under!

cheers

ross

[Av8r3400]

I will second vibration as an indicator of gearbox issues.

My vibrations stemmed from carburetor trouble, but eventually damaged the gearbox. I believe compounded by the use of a heavy prop (Warp Drive) and lack of maintenance. A little bit of maintenance on the gearbox every couple hundred hours makes a lot of different.

[jiott]

What do you do every couple hundred hours? Do you take it off and open it up?

[Av8r3400]

Yes. The box comes off and the stack up of components on the output shaft are inspected for wear. You would look for things like the retainer clips or belview washers to be worn or damaged and the general condition of the gears and drive dog faces.

[neville]

Here is my opinion on the gearbox issue; (1) I bought and flew 80 hrs with the original 912iS. Then I installed the sport upgrade. In its original configuration the iS was low on torque so Rotax modified the air intake system which increased the torque above the 912 carb version. The iS is limited to 5500 RPM
continuous cruise. I expect that is because torque becomes too high at the higher RPM's. (2) I have never had vibration in a steady climb when the engine/gearbox/prop were in a steady load. But once the gearbox is worn enough and the system is in a normal cruise configuration moderate turbulence would induce the vibration. It could be stopped by raising the nose to load the system more or reducing the power +/- 500RPM. If the flights continue the wear will become severe in a few hrs. I did that once, made enough metal that I had to do the oil system flush procedure including
new oil cooler. The manual says the gear box must be inspected at 500 hrs.
With the increased torque of the sport upgrade I expect that time should be greatly reduced. Note: All work done has been in warranty.

[Floog]

I have no plane in the Portland, OR area! The weather was so bad I had to drive from central WA where I live. (A six hour drive through the Columbia River Gorge in a blizzard vs. a 1 1/2 hour flight.) My plane is fine, albeit still waiting on back ordered replacement carb floats. I always look forward to flying with Scott because his plane is identical to mine. Seems like we're ALL trying to control vibration, the ROTAX achilles heel. I've got (915) hours on the plane and have never had vibration that wasn't corrected by carb syncing or prop balance. Sounds like the 1000 hour gearbox maintenance is not something to ignore. Dogs, washers, shims are all normal wear items that if left unaddressed will only get worse over time. In my experience, the engine runs very smooth all the time except between about 3,000 - 4,000 RPM. So I just avoid/minimize operating in that range. I'm gonna do a slipper clutch test out of curiosity. A low number there would indicate dog wear I believe. I love the plane and the engine!