Can a 912is be converted back to a 912 with proper carburretors & magneto's ?
Our 912is is becoming unreliable and difficult to maintain, it has now got to the
point where the downtime is affecting our operation.
More info please.
It would be "possible" but I suspect the change back would be for more work than finding a qualified 912IS mechanic or someone whom wants to learn the new technology. I am sure the problems can be solved with the right people working on it. Where are you ? what resources do you have around you ? what are you trying to do that is different.
I "live" at a little field about as far from ROTAX as possible (south Island New Zealand) it has taken time for the support infrastructure to get their head around the new tech, if you are having trouble find a modern race car guy they know ECU's and fuel injection management very well it is their daily bread, perhaps they can help you ?
It appears that 912iS goes through gearboxes whereas all the 912 don't suffer from this as much. We have had 3 gearboxes in 600 hrs. The symptoms are vibration which cracks Exhaust systems. There are approx. 17 Eurofox Glider Tugs on the UK Register only 5 of them including ours is a 912iS. Ours has the highest number of hours, there are Eleven 912 which don't seem to suffer the same gearbox problems.
There maybe some Operating techniques or Maintenance procedures that might help but Rotax are not giving us any help in this matter.
What engine are you referring to?
912 only designates an engine series. The 912 comes in the 912A, F, S, UL, ULS, and iS variations.
A 912UL is way different from a 912 ULS.
Gearbox issues usually point to excessive 'Moment of Enertia' in the Propeller. (Too Heavy of a Prop)
Excessive Moments of Enertia are hard on the gears and can damage the clutch quickly.
What Propellers are you using? Have they been Balanced?
I think it must be your specific installation.
we have about 7 912IS engines in my local area and so far no gearbox issues. I would also look at the Prop, inertia, balancing, and any places that are non standard that could setup a harmonic. That is things like rubber isolators of incorrect shore hardness etc.
Check that you have a battery as large as specified in the 912 IS installation manual, it is bigger than a ULS one low voltage on starting is hard on gearboxes and sprag clutches.
Malcolm, what fuel are you using? I am aware of a commercial user who has done 3 gearboxes - all on 100LL. There is a suggestion that the gear backlash settings on the 912 iS might be a little tight for regular Avgas use with lead buildup.
I don't think there is a general problem with gearboxes, otherwise it would be all over the internet.
1 month 6 days ago - 1 month 6 days ago#15329by richard Boslaugh
I have had my 912iS gear box rebuilt 3 times. Engine has 200hrs. total time. I have used 92 mogas all 200 hrs. I am inspecting oil filter every 25 hrs. as at the second rebuild enough metal was found to require the Rotax contaminated oil proceedure including new oil cooler. All rebuilds were rotax warranty.
Last Edit: 1 month 6 days ago by richard Boslaugh.
Hi Glen, Richard Boslaugh here. I am located in the US. The normal octane rating in the US is AKI. (average of RON and MON). So 90-94 AKI is equivalent to 95-99 RON. For those reading that have never heard of AKI it is the anti knock index of the particular blend. Also 92 Mogas has no ethanol added.
The following user(s) said Thank You: Glenn Martin
Malcolm, what propeller are you using? Is it the same as the other injected rotax users? I believe 'Ive heard I knowledgeable Rotax person suggest that unsuitable propellers are often to blame for gearbox problems. its not just a moment of inertia issue, it can also involve blade vibration at certain rpm's.