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Noticeable vibration at 200+ hours 912iS Sport

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2 months 2 weeks ago #17399 by Roger Lee
Roger Lee replied the topic: Noticeable vibration at 200+ hours 912iS Sport
Hi Jim,
I kind of depends on how bad the vibration was and if you have ruled out all the factors on the plane that can cause vibration.
Common causes;
Tire out of balance
elevator loose
prop blades not at the same pitch
prop out of track
loose wheel pants
prop needs dynamic balance
gearbox needs reshimming

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell

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2 months 2 weeks ago #17400 by richard Boslaugh
richard Boslaugh replied the topic: Noticeable vibration at 200+ hours 912iS Sport
Check the magnetic plug often. Metal above the Rotax limit is BAD. The you get to do the Rotax " flush the oil system procedure" including new oil cooler.

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2 months 2 weeks ago - 2 months 2 weeks ago #17403 by Jim Flock
Jim Flock replied the topic: Noticeable vibration at 200+ hours 912iS Sport
Not too bad of a vibration, but it was noticeable. I'm only 20 hours past a fresh annual, but I will double check all of the above tomorrow. Thanks for the input.
Last Edit: 2 months 2 weeks ago by Jim Flock.

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2 months 2 weeks ago #17405 by Roger Lee
Roger Lee replied the topic: Noticeable vibration at 200+ hours 912iS Sport
I'm not accusing anybody, but a mechanic could have overlooked something. Now you need to do a good diagnostic check for vibration causes.

I just had a 912iS engine plane show up for my class. It was the first flight since the annual. The tail pipe fell off, the hot exhaust melted the coolant bottle and damaged the fire wall.
Then I did a walk around and found 8 other things the annual mechanic didn't do that were glaring enough I saw them on just a walk around.

I'm never going to understand why some mechanics refuse to use a checklist for the engine and fuselage. Saying I didn't know where to get a manual, service bulletins or know what to do on a Rotax just means you probably shouldn't have touched it.
1-2 Rotax classes can be gold for information and prevent mechanic induced damage.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell

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2 months 2 weeks ago - 2 months 2 weeks ago #17430 by Peter Collins
Peter Collins replied the topic: Noticeable vibration at 200+ hours 912iS Sport
My plane has vibration while descending in the approximate rev range 4000-4800. This has been present for about a year, maybe more. First ran the engine April 2014, now at 430 hours. Oil analysis and mag plug are clean. I pretty much ignore it and or close the throttle further. Not present with the engine under load.
Just my two cents.
Last Edit: 2 months 2 weeks ago by Peter Collins. Reason: typo

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2 months 2 weeks ago #17432 by Genival Pacheco
Genival Pacheco replied the topic: Noticeable vibration at 200+ hours 912iS Sport
Roger wrote

"Hi Jim,
I kind of depends on how bad the vibration was and if you have ruled out all the factors on the plane that can cause vibration.
Common causes;
Tire out of balance
elevator loose
prop blades not at the same pitch
prop out of track
loose wheel pants
prop needs dynamic balance
gearbox needs reshimming "


I´m not an expert but should consider including the verification of the rubber lords of the engine mount too.
They are always submitted to stress, even when the plane is not flying (most of the time) due to the gravity forces the upper rear and the bottom front ones are squeezed, the opposite occurs when flying.
This plus the aging effects cause their deformation and lose of flexibility that can cause vibrations normally absorbed by them to be transferred to the plane structure. So, the age of the plane is more important than number of hours flied.

I would like to know Roger´s experience on that.

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2 months 2 weeks ago - 3 weeks 4 days ago #17436 by Jim Flock
Jim Flock replied the topic: Noticeable vibration at 200+ hours 912iS Sport
Checked all of the above recommendations and everything appears to be OK. Went flying and the vibration was no longer present.:S
Last Edit: 3 weeks 4 days ago by Jim Flock.

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2 months 2 weeks ago #17437 by Roger Lee
Roger Lee replied the topic: Noticeable vibration at 200+ hours 912iS Sport
Hi Genival,

Rubber engine mounts are a 5 year rubber replacement item. They can go bad like you said just due to time, but also if excessive heat gets to them or chemicals like oil, fuel. solvents and just the weight of the engine over time. Some get harder, but some get softer to. I'm doing a rubber replacement on a Flight Design CTSW today and the rubber engine mounts get replaced.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell
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2 months 2 weeks ago #17438 by Genival Pacheco
Genival Pacheco replied the topic: Noticeable vibration at 200+ hours 912iS Sport
Thanks Roger,

It seems to me that the rubbers doesn´t last 5 years in good conditions depending on the installation and exposition to heat and chemicals like you said. They visually appear OK but, in fact, they lose their efficiency causing the transference of vibrations to the plane structure.
My experience is that after 2 to 3 years they start to significantly lose their anti-vibration capabilities.

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1 month 4 weeks ago - 1 month 4 weeks ago #17572 by james porter
james porter replied the topic: Noticeable vibration at 200+ hours 912iS Sport
The examination of the gearbox indicated several areas of wear. As a result virtually everything inside the housing was replaced.
Since re-installation, I have flown about 2.5 hours at various airspeeds and power settings. So far I haven't experienced the vibration.
Last Edit: 1 month 4 weeks ago by james porter.

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4 weeks 18 hours ago #17830 by Roger Rowe
Roger Rowe replied the topic: Noticeable vibration at 200+ hours 912iS Sport
Gentlemen: I am one of the many with a Rotax 912IS engine who has to get my gearbox rebuild every 100 hours because of excessive noise and vibration. After rebuild the noise and vibration is gone, but it doesn't last long. I know many with ULS engines who never have issues with a gearbox, but everyone has issues with a 912IS.. There is something wrong with the 912IS gearboxes which Rotax has not been able to solve.

I attended a seminar at EAA-Oshkosh this summer taught by one of the Rotax experts. Among many topics discussed was the 912IS gearbox. He said they have been very unreliable and Rotax is quite aware of the issue and has been trying to improve the situation. He said the new 2017 gearboxes for the 912IS are a definite improvement. Of course, we all have 2014, 2015 and 2016 gearboxes, which are being rebuild every 100 hours or so, so it doesn't help up. Replacing parts in a poor design does not help a bit. Just gets us another 100 hours.

I would like to hear from ROTAX on this issue. My question is can I purchase a brand new gearbox of 2017 design, which would solve the problem? Of course, another $5000 down the drain, but I would pay almost anything to get this issue solved. I would need to know above what serial number would improve the situation. One cannot just purchase a new gearbox because there is no way of knowing when the manufacture data for the components might have been. Does ANYONE have insight on this issue?

We owners do not need to hear anymore about how it is our fault and it is because there are other problems with our airplane. This is a Rotax issue and can only be solved by Rotax. I am not asking for warranty or for any freebies. I am more than willing to spend the big bucks to get this problem solved before it kills me. It is just so difficult to get reliable and knowledgable information on the subject.

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4 weeks 5 hours ago #17831 by richard Boslaugh
richard Boslaugh replied the topic: Noticeable vibration at 200+ hours 912iS Sport
I wish I could get 100 hrs on a gearbox. I am averaging under 60 hrs. per overhaul .Engine is at 245 hrs. I wonder how the 195iS is going to treat gearboxes? Perhaps we could change to that gearbox?

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4 weeks 56 minutes ago #17834 by james porter
james porter replied the topic: Noticeable vibration at 200+ hours 912iS Sport
I can't find any evidence that the gearbox has been redesigned and currently installed on 2017 delivered engines.
The engine manuals haven't changed recently and the Illustrated Parts Manual only had a change to the starter in 2017.
It seems to me that unless the parts were completely interchangeable there would have to be a change in part number or design. If the parts were interchangeable, then how would the vibration be resolved?
I understand that the 915 iS gearbox is definitely a different design with a torque tube final drive.
I'm not trying to be argumentative, I just don't understand how there could be a design change without an amendment to the manuals.
Like you, I have heard that Rotax is in the process of doing a redesign of the gearbox for the 912 iS.

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3 weeks 6 days ago - 3 weeks 6 days ago #17838 by Roger Lee
Roger Lee replied the topic: Noticeable vibration at 200+ hours 912iS Sport
Hi James,
I believe there is a fix being tested right now.
My guess is as soon as it is good to go everyone should get helped.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell
Last Edit: 3 weeks 6 days ago by Roger Lee.

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3 weeks 5 days ago #17846 by Rodrigo Echenique
Rodrigo Echenique replied the topic: Noticeable vibration at 200+ hours 912iS Sport
I hate the Rotax gearbox with 100 hrs inspections, mine is also vibrating a lot and I have done everything, my engine have only 166 hrs, this gearbox is a garbage for the price Rotax charge for his engines!
I even think to change my gearbox with clutch to the one without, all my friends fly their Rotaxs without any problem and the two that have the clutch gearbox we have a lot of problems and vibration.

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3 weeks 4 days ago #17849 by Roger Lee
Roger Lee replied the topic: Noticeable vibration at 200+ hours 912iS Sport
Hi Rodrigo,
Is this a 912UL , 912ULS or a 912 iS engine?
The 912 UL and ULS should not have any issues. The 912iS has had a little trouble with the gearbox, but it is being rectified. Part of the difference is the UL and ULS have a 30 degree dog hub set and the 912iS has a zero dog gear setup.The 912iS needs more oil on top of the gear setup in the box and they are working on it.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell

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3 weeks 4 days ago #17851 by René Caissy
René Caissy replied the topic: Noticeable vibration at 200+ hours 912iS Sport
Hello Roger,

Someone wrote that only 20 % of 912 iS owner have this issues. Do you know how it is possible ? Gearbox on iS are not all the same ?!

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3 weeks 4 days ago - 3 weeks 3 days ago #17853 by Jim Flock
Jim Flock replied the topic: Noticeable vibration at 200+ hours 912iS Sport

René Caissy wrote: Someone wrote that only 20 % of 912 iS owner have this issues. Do you know how it is possible ? Gearbox on iS are not all the same ?!


I have the same question. I just rolled past 350 hours (2016 engine) with no apparent issues with my gearbox. I am now hyper sensitive to any vibrations. Hope they figure out a solution soon.
Last Edit: 3 weeks 3 days ago by Jim Flock.
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3 weeks 4 days ago #17854 by René Caissy
René Caissy replied the topic: Noticeable vibration at 200+ hours 912iS Sport
Jim, i understand that "no apparent issues" is a kind of problem for you :-)

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3 weeks 3 days ago #17866 by richard Boslaugh
richard Boslaugh replied the topic: Noticeable vibration at 200+ hours 912iS Sport
Historically engineering aircraft engine gearboxes has been a huge challenge. As the engine manufactures were producing more and more powerful engines for the second world war they introduced more gear boxes because the massive increases in HP were achieved in part by running engines at higher RPM. Thus gearboxes to keep props in proper RPM. From that time gearboxes became the stone around the necks of design engineers. The gearboxes required frequent replacement for the same reasons they do today. There are now engines used on general aviation a/c that some owners keep a spare gearbox on hand to avoid extended down time. Rotax has a problem with the iS gearbox .I feel confident that Rotax is addressing the problem and will provide a solution. I purchased my 912iS before the modification to Sport. At about 40 hrs engine time Rotax came out with the sport upgrade which increased the torque a significant amount. I installed the sport mod and then started having vibration issues. I often wonder if I had kept the engine original if there would have been vibration problems. Bottom line for me is have faith in Rotax that the issue will be resolved. Keep in mind that even the gearbox used on the carb version 912, require an inspection at specific hours depending on the use of Mogas vs low lead fuel.

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