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Noticeable vibration at 200+ hours 912iS Sport

  • Roger Lee
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2 weeks 6 days 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 weeks 6 days 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 weeks 6 days ago - 2 weeks 6 days 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 weeks 6 days ago by Jim Flock.

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  • Roger Lee
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2 weeks 6 days 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 weeks 3 days ago - 2 weeks 3 days 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 weeks 3 days ago by Peter Collins. Reason: typo

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  • Genival Pacheco
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2 weeks 3 days 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 weeks 2 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.

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  • Roger Lee
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2 weeks 2 days 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
The following user(s) said Thank You: Genival Pacheco

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2 weeks 2 days 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 day 2 hours ago - 1 day 2 hours 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 day 2 hours ago by james porter.

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