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From: Robert R Pastusek <rpastusek@htii.com>
To: Lancair Mailing List <lml@lancaironline.net>
Subject: RE: [LML] Vibration
Thread-Topic: [LML] Vibration
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Date: Mon, 25 Nov 2013 22:50:10 +0000
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Dan,
A -550 "thumper" in a Legacy will generate vibration...that and noise are w=
hat you spend all the gas money for... Now, a little Rotax might not win at=
 Reno, but you'd likely have less vibration... :-)

But seriously, the engine is a source of vibration, no matter how good the =
balance. At certain frequencies, it can resonate with other airframe compon=
ents to be truly annoying, even dangerous. Check your flight control hinges=
, attachments and any other moveable parts of the airframe for security and=
 free play. Ditto for the flight control linkage. Any of these can be "exci=
ted" by the big thumper engine you have up front.... Get rid of any "free p=
lay" whatsoever in these components.

Bob

-----Original Message-----
From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Dan =
Ballin
Sent: Monday, November 25, 2013 8:09 AM
To: lml@lancaironline.net
Subject: [LML] Vibration

I am trying to figure out the source of a vibration in a fixed gear Legacy =
with an IO-550.  The plane had a recent condition inspection and raced at R=
eno- vibration present before Reno but maybe worse now.
It is RPM related with the worst being about 24-2500 RPM better at 26 to 27=
00 RPM.  Somewhat speed related - worse with higher speed, but mostly it is=
 RPM that determines the severity.  The prop has been balanced dynamically =
and I actually hooked it up to another instrument just to see if the equipm=
ent was OK.

We have looked for anything rubbing or loose including engine mounts and is=
olators, baffling.  All EGT and CHT's are fine and close together - haven't=
 done an in flight mag check, but will soon.
Compressions are fine on all cylinders.  All the wheel pants and struts loo=
k good and nothing was seen vibrating on close inspection in the air.

So one question is can the vibration be engine related if the prop balance =
is good or does that pretty much rule it out.

Any thoughts or suggestions would be appreciated.

Dan Ballin

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