Gordon,
Just for giggles, clean and re-lubricate the throttle cables and insure
that there is no binding in the system, check the return springs, that
they are plenty strong, then re-balance the carbs at the exact rpm the
vibration is occurring. Also, be very sure that no exhaust gas is
making it's way up to the carb bowl area. This should rule out a leaky
exhaust system (causing vapor lock) and any carb balance issue. The
very design of the throttle cable system causes the carbs to go slightly
in and out of sync, as the throttle in manipulated, due to the cables
changing length, slightly, in relation to each other. Nothing to lose
but time and everything to gain...
Jeff - Baby Blue
600+ hours
On 7/31/2011 1:13 PM, GBWFH2010 wrote:
> --> Europa-List message posted by: "GBWFH2010"<gcgrant@supanet.com>
>
> Aircaft: Europa Tri Gear
> Engine: Rotax 912 UL
> Propeller: Airmaster 322
>
>
> Help! I would welcome any advice or suggestions regarding a problem which is
afflicting my aircraft. It has developed a strange vibration/resonance which
occurs
after establishing the cruise. For example, after a normal take off and
climb I set the prop to Cruise, reduce the MFP to 26 which gives approx. 100Kts
at an indicated 5200 RPM. Everything appears normal at this stage. If I increase
the cruise setting to 27, or greater, everything remains smooth, but reducing
back to 26 re-introduces the vibration (which is noticeable unless the throttle
is reduced almost to idle), which although it does not shake the aircraft
to pieces, is most noticeable. The vibration remains through reduced throttle
settings and can only be cleared temporarily by adjusting prop pitch to use
a higher RPM and power settings.
>
> Initially I was convinced it was a propeller issue, but detailed checks have
so far failed to highlight any problem. Airmaster are convinced it is not their
propeller at fault but gave me several thing to check, all of which I have done.
Europa suggested the prop carbon brushes and tracking should be cleaned which
I have done. For a while I thought this might have cleared the fault, but
it returned after 55 mins of flight. Interestingly At the same time as I had
cleaned the tracking I had removed the whole exhaust system for inspection. I
could not find anything wrong, no holes, or loose pipes so I refitted it and
lock
wired everything.
>
> I have inspected the carburettors, replaced the rubber mountings and balanced
the system and everything appears to be normal.
>
> I have to admit I am at a loss to know what to check next. It may be related
to something that was removed and refitted during the exhaust inspection, but
I cannot find anything obvious and I do not understand why the problem is not
apparent as soon as cruise power is applied.
>
> I would welcome any thoughts on this matter as it is driving me mad!
>
> --------
> Gordon Grant
>
> G-BWFH
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=348173#348173
>
>
> -----
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>
>
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