John,
During a descent especially the prop to gearbox/engine combination causes a
vibration
when the prop windmilling force and drive force are nearly equal.
If the slop in the gearbox due to a worn slipper clutch or just the gear lash
becomes
too much you get vibration and noise all the time. On taxi even.
To test: If all is smooth at cruise and takeoff when the prop is pulling,
simply
hold your speed constant and reduce power (throttle) until the vibration starts.
On the Airmaster AC200, go to MANUAL and move the prop to a course setting.
If it stops the vibration, as the prop begins to pull, it is just normal
gear box lash.
In a descent, my Airmaster/914 will vibrate and I either pull more power off to
force the windmilling prop to compression brake, or change the pitch to a course
setting to allow the prop to pull.
Common areas to feel this: High speed descent with small power reduction or in
the pattern at 4000 RPM / 17 inches turning base leg. Either ceases with power
lever movement to get the prop to fully brake, or pull.
Regards,
Bud Yerly
Sent from my iPad
> On Jul 13, 2015, at 7:06 PM, Robert Borger <rlborger@mac.com> wrote:
>
>
> John,
>
> I agree with Dave Watts. First place Id look is the gearbox. Have a good
> Rotax
tech go through the various checks in the maintenance manual. I bet you need
new Bellville springs. Hopefully, nothing further needs replacing.
>
> Blue skies & tailwinds,
> Bob Borger
> Europa XS Tri, Rotax 914, Airmaster C/S Prop (75 hrs).
> Little Toot Sport Biplane, Lycoming Thunderbolt AEIO-320 EXP
> 3705 Lynchburg Dr.
> Corinth, TX 76208-5331
> Cel: 817-992-1117
> rlborger@mac.com
>
> On Jul 13, 2015, at 3:29 PM, JohnFrance <77alembert@gmail.com> wrote:
>
>
> Hi All,
> during a recent flight I experienced (propeller!) vibration at the start of
> the
descent when I reduced power. This was after about two hours in cruise flight.
The frequency was quite high and I could feel a tingling sensation in the
feet in contact with the rudder pedals which makes me think the vibration is
coming
---From the propeller/engine combination.
> Upon landing I made a close inspection of the propeller and everything seemed
normal except for some flies and bugs. After cleaning, during the next flight
I experienced the same problem. The vibration is at its worst at 4800 rpm and
reduces slightly at 5000 but it is still noticeable.
> Before I start taking everything to pieces does anyone have an idea what could
cause this sudden change?
> Regards,
> John
>
> --------
> Europa mono Nr 192
>
>
>
>
>
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