REFLECTOR: Front Vibration revisited

[Scott Derrick]

Possibles:

Do you have the nose oil cooler?

Do you have a speed brake?

My nose gear would bob a bit when it was in the up position, I put a hard
foam block on the fusalage that it retracts onto and now it is firm when
retracted.

Maybe somthing flapping in the engine compartment?  baffling, look for
marks..

Scott

> Folks,
>
> Five weeks ago I began chasing a vibration in my XL that only occurs
> over 160 knots.  Some helpful suggestions have been received and pursued
> to no avail.  I spoke with the factory today and they don’t know what it
> could be but suggested I keep looking.  This symptom is a shimmy that
> starts at over 160 kts and gets slightly worse all the way to 200 knots.
> It is not uncomfortable but VERY annoying.  It does not change with pull
> ups or ½ g unweighting or turns.  Prop speed or engine RPMs eo not
> affect the shimmy.  No vibration can be felt in the stick ( I have 230
> hrs of experience in this plane and this is new.)  No visible shake is
> noted in the canard winglets or wings.  Slight pressure on the rudders
> does not change it and no vibration is transmitted to my feet.  No
> increase vibration is felt in the torque tubes to the elevators or in
> the canard with my feet or hands.  Back seat passengers can feel the
> vibration.
>
> I have
>
> Removed the wings and confirmed incidence and tight bolts.
>
> Removed the canard and confirmed bulkhead is ok and bolts are tight.
>
> Elevator matched and balanced and hinges snug.
>
> Elevators adjusted up 1/8th inch and then down 3/8th inch no changes.
>
> Front gear doors tightened –Very snug.
>
> Main gear doors adjusted x five no change
>
> Main Gear doors removed no change
>
> Doors confirmed snug and vibration the same as entire plane
>
> Cowl removed and realigned x five
>
> Left wing incidence increased 0.2 degrees no change
>
> Discussed canard vortex hitting wing – Why a change and factory states a
> non problem.
>
> No glass cracks found.  Fuselage and wings and canard all very solid.
>
> No fuel leaks.
>
> Spinner tight rotates very centered.
>
> Prop balanced.
>
> Windows not loose.
>
> Heated Pitot tube snug no slack.
>
> Door handles not moving.
>
>             Same problem solo or with slightly over gross wt.
>
> Only external scoop is ram air to engine just behind the firewall  very
> stable.  Unable to move on the ----ground at all.
>
> Not expecting cures but ideas?
>
>
>
> Rene’ Dugas
>
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