REFLECTOR: Front Vibration revisited

[Rene Dugas]

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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