REFLECTOR: Flying front vibration

[Herb Sanders]

Rene', You indicated your XL is running 3 deg nose high at cruise. If you
can duplicate that pitch angle in the hanger by shimming the nose up, take
the spinner off and check the engine angle with an electronic level - you
may need to take the safety wire off and use a straight edge to space the
level up and get an accurate reading of the crush plate in the vertical
plane. The center line of the engine should be running level at cruise so
the load on the blades will be symmetrical as they rotate.  If the engine is
pitched the same as the centerline of the airplane, and the fus is running
3deg nose high, the engine would be running 3 deg tail low, and the load on
the blades would be asymmetrical.

The yaw of the engine needs to be zero. 

Herb Sanders

 

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Rene Dugas
Sent: Monday, September 27, 2004 6:37 PM
To: reflector at tvbf.org
Subject: REFLECTOR: Flying front vibration

 

Dear folks,

XLRG if flying faster than 170 kts a slight vibration is felt in my feet
near the canard bulkhead.  It gets worse up to 200 kts. but only slightly.
No vibration in the stick and none visible in canard or elevators.  Gear
doors are up and tight.  I tightened them and checked on jacks yesterday.
No slack in elevators or hinges detectable.  Canard bolts are tight and no
motion detectable with lifting plane's nose by canard.  Rear gear doors are
closed and flush and snug.  Doors are not vibrating.  No vibration in rudder
pedals or visible in winglets or wings.

At above 160 knots indicated my trailing edge of the elevator is about 1/8th
inch up for level flight.  Have others encountered this.  I feel it is
canard turbulence as the air goes over the canard and hits the upward
deflected elevator there is a resonance or harmonic that is disconcerting
but not particularly unpleasant.  Others do not notice.  The plane with prop
balanced is amazingly smooth in operation except at cruise over 170 kts. I
am considering a slight change in canard incidence.  My angle of attack
indicator states at cruise I am at 3 degrees up.  The vibration is sort of
like when both windows are down on a pickup  at 60 mph.  a slight pop or
"whop" can be felt.  I closed the vent to no avail.  This is a vibration not
a sound.

Ideas?

250 hrs

Rene'

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