REFLECTOR: Front Vibration

Rene Dugas dugasd at bellsouth.net
Thu Sep 30 17:44:24 CDT 2004


Thanks again for the thoughts.

I will try to address each suggestion with my facts:

Bumping each control in fact marked control surface changes were
performed at over 200 knots with parachute.  No Flutter.

Gear doors are VERY tight.

Fuselage seals are good but never sealed.  Tried changes to overhead and
side vents - no change.

This vibration is not a buzz.

I have entered a constant airspeed descent at anything over 175 knots
and the vibration is there.  Engine speed and prop speed do not affect
it.  Heater flapper - no change with changes in position.  Front oil
cooler tight.  Oil cooler aluminum lines seem snug and I am unable to
move them.

Taped front air scoop closed with foam in NACA for front air cooler -
still there.  (Oil temps 195)

No vibration in the stick at any time.  Changes in elevator or trim
changes do not affect it.  Example:  If I  pull out of my descent at
over 175 knots the vibration continues in a (approx 2 g) pull up.

 

Landing light cover is sealed and tight.

Gear extension speed is 120 knots.  Jacked plane up to be sure rear (and
front) doors are tight and unable to vibrate - ok.  Very flush in
retraction.  Front gear is not touching gear guides on retraction on
jacks and not touching gear doors.  Pump is not running.  Pump bolts are
tight to bulkhead.  Battery is tight.  Pitch servo is tight to top of
canard.  Servo linkage seems snug.  Slight slop in trim spring to trim
servo BUT no vibration in stick in flight.

Will slip shoes off and place them on torque tubes next flight to feel
for vibration in tubes.

Rear passengers do not feel vibration.  Vibration decreases with copilot
(increased canard loading?)  No slack in canard bolts top or through
bulkhead found. 

 

I have raced motorcycles, boats and cars for over 30 years and notice
vibrations.  When a car has a front end shimmy from a bulge on a tire,
warped rotor or a bent wheel the steering wheel will vibrate.  If you
then drove this car at about a hundred mph that would be the feeling.
My stick does not vibrate.  The floor of the plane under the rudders and
up on the bulkhead has a transmitted high speed vibration non audible.
It is worse slightly as speed increases.  Bulkhead structure is intact.

 

All your points are well taken and will be pursued.  I may have to live
with it.  Four corporate pilots have flown with me and none have noticed
it. The Velocity with a balanced Prop and Lycoming 6 cyl is sooooo much
smoother than a 4 banger most are amazed.   They usually ask about wing
loading.

 

Thanks again for each of the evaluations and as always appreciate others
views and ideas.  Still looking.

Best to all.

Rene'

N129RD XL RG 250+ hrs.

 

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