|
Justin,
Appreciate your thread on Control Surface and
Flutter. I flew 235/320 Lancair N320J for about 900 hrs and in that time I
experienced a couple of "flutter events" .. One, at about 400 hrs started
with a "buzz" when reflexing the flaps when establishing cruise speed and
configuration at 6 to 10 thousand feet range and 185 kts indicated. I
could make it come and go depending upon moving the flap
position to the fully relexed position of about 5/8" up,
reflex. Replaced the outboard left elevator hinge which had
some 1/16" play (about).. Buzz went away at all speeds etc. Our
thoughts at the time, and old A&I and me, was that there was inter
reaction between the air flow past the flap and that particular side
of the horiz stabilizer/elevator had set it up, at that specific set of
conditions,since the flaps were tight. I have no more data to
describe,other than that the elevator hinge replacement fixed the
problem.
The second occurred at about 750 Hrs
airframe. N320J had a vertical strake starting just behind the wing
TE and ending at 7" vertical at the larger tail. It had a foam
core with 2 bids of light cloth over a Sterling Polyurethane paint
job. The 18 year old paint job showed a vertical crack
on either side of, only the strake, located below the LE of the horiz
stabilizer. After sanding off the cracked paint area, there was no apparent
damage to the strake itself. Did a 2 bid light cloth across the area
a foot or so either side and repainted. The forces that cracked
the quite brittle paint appeared tobe a sideways deflection of the
entire tail section. Russ Connel suggested that installing a bulkhead at
this point would help. This all occurred just below the smallest
cross-section of the fuselage. Might be something other builders might
want to consider, especially with the larger tail. She was a great
machine and a delight to fly.. Regards
|