Jim,
etal
I’m presuming that
you suspect that the nose gear shimmy might (perhaps) be induced by the
behavior of the main gear. I believe others have hypothesized this
before also.
I do know that the
gear legs on my high-wing C172 can/do rapidly oscillate for-aft much more than
one would normally imagine during landing/braking (sometimes as much as 4-6
inches, or more) and the gear legs are solidly mounted to the
fuselage.
A video of an ES main
gear (during breaking/shimmy) would be very interesting. Perhaps you
might be able to just try a small/portable usb PC/Laptop camera taped to the
ES step (and wired to a laptop in the cabin). They are pretty small and
relatively in-expensive. Duct tape and a long USB cable would probably
do the trick. Recording audio from inside the cabin and calling-out
deceleration speeds/events would help correlate the two. You could also
re-aim it and video the front pant from the step on subsequent
landings.
Has anyone with
relatively high ES hours/landings also closely checked the main gear
receptacles for signs of fatigue/fracture in the for/aft direction? It
seems/appears the design is very stiff/strong in that orientation and thus I
don’t suspect much would happen to it – except to transfer the energy to the
spar bulkheads and fuselage. Ideally most of it would get damped by the
composite fuselage – but perhaps not. If the energy/excitation were
resonant with the nose pant’s Fn it wouldn’t take much to get the nose
pant/wheel going. Then, if the front strut’s damping where degraded in
any way (heat, seals, etc), hold on.
FYI, I believe the
Columbia main
gear is quite different than an ES. The Columbia gear mounts to the
fuselage “behind” the wing, since the Columbia wing is one continuous piece
(tip-2-tip) and is mated to the fuselage from the bottom (versus two ES wing
halves mated into the sides). I have never seen a Columbia gear without the
leg fairings. I also don’t know if the Columbia brakes are the same/similar (I
assume so)?
Also note that the
factory ES (407L) has an earlier/preliminary gear leg design. It’s gear
sits much lower than all of ours. Tim, would know if it’s legs are made
from a metal bar/plate (versus tapered tubes) and/or all composite (like my
Corvette suspension springs).
Rick