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Date: Sunday, March 10, 2002 10:36 AM
It was the end of a perfect flight. I had just flown our recently restored
301 Libelle for the first time. Everything worked just fine, No writeups.
Down to Rumsey Gap, over to St. Johns and then a leisurely glide back to
Williams, played in a thermal over the town for ten minutes and logged four
hours.
Touched down at 40 and let her rollout. At about 10 knots the left wing started
to drop, so I pulled on some wheel break, BAM, I'm skidding on the belly.
What happened? The gear collapsed, but why? Something to do with the wheel
brake, but what does that have to do with the landing gear?
Got her into the shop and found some very interesting things:
- The little *post* on the forward gear leg, that prevents
the wheel brake from rotating, was missing. It must have broken off. This
Post serves an essential function, it prevents the brake shoes from rotating
with the brake drum whenever the beaks are applied.
- When I applied the brakes, the little post broke off and allowed the
break shoes to rotate. They spun around about 270 degrees and stopped when
the brake cable came taunt, which also applied full brakes because of the
pulling action of the restraining brake cable.
- The force now being applied to the landing gear is in a
forward direction and it's pulling hard because the brakes are locked. Originally
the braking force was in a downward direction through the *post* and into
the forward gear leg which is oriented in a downward direction. After the
brake spun, the force was then being applied in a forward direction as it
pulled on the brake cable that was now wrapped around the axle.
- The forward force (push) of the brake started to move the
landing gear *over-center* mechanism forward (open) and once it had moved
about an inch, the full weight of the glider helped to collapse the over-center
mechanism. BAM, the gear collapsed.
I'm sure the little *post* was cracked before my landing (a smooth landing
was verified by Noelle). It is almost impossible to inspect for cracks
without removing the wheel, but I have learned this little *post* serves
a vital function.
JJ Sinclair,
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About the Author:
JJ Sinclair retired from the Air Force in 1974 after 22 years of service.
He flew as crew member on:
- B-29 (left gunner)
- KC-97 (boom operator)
- B-52 (navigator & radar navigator)
- RF-4C (navigator)
- F-111F (navigator).
After retiring, JJ established an FAA Certified Glider Repair Station in
Placerville, California, and operated that facility for over 20 years. He
has flown 1000K zig-zag in his LS-7 as well as a 1000K triangle in his Nimbus-3,
but takes more pride in having flown Silver, Gold and Diamond Badge Flights
in the wooden Duster that he constructed in 1973.
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