Frozen spoilers

Probably the strangest incident of this kind happened in the sixties to
the well-known pioneer of alpine flight, Jochen von Kalckreuth. See his
book: Das stille Abenteuer (The silent adventure - I don't now if it
has ever been translated to English)

He was cloud-flying over northern Italy in an M-100 (Italian wooden
standard glider) when his turn and slip indicator malfunctioned. He
lost control of the ship, the speed built up, he pulled the airbrake
lever, but the speed kept building up, and the centrifugal forces did
the same. Suddenly there was an awful noise, and a powerful
deceleration that sent everything that was not secured crashing against
the instrument panel. The speed diminished, and Kalckreuth exited the
cloud. All the controls were still functioning normally, except the
airbrakes which refused to retract.

Kalckreuth landed on a nearby aerodrome. The local glider pilots
surrounded him and asked what kind of glider he was flying. He
answered: "Well, an M-100, don't you recognize it?" "Well, they said,
just look at your wings, they don't look like M-100 wings, you know!"
Indeed, the wings now had a 20° dihedral! The steel connection
fittings, proofed to 12 tons, had been bent that much without the
wooden wing disintegrating!

In fact, what had happened? When Kalckreuth pulled the airbrake lever,
the airbrakes didn't move because they were frozen shut, a push-pull
tube somewhere in the control system was bent and remained under
tension, like a spring. When the ice broke away from the wing under the
excessive load it was undergoing (probably in spiral dive), the
airbrakes shot open during overspeed, with the aforementioned effect.


--
stephanevdv
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