Daniel Vélez Bravo <<danielvelezbravo>>
writes:

Today during a free flight day on our Colombian Nationals (some
ugly clouds called the day but about 10 pilots took off to a soft and peaceful
flight) one of the Aeros pilots had an emergency when his left carbon crossbar
broke on mid air for no apparent reason.

Weather was not an issue, with smooth 8 km winds, some localized rain a few
kilometers away, but that did not represent any danger. Smooth air and slow and
consistent climbs of 1.5 - 2.5 m/s.

The pilot was flying with 75% vg at 65km/h on a straight line, when glider made
a hard sound, then started to spin left. Pilot was at 600 meters above the
ground. He tried to straighten the flight with no luck, even when glider looked
ok. He threw the chute successfully and went down in 75 seconds according to
tracklog. After fighting with the glider pointing down, he let the glider tumble
and fell slowly on his back, keel first on the ground.

Damage included a broken keel near the cables and bent downtube. Sail, battens,
leading edges were ok. Only one broken crossbar was visible as the cause of the
problem.

We have some local pilots (engineers) doing some analysis and some writing.

At the moment it looks like the crossbar had a lot of porosity showing perhaps a
lack of resin. Also there's some delaminating at the fracture, like if there
where two different layers that were working separately without cohesion in
between, lowering the total strength.

Pilot is ok. Fortunately he is also a skydiver with a lot of experience so he
didn't feel that bad.

Glider was almost new (June 2012) with less than 40 flights, only one downtube
bent on all it's lifespan. No whacks nor extremely hard landings.

The local Columbian pilots are trying to determine what would have
caused this problem and are looking for any assistance that Oz Reports can
provide.