Foka 4 glider AAIB report out now [Archive]

mary meagher

12th May 2011, 19:08

Impossible to tell if the bolt holding the wing in place was secure....and in this sad case, it wasn't. How very careful we must be when rigging a glider to be sure it is safe. Glider pilots as a routine perform the task of attaching the wings to the fuselage before flying, and connecting the controls.

oversteer

12th May 2011, 22:52

Tragic, and how awful for her friends who witnessed it.

So to check my understanding, the wings were not quite properly aligned during rigging (wingtips not quite at the right angle) so when the vertically-aligned pin / bolt 'expanded' downwards, the visible top part expanded correctly, but the bottom part pushed against one spar or only expanded through one hole? So presumably this held securely under positive G, even during the first flight, but I assume there was little stopping the wings moving upward under negative G which must have occured on the second lauch.

This particular arrangement of an invisible pin section with reliance on 'touch' and wings held at the precise angle seems a very error-prone process, especially to those not familiar with the potential foibles. A sensible approach by the other Foka owner mentioned who has added an inspection hatch to check the bottom pin.

You get used to being able to ask others on gliding sites if you are not confident about something, maybe others at Bicester weren't aware what could happen with this particular type, assumed the 'owner' would know, or weren't asked.

I am glad most mainstream kit (70s on?) uses pins which are very visible, and generally only fit securely in one way, with no tooling required. e.g. the Discus, the wings slot in, a single pin pushes in, tailplane pushes on, and the glider is essentially flyable. But of course, more modern, and so quite expensive.