In Denmark we had a serious incident regarding an Arcus.

The left wing airbrake bell crank ruptured as a consequence of inadequate weld quality. The strength of the welds was insufficient to withstand airbrake bell crank operational loads. The bell crank broke as the glider was in 600ft and had a speed of 108t. The left airbrake extended, The pilot made a brilliant recovery extending the right airbrake and landed the glider 32 seconds later.

You find the full report http://www.hcl.dk/index.php?option=c...order=&lang=da

-Peter