What was found
AIR BRAKE FAILURE DUE TO A DEFECTIVE WELD IN A CLEVIS WHICH IS COMPRISED OF A BOLT WELDED INTO A U SHAPED PIECE OF METAL. THE WELD FAILED CAUSING THE BOLT TO PUSH THROUGH THE U SHAPED METAL. THIS CAUSED THE OUTBOARD END OF THE AIR-BRAKE TO RAISE UP ABOVE THE WING SURFACE EVEN THOUGH THE OVER CENTER LOCKING LEVER IN THE COCKPIT WAS IN THE LOCKED POSITION. A POSITIVE CONTROL CHECK AND VISUAL INSPECTION OF THE SAILPLANE AFTER ASSEMBLY REVEALED THE PROBLEM. ALL CONTROL SURFACES OF THIS SAILPLANE CONNECT AUTOMATICALLY WHEN THE WINGS AND HORIZONTAL STABILIZER ARE INSTALLED. A WELDING ENGINEER INSPECTED THE FAILED PART AND SAID INSUFFICIENT PPENETRATION CAUSED THE FAILURE.