pdf GFA AD 623 Issue 2 Popular

FAILURE OF PUSHROD END BEARING IN ELEVATOR CIRCUIT

A failure occurred in the elevator control circuit of a SZD-50-3 Puchacz which resulted in total loss of elevator control from the front cockpit. Fortunately the aircraft was being flown dual and the rear pilot landed the glider safely. Had the failure occurred during solo flight or with an inexperienced person in the rear the outcome could have been serious indeed. On inspection it was found that the rear rod end bearing of the elevator pushrod which connects the front and rear control columns had broken at the point where the threaded portion enters the locknut. The pushrod was therefore completely detached from the rear stick. Continuing investigations indicate that the end bearing which failed was mechanically damaged well prior to the failure, and although not yet positively established, it is believed that the end bearing was bent by a person treading on the push rod or end bearing while entering or exiting the rear cockpit; not by loads imposed during flight. Accordingly, Issue 2 of this AD removes the requirement to disassemble all pushrod ends which have a keyway cut into the threaded portion (Item 3 of Action A, Issue  1).