pdf Gfa ad 648 issue 1 Popular

FLIGHT CONTROLS - FAILURE OF ELEVATOR BELLCRANK BEARING ATTACHMENT BOLT

In a DG-500 Elan Trainer the bolt in the bearing mount 5RU61, which is the pivot for elevator bellcrank 5Stl9,  failed for as yet unconfirmed reasons.   This led to loss of control of the aircraft which subsequently crashed & was  destroyed by impact forces. Fortunately, the occupants were able to escape by parachute.   The failure occurred in the shank of the bolt within the glassfibre matrix & thus would not have been detectable during routine inspections or maintenance. Although the reason for the failure of the bolt has not yet been confirmed it is believed to be fatigue resulting  from insufficient assembly torque of the retaining nut which could result in the shank of the bolt undergoing excessive cyclic bending loads. The LBA has issued AD 2007-219, the BASA has issued AD 2007-0176-E  &  Glaser Dirks has  issued Technical Notes  348/19  and 843/26 (same document). The TN and Work Instructions 1 & 2 form part of this Airworthiness Directive.  Work instruction No 3 for installation of an optional support bracket has yet to be issued.