COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
Robin Aviation Series Aeroplanes
AD/ROBIN/21
Amdt 1
Stabilator Spar and Attachment Brackets 8/95
Applicability: All Models R2000 series.
Requirement: 1. Visually inspect, with the aid of strong lighting, the forward face of the rear fuselage bulkhead, which supports the stabilator hinge brackets. Look for cracks and corrosion. Pay particular attention to the area outboard of the stabilator hinge bracket bolt holes and around the stabilator balance weight cutout.
2. Remove the stabilator from the aircraft, in accordance with the Avions Pierre Robin R 2000 Service Manual Para 4.4.1, then:
remove the stabilator hinge brackets from the stabilator spar.
Inspect around the bolt holes and nut plate rivets in the stabilator spar using the fluorescent dye penetrant method as per CAO 108.10; and,
remove the stabilator hinge brackets from the rear fuselage bulkhead. Inspect the forward and aft faces of the bulkhead, outboard of the hinge bracket bolt holes and around the balance weight cutout, using the fluorescent dye penetrant method as per CAO 108.10.
Compliance: 1. Inspect in accordance with Requirement 1 before 1000 hours time in service or before further flight after 22 February 1995, whichever occurs later. Re-inspect at intervals not to exceed 100 hours.
2. Inspect in accordance with Requirement 2 before 2000 hours time in service or before 25 hours time in service after 22 February 1995,whichever occurs later. Re- inspect at intervals not to exceed 750 hours.
This amendment is effective 20 July 1995.
Background: During a precautionary inspection, not required by the maintenance schedule, a number of cracks were found in the rear fuselage bulkhead. Removal of the stabilator to facilitate repair revealed widespread cracking of the bulkhead and cracking of the stabilator spar near the hinge bracket bolts. The structural integrity of the stabilator attachment is critical to flight safety.
This amendment includes repeat inspections of the stabilator spar. Laboratory examination of the cracked stabilator spar has indicated that the condition of the rear fuselage bulkhead cannot be used to gauge the condition of the stabilator spar. The fatigue cracks in the stabilator spar started from fretting damage due to free movement of the stabilator hinge fittings and the balance weight attachment fitting.