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AD/ROBIN/21 Amdt 2 - Stabilator Spar and Attachment Brackets

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AIRWORTHINESS DIRECTIVE
On the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/ROBIN/21 Amdt 1 and issues the following AD under subregulation 39.001(1) of CASR 1998.  The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.
Robin Aviation Series Aeroplanes
AD/ROBIN/21 Amdt 2
Stabilator Spar and Attachment Brackets
2/2009
 
Applicability:
Model R2000 series aircraft.

Requirement:
1.    For all Models excluding aircraft with Major Mod 79 bulkhead reinforcement embodied:  Note:  Alpha Aviation models R2160, R2160i & R2120U are manufactured with this modification embodied.
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.    For all Models:
Remove the stabilator from the aircraft, in accordance with the Avions Pierre Robin R2000 Service Manual Para 4.4.1, then:
a)    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,
b)    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.  Reinspect at intervals not to exceed 750 hours.

 
This Amendment becomes effective on 12 February 2009.

 
 
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.
Amendment 1 included 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.
This amendment alleviates all R2000 aircraft with rear bulkhead strengthening modification (Major Mod 79) embodied, from the requirement for repetitive inspections to the forward face of the rear bulkhead structure.

David Punshon
Delegate of the Civil Aviation Safety Authority
11 December 2008