Ad/R22/51 Amdt 2 - Main Rotor Clutch Shaft (Cth)

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/R22/51 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.

Robinson R22 Series Helicopters

AD/R22/51 Amdt 2 Main Rotor Clutch Shaft 11/2005

Applicability:

All R22 helicopters.

Requirement:

Requirement 1:

Drive shaft and yoke assemblies that have not been disassembled since assembly at manufacture are excluded from Requirement 1.  If the time since new is unknown, the item cannot be regarded as a new item.

Disassemble the main rotor A907 yoke to A166 clutch shaft joint and:

a.    Inspect the A907 yoke to A166 clutch shaft joint for evidence of major fretting in the yoke to shaft joint bolt holes.  For the purpose of this directive, major fretting is defined as; any evidence of the machining marks in any of the bolt holes being partly or fully obliterated.  Remove from service A907 yokes and A166 shafts exhibiting evidence of major fretting in any hole, before further flight.

b.    Inspect the A907 yoke to A166 clutch shaft joint assembly bolts for evidence of fretting.  Remove from service any A907 yoke to A166 clutch shaft joint assembly bolt exhibiting evidence of fretting, before further flight.

c.    Inspect the A166 clutch shaft for evidence of cracking in the area of the yoke to shaft joint bolt holes.  Remove from service A166 clutch shafts exhibiting evidence of cracking, before further flight.

d.    Inspect the A907 yoke for evidence of paint in the area where the yoke to clutch shaft joint block plates contact the yoke.  Remove any evidence of paint in the area where the yoke to clutch shaft joint block plates contact the yoke, before further flight.

e.    Inspect the A907 yoke to A166 clutch shaft joint for evidence of a non Robinson Helicopter Company approved jointing compound in the mating surfaces.  Remove all evidence of an unapproved jointing compound in the mating surfaces, before further flight.

Requirement 2:

a. In accordance with a Robinson Helicopter Company or a Civil Aviation Regulation (1988) CAR 2A(4) approved magnetic particle inspection (MPI) procedure; carry out a MPI of A907 yokes, removed from service in accordance with Requirement 1.

b.     In accordance with a Robinson Helicopter Company or a CAR (1988) 2A(4) approved MPI procedure; carry out a MPI of A166 clutch shafts removed from service in accordance with Requirement 1.

Compliance:

Requirement 1:  Unless previously accomplished in accordance with the original issue of this directive, within 10 hours time in service from the effective date of this directive.

Requirement 2:

a.     Before installation in a helicopter when removed per Requirement 1.

b.     Before installation in a helicopter when removed per Requirement 1.

This Airworthiness Directive becomes effective on 27 October 2005.

Background:

This Airworthiness Directive has been issued in response to the preliminary findings of the investigation of a fatal R22 accident.  That investigation has disclosed evidence of fatigue in a fractured main rotor clutch drive shaft.  The failed shaft had been assembled with the yoke painted in the area of the yoke to shaft assembly bolts and a non-approved jointing compound was found in the area of the joint mating surfaces.  A combination of the two discrepancies probably resulted in a loss of assembly torque and movement of the joint in service.

Amendment 2 has been issued to remove implied repetitive NDI requirements for serviceable drive shaft and yoke assemblies.

Amendment 1 was issued in order to exclude newly manufactured helicopters from Requirement 1, and to remove NDI requirements for zero time since new drive shaft and yoke assemblies.

The original issue of this Airworthiness Directive became effective on 12 November 2003.

James Coyne
Delegate of the Civil Aviation Safety Authority

10 September 2005