AIRWORTHINESS DIRECTIVE

For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (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 R44 Series Helicopters

AD/R44/19 Main Rotor Clutch Drive Shafts 1/2004

DM

Applicability: R44 helicopters that have had the main rotor part number (P/N) C166 clutch drive shaft disconnected from the P/N C907 yoke since assembly by the Robinson Helicopter Company, regardless of the reason for disconnecting the C166 clutch shaft.

Requirement: Requirement 1:

Disassemble the main rotor C907 yoke to C166 clutch shaft joint and:

1. Inspect the C907 yoke to C166 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 C907 yokes and C166 shafts exhibiting evidence of major fretting in any hole, before further flight.

b.         Inspect the C907 yoke to C166 clutch shaft joint assembly bolts for evidence of fretting. Remove from service any C907 yoke to C166 clutch shaft joint assembly bolt exhibiting evidence of fretting, before further flight.

c.         Inspect the C166 clutch shaft for evidence of cracking in the area of the yoke to shaft joint bolt holes. Remove from service C166 clutch shafts exhibiting evidence of cracking, before further flight.

d.         Inspect the C907 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 C907 yoke to C166 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.

Note: The Robinson Helicopter Company does not approve the use of a jointing compound such as Mastinox or Duralac during the assembly of the clutch drive shaft.

Robinson R44 Series Helicopters

AD/R44/19 (continued)

Requirement 2:

1. In accordance with a magnetic particle inspection (MPI) procedure approved either by the Robinson Helicopter Company or a Civil Aviation Regulation (1988) CAR 2A(4) delegate; carry out a MPI of C907 yokes removed from service in accordance with Requirement 1 of this directive.

b.         In accordance with a MPI procedure approved by the Robinson Helicopter Company or a CAR (1988) 2A(4) delegate; carry out a MPI of C166 clutch shafts removed from service in accordance with Requirement 1 of this directive.

Compliance: 1. Unless previously accomplished; within 10 hours time in service from the effective date of this directive.

2. Before installation in a helicopter.

This Airworthiness Directive becomes effective on 3 December 2003.

Background: Airworthiness Directive AD/R22/51 was issued 12 November 2003 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.

This directive has been issued to address R44 helicopter clutch shafts that may have been installed using maintenance practices similar to those that contributed to a fatal R22 accident.

Neville Probert

Delegate of the Civil Aviation Safety Authority 28 November 2003

The above AD is notified in the Commonwealth of Australia Gazette on 3 December 2003.