COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Robinson R22 Series Helicopters AD/R22/37 Amdt 2 Forward Flexplate 9/98 DM Applicability: All R22 series helicopters fitted with flexplates P/N A193-1 or A947-1 Rev A thru D. Requirement: Replace all flexplates P/N A193-1 or A947-1 Rev A thru D with a flexplate P/N A947-1 E or F in accordance with Robinson R22 Service Bulletin SB75. Note: FAA Priority Letter AD 98-14-08 refers. Compliance: Unless previously accomplished, within 25 Hours TIS from issue of this directive or by 31 July 1998, whichever occurs first. This amendment becomes effective on 8 July 1998. Background: In 1993 the Australian CAA received advice that two flexplates located in the forward position of the tail rotor drive shaft had failed. In 1994 the NZ Airworthiness Authorities advised that a similar flexplate failure had recently occurred there. One flexplate had taken approximately 300 flights from the corrosion pit initiation until the final failure. The FAA and the manufacturer were advised with the FAA subsequently issuing AD 94-11-01. In May 1998 an aircraft crashed in NZ due to a flexplate failure. This aircraft had the pre A947-1 Revision E flexplate fitted. FAA has subsequently determined that repetitive inspections are insufficient to ensure airworthiness. This amendment provides closing action by requiring replacement of faulty flexplates. Amendment 1 to this airworthiness directive became effective on 14 December 1994. The original issue of this airworthiness directive became effective on 15 June 1994.