COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Robinson R22 Series Helicopters AD/R22/44 V Belt Upper Sheave 9/96 Applicability: All R22 helicopters fitted with P/N A170-1 or -2 Revision I or J sheaves. These sheaves were originally installed on R22 helicopters S/N 1441 through 2096 and on overhauled R22s completed from May 1990 through May 1992. Requirement: Unless previously carried out action in accordance with Robinson Service Bulletin SB-77. Note: FAA AD 96-09-29 Amdt 39-9605 refers. Compliance: Within 100 hours time in service from 15 August 1996 or by 20 November 1996, whichever occurs first. Background: The manufacturer has advised that cracked sheaves have been reported and, if not detected in time, failure of a cracked sheave could lead to a catastrophic failure of the drive system.