COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Sikorsky S-76 Series Helicopters AD/S-76/31 Amdt 1 Upper Fuselage Station 215 Bulkhead 9/85 Applicability: All models not incorporating structural modification kits in accordance with Sikorsky Customer Service Notice No. 76-150 or a manufacturer-installed equivalent, which have achieved more than 1000 hours time in service. Requirement: Inspect in accordance with Sikorsky Alert Service Bulletin 76-53-18 (155) Modify in accordance with either: 1. Sikorsky Alert Service Bulletin 76-53-26 (166), Sikorsky Customer Service Notice No. 76-151 or 2. Sikorsky Customer Service Notice No 76-150. Note: Modification in accordance with CSN 76-150 constitutes terminating action for this AD. Compliance: Inspect at intervals not exceeding 50 hours time in service, until modified in accordance with this Directive. Modify within the next 500 hours time in service after 30 September 1985. After modification, inspect at intervals not exceeding 100 hours time in service, unless terminating action has been accomplished in accordance with Sikorsky CSN No. 76-150. Background: Cracks have occurred in Station 215 bulkhead installation, upper fuselage section, left side. Production modifications and two types of retro-fit kits are now available. One of these, a simple skin doubler reinforcement, minimises the potential of a crack developing but still requires repetitive inspections. The other, a more extensive reinforcement of the upper left fuselage longeron, constitutes terminating action.