COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Eurocopter AS 355 (Twin Ecureuil) Series Helicopters AD/AS 355/10 Amdt 4 Main Rotor Mast 5/88 Applicability: All models with main rotor masts P/N 350A37.1076.04, .05 or .06. Requirement: 1. (a) Perform the visual check and if necessary, the dye penetrant/inspection called for in Aerospatiale SB 05-08 Rev 2 para's C(1) and C(2). (b) Protect any reworked surfaces in accordance with Aerospatiale SB 05-08 Rev 2 para C(3). 2. Aerospatiale SB 05-08 Rev 2. Note 1: Magnetic particle inspection may be carried out in lieu of dye penetrant and is the preferred technique. Note 2: Bureau Veritas AD 85-94-25(b) and Bureau Veritas AD 83-174-20(b) refer. Compliance: 1. Within 10 hours time in service after 30 November 1985, unless already accomplished. 2. As detailed in the Requirement Document - Aerospatiale SB 05-08 Rev 2 para D. Background: A fatigue crack initiated from an undetected corrosion pit on an overseas operated helicopter, and propagated to a critical size in 170 hours time in service. This AD has been amended in accordance with the requirement of Bureau Veritas AD 85-94-25(B) which requires a one time 10 hour inspection of the main rotor shaft. The requirements of Bureau Veritas AD 85-94-25(B) supplement those of Bureau Veritas AD 83-174-20(b), which were noted in the previous issue of this AD. This Amendment incorporates Revision 2 of the Service Bulletin.