COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Eurocopter AS 350 (Ecureuil) Series Helicopters AD/ECUREUIL/23 Amdt 4 Main Rotor Mast 5/88 Applicability: All models with main rotor masts P/N 350A37.1076 .00 to .06 Requirement: 1. (a) Perform the visual check and if necessary, the dye penetrant check called for in Aerospatiale SB 05-13 Rev 3 para's C(1) and C(2). (b) Protect any reworked surfaces in accordance with Aerospatiale SB 05-13 Rev 3 para C(3). 2. Aerospatiale SB 05-13 Rev 3. Note 1: Magnetic particle inspection may be carried out in lieu of dye penetrant and is the preferred technique. Note 2: Bureau Veritas AD 85-95-40(B) and Bureau Veritas AD 83-173-36(c) 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 05-13 Rev 3 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 85-94-40(B) which required a one time 10 hour inspection of the main rotor shaft. The requirements of Bureau Veritas AD 85-95-40(B) supplement those of Bureau Veritas AD 83-173-36(c), which were noted in the previous issue of this AD. This Amendment incorporates Revision 3 of the S.B.