COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Boeing 747 Series Aeroplanes AD/B747/166 Replacement of Hydraulic Fuses 2/97 Applicability: Model 747-100, -200, -300 and SP series aeroplanes, as identified in Boeing Service Letter 747-SL-32-19, dated January 16, 1980, certificated in any category. Requirement: Waterman hydraulic fuse assemblies part number (P/N) G905-120 are to be replaced with PneuDraulics Hydraulic Fuse Assembly P/N 6105 in accordance with Boeing Service Letter 747-SL-32-19 dated January 16, 1980. Note: FAA AD 96-22-11 refers. Compliance: Requirements above are to be completed within 24 months of the effective date of this Directive. This Airworthiness Directive becomes effective on 30 January 1997. Background: The FAA has received reports of failure of Waterman hydraulic fuses which lead to hydraulic system failures. The fuses failed due to corrosion of the magnesium pistons in the fuses which then failed to close when required. Replacement of the fuses prevents this failure mode and the resultant possibility of reduced controllability of the aircraft through hydraulic system loss.