COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Boeing 737 Series Aeroplanes AD/B737/62 Amdt 1 Main Fuel Tank Float Switch Electrical Harness 2/94 Applicability: All model 737 series aeroplanes identified in Boeing Service Letters 737-SL-28-36 and 737-SL-28-42 dated 30 November 1990 and 15 December 1992 respectively. Requirement: 1. For aircraft identified in Service Letter 737-SL-28-36 inspect the wing main tank float switch electrical conduit for fuel leaks and condensation build up in accordance with the Service Letter 737-SL-28-36. If evidence of fuel leakage or water condensation is found then, before the next flight, purge and install a new vapour seal assembly in accordance with the Service Letter. 2. For aircraft identified in Service Letter 737-SL-28-42 inspect the wing main tank float switch electrical conduit for fuel leaks and condensation build up in accordance with the Service Letter 737-SL-28-36. If evidence of fuel leakage or water condensation is found then, before the next flight, purge and install a new vapour seal assembly in accordance with Service Letter 737-SL-28-36. 3. Fill the interior of the wing main tank float switch electrical conduits with grease in accordance with either: 1. Boeing Service Letter 737-SL-28-42 dated 15 December 1992, b. Boeing Service Letter 737-SL-28-42A dated 15 July 1993; or c. Ansett Airlines Engineering Release B73-28-10-6B. Note: FAA AD 93-17-02 Amdt 39-8672 refers. Compliance: 1 - The Compliance was originally prior to 7 February 1992, and thereafter at intervals not exceeding 1500 hours time in service. This amendment is effective from 3 February 1994 and thereafter at intervals not exceeding 1500 hours time in service. 2 - Prior to 1 April 1994 and thereafter at intervals not exceeding 1500 hours time in service. 3 - Prior to 1 January 1997. This Requirement is considered terminating action for the repetitive 1500 hour inspections. Background: Several incidents of wing main tank float switch electrical conduit failure have been reported. This condition, if not corrected, could result in a fuel leak from the wing main tank which could propagate down the wing leading edge cavity to the respective engine tail pipe, and cause an external fire under the wing. This amendment introduces initial and repetitive inspections for additional aeroplanes and provides terminating action for the repetitive inspections. COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES