COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Boeing 737 Series Aeroplanes AD/B737/46 Engine Fire/Overheat Detection System 10/90 Applicability: All model 737-300 and 737-400 series aircraft fitted with Kidde engine fire and overheat detection systems as listed in Boeing SB 737-26-1055 Revision 1. Requirement: Modify the engine fire and overheat detection system in accordance with Boeing SB 737-26-1055 Revision 1. Note: FAA AD 90-15-14 also refers. Compliance: Prior to 4 April 1992. Background: Boeing have advised that multiple reports have been received from operators describing short circuits in the engine fire detection system which have resulted in false fire warnings. The problem has been attributed to contamination in the electrical connectors at the detector sensor unit. Action in accordance with this AD is necessary to reduce false fire warnings which may result in unnecessary engine shut down which could unduly jeopardise continued safe flight of the aircraft.