COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Bombardier (Boeing Canada/De Havilland) DHC-8 Series Aeroplanes AD/DHC-8/27 Amdt 1 Passenger Service Units Printed Circuit Boards 2/94 Applicability: All DHC-8 aircraft serial number 3 to 369, which have accumulated more than 600 flight hours and which are fitted with Passenger Service Units (PSU) with the following part numbers: 10-1418-1 10-1081-1 10-1081-4 10-1081-7 10-1418-2 10-1081-2 10-1081-5 10-1081-8 10-1081-3 10-1081-6 Requirement: Action in accordance with Bombardier Regional Aircraft Division Alert Service Bulletin A8-33-30 Revision A dated 18 December 1992. Note: Transport Canada CF-93-01R1 dated 3 December 1993 refers. Compliance: The original compliance was prior to 1 May 1993, unless already accomplished in the 300 flight hours before 1 April 1993 and thereafter at intervals not to exceed 600 flight hours until Modification No 8/1950 is incorporated. The compliance for this amendment is: unless previously accomplished in accordance with the previous issue of this Directive, then prior to 3 March 1994 and thereafter at intervals not to exceed 600 hours time in service, until Modification No 8/1950 is incorporated in accordance with Bombardier Regional Aircraft Division Service Bulletin 8-33-34 dated 10 August 1993. Background: Signs of overheating of the PSU printed circuit boards (PCB) and power supply connectors have been reported by DHC-8 operators. An investigation has indicated that this overheat problem was caused by moisture ingress into the PSU connectors which led to corrosion of the PCB pins/connector interfaces. The corroded PCB and/or connectors, if not detected and corrected, may lead to an excessive overheat condition and a potential fire hazard. This amendment clarifies the aircraft serial number range, increases the number of affected PSUs and advises the Service Bulletin Number which provides terminating action.