AD/DHC-8/20 - Microwave Landing System Wiring (Cth)

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-8/20 Microwave Landing System Wiring 8/92

Applicability: All DHC-8 series aircraft listed in Boeing Canada, de Havilland Division, Service Bulletin 8-34-60 Revision C dated 1 November 1991, having Microwave Landing System (MLS) or MLS provisions installed.

Requirement: Inspect the vertical deviation wiring interconnecting the MLS and the Ground Proximity Warning System and if necessary, rectify the wiring in accordance with the Boeing Canada, de Havilland Div, Service Bulletin 8-34-60 Revision C dated 1 November 1991.

Note: Transport Canada AD CF-89-18R1 dated 11 May 1992 refers.

Compliance: Prior to further operation of the Microwave Landing System or by 30 June 1993, whichever occurs first.

Note 1: Previous accomplishment of the inspection and rectification in accordance with the original issue of SB 8-34-60 (12 August 1988) does not satisfy the requirements of this Directive.

Note 2: The applicability of paragraphs III.c and III.d of the accomplishment instructions of SB 8-34-60 Revision A (21 September 1990) and Revision B (30 November 1990) differ from the applicability of the same paragraphs in SB 8-34-60 Revision C (1 November 1991). Because the applicability of these paragraphs was revised in Revision C of the Service Bulletin, operators of aircraft that had SB 8-34- 60 Revision A or B incorporated must verify that all applicable inspections and rectifications as required in SB 8-34-60 Revision C have been accomplished.

Background: The issue of this Directive was prompted by advice from the manufacturer that some aircraft prior to serial number 179, with provisions for MLS, were incorrectly wired.