AIRWORTHINESS DIRECTIVE For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CASR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section. British Aerospace BAe 146 Series Aeroplanes AD/BAe 146/109 Thales Avionics Distance Bearing Indicator 5/2004 Applicability: Model Avro 146-RJ Series RJ70, RJ85 and RJ100 aeroplanes fitted with Thales Avionics Distance Bearing Indicator (DBI) part number (P/N) 63543-280-1 with the following serial numbers: 3084 3551 to 3554 3687 3955 to 3958 3171 3576 3697 to 3700 3986 to 3989 3442 3577 3717 to 3719 4017 to 4020 3443 3602 to 3605 3762 to 3765 4042 to 4045 3485 to 3488 3624 to 3627 3787 to 3790 4070 3504 3664 3830 to 3833 4071 3505 3665 3858 to 3861 4099 to 4104 3518 to 3521 3672 3901 4137 3528 to 3531 3673 3902 4138 3544 to 3547 3686 3912 to 3915 Requirement: Determine the part number and serial number of the DBI in accordance with BAE Systems (Operations) Service Bulletin SB 34-371-70671A dated 19 September 2003. If the DBI is found to be one of those identified in the above Applicability Statement, remove the DBI from the aeroplane and replace it with a modified Thales DBI P/N 63543-280-2 or a DBI P/N 63543-280-1, whose serial number is not listed in the Applicability Statement, in accordance with SB 34-371-70671A. Note: CAA(UK) AD G-2004-0006 refers. Compliance: Within four calendar months after the effective date of this Directive. This Airworthiness Directive becomes effective on 13 May 2004. British Aerospace BAe 146 Series Aeroplanes AD/BAe 146/109 (continued) Background: A manufacturing fault with the DBI PSU transformer could result in the propagation of the aircraft 115VAC input power supply through the instrument onto the DBI ARINC 429 Input/Output interfaces. An analysis of this failure concluded that at the aircraft level the failure effect could be loss of all aircraft primary navigation instruments. James Coyne Delegate of the Civil Aviation Safety Authority 1 April 2004 The above AD is notified in the Commonwealth of Australia Gazette on 21 April 2004.