AD/BAe 146/124 Three-Phase Circuit Breakers (Cth)

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 39.001(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 146/124 Three-Phase Circuit Breakers 8/2006

Applicability:	All BAe 146 series aeroplanes.
Requirement:	1.    If not previously accomplished, inspect and test all three-phase circuit breakers, terminal leads, wire looming and circuit breaker panels in accordance with Paragraph 2.C. of BAe Systems (Operations) Ltd Inspection Service Bulletin 24-141 Revision 0 dated 15 August 2005 or later revision approved by the European Aviation Safety Agency (EASA).
2.    Rectify any damage found and replace unserviceable units detected during the Requirement 1 inspection and test.
Inspections and tests completed in accordance with National Jet Systems Technical Service Instruction Number TSI-146-24-007 Issue 1 dated 9 December 2003 are considered acceptable for inspections and tests required by this Directive.
Note:  EASA AD 2006-0132 refers.
Compliance:	For Requirement 1 - Within 12 months after the effective date of this Directive.
For Requirement 2 - Before further flight after the Requirement 1 inspection and test.
This Airworthiness Directive becomes effective on 3 August 2006.
Background:	Investigation into the cause of overheating of three-phase circuit breakers, used at various locations throughout the aircraft (but predominantly in the under floor electrical bay and the flight deck), has identified a possible age related deterioration of the units.  Failure of a circuit breaker will result in the generation of smoke or flames, and prevent the electrical load from being isolated from its electrical supply.

This Directive requires the inspection of all three-phase circuit breakers and wiring for cracking, discoloration, corrosion, security or burning and, if necessary, the rectification of any damage found together with the replacement of any defective circuit breakers.

James Coyne
Delegate of the Civil Aviation Safety Authority

21 June 2006