AD/B747/383 APU Power Feeder Wire Bundle (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.

Boeing 747 Series Aeroplanes

AD/B747/383 APU Power Feeder Wire Bundle 11/2008

Applicability:	Model 747-400 and 747-400D series aeroplanes, certificated in any category; as identified in Boeing Special Attention Service Bulletin (SASB) 747-24-2257, Revision 1, dated 2 August 2007.
Requirement:	1.    Carry out a general visual inspection of the power feeder wire bundle of the auxiliary power unit (APU) where it crosses the hydraulic system number 4 return tube to determine if parts are installed to provide separation between the wire bundle and hydraulic tube, in accordance with SASB 747-24-2257, Revision 1.
2.    Carry out all the related investigative and corrective actions as specified in the Accomplishment Instructions of SASB 747-24-2257, Revision 1.
Note 1:  Actions accomplished before the effective date of this Directive in accordance with SASB 747-24-2257 dated 18 May 2006, are acceptable for compliance with the corresponding requirements of this Directive.
Later revisions of the SASB 747-24-2257, approved by the United States Federal Aviation Administration (FAA) as an Alternate Method of Compliance (AMOC) to FAA AD 2008-14-14, are considered acceptable for compliance with the equivalent Requirements of this Directive.
Note 2:  FAA AD 2008-14-14 Amdt 39-15609 refers.
Compliance:	For Requirement 1 - Before 21 August 2010.
For Requirement 2 - Before further flight after the Requirement 1 inspection.
This Airworthiness Directive becomes effective on 23 October 2008.

Background: The FAA has advised of receiving a report that the power feeder wire bundle of the APU was found touching the hydraulic system return tube during inspection of an aeroplane.  This directive is issued to prevent insufficient clearance between the wire bundle and hydraulic tube that could lead to chafing of the wire bundle.  This chafing could cause arcing and a consequent hydraulic fluid fire in an area outside of the smoke detection and fire extinguishing zone; this condition could result in an uncontrolled fire on the aeroplane.

Charles Lenarcic
Delegate of the Civil Aviation Safety Authority

9 September 2008