AD/B737/238 Amdt 1 Digital Transient Suppression Units (Cth)

AIRWORTHINESS DIRECTIVE

On the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/B737/238 and issues the following 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 737 Series Aeroplanes

AD/B737/238 Amdt 1 Digital Transient Suppression Units 7/2005

Applicability:	Model 737-300, -400 and -500 series aeroplanes, modified in accordance with United States Federal Aviation Administration (FAA) Supplemental Type Certificate (STC) ST00127BO.
Requirement:	1.    If not previously accomplished in accordance with the original issue of this Directive, modify the safe side harness connectors at the fuel tank penetrations and the digital transient suppression devices, in accordance with the Accomplishment Instructions of Goodrich Fuel & Utility Systems Service Bulletin 737-300766-28-2, Revision 2, dated 28 July 2004.
2.    Safe side harness, part number 50367-01XX may not be installed on any aeroplane as a replacement spare or part of a new installation, unless that safe side harness has been modified in accordance with SB 737-300766-28-2, Revision 2.
Note:  FAA AD 2005-05-17 Amdt 39-14006 correction refers.
Compliance:	For Requirement 1 - Within 12 months after the effective date of this Directive.
For Requirement 2 - As of the effective date of this Amendment.
This Amendment becomes effective on 7 July 2005.
Background:	The FAA has received a report of the results of fuel system reviews conducted by the STC holder which identified deficiencies in the system.  These deficiencies could allow unsafe levels of current or energy to enter the fuel tank, due to electrical short faults or threat conditions associated with the safe side harness assembly, which could result in a fire or explosion of the fuel tank.
The original issue of this Directive required installation of bonding straps to the safe side harnesses of the digital transient suppression device of the fuel quantity indicating system to correct the identified deficiencies.

This Amendment continues the requirements of the original issue and introduces a restriction on new or replacement installations of safe side harnesses unless they have been modified.

The original issue of this Directive became effective on12 May 2005.

James Coyne
Delegate of the Civil Aviation Safety Authority

19 May 2005