AD/B737/238 Digital Transient Suppression Units (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 737 Series Aeroplanes

AD/B737/238 Digital Transient Suppression Units 5/2005

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:

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.

Note:  FAA AD 2005-05-17 Amdt 39-14006 refers.

Compliance:

Within 12 months after the effective date of this Directive.

This Airworthiness Directive becomes effective on 12 May 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.

This Directive requires 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.

James Coyne
Delegate of the Civil Aviation Safety Authority

31 March 2005