AD/B737/284 Wire Bundle Chafing (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/B737/284 Wire Bundle Chafing 4/2006

Applicability:	Model 737-100, -200, -200C, -300, -400 and -500 series aeroplanes.
Requirement:	1.    Carry out detailed inspections in accordance with the Accomplishment Instructions of Boeing Service Bulletin (SB) 737-28-1208, Revision 1, dated 25 August 2005 to detect discrepancies as follows:
a.     Chafing of the wire bundles located below the passenger compartment, above the centre fuel tank, aft of station 540 to approximately station 663.75, right buttock line (RBL) and left buttock line (LBL) 24.50.
b.    Damage to the fuel vapour barrier area located below the wire bundles, as applicable
Note 1:  For the purposes of this Directive, a detailed inspection is: "An intensive examination of a specific item, installation, or assembly to detect damage, failure, or irregularity.  Available lighting is normally supplemented with a direct source of good lighting at an intensity deemed appropriate.  Inspection aids such as mirror, magnifying lenses, etc., may be necessary.  Surface cleaning and elaborate procedures may be required."
2.    Rectify any discrepancies, detected during the Requirement 1 inspections, in accordance with SB 737-28-1208, Revision 1.
3.    Adjust and replace, as applicable, the wire bundle clamps located aft of station 540 and install a protective sleeve on the upper bundle of the bundle run at station 616, RBL and LBL 24.50; by accomplishing all of the applicable actions specified in the Accomplishment Instructions of Boeing SB 737-28-1208, Revision 1.
Later revisions of the above SB, approved by the United States Federal Aviation Administration (FAA) as an Alternate Method of Compliance (AMOC) to FAA AD 2006-03-12, are considered acceptable for compliance with the equivalent Requirements of this Directive.
Note 2:  FAA AD 2006-03-12 Amdt 39-14476 refers.
Compliance:	For Requirement 1 - Within 60 months after the effective date of this Directive.

For Requirements 2 and 3 - Before further flight after the Requirement 1 inspections.
This Airworthiness Directive becomes effective on 13 April 2006.
Background:	This Directive requires an inspection for chafing of certain wire bundles located above the centre fuel tank, corrective actions if necessary, and replacement of wire bundle clamps with new clamps.  The Directive also requires an inspection for damage to the fuel vapour barrier area located below the wire bundles and, if necessary, corrective action.  The Directive results from fuel system reviews conducted by the manufacturer.
Actions required by the Directive prevent chafed wire bundles near the centre fuel tank, which could cause electrical arcing through the tank wall and ignition of fuel vapour in the fuel tank, and result in a fuel tank explosion.

James Coyne
Delegate of the Civil Aviation Safety Authority

3 March 2006