AD/B737/335 Fuselage Upper Skin Panel Chemically Milled Steps (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/B737/335 Fuselage Upper Skin Panel
Chemically Milled Steps 8/2008

Applicability:	Model 737-600, -700, -700C, -800, and -900 series aircraft; as identified in Boeing Special Attention Service Bulletin 737-53-1232, dated 2 April 2007, or later FAA approved revision.
Requirement:	Action in accordance with the technical requirements of FAA AD 2008-12-04 Amdt 39-15547.
Compliance:	As specified in the Requirement document, with a revised effective date of 31 July 2008.
This Airworthiness Directive becomes effective on 31 July 2008.
Background:	FAA AD 2008-12-04 resulted from a fatigue test that revealed numerous cracks in the fuselage upper skin panel at the chemically milled step above the lap joint.  This Directive requires inspections at the chemically milled step at stringers 4 and 10, between STA 360 and STA 887, to detect fatigue-related cracks.  Such cracking, unless detected and corrected, could result in skin failure and consequent decompression of the aircraft.

David Villiers
Delegate of the Civil Aviation Safety Authority

20 June 2008