AD/B747/128 Amdt 3 Lower Lobe Lap Joints at Wing to Body Fairing (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/B747/128 Amdt 2 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 747 Series Aeroplanes

AD/B747/128 Amdt 3 Lower Lobe Lap Joints at Wing to Body Fairing 11/2008 DM

Applicability:

Model 747-100, -100B, -100B SUD, -200B, -200C, -200F, -300, -400, 747SR, and 747SP series airplanes, certificated in any category, as identified in Boeing Alert Service Bulletin 747-53A2312, Revision 3, dated February 8, 2007 or later FAA approved revision.

Requirement:

Action in accordance with the technical requirements of FAA AD 2008-16-14 Amdt
39-15632.

Note:  Boeing Alert Service Bulletin (ASB) 747-53A2312 Revision 3 or later FAA approved revision refers.

Compliance:

As specified in the requirement document.

This Amendment becomes effective on 17 September 2008.

Background:

This Directive was prompted by reports of cracking in the stringer 34 lap joint near the interface with the wing-to-body fairing.  This condition, if not corrected, could result in an in-flight depressurisation of the aircraft.

Amendment 1 reduced the number of aircraft to be inspected and widened the inspection area to include all lap splice upper rows under the wing-to-body fairing.

Amendment 2 allowed use of ASB 747-53A2312 Revision 3 as an alternative method of compliance with the requirements of FAA AD 94-15-06.

Amendment 3 is issued to change the requirement document.  FAA AD 94-15-06 Amdt 39-8977 is superseded by FAA AD 2008-16-14 Amdt 39-15632.  This results in a change to the High Frequency Eddy Current inspection method due to possible faulty results when inspecting Alodine-coated rivets; adds an additional one time inspection for cracking; and terminates the adjusting factor for the inspection compliance times based on cabin differential pressure.

David Villiers
Delegate of the Civil Aviation Safety Authority

18 August 2008