AD/B747/176 Amdt 1 - Centre Wing Tank Front Spar Web (Cth)

COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES

Boeing 747 Series Aeroplanes

AIRWORTHINESS DIRECTIVE

For the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/B747/176 and issues the following AD under subregulation 39.1 (1) of CAR 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.

AD/B747/176 Amdt 1

Centre Wing Tank Front Spar Web 9/2000

Applicability: Model 747-200, -300, and -400 series aircraft, line numbers up to and including 744.

Requirement: Inspect in accordance with the technical requirements of FAA AD 2000-11-07 Amdt 39-11755.

Note: Boeing Alert Service Bulletins 747-57A2298 Revision 1, Revision 2, and Revision 3 refer.

Compliance: As specified in the Requirement document for the initial and repetitive inspection requirements, with a revised effective date of 7 September 2000.

This Amendment becomes effective on 7 September 2000.

Background: The FAA received reports of fatigue cracking of the front spar web of the centre wing tank. The actions specified by this Directive are intended to prevent the leakage of fuel into the forward cargo bay, as a result of the fatigue cracking, which could result in a potential fire hazard.

Amendment 1 is issued in response to a new FAA AD which requires that the existing inspection be accomplished at a reduced threshold, and adds a requirement that the existing High Frequency Eddy Current inspection be accomplished on repaired areas. This action was prompted by reports of cracking in repaired areas of the front spar web and cracking of the front spar web on an aircraft that had accumulated fewer flight cycles than the currently required inspection threshold.