AD/B747/321 Body Station 2231 Frame Inner Chord (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 747 Series Aeroplanes

AD/B747/321 Body Station 2231 Frame Inner Chord 3/2005

Applicability:

Model 747-100, -200B, -200F, -200C, -100B, -300, 100B SUD, -400, -400D, -400F, and 747SR series aircraft; line numbers 1 through 1333.

Requirement:

Inspect in accordance with the technical requirements of FAA AD 2005-01-09 Amdt 39-13933.

Note:  Boeing Alert Service Bulletin 747-53A2494, or later FAA approved revision, refers.

Compliance:

As specified in the Requirement document, with a revised effective date of 17 March 2005.

This Airworthiness Directive becomes effective on 17 March 2005.

Background:

A report was received of cracked inner chords (forward and aft) at station 2231 and stringer 26L.  The door 5 lower main sill goes through a cutout in the station 2231 frame at stringer 26.  Investigation revealed that during production, the door lower main sill chord can rub the station 2231 frame.  Undetected discrepancies of the frame web and inner chords could result in cracking, subsequent severing of the frame, and consequent rapid depressurising of the aircraft.

David Punshon
Delegate of the Civil Aviation Safety Authority

4 February 2005