AD/B747/356 Trim Air Diffuser and Sidewall Riser Ducts (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/B747/356 Trim Air Diffuser and Sidewall Riser Ducts 6/2007

Applicability:

Model 747-100, -100B, -100B SUD, -200B, -200C, -200F, -300, -400, -400D, -400F, 747SR, and 747SP aircraft, line numbers 1 to 1316 inclusive.

Requirement:

Action in accordance with the technical requirements of FAA AD 2007-07-03 Amdt 39-15003.

Note:  Boeing Service Bulletin 747-21A2418 Revision 4, or later FAA approved revision, refers.

Compliance:

As specified in the Requirement document, with a revised effective date of
7 June 2007.

This Airworthiness Directive becomes effective on 7 June 2007.

Background:

The FAA received reports of sealant deteriorating on the outside of the centre wing fuel tank and analysis that sealant may deteriorate inside the tank due to excess heat from leaking trim air diffuser ducts or sidewall riser duct assemblies.  Undetected leakage of fuel or fuel vapours into areas where ignition sources may be present, could result in a fire or explosion.

David Villiers
Delegate of the Civil Aviation Safety Authority

24 April 2007