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 39.1 (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. Boeing 737 Series Aeroplanes AD/B737/157 Oxygen Generators 7/2001 DM Applicability: Model 737 series aeroplanes, equipped with chemical oxygen generators, as listed in the following Boeing Special Attention Service Bulletins: B737-35-1076 dated 1 March 2001, and B737-35-1077 dated 1 March 2001. Requirement: 1. For airplanes having any chemical oxygen generator and/or passenger, attendant, or lavatory service unit assembly that contains a chemical oxygen generator that has been replaced, carry out a detailed visual inspection of the chemical oxygen generator of the applicable assembly to verify correct installation of the release pin in the generator firing mechanism in accordance with the Accomplishment Instructions of either Service Bulletin (SB) B737-35-1076 or B737-35-1077, as applicable. Note 1: For the purposes of this Directive, a detailed visual inspection is defined as: "An intensive visual examination of a specific structural area, system, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at intensity deemed appropriate by the inspector. Inspection aids such as mirror, magnifying lenses, etc., may be used. Surface cleaning and elaborate access procedures may be required." Note 2: The release pin and safety pin are located in the generator firing mechanism. The safety pin hole is the hole in the generator firing mechanism that is closest to the main body of the generator. The release pin hole is the hole in the generator firing mechanism located furthest from the main body of the generator. The centre axis of the release pin hole is perpendicular to the centre axis of the safety pin hole. Note 3: Inspections and corrective action carried out before the effective date of this Directive, per Boeing Telex M-7200-00-02474, dated 9, 13, 19, or 31October 2000; or Boeing Telex M-7200-00-03040, dated 18 December 2000; are considered acceptable for compliance with the initial inspection and corrective action specified in Requirement 1. However, prior accomplishment of the inspections and corrective action specified in the telexes does not eliminate the need for the inspection each time an oxygen generator is replaced. Boeing 737 Series Aeroplanes AD/B737/157 (Continued) 2. If any discrepancy is found during the Requirement 1 inspection carry out the corrective action per the applicable SBs listed in Requirement 1 above. Note 4: FAA AD 2001-10-14 Amdt 39-12240 refers. Compliance: For Requirement 1 - Initially, within 90 days after the effective date of this Directive. In addition, before further flight, after each replacement of any chemical oxygen generator and/or passenger, attendant, or lavatory service unit assembly that contains a chemical oxygen generator. For Requirement 2 - Before further flight after the Requirement 1 inspection. This Airworthiness Directive becomes effective on 9 June 2001. Background: This Directive requires the repetitive inspection of any chemical oxygen generators and/or passenger, attendant, or lavatory service unit assemblies of the passenger oxygen system that have been replaced. This inspection is to verify correct installation of the release pin in the generator firing mechanism of the oxygen generator. The Directive also requires any necessary corrective action to be accomplished. This action is necessary to find and fix incorrect installation of the release pin in the generator firing mechanism, which could result in the unavailability of supplemental oxygen and possible incapacitation of passengers and cabin crew during an in-flight decompression. Eugene Paul Holzapfel Delegate of the Civil Aviation Safety Authority 29 May 2001 The above AD is notified in the Commonwealth of Australia Gazette on 6 June 2001.