COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Boeing 747 Series Aeroplanes AD/B747/199 Cabin Pressure Control System 6/99 Applicability: Model 747-400, -400D and -400F series aeroplanes identified in Boeing Alert Service Bulletin (ASB) 747-21A2381 dated 27 June 1996 and Service Bulletin (SB) 747-24- 2193 dated 26 January 1995. Requirement: 1. Modify the P212 and P213 panels of the cabin pressure control system in accordance with Boeing ASB 747-21A2381 as follows: 1. For Groups 1 through 7 aeroplanes, as identified in the ASB - Change the wiring in the P212 and P213 panels, replace the existing two-pole relays with new four-pole relays and perform a test of both panels. b. For Group 8 aeroplanes, as identified in the ASB - Change the wiring in the P212 panels, replace the existing two-pole relays with new four-pole relays, replace the existing P213 panel with a new P213 panel and perform a test of both panels. 2. For aeroplanes having line positions 696 through 1021 inclusive modify the P5, P6 and P7 panels, together with wire bundles W4701, W4703 and W4908, as applicable, in accordance with either SB 747-24-2193, as revised by Notices of Status Change (NSC) 747-24-2193 NSC 1 dated 13 April 1995, NSC 2 dated 5 October 1995, NSC 3 dated 22 November 1995, NSC 4 dated 21 December 1995, NSC 5 dated 2 May 1996 and NSC 6 dated 13 March 1997; or ASB 747- 24A2193 Revision 1 dated 19 June 1997, as follows: 1. For all aeroplanes identified above - modify the wiring in the P5, P6 and P7 panels together with the wiring in the W4701 and W4908 wire bundles and install diodes in the P6 panel. b. For Group 1 and 2 aeroplanes, as identified in the Accomplishment Instructions, paragraph I, of the SB or ASB - modify the wiring in the W4703 wire bundle. Note: FAA AD 99-06-18 Amdt 39-11082 refers. Compliance: 1. Within 12 months after the effective date of this Directive. 2. Within 12 months after the effective date of this Directive. This Airworthiness Directive becomes effective on 17 June 1999. Background: The FAA has received a report of an in-flight loss of cabin pressurisation control due to a single failure of the auxiliary power unit battery. This directive introduces measures which are intended to prevent loss of the cabin pressurisation system, which could result in rapid depressurisation of the aeroplane.