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. Dornier 328 Series Aeroplanes AD/DO 328/33 Cabin Pressure Control System 1/2006 Applicability: Model 328-100 aeroplanes. Requirement: For aeroplanes, serial number (S/N) 3005 to 3086 inclusive, without a placard installed on the Cabin Pressure Control System (CPCS) panel in accordance with the Accomplishment Instructions of Dornier Service Bulletins SB-328-21-225, dated 27 June 1997, install a placard in accordance with SB-328-21-225. Note 1: For S/Ns after 3086, SB-328-21-225 was incorporated during production. Note 2: Fitment of a modified Pressurisation Control Unit (PCU) part number 22260A030201 in accordance with the Accomplishment Instructions of SB-328-21-261, dated 27 January 1999, is an optional alternate method of compliance for this Directive for aeroplanes S/N 3005 to 3086 inclusive. Additionally, fitment of a modified PCU in accordance with SB-328-21-261 to aeroplanes 3087 to 3098 inclusive, 3100, 3101, 3104, 3106, 3107, 3109, 3110, 3112, 3113, 3115, 3117 and 3119 is optional. Note 3: Placards installed in accordance with SB-328-21-225 or during production must be removed when the modified PCU is fitted. Note 4: LBA AD 1997-242/3 refers. Compliance: Within 30 days after the effective date of this Directive. This Airworthiness Directive becomes effective on 19 January 2006. Background: The German Luftfahrt-Bundesamt(LBA) has advised during flight above FL250, when the pressurisation control is set to the MAN mode, a pressurisation drop of approximately 1 000ft may occur for a short time if the pressurisation control is switched back to manual mode. Initially, earlier issues of the LBA Airworthiness Directive required placarding of the CPCS panel on aeroplanes S/N 3005 to 3086, this is reflected in this Directive. However, in late 1999 the LBA introduced the fitment of a modified PCU (SB-328-21-261), as an optional alternate method of compliance (AMOC) to the placarding of the CPCS panel. The AMOC is equally applicable to aeroplanes S/N 3005 to 3086, which were placarded in accordance with SB-328-21-255, and to later aeroplanes which were placarded during production. Following installation of the modified PCU the placard may be removed from the CPCS panel. This information is reflected in Notes 2 and 3 of this Directive. James Coyne Delegate of the Civil Aviation Safety Authority 1 December 2005