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/B737/160 Hydraulic Shutoff Valves 9/2001 Applicability: All Boeing 737-100, -200, -300, -400, -500, -600, -700, -800 series aeroplanes equipped with hydraulic shutoff valves manufactured by Circle Seal Controls. Note 1: Only motor operated hydraulic shutoff valves manufactured by Circle Seal Controls that are installed in the locations specified in applicable alert service bulletin (ASB) are subject to this Directive. Requirement: 1. Perform an operational check of affected motor operated hydraulic shutoff valves in accordance with Boeing ASB 737-29A1073, Revision 3, dated 2 December 1999 or ASB 737-29A1081, dated 2 December 1999, as applicable. If any malfunction of the valve is detected, prior to further flight, replace the valve with a new or serviceable Whittaker Controls or Circle Seal Controls valve in accordance with ASB 737-29A1073, Revision 3 or ASB 737-29A1081, as applicable. 2. Repeat the operational checks for the valves in accordance with ASB 737- 29A1073, Revision 3 or ASB 737-29A1081, as applicable, until the terminating action required by the Requirement 3 of this Directive is accomplished. 3. Replace the existing Circle Seal Controls valve (identified by Requirement 1), in accordance with ASB 737-29A1078, dated 7 December 2000 or ASB 737- 29A1082, dated 7 December 2000, as applicable. Note 2: FAA AD 2001-11-07 Amendment 39-12249 refers. Note 3: Operational checks done before the effective date of this Directive as per Boeing ASB 737-29A1073, Revision 2, dated 1 July 1999 meet Requirements 1 and 2 of this Directive. Note 4: Replacement of Circle Seal Controls valve done before the effective date of this Directive as per Boeing ASB 737-29A1073, Revision 2, dated 1 July 1999, meets the Requirement 3 of this Directive. Boeing 737 Series Aeroplanes AD/B737/160 (Continued) Compliance: 1. Unless already accomplished, within 6 months from the effective date of this Directive. 2. At intervals not to exceed 6 months. 3. Unless already accomplished, within 3 years from the effective date of this Directive. This Airworthiness Directive becomes effective on 6 September 2001. Background: This Directive is issued to prevent failure of the motor operated hydraulic shutoff valves, which could result in leakage of hydraulic fluid to the engine fire zone, reduced ability to retract the landing gear, loss of backup electric power or other combination of failures, and consequent reduced controllability of the aeroplane. Eugene Paul Holzapfel Delegate of the Civil Aviation Safety Authority 27 July 2001 The above AD is notified in the Commonwealth of Australia Gazette on 15 August 2001.