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.
Overview
The Civil Aviation Safety Authority (CASA) introduced the Airworthiness Directive AD/B737/160 in 2001 to address a critical safety concern related to the hydraulic shutoff valves in certain Boeing 737 series aeroplanes. This directive was necessitated by the risk of failure in motor operated hydraulic shutoff valves manufactured by Circle Seal Controls, which could lead to severe consequences such as hydraulic fluid leakage into the engine fire zone, compromised landing gear retraction, loss of backup electric power, and other failures that could adversely affect the aircraft's controllability. The policy objective of this directive is to enhance aviation safety by mandating specific checks and replacements of the identified faulty components to mitigate the associated risks. Compliance with this directive is essential for operators of affected Boeing 737 aircraft to ensure continued airworthiness and safety in operations.
Scope and Application
The Airworthiness Directive AD/B737/160 issued by the Civil Aviation Safety Authority (CASA) pertains specifically to all Boeing 737 series aeroplanes equipped with hydraulic shutoff valves manufactured by Circle Seal Controls. This directive applies to all variants of the Boeing 737 series, namely the 737-100, -200, -300, -400, -500, -600, -700, and -800, provided they have motor operated hydraulic shutoff valves produced by Circle Seal Controls. The directive mandates that operational checks and replacements of the affected valves must be carried out as specified in Boeing’s Alert Service Bulletins (ASB) 737-29A1073, Revision 3, dated 2 December 1999, and ASB 737-29A1081, dated 2 December 1999. These requirements are designed to mitigate the risk of valve failure, which could lead to hazardous conditions such as hydraulic fluid leakage to the engine fire zone, compromised landing gear retraction, loss of backup electric power, or other failures that could compromise the aircraft's controllability. The directive sets out a compliance timeline, with initial checks and replacements to be completed within six months of the directive’s effective date of 6 September 2001, followed by ongoing checks at intervals not exceeding six months, and final replacements to be completed within three years from the directive’s effective date.
Key Provisions
The Airworthiness Directive AD/B737/160 applies to all Boeing 737 series aeroplanes that have hydraulic shutoff valves manufactured by Circle Seal Controls (sections 1 and 2). It mandates that an operational check of the affected motor-operated hydraulic shutoff valves be performed in accordance with specified Boeing Air Service Bulletins (ASB) (section 3). If a malfunction is detected during these checks, the valve must be replaced with a new or serviceable Whittaker Controls or Circle Seal Controls valve, as per the same ASBs (section 4). These checks must be repeated until the termination action is completed, which involves replacing the Circle Seal Controls valve according to another set of ASBs (sections 5 and 6).
The AD imposes specific obligations on the operators of Boeing 737 aeroplanes with the mentioned hydraulic shutoff valves. They must ensure that operational checks are performed within six months from the effective date of the AD and at intervals not exceeding six months thereafter (section 7). Furthermore, the replacement of the Circle Seal Controls valve must be completed within three years from the effective date of the AD, unless it has already been done (section 8).
Failure to comply with the requirements of this Airworthiness Directive could result in serious safety risks, as the AD is issued to prevent potential failures of the hydraulic shutoff valves that could lead to hydraulic fluid leakage, loss of landing gear retraction capability, loss of backup electric power, and reduced controllability of the aeroplane (section 9). While the specific civil or criminal penalties for non-compliance are not detailed in the AD, it is clear that failure to adhere to these safety requirements could lead to significant consequences under Australian aviation law.