AD/B737/88 - Horizontal Stabiliser Trim Electric Actuator

Overview

The Civil Aviation Regulations 1998 were enacted to establish a comprehensive regulatory framework for ensuring civil aviation safety in Australia. This legislation, overseen by the Australian Parliament, addresses the critical need for maintaining high safety standards in the operation of civil aircraft. One specific instance where these regulations are applied is in Airworthiness Directives, such as AD/B737/88, which targets the maintenance and modification of aircraft components to prevent safety issues. This directive was introduced to address a specific problem identified with the Boeing 737 series aeroplanes, where a binding condition of a clutch disc in the horizontal stabilizer trim electric actuator was causing the stabilizer trim wheel to continue turning after the switches were operated and released, thereby risking reduced controllability of the aircraft. The objective is to ensure that all applicable aircraft are modified to prevent such safety hazards, thereby maintaining the highest possible standards of aviation safety. The Civil Aviation Regulations 1998, administered by the Civil Aviation Safety Authority, provide a structured approach to ensuring aircraft are maintained in a safe condition. This is evident in the directive AD/B737/88, which mandates the replacement of the horizontal stabilizer trim electric actuator on certain Boeing 737 models to mitigate the risk of binding clutch issues. The directive not only specifies the requirement to replace the actuator with a modified version but also sets compliance timelines to ensure timely action. By enforcing these measures, the regulations aim to prevent potential safety incidents, thereby protecting both the aircraft and its occupants.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 105, applies to the Civil Aviation Safety Authority's schedule of airworthiness directives concerning Boeing 737 Series aeroplanes. The directive in question, AD/B737/88, pertains to the horizontal stabilizer trim electric actuator and mandates the replacement of Part Number (P/N) 10-62033-3 with a modified and re-identified P/N 10-62033-4 actuator, in line with Boeing Alert Service Bulletin 737-27A1191 Revision 1 dated 3 November 1994. This directive applies to Boeing 737-300, -400, and -500 series aircraft identified in the specified bulletin and aims to ensure compliance to prevent reduced controllability due to clutch binding. Compliance with this directive is required before 12 June 1996, with an earlier prohibition on the installation of P/N 10-62033-3 after 12 December 1995, though previously installed actuators may remain in service until they are replaced in accordance with the directive.

Key Provisions

The Civil Aviation Regulations 1998, specifically Part 39 - 105, includes an Airworthiness Directive (AD) concerning the Boeing 737 Series Aeroplanes. The AD AD/B737/88 focuses on the horizontal stabilizer trim electric actuator (section 1). It applies to the Model 737-300, -400, and -500 series aircraft identified in Boeing Alert Service Bulletin 737-27A1191 Revision 1 dated 3 November 1994 (section 2). The directive mandates that the horizontal stabilizer trim electric actuator Part Number (P/N) 10-62033-3 must be replaced with an actuator that has been modified and re-identified as P/N 10-62033-4, in accordance with the aforementioned Boeing Alert Service Bulletin (section 3). Operators of the specified Boeing 737 series aircraft must ensure compliance with the directive by replacing the specified part before 12 June 1996. Actuators P/N 10-62033-3 may not be installed in an aircraft after 12 December 1995. However, if such actuators were installed before 12 December 1995, they may remain in service until they are removed in accordance with the directive's requirements (section 4). The directive is aimed at preventing reduced controllability of the airplane caused by the binding clutch condition in the horizontal stabilizer trim electric actuator, which has been identified as a safety issue. The Civil Aviation Regulations impose obligations on aircraft operators to adhere to the Airworthiness Directives issued by the Civil Aviation Safety Authority (CASA). Operators must ensure that the specified aircraft meet the airworthiness standards set by CASA. This includes replacing the affected actuators as per the directive to maintain the safety and airworthiness of the aircraft (section 5). Failure to comply with these requirements could result in civil or criminal penalties, as detailed in the regulations. CASA may take enforcement actions against operators who do not comply with the AD, potentially leading to fines or other legal consequences (section 6). Under the Civil Aviation Regulations 1998, non-compliance with the Airworthiness Directives can lead to both civil and criminal consequences. Operators who fail to adhere to the requirements of AD/B737/88 may face enforcement actions from CASA, which can include fines and other penalties. In severe cases, individuals responsible for non-compliance could face criminal charges, leading to potential imprisonment or additional fines. The specific penalties are outlined in the regulations, with maximum penalties for serious breaches potentially including substantial fines and imprisonment terms, depending on the severity of the violation (section 7).