AD/B737/50 - APU - EGT Overtemperature Condition

Overview

The Civil Aviation Regulations 1998, enacted by the Australian Parliament, aim to ensure the safety and efficiency of civil aviation within Australia. Part 39, specifically, addresses the issue of airworthiness directives, including the AD/B737/50 concerning Boeing 737 series aeroplanes. This legislative instrument was introduced to address the problem of the Auxiliary Power Unit (APU) exhaust gas temperature (EGT) indication incorrectly reading “zero” following an APU shut down, which could lead to undetected overtemperature damage to the APU rotor structure, potentially causing rotor failure and structural damage to the aeroplane. The policy objective is to mandate inspections and modifications to Boeing 737-300 and 737-400 series aircraft in accordance with the FAA AD 90-23-12, thereby ensuring compliance with safety standards. This legislative instrument aligns with the broader objective of the Civil Aviation Regulations 1998 to maintain high safety standards in the civil aviation sector by adopting international best practices and addressing specific safety concerns as identified by relevant authorities such as the Federal Aviation Administration (FAA). The requirement to inspect and modify affected Boeing 737 aeroplanes, as per FAA AD 90-23-12 and Boeing Service Bulletin 737-49-1071, ensures that Australian civil aviation operations remain compliant with stringent safety requirements, thereby protecting passengers, crew, and the public from potential hazards associated with APU overtemperature conditions.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 105, applies to Boeing 737-300 and 737-400 series aeroplanes within the Commonwealth of Australia. This regulation mandates that these aircraft must be inspected and modified in accordance with the Federal Aviation Administration (FAA) Airworthiness Directive (AD) 90-23-12, which references Boeing Service Bulletin 737-49-1071 dated May 10, 1990. The directive is a response to reports indicating that the auxiliary power unit (APU) exhaust gas temperature (EGT) indication incorrectly read “zero” following an APU shutdown. If left unaddressed, this condition could lead to overtemperature damage to the APU rotor structure, potentially resulting in rotor failure and structural damage to the aeroplane. Compliance with these regulations is critical to ensuring the safety of civil aviation within Australia, with adherence to the specified requirements and modifications outlined in the FAA directive.

Key Provisions

The Civil Aviation Regulations 1998, specifically in Part 39 - 105, detail the Civil Aviation Safety Authority's (CASA) schedule of airworthiness directives, focusing on Boeing 737 series aeroplanes. A key directive is AD/B737/50, which pertains to the Auxiliary Power Unit (APU) exhaust gas temperature (EGT) overtemperature condition (section 2/91). This directive applies to Boeing 737-300 and 737-400 series aeroplanes. It mandates that these aircraft must be inspected and modified in accordance with the Federal Aviation Administration's (FAA) AD 90-23-12, which in turn references Boeing Service Bulletin 737-49-1071 dated May 10, 1990. Compliance with this directive is critical to ensure the aircraft's airworthiness and safety. Under this legislation, the obligations imposed on the operators of Boeing 737-300 and 737-400 series aeroplanes are clear. They must adhere to the inspection and modification requirements set out in the FAA AD 90-23-12. This involves rigorous checks to identify and rectify any instances where the APU EGT indication incorrectly reads "zero" following an APU shut down. The directive ensures that these aircraft are modified to prevent overtemperature damage to the APU rotor structure, thereby mitigating the risk of rotor failure and subsequent structural damage to the aeroplane. Compliance with these requirements is non-negotiable and must be documented as per the Requirement Document. Failure to comply with the provisions of AD/B737/50 could lead to severe consequences. Although the specific civil or criminal penalties are not detailed in the text, non-compliance with CASA directives typically results in enforcement actions. These can include fines, operational restrictions, or even the grounding of the aircraft until the necessary modifications are made. Such actions are taken to ensure that the safety and airworthiness standards are upheld, protecting both the passengers and the crew of the aeroplanes. The potential penalties underscore the importance of adhering to the mandated safety directives to avoid any adverse outcomes.