AD/APU/10 - GTCP 85 Series APU Axial Containment

Overview

The Civil Aviation Regulations 1998, as amended, contain Airworthiness Directives designed to maintain the safety of aircraft operations within Australia. One such directive, AD/APU/10, specifically addresses issues related to the GTCP 85 Series Auxiliary Power Units (APU) and mandates the installation of an exhaust centrebody to mitigate the risk of uncontained failures. This directive applies to AlliedSignal Aerospace GTCP85 Series APUs that feature a one-piece cast turbine rotor, with exceptions for those installed on Boeing 737 and British Aerospace BAC 1-11 series aircraft. The objective of this directive is to prevent turbine wheel fragments from exiting the APU exhaust axially and causing damage to the aircraft, a problem that has been evidenced by previous incidents. Compliance with this directive is mandatory, with specific deadlines for modifying flight operable and ground operable only APUs, set at 30 June 1997 and 30 June 1998, respectively. The enactment of this directive by the Civil Aviation Safety Authority underscores the commitment to ensuring the highest safety standards in civil aviation.

Scope and Application

The Civil Aviation Regulations 1998, as amended, apply to all aircraft operating in Australia, with specific directives under Part 39 focusing on safety and airworthiness standards. AD/APU/10 pertains to GTCP 85 Series Auxiliary Power Units (APU's) installed in aircraft, excluding those on Boeing 737 and British Aerospace BAC 1-11 series aircraft, which are deemed exempt due to their differing exhaust configurations. The directive mandates the installation of an exhaust centrebody to mitigate the risk of turbine wheel fragments causing damage if an uncontained failure occurs. Compliance requires that flight-operable APU's must be modified by 30 June 1997, while ground-operable APU's must be modified by 30 June 1998. This directive is part of a broader regulatory framework aimed at enhancing aviation safety and is supported by related service bulletins and corresponding Federal Aviation Administration directives.

Key Provisions

The key provisions of the Civil Aviation Regulations 1998, specifically Part 39, involve the applicability and requirements of Airworthiness Directives (AD) concerning the GTCP 85 Series Auxiliary Power Units (APU). The regulation, AD/APU/10, applies to AlliedSignal Aerospace GTCP85 Series APUs that have a one-piece cast turbine rotor, with the exception of those APUs installed on Boeing 737 and British Aerospace BAC 1-11 series aircraft (subsection 1). The main requirement is the installation of an exhaust centrebody in accordance with specific service bulletins issued by AlliedSignal Aerospace: GTCP85-49-A6831 or GTCP85-49-6919, as applicable (subsection 2). This directive references an equivalent FAA AD 95-07-03. The obligations under this directive are clear and time-bound. Flight-operable APUs must be modified by 30 June 1997 to comply with the AD. For APUs that are only operable on the ground, the modification deadline is set for 30 June 1998 (subsection 3(a) and (b)). The directive aims to mitigate the risk of uncontained failures, which have resulted in turbine wheel fragments exiting the APU exhaust axially and causing damage to the aircraft. The background to this AD reveals that there have been incidents where such uncontained failures occurred, leading to significant damage. The Boeing 737 and BAC 1-11 aircraft are exempt from this directive due to the design of their APU exhaust configuration, which significantly reduces the likelihood of aircraft damage in the event of an uncontained turbine wheel failure (subsection 4). In terms of consequences, the regulations do not explicitly state penalties for non-compliance with this AD. However, non-compliance could potentially result in severe civil or criminal penalties under broader civil aviation legislation, including fines and imprisonment, depending on the severity of the safety breach and any resulting harm. The exact penalties would depend on the specific circumstances of the breach and the applicable sections of the Civil Aviation Act 1988 or other relevant legislation.