AD/TFE 731/22 - Low Pressure Turbine Third Stage Disc Material Anomalies

Overview

The Civil Aviation Regulations 1998, specifically under PART 39 - 106, address the safety concerns related to the AlliedSignal (Garrett/AiResearch) Turbine Engines of the TFE731 series. Enacted by the Commonwealth of Australia, this legislation was introduced to address safety issues identified in certain low pressure turbine third stage discs of the TFE731 series engines. The primary objective is to ensure the airworthiness of these engines by mitigating the risk of uncontained engine failure due to material anomalies in the turbine rotor discs. This regulation requires compliance with the Allied-Signal Aerospace Company's Alert Service Bulletin TFE731-A72-3474 dated 3 April 1992, which outlines specific actions for the replacement of affected components. The aim is to ensure that these engines meet safety standards by taking appropriate action before the next access to the turbine rotor assembly or before the engine accumulates 50 hours of time in service after 25 January 1993.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 106, under the Civil Aviation Safety Authority (CASA) Schedule of Airworthiness Directives, mandates the application of AD/TFE731/22 for specific Garrett engine models within the AlliedSignal (Garrett/AiResearch) Turbine Engines - TFE731 Series. This directive applies to Garrett Engine Models TFE731-2, -3, -3A, -3AR, and -3R, which are equipped with particular low pressure turbine rotor discs identified by serial numbers listed in the Allied-Signal Aerospace Company Garrett Engine Division Alert Service Bulletin TFE731-A72-3474 dated 3 April 1992. The directive necessitates compliance with the requirements outlined in the aforementioned service bulletin. This requirement must be fulfilled either at the next access to the turbine rotor assembly or before the engine accumulates 50 hours of time in service after 25 January 1993. The directive aims to address the risk of uncontained engine failure caused by random oxide inclusions and subsequent cracking in the low pressure turbine discs, ensuring the safety and airworthiness of the affected engines within the Australian aviation industry.

Key Provisions

The key operative sections of this Airworthiness Directive (AD) (AD/TFE731/22) are the "Applicability" and "Requirement" sections. The "Applicability" section specifies that the directive applies to Garrett Engine Models TFE731-2, -3, -3A, -3AR and -3R equipped with certain low pressure turbine rotor discs identified by specific serial numbers. This is a precise identification of the engines and parts affected by the directive (section 1). The "Requirement" section mandates that actions be taken in accordance with the procedures outlined in the Allied-Signal Aerospace Company Garrett Engine Division Alert Service Bulletin TFE731-A72-3474 dated 3 April 1992 (section 2). This bulletin provides the detailed procedures for identifying, inspecting, and, if necessary, replacing the affected parts to prevent potential failures. The obligations imposed by this Act are primarily on the operators and maintenance personnel of the affected aircraft. They must ensure that the low pressure turbine rotor discs identified in the applicability section are inspected and, if necessary, replaced in accordance with the procedures in the service bulletin. The requirement to comply must be met at the next access to the turbine rotor assembly or before the engine accumulates 50 hours of time in service after 25 January 1993 (section 3). This imposes a clear timeline and procedural obligation on those responsible for the maintenance of the affected engines. The consequences for non-compliance with this Airworthiness Directive are not explicitly stated in the directive itself. However, non-compliance with airworthiness directives in Australia can lead to significant civil and criminal penalties. Civil penalties can include fines and potential grounding of the aircraft until compliance is achieved. Criminal penalties may apply if the non-compliance results in an accident or incident, leading to potential imprisonment for the responsible parties. The specific maximum penalties would be determined by the relevant aviation authorities and the courts, but they can be severe given the potential safety implications of such non-compliance (section 4).