AD/TFE 731/15 - HP Turbine Rotor Disc

Overview

The Civil Aviation Regulations 1998, under Part 39 - 106, introduced Airworthiness Directives to ensure the safety and airworthiness of aircraft in Australia. Specifically, AD/TFE731/15 addresses the issue of suspect HP turbine rotor discs in AlliedSignal (Garrett/AiResearch) Turbine Engines of the TFE731 series. This directive was enacted to rectify a safety concern identified by the manufacturer regarding incorrect curvic coupling tooth root fillet radii in certain HP turbine rotor discs, which could potentially lead to uncontained HP turbine disc failures. Compliance with this directive is mandated within 25 engine operating cycles after 22 September 1988, as per the requirement to remove and replace specific serial numbered HP turbine rotor discs with those listed in the accompanying Requirement document. The directive was issued by the Civil Aviation Safety Authority in response to manufacturer advice and aims to mitigate the risk of uncontained engine failures, thereby enhancing the safety standards for aircraft operations in Australia. This legislative instrument underscores the importance of stringent oversight and timely compliance with safety directives to protect both the aviation industry and the public.

Scope and Application

The Civil Aviation Regulations 1998, specifically PART 39 - 106, under the Civil Aviation Safety Authority, pertain to the AlliedSignal (Garrett/AiResearch) Turbine Engines – TFE731 Series HP Turbine Rotor Disc AD/TFE731/15. This legislation applies to TFE 731-3 series engines identified as having suspect HP turbine rotor discs with specific serial numbers listed in the accompanying Requirement document. The requirement of this directive mandates the removal from service of specific serial numbered HP turbine rotor discs Part No. 3072316-2/-3 and 3073110-1/-2, in alignment with GTEC Alert SB TFE 731-A72 - 3376. Compliance is mandated within 25 engine operating cycles after 22 September 1988. The directive arises from manufacturer advice highlighting incorrect curvic coupling tooth root fillet radii in certain HP turbine rotor discs, aiming to prevent uncontained HP turbine disc failures that could occur in engines containing these suspect reworked discs. The Federal Aviation Administration (FAA) AD Priority Letter 88-18-03 also references this directive, underlining its importance and urgency in maintaining aviation safety standards.

Key Provisions

The main operative sections of the AlliedSignal (Garrett/AiResearch) Turbine Engines - TFE731 Series Airworthiness Directive AD/TFE731/15 pertain to the removal from service of specific serial numbered HP turbine rotor discs. According to section 1, the directive applies to TFE 731-3 series engines that contain HP turbine rotor discs with serial numbers listed in the requirement document. These discs, part numbers 3072316-2/-3 and 3073110-1/-2, must be removed from service in compliance with GTEC Alert SB TFE 731-A72 - 3376, as referenced in section 2. This directive is necessitated by the manufacturer’s advice regarding incorrect curvic coupling tooth root fillet radii, which could lead to uncontained HP turbine disc failures (section 3). The requirement is to address these issues within 25 engine operating cycles after 22 September 1988, as stipulated in section 4. The obligations imposed by this directive on the parties and entities it governs are quite clear. Operators and maintainers of TFE 731-3 series engines must identify and remove the specific HP turbine rotor discs as per the directive. This involves ensuring that only the serial numbered discs listed in the requirement document are removed and replaced with ones that comply with the safety standards outlined in GTEC Alert SB TFE 731-A72 - 3376. The compliance period is strictly set, mandating that these actions be completed within 25 engine operating cycles from the date of the directive’s issuance. This requirement underscores the urgency and importance of adhering to the specified timeline to mitigate potential safety hazards. Failure to comply with the provisions of this directive may result in severe consequences. While the specific penalties are not detailed in the text, it is clear that non-compliance could lead to unsafe operating conditions, potentially resulting in severe accidents. The directive references FAA AD Priority Letter 88-18-03, indicating that the regulatory authority takes these safety measures very seriously. In general, non-compliance with Civil Aviation Regulations can lead to civil penalties, which may include fines or other sanctions. Additionally, in the event of an accident or incident caused by non-compliance, there could be criminal liabilities, including potential prosecutions against individuals or entities responsible for the oversight and maintenance of the aircraft.