AD/TFE 731/14 - First Stage L.P. Turbine Disc

Overview

The Civil Aviation Regulations 1998, enacted by the Commonwealth of Australia, aim to ensure the safety of civil aviation operations within the country. The legislation, overseen by the Civil Aviation Safety Authority (CASA), establishes various safety standards and requirements for aircraft, personnel, and operations. One such regulation is found in Part 39, which addresses airworthiness directives to mitigate specific safety issues. For instance, AD/TFE731/14 pertains to the AlliedSignal (Garrett/AiResearch) Turbine Engines of the TFE731 Series, specifically targeting the first stage L.P. turbine disc. This directive was introduced to address the problem of potential failure in the first stage L.P. turbine disc due to manufacturing defects, as highlighted in GTEC Alert SB TFE 731-A72-3371, which documented an in-flight shutdown caused by the separation of firtree posts and the release of turbine blades. The policy objective is to ensure that affected turbine discs are removed from service or replaced within specified timeframes to prevent any in-flight failures.

Scope and Application

The Civil Aviation Regulations 1998, as amended, pertain specifically to the aviation sector in Australia and encompass a comprehensive regulatory framework aimed at ensuring the safety and efficiency of civil aviation operations. Under Part 39, the Civil Aviation Safety Authority (CASA) issues airworthiness directives to address specific safety concerns that may arise in the operation of aircraft and their components. One such directive, AD/TFE731/14, pertains to the AlliedSignal (Garrett/AiResearch) Turbine Engines of the TFE731 series, specifically targeting the first stage low-pressure turbine discs that are identified as having potential defects. This directive applies to all TFE 731-5 series engines equipped with first stage low-pressure turbine discs whose serial numbers are listed in the requirement document. The directive mandates the removal from service of affected discs to mitigate the risk of in-flight shutdowns caused by the separation of adjacent firtree posts and the release of turbine blades, a risk identified through an engineering investigation linked to a suspect forging lot. Compliance with this directive is required based on the number of operating cycles the disc has accumulated, with specific timelines provided for both discs with fewer than 750 cycles and those with more than 750 cycles. The directive reflects the GTEC Alert SB TFE 731-A72-3371, underscoring the importance of adhering to the stipulated requirements to ensure the continued airworthiness and safety of the affected aircraft.

Key Provisions

The key provision of this Airworthiness Directive (AD/TFE731/14) focuses on the removal and replacement of specific first stage low-pressure (L.P.) turbine discs for the AlliedSignal (Garrett/AiResearch) Turbine Engines - TFE731 Series (sections 1-3). The directive applies to TFE 731-5 series engines with certain serial numbers identified in the Requirement document. The requirement (section 4) is to remove from service any affected first stage L.P. turbine discs in accordance with the G.T.E.C. Alert SB TFE 731-A72-3371. The compliance timelines (section 5) are different for discs based on their operating cycles: for discs with less than 750 operating cycles, they must be removed before exceeding 750 cycles; for discs with more than 750 operating cycles, they must be replaced within 25 operating cycles after 27 June 1988. The obligations imposed by this Act on the parties or entities it governs are primarily focused on ensuring the safety of the aircraft by adhering to the specified timelines and procedures for the removal and replacement of the affected turbine discs. The directive mandates that operators of TFE 731-5 series engines must identify the affected discs through the serial numbers provided, and act in accordance with the G.T.E.C. Alert SB TFE 731-A72-3371, which includes the engineering investigation findings and recommendations. This involves conducting a thorough assessment of the operating cycles of the affected discs and ensuring that the required actions are taken within the specified timeframes to maintain airworthiness and safety standards. In terms of potential consequences for non-compliance, the Civil Aviation Regulations 1998, under which this Airworthiness Directive is issued, provide for a range of civil and criminal penalties. The exact nature and severity of these penalties are governed by other sections of the Civil Aviation Act 1988 and associated regulations, but generally, non-compliance with airworthiness directives can lead to severe financial penalties, suspension or revocation of aircraft certificates, and potential criminal charges for individuals or entities found responsible for the non-compliance. The specific maximum penalties for breaches of airworthiness directives are not detailed within the directive itself, but they can include fines up to a substantial amount and imprisonment for individuals, as per the Civil Aviation Act 1988. Ensuring adherence to these directives is crucial for maintaining the highest safety standards in civil aviation.