AD/ATF3/4 - High Pressure Turbine Disc Inspection

Overview

The Civil Aviation Regulations 1998, enacted by the Commonwealth of Australia, form part of a comprehensive regulatory framework aimed at ensuring the safety and efficiency of civil aviation. Part 39, which focuses on the Civil Aviation Safety Authority’s (CASA) schedule of airworthiness directives, includes provisions designed to address specific safety concerns and enhance operational reliability. One such directive is AD/ATF3/4, introduced to address the risk of cracks in the high pressure turbine (HPT) disc of AlliedSignal Model ATF3-6 and -6A engines, a problem identified through routine inspections. The policy objective of this directive is to mitigate safety risks by mandating a thorough inspection of the HPT disc in accordance with detailed industry standards. The AlliedSignal (Garrett/AiResearch) Turbine Engines ATF3 Series High Pressure Turbine Disc Inspection directive was implemented to ensure that any potential defects are identified and rectified before they can compromise flight safety. This requirement, effective from 2 March 1995, applies to engines with specific cycle thresholds and aims to prevent the occurrence of cracks in the HPT disc, thereby maintaining the airworthiness of the aircraft and protecting passengers and crew. The directive references the Federal Aviation Administration’s (FAA) Airworthiness Directive 94-23-04 for additional guidance, ensuring alignment with international safety standards.

Scope and Application

The AlliedSignal (Garrett/AiResearch) Turbine Engines - ATF3 Series AD/ATF3/4 High Pressure Turbine Disc Inspection applies specifically to AlliedSignal Model ATF3-6 and -6A engines as outlined in AlliedSignal Alert Service Bulletin No. ATF3-A72-6184 Revision 1. This legislation mandates that the high pressure turbine (HPT) disc must be inspected in accordance with the specified service bulletin. The requirement is to identify and address any cracks in the HPT disc curvic and bore area, as reported incidents have shown that such cracks can be found during routine inspections. The directive references FAA Airworthiness Directive 94-23-04, indicating a broader international alignment in addressing similar safety concerns. The inspection is mandatory for engines with 1550 or more HPT disc cycles since new, within 50 cycles, and for engines with fewer than 1550 HPT disc cycles since new, within 300 cycles or prior to accumulating 1600 cycles since new, whichever occurs first. This regulation is effective from 2 March 1995 and is enforced under the Civil Aviation Regulations 1998, which are applicable across the Commonwealth of Australia, ensuring uniform standards in civil aviation safety.

Key Provisions

The Civil Aviation Regulations 1998, specifically Part 39 - 106, mandate the AlliedSignal (Garrett/AiResearch) Turbine Engines - ATF3 Series AD/ATF3/4 High Pressure Turbine Disc Inspection. This requirement is outlined in section 3/95 of the Act. The directive applies to AlliedSignal Model ATF3-6 and -6A engines as specified in AlliedSignal Alert Service Bulletin No. ATF3-A72-6184 Revision 1. The primary requirement under this directive is to inspect the high pressure turbine (HPT) disc in accordance with the aforementioned bulletin. This inspection is necessitated by reports of cracks found in the HPT discs during routine maintenance, as referenced in the FAA Airworthiness Directive 94-23-04. The obligations imposed by this directive on the parties involved include conducting a thorough inspection of the HPT disc, focusing on the curvic and bore area, to check for any cracks. Compliance with this directive is critical and is enforced within specific timeframes. For engines that have accumulated 1550 or more HPT disc cycles since new, the inspection must be conducted within 50 cycles. For engines with fewer than 1550 HPT disc cycles since new, the inspection must occur within 300 cycles or before the engine accumulates 1600 cycles since new, whichever comes first. These timelines ensure that the inspections are carried out in a timely manner to maintain the safety and airworthiness of the aircraft. The consequences for non-compliance with these directives are significant. Failure to adhere to the inspection requirements can result in severe civil or criminal penalties. Although the specific penalties are not detailed in the excerpt provided, it is clear that non-compliance could lead to serious repercussions. The Civil Aviation Safety Authority has the authority to enforce these regulations strictly to ensure the safety of air travel. Non-compliance could potentially result in grounding of the aircraft, fines, or other legal actions, depending on the severity and impact of the non-compliance. Ensuring adherence to these directives is crucial for maintaining the high safety standards expected in civil aviation.