AD/CT7/5 - Rotor Parts

Overview

The Civil Aviation Regulations 1998, specifically within Part 39 under the Civil Aviation Safety Authority's Schedule of Airworthiness Directives, address the issue of maintaining the airworthiness of General Electric CT7 series turbine engines. Enacted by the Commonwealth of Australia, this legislation was introduced to ensure the safety and reliability of specified turboprop and turboshaft engines used in aviation. The primary objective is to mitigate the risk associated with certain rotor parts that may have compromised structural integrity due to the manufacturing process. Compliance with this directive is mandatory, requiring adherence to the specified service bulletins to ensure the safe operation of the engines. The Civil Aviation Regulations 1998, through the Schedule of Airworthiness Directives, mandate actions to address identified safety concerns related to the CT7 series turbine engines. This legislative instrument was enacted by the Commonwealth of Australia's Parliament and is aimed at ensuring the continued airworthiness of the affected engines. The directive mandates the removal or modification of certain rotor parts based on specific service bulletins to prevent potential fatigue-related failures. The requirement arises from material testing results indicating that the plasma-spray manufacturing process can reduce the low cycle fatigue capability of the material, thereby necessitating timely and specific maintenance actions.

Scope and Application

The Civil Aviation Regulations 1998, under Part 39 - 106, specifically address the airworthiness directives for General Electric Turbine Engines, notably the CT7 series, through the legislative instrument F2006B08689. This regulation applies to the CT7-5A2, -7A, and -9C turboprop engines, as well as the CT7-2A and -6 turboshaft engines. It mandates compliance with specific General Electric Service Bulletins that detail actions to be taken to address issues identified in the gas generator rotor assembly parts, which were plasma sprayed during manufacture. The requirement stems from material testing results that highlighted a reduction in low cycle fatigue capability due to the plasma-spray process. The scope of this regulation is national, falling under the jurisdiction of the Commonwealth of Australia, and it extends to all entities operating these specified engines within the Australian aviation industry. Compliance is necessary before exceeding the maximum total allowable cycles as specified in the relevant service bulletins. The directive does not explicitly state any exclusions or exemptions, but the requirement is contingent on the specific conditions outlined in the service bulletins referenced.

Key Provisions

The Civil Aviation Regulations 1998, specifically Part 39 - 106, mandates the maintenance and safety requirements for certain turbine engines through Airworthiness Directives (AD). In this context, AD/CT7/5 focuses on the General Electric CT7 Series engines, specifically those identified as CT7-5A2, -7A, -9C turboprop engines, and CT7-2A, -6 turboshaft engines. This directive mandates actions in accordance with particular General Electric Service bulletins, which are SB A72-252 for CT7-5A2, -7A, and -9C, SB A72-18 for CT7-2A, and SB A72-17 for CT7-6. These service bulletins were issued on 31 August 1990 and 10 September 1990 respectively. The directive references FAA AD 93-25-17 for further context. The AD requires operators to take specific actions before the engines exceed the 'Max total allowable cycles' specified in the relevant service bulletins. The directive is centred on the need to remove from service certain gas generator rotor assembly parts that were plasma sprayed during manufacture. This requirement stems from material testing results that indicate the plasma-spray process diminishes the low cycle fatigue capability of the material, thus posing a safety risk. Operators of the specified engines must adhere to the directives by following the procedures outlined in the service bulletins. This includes the removal and replacement of the affected rotor parts as stipulated, ensuring that the engines do not exceed the allowable cycles before compliance is achieved. The regulations demand that these actions are taken promptly and in accordance with the prescribed timelines to maintain airworthiness and ensure safety. Failure to comply with the requirements set out in AD/CT7/5 may result in significant consequences. The Civil Aviation Safety Authority (CASA) has the authority to take enforcement actions against operators who do not adhere to the directive. Potential penalties include fines, operational restrictions, and the possibility of grounding the affected aircraft until compliance is achieved. It is imperative that operators remain vigilant and ensure strict adherence to the directive to avoid these serious repercussions.