Overview

The Civil Aviation Regulations 1998 (CAR 1998) were enacted to ensure the safety of civil aviation in Australia, providing a comprehensive framework for the regulation of civil aviation and aeronautical products. One particular legislative instrument, F2006B07408, issued under the authority of the Civil Aviation Regulations, focuses on the maintenance and safety of aircraft engines. Specifically, the Airworthiness Directive (AD) AD/TFE731/31, issued on 4 April 2001 by the Civil Aviation Safety Authority (CASA), addresses the critical issue of potential low cycle fatigue cracking in the high pressure compressor (HPC) impellers of Alliedsignal (Garrett/Airesearch) Turbine Engines - TFE 731 Series. This directive was implemented to prevent uncontained impeller separation, thereby ensuring the continued airworthiness and safety of affected aircraft. The policy objective behind this directive is to mandate the inspection and, if necessary, the replacement of specified HPC impellers to mitigate the identified safety risk.

Scope and Application

This Airworthiness Directive applies to specific TFE 731 series turbine engines manufactured by Alliedsignal (Garrett/Airesearch) and detailed by model in Honeywell Alert Service Bulletin TFE731-A72-3641 Revision 2, which incorporate a high pressure compressor (HPC) impeller part number (P/N) 3073393-1, 3073394-1, 3073433-1, 3073434-1, 3073398-All, 3073435-All, 3075171-All, 3075765-1, 3075768-1 and 3075769-1. The directive mandates that the applicable HPC impeller be removed and inspected in accordance with the specified Honeywell bulletin, with the aim of addressing potential low cycle fatigue cracking that could result in uncontained impeller separation, thereby ensuring aviation safety. The directive applies on a Commonwealth-wide basis, falling under the jurisdiction of the Civil Aviation Safety Authority (CASA), which is the delegate of the Commonwealth of Australia under the Civil Aviation Regulations 1998. The directive extends to all relevant aircraft and aeronautical products within Australia, and it is enforced through subordinate instruments as detailed in the Civil Aviation Regulations 1998.

Key Provisions

The Civil Aviation Regulations 1998 (CAR 1998) include a provision for Airworthiness Directives (AD) which are issued by a delegate of the Civil Aviation Safety Authority (CASA) under subregulation 39.1 (1). These ADs mandate specific actions to address unsafe conditions in aircraft or aeronautical products, as outlined in the requirement section (CAR 1998, 39.106). In this instance, AD/TFE731/31 pertains to the TFE 731 Series HP Compressor Impeller (CAR 1998, 39.106(a)-(c)). The applicability section specifies the particular engines affected by this directive, namely those with HPC impellers of certain part numbers (CAR 1998, 39.106(a)). The requirement section mandates the removal and inspection of the HPC impeller as per Honeywell Alert Service Bulletin TFE731-A72-3641 Revision 2 (CAR 1998, 39.106(b)). The compliance section sets the timeframes for these inspections, either at the next compressor zone inspection or access to the HPC module, whichever comes first, and thereafter at each compressor zone inspection, or if the HPC impeller has accumulated more than 1,000 cycles since the last eddy current inspection (CAR 1998, 39.106(c)). The AD imposes specific obligations on the operators and maintainers of aircraft equipped with the affected engines. They are required to follow the detailed inspection procedures outlined in the Honeywell Alert Service Bulletin TFE731-A72-3641 Revision 2 (CAR 1998, 39.106(b)). This includes the removal and inspection of the applicable HPC impeller at the specified intervals mentioned in the compliance section (CAR 1998, 39.106(c)). Failure to comply with these obligations may result in serious safety risks, including the potential for uncontained impeller separation due to low cycle fatigue cracking in the high-stress areas of the impeller (CAR 1998, 39.106(a)). Breach of the requirements set out in this Airworthiness Directive may lead to severe consequences. Although specific penalties are not detailed in the text provided, non-compliance with ADs generally could result in civil or criminal penalties under other sections of the Civil Aviation Act 1988 and the Civil Aviation Regulations 1998. These may include fines, suspension or revocation of airworthiness certificates, or even criminal charges if the breach leads to an accident or serious incident. The AD serves as a critical safety measure, and adherence to it is essential to maintain the airworthiness of the affected aircraft.