AD/TPE 331/37 - Second Stage Turbine Rotor Assembly - Cyclic Life Reduction

Overview

The Civil Aviation Regulations 1998, under Part 39 - 106, were enacted to ensure the safe operation of civil aviation in Australia, addressing safety concerns by setting stringent standards and requirements for aircraft and their operation. This legislative instrument, F2006B07447, was introduced to tackle a specific safety issue identified in AlliedSignal (Garrett/AiResearch) Turbine Engines of the TPE 331 series, particularly focusing on the second stage turbine rotor assembly. The Civil Aviation Safety Authority, acting under the authority of the Australian Parliament, established this directive to mandate the replacement of second stage turbine wheels to prevent potential separation and ensure continued airworthiness. The policy objective is to maintain and enhance aviation safety by implementing stringent maintenance schedules and compliance requirements based on the manufacturer’s updated cycle life limits.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39, applies to the TPE 331 series engines used in civil aviation within Australia, and more broadly, to any aircraft utilising these engines worldwide, provided they are registered in Australia. This legislation mandates the replacement of the second stage turbine wheels in TPE 331-10 and -11 series engines equipped with specific turbine wheel assemblies. The regulation requires adherence to Garrett’s Service Bulletin TPE 331-A72-0571 Accomplishment Instructions. Compliance must be immediate, effective from 9 May 1988, and follows a detailed schedule based on the cycle number since the engine's new serial number (CSN). Notably, all turbine wheel assemblies reaching 4800 cycles must be replaced before 1 January 1989 and must not exceed a total of 6800 cycles. This directive extends its applicability through subordinate instruments which provide further detail on compliance and enforcement, ensuring that the aviation safety standards are met uniformly across the relevant fleet.

Key Provisions

The Civil Aviation Regulations 1998, specifically Part 39 - 106, addresses airworthiness directives for various aircraft components and systems. The section on the AlliedSignal (Garrett/AiResearch) Turbine Engines - TPE 331 Series, specifically AD/TPE 331/37, pertains to the second stage turbine rotor assembly and its cyclic life reduction (Section 7/88). This airworthiness directive applies to TPE 331-10 and -11 series engine models that have second stage turbine wheel assemblies with part numbers 3102106-1/-6 and -8. The directive requires these turbine wheels to be replaced in accordance with the accomplishment instructions detailed in Garrett Service Bulletin TPE 331-A72-0571. The directive mandates the replacement of the second stage turbine wheels under specific conditions based on the number of cycles since new. The replacement schedule is detailed in the requirement document, which stipulates that wheels with 0 to 4400 cycles must be replaced prior to reaching 4800 cycles. For wheels with 4401 to 5000 cycles, the replacement must occur within an additional 400 cycles or before reaching 5200 cycles. Similarly, for wheels with 5001 to 5900 cycles, replacement must happen within an additional 200 cycles or before reaching 6000 cycles, and for those with 5901 to 6800 cycles, within an additional 100 cycles or before reaching 6800 cycles. A notable note is that all second stage turbine rotor assemblies with 4800 or more cycles must be replaced before 1 January 1989, and no assembly shall exceed a total of 6800 cycles. The obligations imposed by this directive are clear and stringent. Aircraft operators and maintenance entities must adhere to the specified replacement schedule based on the number of cycles since new. Compliance must be achieved forthwith from 9 May 1988, as per the schedule detailed in the requirement document. Failure to comply with these airworthiness directives can lead to significant consequences. Breaches of these regulations can result in severe civil or criminal penalties, as the safety of aircraft and passengers is paramount. The exact penalties are not specified in the legislative instrument but generally, non-compliance with airworthiness directives can result in hefty fines, suspension of airworthiness certificates, or even criminal charges if the breach leads to an aviation incident. In summary, the Civil Aviation Regulations 1998 mandate specific requirements for the replacement of second stage turbine wheels in certain AlliedSignal (Garrett/AiResearch) Turbine Engines to ensure safety. Failure to comply with these requirements can lead to serious civil or criminal consequences, underscoring the importance of adherence to these airworthiness directives.