AD/ARRIEL/10 - 2nd Stage Turbine Nozzle Guide Vanes

Overview

The Civil Aviation Regulations 1998, as amended by PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES, introduce specific directives to address the issue of 2nd stage turbine nozzle guide vane deterioration in Turbomeca Arriel Series turboshaft engines, particularly the Arriel 1 models. This legislative instrument, known as AD/ARRIEL/10, was enacted to mitigate the risks associated with the deterioration of the 2nd stage turbine nozzle guide vanes, which had previously led to turbine failures. The Civil Aviation Safety Authority, under the authority of the Commonwealth of Australia, introduced this directive to ensure compliance with updated inspection and maintenance protocols to safeguard airworthiness and flight safety. The overarching policy objective is to enhance the safety and reliability of aircraft equipped with these engines by ensuring that they are maintained in accordance with the latest safety standards and recommendations from the engine manufacturer, Turbomeca.

Scope and Application

The Civil Aviation Regulations 1998, as specified in Part 39 - 106 of the Civil Aviation Safety Authority Schedule of Airworthiness Directives, pertain to the maintenance and operation of Turbomeca Arriel Series turbine engines, specifically the Arriel 1 variants. This legislation applies to all Arriel 1 turboshaft engines used in aircraft within Australia, ensuring adherence to strict airworthiness standards. The directive mandates specific checks and modifications based on engine type and modification status to maintain the structural integrity and operational safety of these engines. For instance, it requires certain Arriel 1 engines to undergo checks for unusual noises and free rotation of the gas generator, while others necessitate boroscope inspections or replacement of the 2nd stage turbine nozzle guide vane. Notably, these directives may be carried out by the pilot in command but exclude student pilots, with certification requirements clearly outlined. This directive became effective on 8 October 1998, replacing an earlier directive that addressed similar issues of turbine vane deterioration.

Key Provisions

The Civil Aviation Regulations 1998, specifically Part 39 - 106, detail a series of airworthiness directives concerning the maintenance and safety checks for Turbomeca Arriel Series turboshaft engines. Within this part, AD/ARRIEL/10 focuses on the 2nd stage turbine nozzle guide vanes. This directive applies to all Arriel 1 turboshaft engines (subsection (1)). The primary requirement is to carry out a check for unusual noises during engine run down and a check of the gas generator for free rotation, as outlined in Turbomeca Service Bulletin No. 292 72 0181, revision 3 dated 15/9/95 (subsection (1)). Additionally, for Arriel 1 engines with modification TU 197, an engine noise check and a boroscope inspection of the 2nd stage turbine nozzle guide vane are mandated, as specified in Turbomeca Service Bulletin No. 292 72 0212, revision 3 dated 25/6/98 (subsection (2)). Notably, these checks may be performed by the pilot in command, provided they are not a student pilot, and must be certified on the maintenance release with the pilot’s signature and licence number (subsection (2)). The obligations under this directive are clear and specific. Operators of Arriel 1 engines must ensure that the required checks and inspections are conducted. For engines with modification TU 197, this involves both an engine noise check and a boroscope inspection. Compliance with these requirements is achieved by following the detailed procedures in the Turbomeca Service Bulletins and documenting the checks on the maintenance release (subsection (1) and (2)). Furthermore, a copy of the directive and the requirement document must accompany the aircraft’s Maintenance Release (subsection (3)). Failure to comply with AD/ARRIEL/10 can result in significant consequences. The directive specifies that the checks and inspections must be completed before further flight after the effective date of 8 October 1998 (subsection (1) and (2)). Non-compliance could lead to the aircraft being deemed unairworthy, potentially resulting in grounding of the aircraft and legal repercussions for the operator. The severity of penalties can vary, but they may include fines, imprisonment, or both, depending on the breach and its impact on aviation safety. The exact penalties are not detailed in the provided text, but they would be governed by the broader Civil Aviation Act 1988 and associated regulations.