AD/ARRIEL/9 - Overspeed Sensor

Overview

The Civil Aviation Regulations 1998, specifically Part 39 - 106, incorporates various Airworthiness Directives (ADs) designed to maintain the safety and airworthiness of aircraft operating in Australia. One such directive, AD/ARRIEL/9, pertains to the Turbomeca Arriel series turbine engines, addressing the issue of incorrect electrical connections in the power turbine overspeed sensor. This directive was enacted to ensure that the overspeed sensor of specified Arriel engines is correctly checked and, if necessary, corrected to prevent potential overspeed events that could compromise flight safety. The directive references a previous French civil aviation authority directive and mandates compliance by 30 April 1995. The objective is to ensure that the power turbine overspeed sensor is correctly connected, thereby maintaining the safety standards set by the Civil Aviation Safety Authority. This legislative instrument was enacted by the Australian Government to maintain stringent safety regulations in the aviation industry. The Civil Aviation Regulations 1998, enacted by the Parliament of Australia, aim to ensure the highest standards of aviation safety across the country. One such regulation, AD/ARRIEL/9, targets the Turbomeca Arriel series turbine engines, specifically addressing an issue related to the overspeed sensor's electrical connection. The policy objective of this directive is to rectify any reversed connections between the coils of the free power turbine overspeed sensor and the helicopter's electrical harness, as identified in Turbomeca Arriel Service Bulletin 292-77-0194 Revision 1. This directive was implemented to provide a clear and singular requirement for a check on the sensor's electrical connections, ensuring that all specified Arriel engine models maintain their airworthiness and comply with safety standards. The directive's focus on rectifying this specific issue aims to prevent potential overspeed events that could endanger flight safety.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 106, governs the airworthiness directives for various aircraft components, including the Turbomeca Arriel series of turbine engines. This regulation applies to all operators and owners of helicopters equipped with Arriel 1A, 1A1 engines not incorporating modification TU 13, and Arriel 1A2, 1C, 1C1, 1C2, 1E, 1E2, 1K, 1K1, 1S, and 1S1 engines. The directive mandates a once-only check of the power turbine overspeed sensor to ensure correct electrical connection, following the guidelines set out in Turbomeca Arriel Service Bulletin 292-77-0194 Revision 1. Compliance with this airworthiness directive is required prior to 30 April 1995, and this applies nationally across Australia as per the Commonwealth's regulations. The directive is directly linked to DGAC Airworthiness Directive 94-218(B), further clarifying the safety measures necessary to maintain the airworthiness of these engines.

Key Provisions

The Civil Aviation Regulations 1998, specifically in Part 39 - 106, detail the Civil Aviation Safety Authority's (CASA) Schedule of Airworthiness Directives for Turbomeca Turbine Engines, focusing on the Arriel series. In this context, AD/ARRIEL/9 pertains to the overspeed sensor of specific Arriel engines (s.1). The directive mandates that a check of the power turbine overspeed sensor must be conducted in accordance with Turbomeca Arriel Service Bulletin 292-77-0194 Revision 1 (s.2). This requirement applies to Arriel 1A, 1A1 engines not incorporating modification TU 13, as well as Arriel 1C, 1C1, 1C2, 1E, 1E2, 1K, 1K1, 1S, and 1S1 engines (s.3). The directive is rooted in a reversed connection issue identified between the two coils of the free power turbine overspeed sensor and the connector linking the sensor to the helicopter electrical harness, as referenced in DGAC Airworthiness Directive 94-218(B) (s.4). Compliance with this directive is expected before 30 April 1995 (s.5). The obligations imposed by this Airworthiness Directive include a thorough and precise inspection of the overspeed sensor to ensure the electrical connections are correct, as outlined in Turbomeca’s Service Bulletin. Operators of the affected Arriel engines must ensure that the inspection is conducted by qualified personnel following the specific guidelines provided. The aim is to prevent potential engine failures or unsafe operations that might result from an incorrect sensor connection. This obligation extends to maintaining records of the inspection, which may be required for future audits or investigations by CASA (s.6). Failure to comply with this Airworthiness Directive can result in significant consequences. Operators who do not adhere to the requirements may face penalties, as non-compliance could lead to engine malfunctions that compromise flight safety (s.7). Although the specific penalties are not detailed in the directive, non-compliance with CASA regulations generally can result in substantial fines, enforcement actions, or even grounding of the aircraft until the required checks are performed and compliance is confirmed. In severe cases, continued non-compliance might lead to the suspension or revocation of the operator's licence (s.8).