AD/EC 120/1 - Tail Gearbox - Load Measurements

Overview

The Civil Aviation Regulations 1998, administered by the Civil Aviation Safety Authority (CASA), were enacted to ensure the safety of civil aviation in Australia. Part 39 - 105 of these regulations includes the Schedule of Airworthiness Directives, which mandate specific actions to address identified safety issues. One such directive, AD/EC 120/1, pertains to Eurocopter EC 120 Series Helicopters, specifically addressing the issue of significant binding of the tail rotor pitch change control rod. This problem was identified through in-service experience and could potentially lead to a loss of control. The policy objective of this directive is to enhance aviation safety by requiring inspections and necessary repairs on the affected tail gearboxes to mitigate the identified risk. Compliance with this directive is mandatory and must be achieved within specified timeframes and conditions to ensure the continued airworthiness of the affected helicopters.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 105 and the Civil Aviation Safety Authority's Schedule of Airworthiness Directives, pertain to Eurocopter EC 120 Series Helicopters. This legislative instrument applies to all EC120B helicopters equipped with tail gearbox part numbers C652A010 1051 or C652A010 1052 and the serial numbers M101 through M124 (inclusive) and M126. The requirements outlined in the legislation mandate the removal and measurement of the operating load of the pitch change control rod in the tail gearbox, with specific instructions referenced from EUROCOPTER EC120 Service Bulletin No. 01.001. Compliance necessitates the reinstallation of the tail gearbox and tail rotor hub following manufacturer instructions, and if the measured loads exceed specified limits, replacement of the tail gearbox with a compliant unit. This directive becomes effective from 12 May 1999, with compliance deadlines set for either 50 flying hours from the effective date or by 30 September 1999, depending on the measured loads. This regulation ensures the continued airworthiness of the specified helicopters by addressing identified safety concerns regarding the tail gearbox.

Key Provisions

The Civil Aviation Regulations 1998, specifically Part 39 - 105, mandates the issuance of airworthiness directives for various aircraft, including Eurocopter EC 120 Series Helicopters. Under this directive (AD/EC 120/1), the focus is on the tail gearbox of EC120B helicopters, particularly those equipped with tail gearbox part numbers C652A010 1051 or C652A010 1052, and serial numbers ranging from M101 to M124, inclusive, and M126. This directive applies to a specific set of helicopters, and its purpose is to ensure the safety of these aircraft by addressing potential defects in the tail gearbox. The directive outlines several key requirements for the affected helicopters. Firstly, the tail rotor hub and tail gearbox must be removed, and the operating load of the pitch change control rod must be measured as per the instructions in para 2B(1) of EUROCOPTER EC120 Service Bulletin No. 01.001 (section 1). Following this measurement, the tail gearbox and tail rotor hub must be reinstalled according to the manufacturer’s instructions, specifically referencing work cards 65.21.00, 4-2 and 64.21.00, 4-2 respectively (section 2). If the measured loads exceed 1.2 daN, the tail gearbox must be replaced with a compliant gearbox, which is defined as one with an inapplicable serial number or one that meets the acceptable operating load criteria as per section 1 (section 3). Compliance with this directive is crucial for maintaining the airworthiness of the specified helicopters. Operators must ensure that the required inspections and repairs are carried out within 50 flying hours of the directive's effective date, which is 12 May 1999, but no later than 30 September 1999 (section 1). If the measured loads are equal to or less than 1.2 daN, compliance is achieved. However, if the measured loads are greater than 1.2 daN, compliance must be achieved before the next flight (section 2). Failure to adhere to these requirements can result in significant safety risks, as the directive was issued in response to service experience indicating significant binding of the tail rotor pitch change control rod, which could lead to loss of control of the aircraft. Breaching the provisions of this directive can have serious consequences. The Civil Aviation Safety Authority (CASA) may take enforcement action against non-compliant aircraft operators. The potential penalties include fines and other sanctions, which can vary depending on the severity and frequency of the breach. In severe cases, CASA may ground the aircraft until the necessary repairs are completed, which could result in significant operational disruptions and financial loss for the operator.