AD/AS 355/33 Amdt 1 - Tail Rotor Front Drive Shaft

Overview

The Civil Aviation Regulations 1998, specifically under PART 39 - 105 and the Civil Aviation Safety Authority Schedule of Airworthiness Directives, address the safety of the Eurocopter AS 355 (Twin Ecureuil) Series Helicopters with a focus on the tail rotor front drive shaft, as outlined in AD/AS 355/33 Amendment 1. Enacted by the Commonwealth of Australia, this legislation was introduced to rectify a safety concern involving the forward drive shaft of the AS 355 helicopters. The issue at hand was a failure of the forward drive shaft due to excessive unbalance in the main gearbox oil cooler fan assembly, which posed significant risk to the operation of the aircraft. The objective of this legislation is to ensure the safety of the aircraft by mandating specific actions and inspections as per the Aerospatiale Service Bulletin No 05-20 Revision 2, thereby mitigating the identified risk and maintaining the airworthiness of the helicopters. This regulatory action was taken in response to a directive from the manufacturer, who identified the need for enhanced safety measures to address the specific failure mode of the forward drive shaft. The legislation outlines clear compliance requirements, including initial inspections within 50 hours of the specified date or by a particular deadline, and subsequent inspections at intervals not exceeding 100 hours of time in service. Furthermore, it necessitates inspections before and after the removal and installation of specific components, as well as in the event of abnormal vibrations or detected cracks, ensuring that any potential issues are promptly identified and rectified.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 105, applies to all model Eurocopter AS 355 helicopters fitted with a forward drive shaft P/N 355A34-1037-00. The regulation is issued under the authority of the Civil Aviation Safety Authority and is applicable nationwide across Australia. The legislation mandates compliance with Aerospatiale Service Bulletin No 05-20 Revision 2, which addresses critical safety issues identified with the tail rotor front drive shaft. The regulation requires that specified actions be taken within 50 hours of time in service after 7 December 1988, or by 31 December 1988, whichever comes first, and subsequently at intervals not exceeding 100 hours. Additionally, inspections must be conducted before the removal and after the installation of certain components, including the forward drive shaft elements, oil cooler, fan, and oil cooler or fan support. Inspections are also required if abnormal vibration in the fan assembly or a crack in the oil cooler or fan supports is observed. The regulation ensures the ongoing airworthiness of these helicopters by addressing specific mechanical issues that could compromise safety.

Key Provisions

The Civil Aviation Regulations 1998, particularly Part 39 - 105, include specific provisions for the airworthiness of Eurocopter AS 355 (Twin Ecureuil) Series Helicopters. These regulations are detailed in the Civil Aviation Safety Authority Schedule of Airworthiness Directives (AD/AS 355/33 Amendment 1), which pertain to the tail rotor front drive shaft of these helicopters. Specifically, Section 5/89 outlines the applicability and compliance requirements for all model AS 355 helicopters equipped with the forward drive shaft part number 355A34-1037-00. The directive mandates actions as per Aerospatiale Service Bulletin No 05-20 Revision 2 to address issues identified with the forward drive shaft. The Act imposes several obligations on the operators of these helicopters. Firstly, operators must ensure compliance within 50 hours of total time in service (TIS) after 7 December 1988, or by 31 December 1988, whichever is earlier. Following the initial compliance, reinspection is required at intervals not exceeding 100 hours TIS. Additionally, inspections must be carried out before removing and after installing specific components: the forward drive shaft elements, oil cooler, fan, and oil cooler or fan support. If abnormal vibration is detected in the fan assembly or if a crack is found on the oil cooler or fan supports, immediate inspection and corrective action are mandated. Failure to adhere to these requirements can result in significant consequences. The regulations do not explicitly state penalties within the provided text, but non-compliance with Civil Aviation Regulations can generally lead to enforcement actions, fines, and potential grounding of the aircraft. The severity of the consequences can vary depending on the nature and frequency of the breach, and may include administrative penalties, civil suits, or criminal charges in cases of severe non-compliance. Operators must therefore ensure strict adherence to the specified requirements to avoid these repercussions.