Overview

The Airworthiness Directive AD/AS 355/61, issued by the Civil Aviation Safety Authority (CASA) on 11 January 2002 and effective from 14 January 2002, was enacted to address a safety concern regarding starter generator wear and vibration in Eurocopter AS 355 (Twin Ecureuil) Series Helicopters. This directive was introduced in response to reports from the Direction Générale de l'Aviation Civile (DGAC) about instances where starter generator wear and vibration had led to cracks that could result in the failure of engine exhaust pipe attachment lugs, potentially causing loss of part of the exhaust pipe system. The policy objective of this directive is to mandate repetitive inspections and vibration checks to detect early signs of starter generator failure, thereby preventing potential in-flight hazards. The directive applies to AS 355N helicopters equipped with specific starter generator parts and outlines the necessary checks and intervals for compliance.

Scope and Application

The Airworthiness Directive (AD) applies specifically to Eurocopter AS 355 (Twin Ecureuil) series helicopters that are fitted with starter generators of Part Number (P/N) 524-060 or 524-061. This includes both new installations and those already in service at the effective date of the directive. The AD mandates particular actions to be taken to ensure the safe operation of these helicopters, specifically addressing potential issues with starter generator wear and vibration that could lead to structural failure. The directive is issued under the authority of the Civil Aviation Safety Authority (CASA) and is applicable throughout the Commonwealth of Australia. The directive requires compliance with specified vibration and torque checks at various intervals post-installation and post-flight hours, ensuring the ongoing airworthiness of the affected helicopters. The directive does not exclude any particular entity or operator, thereby imposing a broad obligation across the industry for all relevant aircraft.

Key Provisions

The Airworthiness Directive (AD) issued under subregulation 39.1 (1) of the Civil Aviation Regulations 1998 applies specifically to Eurocopter AS 355 (Twin Ecureuil) Series Helicopters equipped with certain starter generators (sections 1 and 2). The directive mandates that all AS 355N helicopters fitted with starter generators part numbers 524-060 or 524-061 must undergo specific checks and maintenance procedures to ensure airworthiness (section 3). For starter generators installed after the effective date of this directive, vibration level checks and tightening torque checks must be performed in accordance with prescribed procedures at specified intervals (section 4). For starter generators already installed before the effective date, tightening torque checks must be conducted if they have accumulated more than 15 hours of time in service (TIS), and vibration level checks must be performed if they have accumulated more than 110 hours TIS (section 5). Operators and owners of the specified helicopters are obligated to comply with these requirements, ensuring that the necessary checks and maintenance are performed before further flight and at the specified intervals (section 6). These obligations include conducting the vibration level checks and tightening torque checks as per the detailed procedures outlined in the Eurocopter Alert Telex No 01.00.45 R3 and the maintenance manual (MET) work card 80.06.00.401 (section 7). The compliance section specifies the exact timing of these checks, detailing that checks must be carried out before further flight after each installation, and then at intervals of 10 to 15 hours TIS, 25 to 35 hours TIS, 45 to 55 hours TIS, 70 to 80 hours TIS, and 100 to 110 hours TIS, and thereafter every 110 hours TIS (section 8). Failure to comply with the requirements of this AD may result in the aircraft being deemed unairworthy, which could lead to serious safety risks (section 9). The AD supersedes the previous AD/AS 355/56 and becomes effective from 14 January 2002 (section 10). The directive was issued to address the issue of starter generator wear and vibration that could lead to cracks and potential failure of the engine exhaust pipe attachment lugs, which could ultimately result in the loss of part of the exhaust pipe system (section 11). This measure is crucial to prevent any risk of in-flight failure that could compromise the safety of the aircraft and its occupants.