Overview

The Civil Aviation Regulations 1998 (CAR 1998) were enacted to ensure the safety of civil aviation in Australia by establishing regulations that govern the operation of aircraft and the certification of personnel and organisations involved in aviation. The regulations are administered by the Civil Aviation Safety Authority (CASA) and are designed to address various safety concerns and maintain high safety standards within the industry. The Airworthiness Directive (AD) issued under subregulation 39.1 (1) of CAR 1998 is a specific legislative instrument that aims to correct unsafe conditions identified in certain aircraft or aeronautical products. In this instance, the AD pertains to the Sikorsky S-76 Series Helicopters and was introduced to address an issue where the attitude and heading reference warning system could fail, potentially leading to a loss of autopilot functionality and control of the helicopter. The policy objective of the AD is to mandate modifications to the aircraft’s electrical power distribution system to prevent such unsafe conditions, thereby enhancing the overall safety of civil aviation in Australia.

Scope and Application

The Airworthiness Directive AD/S-76/67 issued by the Civil Aviation Safety Authority (CASA) under the Civil Aviation Regulations 1998, pertains specifically to certain models of Sikorsky S-76 helicopters. This legislation applies to Model S-76B helicopters with serial numbers 760430, 760441 through 760445, 760448 through 760452, 760454, 760455, 760458, 760462, and 760465, as well as Model S-76C helicopters with serial numbers 760420, 760436, 760438, 760440, 760453, 760456, 760457, 760459, 760460, 760461, 760463, 760464, 760466 through 760487. The directive mandates specific modifications to the Nos. 1 and 2 attitude and heading reference system (AHRS) WARN circuits, which are to be carried out in accordance with the instructions detailed in the Accomplishment Instructions of the Sikorsky Aircraft Corporation Alert Service Bulletin 76-34-7A (320A), Revision A. This action is necessitated to prevent potential failures of the autopilots and subsequent loss of control of the helicopter due to a failure of the essential bus. The directive requires compliance by 21 April 2002 and became effective on 21 March 2002.

Key Provisions

The Civil Aviation Regulations 1998, under Part 39 - 105, issue an Airworthiness Directive (AD) for Sikorsky S-76 Series Helicopters. Specifically, AD/S-76/67 dated 3/2002, focuses on the modification of the attitude and heading reference warning (AHRS WARN) circuits in certain model S-76B and S-76C helicopters. The applicability section of the AD (section 1) specifies the serial numbers of the S-76B and S-76C helicopters that are subject to the directive. This includes S-76B models with serial numbers ranging from 760430 to 760465, and S-76C models with serial numbers from 760420 to 760487. The requirement section (section 2) mandates that modifications be made to the number 1 and 2 AHRS WARN circuits according to the instructions outlined in paragraphs 3.A through 3.D of Sikorsky Aircraft Corporation Alert Service Bulletin 76-34-7A (320A), Revision A, dated 17 September 2001. This is intended to address a potential unsafe condition that could lead to both autopilots going offline during a ground test simulating a loss of the essential bus. The AD imposes specific obligations on the parties it governs. Firstly, the owner or operator of any S-76B or S-76C helicopter within the specified serial number range must ensure that the AHRS WARN circuits are modified as instructed. This involves following the Accomplishment Instructions in the referenced Sikorsky Aircraft Corporation Alert Service Bulletin. The compliance section (section 3) stipulates that these modifications must be completed no later than 21 April 2002. The directive itself became effective on 21 March 2002, providing a clear timeframe within which compliance must be achieved. The background section (section 4) explains that this directive was issued in response to a safety concern identified by the United States Federal Aviation Administration, where a ground test simulation resulted in both autopilots going offline due to a failure of the essential bus. This safety concern necessitated changes to the electrical power distribution system to mitigate the risk of an AHRS fail signal leading to the loss of autopilot functions and subsequent loss of control of the helicopter. Failure to comply with the Airworthiness Directive can result in serious consequences. The AD explicitly states that the modifications must be carried out by the specified deadline. Non-compliance with this requirement could potentially lead to the grounding of the affected helicopters until the modifications are completed. The regulatory authority, the Civil Aviation Safety Authority (CASA), has the power to enforce compliance and may take action against operators or owners who fail to adhere to the directive. Such actions could include fines, suspension of airworthiness certificates, or other regulatory penalties. The severity of these consequences underscores the importance of timely compliance with the AD to ensure the continued airworthiness and safety of the affected helicopters.