AD/EMB-120/3 Amdt 1 - Autopilot Disengagement Logic

Overview

The Civil Aviation Regulations 1998, administered by the Civil Aviation Safety Authority (CASA), establish a comprehensive framework for ensuring the safety and efficiency of civil aviation in Australia. Specifically, Part 39 of these regulations includes the Airworthiness Directives that address safety concerns for various aircraft types, such as the Embraer EMB-120 Brasilia series aeroplanes. One such directive, AD/EMB-120/3 Amendment 1, pertains to the autopilot disengagement logic and was introduced to address a significant safety issue involving elevator trim runaway. The directive was enacted in response to an incident where an elevator trim runaway during descent led to a severe pitch-down condition, making it difficult for the crew to maintain control. The policy objective of this directive is to ensure that the crew can quickly disengage the autopilot and power from the affected servo motor when the "AP DISCONNECT" button is activated, thereby mitigating the risk of a similar incident occurring. The directive requires compliance within specific timeframes to ensure the safety of the aircraft and its occupants.

Scope and Application

The Embraer EMB-120 (Brasilia) Series Aeroplanes AD/EMB-120/3 Amendment 1, which is part of the Civil Aviation Regulations 1998, applies to the specific technical requirement outlined in the Brazilian AD 91-03-02 R2 concerning the autopilot disengagement logic. This legislation targets the operators and owners of the Embraer EMB-120 Brasilia series aeroplanes, mandating compliance with certain technical modifications to ensure safety during flight. The geographic reach of this regulation is limited to the Commonwealth of Australia, applying to all aircraft registered within the country that fall under this category. The regulation sets clear timelines for compliance, with specific deadlines for different parts of the requirement document, ensuring that all necessary modifications are completed within a defined period to mitigate the risk of elevator trim runaway during descent. This Act does not explicitly mention any exclusions or exemptions, but its application may be further defined or extended through subordinate instruments issued by the Civil Aviation Safety Authority.

Key Provisions

The Civil Aviation Regulations 1998, specifically Part 39 - 105, includes an Airworthiness Directive (AD) concerning Embraer EMB-120 (Brasilia) Series Aeroplanes, identified as AD/EMB-120/3 Amendment 1. This AD addresses the autopilot disengagement logic, as detailed in the requirement document (section 1). The directive mandates actions to be taken in accordance with the technical requirements of Brazilian AD 91-03-02 R2. Compliance with this AD is divided into three parts: Parts I and II must be actioned within 300 hours of time in service after 2 April 1991, or prior to 13 August 1991, and Part III must be completed before 31 December 1991 (section 2). Under this legislation, the entities governed by the AD are required to implement modifications to the autopilot system of Embraer EMB-120 aircraft. Specifically, the modifications must allow the crew to quickly disconnect power from the affected servo motor by disengaging the autopilot when the “AP DISCONNECT” button is activated. This is a direct response to an incident where an elevator trim runaway during descent caused significant difficulties for the crew in maintaining control of the aircraft (section 3). The purpose of these changes is to enhance the safety and control of the aeroplane by ensuring that the autopilot can be disengaged effectively in the event of a malfunction. Failure to comply with the requirements set out in the AD may result in significant consequences. Although the specific offences, penalties, or civil/criminal consequences are not detailed in the provided text, it is understood that non-compliance with ADs under the Civil Aviation Regulations 1998 can lead to severe repercussions. These may include enforcement actions by the Civil Aviation Safety Authority, which could potentially lead to fines, operational restrictions, or even grounding of the non-compliant aircraft. The severity of the penalties would depend on the nature and extent of the non-compliance and could be subject to the broader provisions of the Civil Aviation Act 1988 and related regulations. The directive’s intent is to ensure the highest safety standards are maintained in the aviation industry, thereby protecting both the crew and passengers.