AD/EMB-120/11 Amdt 1 - AHRS Power Interruption

Overview

The Civil Aviation Regulations 1998, enacted by the Commonwealth of Australia, address the critical issue of ensuring the safety and airworthiness of aircraft operating within Australia's airspace. One of the specific amendments under this act is the Airworthiness Directive (AD) concerning Embraer EMB-120 Brasilia Series Aeroplanes, which was introduced to mitigate risks associated with erroneous heading information displayed during certain electrical system failures. The AD/EMB-120/11 Amendment 1 aims to prevent power interruptions in the Aircraft Horizontal Reference System (AHRS) by implementing specific actions for aircraft operators, including deactivating certain circuit breakers and placarding to ensure compliance with safety standards. The policy objective of this AD is to maintain the highest safety standards by providing clear and enforceable measures to address identified risks in the operation of the EMB-120 series aircraft.

Scope and Application

The Embraer EMB-120 (Brasilia) Series Aeroplanes Airworthiness Directive, AD/EMB-120/11 Amendment 1, applies to all Brasilia model EMB-120, EMB-120RT and EMB-120ER aircraft, with specific serial numbers excluded from the scope. This directive, issued by the Civil Aviation Safety Authority under the Civil Aviation Regulations 1998, is applicable on a Commonwealth level across Australia. The directive aims to address erroneous heading information that may be displayed on the Electronic Horizontal Situation Indicators (EHSIs) following certain electrical system failures. The directive mandates actions including the deactivation of certain circuit breakers, installation of circuit breaker collars or equivalent, and placarding to prevent the closure of specified circuit breakers. For aircraft equipped with an Auxiliary Power Unit (APU), the directive further requires changes to the Minimum Equipment List. Compliance with the directive is required prior to specified dates, with the directive superseding any prior temporary procedures issued to address the issue.

Key Provisions

The Embraer EMB-120 (Brasília) Series Aeroplanes Airworthiness Directive AD/EMB-120/11 Amendment 1, titled "AHRS Power Interruption" (2/95), applies to all Brasilia model EMB-120, EMB-120RT and EMB-120ER aircraft, except those with specific serial numbers (section 1). This directive mandates several actions to address a reported issue of erroneous heading information following certain electrical system failures. For aircraft not equipped with an Auxiliary Power Unit (APU), it requires the operators to pull circuit breakers CB 534 and CB 535, install collars to prevent their closure, and affix a placard stating "Do not close CB 534 or 535" (section 1(a)-(c)). For aircraft equipped with an APU, operators must either deactivate the Automatic Horizontal Situation Indicator/Electronic Flight Instrument System automatic power transfer system in accordance with the instructions for aircraft not equipped with an APU or alter the Minimum Equipment List by removing items 24-30-1 and 24-30-2 (section 1(b)(i)-(ii)). Additionally, operators must follow Embraer Service Bulletin 120-24-0008 Revision 3 dated 19 August 1994 (section 1(c)). Operators of the affected aircraft must ensure compliance with the directive's requirements. Specifically, for aircraft not equipped with an APU, compliance remains unchanged as it was prior to 5 July 1994 (section 2(1)). For aircraft equipped with an APU, compliance must be achieved prior to 10 May 1995 (section 2(2)). Operators must adhere to these timelines and ensure the necessary modifications and placarding are completed according to the directive's specifications to maintain the airworthiness of the aircraft. Failure to comply with the provisions of AD/EMB-120/11 Amendment 1 may result in significant consequences. The Civil Aviation Safety Authority (CASA) enforces strict compliance with airworthiness directives to ensure the safety of aviation operations. Non-compliance could lead to penalties, including fines, suspension or revocation of the aircraft's certificate of airworthiness, and potential criminal charges against the operator or responsible individuals. The severity of the penalties may depend on the extent of the non-compliance and any resulting safety risks. It is imperative for operators to adhere to the directive to avoid these adverse outcomes.