Overview

The Airworthiness Directive AD/A330/42, issued in 2004, addresses a critical safety concern related to the Integrated Standby Instrument System (ISIS) in Airbus A330 aeroplanes. This directive was enacted by the Civil Aviation Safety Authority (CASA) under the Civil Aviation Safety Regulations 1998. The problem it was introduced to address is the potential failure of the ISIS, which can lead to the loss of all Electronic Instrument System (EIS) Display Units. This situation is particularly hazardous during certain phases of flight. The policy objective behind this directive is to ensure the safety of flight operations by mandating a periodic reset of the ISIS to prevent failures caused by a time counter fault after prolonged continuous power supply. This measure aims to mitigate the risk of simultaneous unavailability of EIS Display Units and ISIS, which could have severe consequences.

Scope and Application

The Airworthiness Directive issued under subregulation 39.1(1) of the Civil Aviation Safety Regulations 1998 pertains specifically to Airbus A330 aeroplanes, applicable to all serial numbers of the aircraft fitted with the Integrated Standby Instrument System (ISIS) part number C16221DB04 installed through Modification 47244 during production or Airbus Service Bulletin A330-34-3120 while in service, and not fitted with Modification 52423 during production or Airbus Service Bulletin A330-34-3141 installed while in service which incorporates the new ISIS standard P/N C16221WA01. This directive aims to address the unsafe condition identified with the ISIS system that leads to potential loss of functionality, particularly during critical flight phases. The directive mandates a specific procedure to reset the ISIS system to prevent the failure caused by a time counter fault, which can occur after 145 hours of continuous power supply. The directive applies nationally within the Commonwealth of Australia and is issued by a delegate of the Civil Aviation Safety Authority. Compliance with the directive involves resetting the ISIS system within specified time frames, with the requirement to perform the reset within three days of the directive's effective date and then at intervals not exceeding five days until the new ISIS standard P/N C16221WA01 is installed. This directive is applicable across all relevant aircraft fitting the specified criteria and does not exempt any aircraft from its requirements unless the specified modifications have been made.

Key Provisions

This Airworthiness Directive (AD) primarily concerns Airbus A330 aeroplanes equipped with a specific version of the Integrated Standby Instrument System (ISIS) that has been linked to a failure mode under certain conditions. Section 13 of the AD outlines the requirement for a reset procedure to be performed on the ISIS system, either manually by opening and closing the INST STBY circuit breaker on the 742VU panel or through a complete electrical shut down of the aircraft (section 13(a)). This reset is necessary to clear a time counter fault that has been identified as a cause of the ISIS failure. The AD also mentions that the installation of a new ISIS standard P/N C16221WA01 cancels the need for this reset procedure (section 13(i)). The AD imposes several obligations on the parties it governs. The most immediate requirement is that the reset procedure must be performed within a strict timeframe: within three calendar days after the effective date of the AD, but not exceeding five calendar days from the last ISIS reset or aircraft complete power off (section 14). This reset must then be repeated at intervals not exceeding five calendar days until the new ISIS standard is incorporated (section 14). The AD also mandates that these procedures should only be performed on the ground, as resetting the ISIS system during flight is explicitly cautioned against (section 13(ii)). Failure to comply with the requirements of this AD can result in significant consequences. Although the AD does not explicitly state penalties for non-compliance, the failure to adhere to such directives can be considered a breach of the Civil Aviation Safety Regulations 1998, potentially leading to enforcement actions by the Civil Aviation Safety Authority (CASA). Such actions could include fines, suspension or revocation of airworthiness certificates, or other regulatory actions deemed necessary by CASA to ensure compliance with safety standards. The potential for civil or criminal liability also exists for operators who fail to adhere to these safety mandates, particularly if such non-compliance results in an incident or accident.