AD/SUPP/16 - Electrical Hoist Assemblies - Earth Bonding Testing

Overview

The Civil Aviation Regulations 1998, under the oversight of the Civil Aviation Safety Authority (CASA), were amended to include supplementary equipment directives, specifically addressing electrical hoist assemblies. The legislation, F2006B07143, was enacted to mitigate the risk of uncommanded initiation of pyrotechnic cable cutting devices in electrical hoist assemblies due to ineffective bonding. This was a critical issue identified in hoists where inadequate bonding between component parts or between the hoist and the aircraft could result in the hoist cable being severed unexpectedly. The policy objective of this directive is to ensure that there is adequate and effective bonding between all adjacent component parts of the hoist assembly, including the control box, electrical motor casing, hoist body, hoist arm, and attachment bracket, as well as between the hoist assembly and the aircraft, with a maximum resistance limit of 0.010 OHM, tested using a bonding tester capable of resolving to 0.002 OHM. This directive mandates compliance checks for uninstalled hoists prior to installation and for installed hoists prior to 12 March 1992 and subsequently at intervals not exceeding 24 months.

Scope and Application

The Civil Aviation Safety Authority's Supplementary Equipment Airworthiness Directive (AD/SUPP/16) applies to all electrical hoist assemblies that do not have specific bonding testing requirements outlined in other Australian Airworthiness Directives. This directive mandates the testing of electrical bonding between all adjacent component parts of the hoist assembly, including the control box, electrical motor casing, hoist body, hoist arm, and attachment bracket, as well as between the hoist assembly and the aircraft. The maximum allowable resistance for these bonds is set at 0.010 OHM, with tests to be conducted using a bonding tester that can resolve to 0.002 OHM. Compliance with this directive requires that bonding tests be performed on uninstalled hoists before installation, on installed hoists before 12 March 1992, and subsequently at intervals not exceeding 24 months. This directive applies across the Commonwealth of Australia and is intended to address the issue of uncommanded initiation of pyrotechnic cable cutting devices, which have been linked to ineffective bonding between various components of the hoist assembly or between the hoist assembly and the aircraft. While various hoist and aircraft manufacturers have already addressed this problem for specific hoists and aircraft, this AD ensures that all hoists meet the required bonding standards to prevent potential safety issues.

Key Provisions

The Civil Aviation Regulations 1998, specifically Part 39, Subpart 107, mandates the requirement for earth bonding testing of electrical hoist assemblies, as outlined in Supplementary Equipment AD/SUPP/16 (sections 1-92). This regulation applies to all electrical hoist assemblies that do not have specific bonding testing requirements stipulated in other Australian Airworthiness Directives (AD). The primary requirement of this directive is to check the electrical bonding between all adjacent component parts of the hoist assembly, including the control box, electrical motor casing, hoist body, hoist arm, and attachment bracket, as well as between the hoist assembly and the aircraft. The maximum allowable resistance for these bonds is 0.010 ohms, and the tests must be conducted using a bonding tester that can resolve to 0.002 ohms. The obligations imposed by this regulation are quite clear. For hoists that are not yet installed, the bonding tests must be conducted prior to their installation. For hoists that have already been installed, the tests must be carried out prior to 12 March 1992, and then at intervals not exceeding 24 months. These requirements aim to ensure that the bonding between the hoist components and between the hoist and the aircraft is adequate and effective, preventing uncommanded initiation of pyrotechnic cable cutting devices. The background to this directive highlights the risks associated with ineffective bonding, such as the uncommanded severing of hoist cables, which has been attributed to bonding issues. Although various hoist and aircraft manufacturers have addressed this issue for specific hoists and aircraft, this directive ensures that all hoists comply with the bonding requirements. Failure to comply with the requirements of this directive can lead to serious consequences. Electrical hoist assemblies that do not meet the specified bonding requirements are likely to pose significant safety risks, potentially leading to the uncommanded initiation of pyrotechnic cable cutting devices. Although the specific offences, penalties, or civil/criminal consequences for breach are not detailed within this particular directive, non-compliance with airworthiness directives in general can lead to enforcement actions by the Civil Aviation Safety Authority. These actions may include fines, suspension or revocation of airworthiness certificates, and other regulatory measures. The severity of these consequences underscores the importance of adhering to the bonding testing requirements set out in this directive.