AIRWORTHINESS DIRECTIVE On the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below repeals Airworthiness Directive (AD) AD/SUPP/16 and issues the following AD under subregulation 39.001 (1) of CASR 1998 and subsection 33 (3) of the Acts Interpretation Act 1901. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct an unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section. Supplementary Equipment (including Rescue Hoists) AD/SUPP/16 Amdt 1 Electrical Hoist Assemblies - Earth 5/2016 Bonding Testing Applicability: For aircraft to which Part 42 of CASR 1998 applies: All electrical hoist assemblies which do not have specific bonding testing requirements called up in any other Australian AD. Requirement: 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) and between the hoist assembly and the aircraft. Maximum resistance is to be 0.010 OHM. The bonding resistance tests are to be carried out using a bonding tester capable of resolving to 0.002 OHM. Compliance: For uninstalled hoists, prior to installation; for installed hoists, prior to 12 March 1992, and thereafter at intervals not exceeding 24 months. The effective date of this AD is 26 February 2016. Background: Electrical hoist assemblies fitted with pyrotechnic cable cutting devices have been shown to be susceptible to uncommanded initiation of the explosive squib resulting in the hoist cable being severed. A large number of these uncommanded cable cuts have been attributed to ineffective bonding between various component parts of the hoist assembly or between the hoist assembly and the aircraft. Various hoist and aircraft manufacturers have adequately addressed this problem for specific hoists and aircraft, however it is possible that not all hoist and aircraft bonding requirements are adequately covered by manufacturers data or other ADs. This original issue of this AD was issued to address this anomaly and ensured that adequate and effective bonding exists between the component parts of the hoist and between the hoist and the aircraft. Amendment 1 is issued to limit the AD's applicability to Part 42 aircraft only. This AD will be repealed after the requirements are incorporated into a future amendment of the Part 42 Manual of Standards. Pieter van Dijk Delegate of the Civil Aviation Safety Authority 22 February 2016