1AD/SUPP/16 - Electrical Hoist Assemblies - Earth Bonding Testing

COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 107 CIVIL AVIATION SAFETY AUTHORITY

SCHEDULE OF AIRWORTHINESS DIRECTIVES

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Supplementary Equipment

AD/SUPP/16 Electrical Hoist Assemblies - Earth Bonding Testing 1/92

Applicability: 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.

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 Airworthiness Directives.

This AD has been raised to address this anomaly and will ensure that adequate and effective bonding exists between the component parts of the hoist and the between the hoist and the aircraft.