AD FAA-2012-0356

We are adopting a new airworthiness directive (AD) for all Eurocopter Deutschland GmbH (ECD) MBB-BK 117 A-3, MBB-BK 117 A-4, MBB- BK B-1, MBB-BK 117 B-2, and MBB-BK C-1 helicopters equipped with a certain external-hoist system (hoist system). This AD requires deactivating the entire hoist system or deactivating the hoist system cable cutter function on the hoist system operator control handle (operator handle). This AD was prompted by an uncommanded activation of the hoist cable cutter function on an MBB-BK117 C-1 helicopter. The actions of this AD are intended to prevent uncommanded cutting of the hoist cable and subsequent injury to persons being lifted by the hoist.