For the cutters to be effective, the helicopter must be flying at speeds greater than 30 knots [14]. The manufacturer states that if a helicopter with a WSPS impacts a wire at an angle less than 60° to the wire, the WSPS may not cut the wire (figure 24). In addition, the maximum pitch angle at which the WSPS should strike the wire and still be effective is ±5°. The system is designed to cut a 3/8-inch steel cable with a breaking strength of 12,000 lb [14].
Taken from this Study:
http://www.tc.faa.gov/its/worldpac/techrpt/ar0825.pdf