The problem of helicopter wirestrikes has existed for many years and has been costly in terms of military hardware and human lives. Loss of helicopters and crew due to strikes against obstacles such as pylons, radio masts and cables is a very serious problem, since actual missions, training exercises and maneuvers of helicopters call for flight profiles below 100 meters and in most cases at or below tree top level. In particular, profiles for combat, search, and rescue missions of military helicopters demand high speed flight at low altitude for operation below the radar horizon. These helicopters make maximum use of terrain masking to avoid detection. Obstacle avoidance during daylight operation is mainly by visual observation and at night by means of night vision goggles and thermal imaging systems.
Power transmission lines and overhead cables and wires, which represent the smallest obstacles, are not detectable by conventional microwave radar owing to their small size, and the specular nature of the return signal at the microwave frequencies. Thermal imaging systems are also inadequate since wires are often at the same temperature as the background or are below the resolution limit of these systems. Accident statistics indicate that the high damage incidents and hence high cost are attributable to collisions with power cables since these are the strongest of all cables.