The helicopter was flying at 40' above ground level to enable the cameraman to film a vehicle. The crew heard a loud bang and the pilot suspected an engine failure so he commenced an autorotation. However, he quickly found that the engine responded normally to power changes but not knowing what had caused the noise, he decided to land on suitable terrain just ahead. After they had exited the helicopter, the cameraman reported to the pilot that he saw a wire just prior to hearing the noise. Inspection of the machine confirmed that it had suffered a wirestrike. The task required a high degree of attention on the movements of the vehicle in order to position the helicopter as required by the cameraman. The pilot did not have a low flying approval and his supervisor had instructed him not to descend below 100 feet above ground level, however he complied with the cameraman's request to fly as low as possible. The person occupying the left seat was not trained as an observer for this type of operation. The supporting poles for the wire struck by the helicopter were widely spaced and one was obscured by a stand of trees.
