N174CD

The pilot reported that during takeoff from a field next to an office building, the helicopter came in contact with one or two power lines, which caught on the left skid, and pulled the helicopter to the left. The main rotor blades contacted two power lines, and cut both of them. The pilot attempted to maintain control of the helicopter but it rolled to the left and impacted the ground. He reported that "the wires hit were invisible to me at the time of departure." A postflight inspection revealed substantial damage to the fuselage, the main rotor blade system, the tail boom, and the tail rotor blade system.

The pilot reported there were no pre-impact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation.

The pilot also stated as a safety recommendation, it would be "Best to walk the entire departure path, look for poles, wires, and guy wires prior to departure, especially with trees present, and a dark day which conceals the presence of wires. Don't get locked into one departure route. Turn the cellphone off when evaluating sites, and look 360 degrees."

ADDITIONAL INFORMATION

Robinson Helicopter Company Safety Notice SN-16

Robinson Helicopter Company has published Safety Notice SN-16 Power Lines Are Deadly (revised June 1994). This safety notice discusses wire strike mitigation techniques. The safety notices states;

Flying into wires, cables, and other objects is by far the number one cause of fatal accidents in helicopters. Pilots must constantly be on the alert for this very real hazard.

Watch for the towers; you will not see the wires in time. Fly directly over the towers when crossing power lines. Allow for the smaller, usually invisible, grounding wire(s) which are well above the larger more visible wires. Constantly scan the higher terrain on either side of your flight path for towers. Always maintain at least 500 feet above ground level (AGL) except during takeoff and landing. By always flying above 500 feet AGL, you can virtually eliminate the primary cause of fatal accidents.