What happened
During an aerial survey of the Central Electric distribution network, a helicopter collided with a high-voltage transmission line. The mission involved using GPS technology to precisely map the locations of individual power poles. On board the aircraft were a pilot, a technician, and a line surveyor from the local electrical supply authority, who was serving as a guide and additional lookout.
While the crew was mapping an 11kV roadside line, the aircraft struck the Roxburgh-Islington A 220kV line. The impact was severe; the reactive forces generated by the rotor strike were powerful enough to tear both the engine and the transmission components away from the airframe. The fuselage of the helicopter landed upside down. The collision resulted in one fatality and left the pilot and technician with serious injuries.
The investigation
The investigation focused on the circumstances surrounding this specific survey method, which was noted as being the first of its kind implemented in New Zealand. Investigators examined the sequence of events leading to the contact with the 220kV line and the structural failure of the aircraft following the rotor strike.
Findings
- The primary cause of the accident was the collision between the helicopter and the 220kV transmission line.
- The survey was being conducted using a new GPS-based mapping technique for electrical infrastructure.
- The crew included a dedicated lookout/guide to assist with obstacle identification.