What aircraft was involved and where did it happen?

The accident on 2000-03-28 involved a aircraft, at NZ.

What was the probable cause of the accident?

The helicopter's main rotor blades struck high-tension power lines during a turn, likely due to difficulty in judging the distance from the wires and a focus on the landing area during the approach.

Fatal Helicopter Wire Strike at Lake Manapouri

A Hughes 369FF helicopter crashed into power lines during a charter flight in New Zealand, resulting in five fatalities.

What happened

On 28 March 2000, a Hughes 369FF helicopter, registration ZK-HJN, was performing a charter flight from Te Anau Aerodrome to West Arm, Lake Manap/pouri. The flight was carrying a pilot and four passengers. As the aircraft was executing a turn to approach the landing area, the main rotor blades struck high-tension power lines spanning the lake. The impact caused the rotor blades to separate from the mast, leading to a total loss of control. The helicopter struck the ground and rolled down a bank near the lake's edge. The accident resulted in 5 fatalities, including the pilot and all passengers, and the aircraft was destroyed.

The investigation

Investigators examined the flight path, the aircraft's mechanical state, and the visibility of the overhead infrastructure. The investigation confirmed that the helicopter was fully serviceable, within weight and balance limits, and that the pilot was appropriately licensed and fit for duty. Meteorological conditions were clear and suitable for flight.

Analysis of the flight path indicated that while the power lines were large and visible, the massive span between the supporting towers made it extremely difficult to accurately judge the distance from the conductors. Evidence suggested the pilot may have been focused on the landing area during the base turn, potentially leading to an oversight of the wires' proximity.

Findings

The primary cause of the accident was the main rotor blades striking the power line conductors.
The pilot may have misjudged the approach or been focused on the landing site rather than the overhead wires during the turn.
While the conductors were visible, the long distance between towers made depth perception and distance assessment highly unreliable.
The accident was not survivable due to the severity of the impact and the structural failure of the rotor system.

Safety action

Following the investigation, recommendations were made to the Director of Civil Aviation to review the criteria for marking overhead wires and structures, specifically prioritizing large spans. The goal was to expedite updated Civil Aviation Rules regarding the assessment and marking of new or altered overhead cables to prevent similar occurrences.