What happened
A MBB BK117A-3 helicopter was conducting a medical transport operation during nighttime conditions under visual meteorological rules (VMC). The aircraft was on its final approach to an asphalt road located near the scene of a traffic accident. During this descent, the helicopter collided with overhead wires.
The pilot reported that he did not visually detect the wires prior to impact and remained unaware of the collision until ground personnel alerted him after the event. Prior to beginning his final descent for landing, the pilot stated that he had performed numerous orbits around the area. He indicated that his visibility was significantly impaired by blowing dust generated by the helicopter's rotor wash. Additionally, the pilot reported being blinded by a spotlight emitted from a law enforcement vehicle on the ground.
The flight nurse, seated in the right seat and facing aft, corroborated these conditions, noting the dusty environment. She also confirmed that ground personnel had directed the spotlight directly into the pilot's face. The pilot further noted that radio communications with ground personnel were frequently garbled, complicating situational awareness during the approach.
Findings
The investigation identified several contributing factors to the collision. Obstructed vision due to blowing dust and intense glare from a ground-based spotlight played significant roles in preventing the pilot from seeing the wires. The combination of these environmental factors, along with garbled communications, hindered the pilot's ability to navigate safely during the final phase of flight.