A Kawasaki KH‑4 helicopter had a forced landing accident while operating a scenic flight, following a loss of engine power likely due to a crack in its exhaust, an ATSB investigation report details.
On the afternoon of 11 September 2024, the Katherine Helicopters operated KH‑4, a licence‑built variant of the Bell 47 helicopter powered by a turbocharged Lycoming TVO‑435 piston engine, was operating a scenic flight with a pilot and two passengers on board.
While flying towards the entrance to the Nitmiluk (Katherine) Gorge, the pilot later reported that the engine did not respond to increased throttle, and the helicopter was losing speed and height.
Due to rocky terrain below the helicopter, the pilot had to find a suitable clear area for a forced landing some distance away.
"The pilot's prompt identification of a suitable landing site was instrumental in ensuring the safety of those on board," ATSB Director Transport Safety Stuart Macleod said.
"However, low main rotor RPM likely led to the reported minimal flare effect experienced by the pilot when they approached the landing site."
During the attempted run‑on landing, the helicopter struck the ground, damaging its tail rotor assembly and skids.
Despite the substantial damage to the helicopter in the impact, the pilot and passengers were uninjured.
Post‑accident inspection identified a large crack in the engine exhaust pipework, which likely resulted in the engine power loss.
"Being a turbocharged engine, the escape of exhaust gases through the crack has likely resulted in the engine power loss during flight due to the loss of boost pressure resulting in the wastegate remaining closed," Mr Macleod explained.
While the pilot's quick identification of a suitable landing area demonstrated the value of emergency procedure knowledge, the accident also highlights the precise positioning and energy maintenance required for a successful autorotation landing.
"Thorough and regular training in emergency procedures is crucial for all pilots," Mr Macleod concluded.
"This is particularly true for pilots operating over rugged terrain with limited safe emergency landing options."
You can find here the final report: Collision with terrain involving Kawasaki KH-4, VH-BEU, 24 km north of Katherine Tindal Airport, Northern Territory on 11 September 2024
