The Australian Transport Safety Bureau (ATSB) this week released the final investigation report into the crash of a Hughes 269 at Moorabbin last year, but was unable to say why the engine lost power.
VH-OBK was at the end of a navigation training flight when the pilot elected to conduct a missed approach to the southern helicopter apron. During the go-around circuit, the pilot discovered the engine had lost power and attempted to conduct an autorotation into a school gound.
The helicopter didn't make the school, forcing the pilot to land on the roof of a house. The pilot was injured and the aircraft substantially damaged.
Investigators declined to make a thorough investigation into the power loss, and instead focused on the pilot's actions during the emergency.
“As the helicopter climbed to about 650 ft above ground level, the engine lost power,” ATSB Director Transport Safety Stuart Macleod said.
“While the pilot identified a reduction in performance at this time, they did not immediately recognise the engine had lost power.
“When the pilot recognised a forced landing was required, they then did not identify a nearby football oval as the closest suitable area, possibly due to it being obscured by the airframe or instrument panel,” Macleod said.
Investigators were able to determine from the amount of damage to the rotor blades that the engine was not developing power at the point of impact.
According to the report, the pilot was not imemdiately aware of the power loss because radio traffic out of Moorabbin masked the loss in RPM, and the Hughes was not fitted with an aural rotor RPM warning.
Asked why the ATSB did not do a thorough break-down of the engine to determine the power loss, an ATSB spokesperson said there was little chance of identifying new safety issues.
"The ATSB scopes its investigative response to consider the likelihood of determining new safety issues and safety lessons for the aviation industry," the spokesperson said.
"As the Hughes 269 helicopter family and the O-360 engine series have been in service for many decades, an assessment of the available evidence in this investigation determined a more detailed inspection of the engine and airframe would be unlikely to uncover new safety lessons, and that the value of the investigation to industry is around the appropriate management of an engine power loss scenario to ensure a safe outcome."
The full investigation report is on the ATSB website.