What happened
At 1115 Eastern Daylight-saving Time on 4 February 2011, a Robinson Helicopter Company R44 Astro helicopter (R44), registered VH-HFH, commenced circuit operations at Cessnock Aerodrome, New South Wales. On board the helicopter were a flight instructor, a pilot and a passenger.
Following a landing as part of a simulated failure of the hydraulic boost system for helicopter's flight controls, the instructor elected to reposition the helicopter to the apron. As the helicopter became airborne, it became uncontrollable and collided with the runway and caught fire. The pilot exited the helicopter; however, the instructor and passenger were fatally injured.
What the ATSB found
The Australian Transport Safety Bureau (ATSB) identified that a flight control fastener had detached, rendering the aircraft uncontrollable. The helicopter manufacturer had not recorded any previous instances of separation of this fastener. A number of separated components could not be located, preventing the identification of the specific reason for the separation.
A number of human factors contributed to the accident, including that the 'feel' of the flight control fault mimicked a hydraulic system failure.
Finally, the ATSB identified that fatal injuries sustained by the instructor and passenger were due to the post-impact fire and that a large number of R44s had not been modified to include upgraded bladder-type fuel tanks that reduce the risk of post-impact fuel leak and subsequent fires.
What has been done as a result
In response to the identification of a number of failures of the same type of self‑locking nuts in other aircraft, the helicopter manufacturer and Civil Aviation Safety Authority have highlighted the issue to operational and maintenance personnel.
The helicopter manufacturer also reduced the compliance time on a current service bulletin requiring that all‑aluminium fuel tanks fitted to older R44 helicopters be replaced with more impact‑resistant bladder‑type fuel tanks. A second bulletin aimed at removing a possible impact‑related ignition source was also issued.
Safety message
This accident reinforces the importance of thorough inspections by maintenance personnel and pilots. It is also a powerful reminder not to take off after identifying a possible problem with an aircraft. In addition, the accident highlights the risk of carrying unnecessary personnel during practice emergencies, and reinforces the safety benefits of incorporating the requirements of manufacturer's service bulletins in their aircraft as soon as possible.
The Australian Transport Safety Bureau encourages all operators of hydraulic system‑equipped R44 helicopters, and organisations performing inspection, testing, maintenance and repair activities on the flight control systems of those helicopters, to note the circumstances detailed in this preliminary report. It is suggested that those operators and maintenance organisations consider inspecting the security of the hydraulic-boost servos on all hydraulic system-equipped R44 helicopters.