The Transport Accident Investigation Commission (TAIC) of New Zealand has released its report on the April 2011 crash of a Robinson R22 helicopter in the country’s Southern Alps, finding that the aircraft broke up in flight in turbulence.
Killed in the crash were Wanaka Helicopters instructor Graham Stott, 31, and student Marcus Hoogvliet, 21. According to the report, Stott and Hoogvliet were on a cross-country training flight in the Southern Alps on April 27, 2011 when they encountered winds that were stronger than forecasted, including gusts of over 30 knots causing turbulence on the leeward side of mountains and passes.
Stott and Hoogvliet were reported overdue that afternoon, and the wreckage of their helicopter was discovered the following day. According to the report, examination of the wreckage revealed that the helicopter had broken up in flight when the main rotor blades deviated from their normal operating plane of rotation and struck the tail boom, causing a separation of the tail rotor assembly.
The TAIC determined that the helicopter had been operating in a high-risk situation at the time of the crash due to a combination of factors: it was at an altitude of approximately 5,500 feet, close to its maximum permissible weight and entering an area of moderate to extreme turbulence. The commission determined that the in-flight break up was likely to have been caused by one or more of the following conditions: severe or extreme turbulence buffeting the helicopter; the main rotor speed being allowed to drop below its lower limit; or the pilots making large and abrupt movements of the controls.
Among the safety issues identified by the TAIC was the possibility that Stott was not fully aware of the risks involved in flying the Robinson R22 helicopter near maximum weight at high altitude, and in moderate to severe turbulence. “The format of the Robinson R22 helicopter flight manual and the terminology it uses do not draw appropriate attention to safety-critical instructions and conditions that could result in serious injury or death,” the TAIC stated.
A further but non-contributing safety issue was the crash survivability of emergency locator transmitters (ELTs), which automatically alert rescue co-ordination centers when an aircraft accident or incident has occurred. When the helicopter crashed, the ELT activated but was so severely damaged that it was unable to transmit a useable location signal. In this case, however, a separate flight tracking device installed on the helicopter had been transmitting position reports to the operator’s base, so when the helicopter was reported overdue search aircraft were directed immediately to the general area where the helicopter had crashed.
The TAIC made two recommendations to the Director of Civil Aviation to address the pilot and instructor ratings on Robinson helicopters, and a further two recommendations to support international efforts to improve the crashworthiness of ELTs and promote the use of alternative aircraft tracking systems to aid search and rescue efforts.
To read the complete report on the TAIC website, click here.
