Limitations of the hydraulic system and pilot control input led to the March 2016 collision with terrain of a helicopter near Smithers, British Columbia
RICHMOND, BC, March 28, 2018 /CNW/ - In its investigation report released today (A16P0045), the Transportation Safety Board of Canada (TSB) found that design limitations of the helicopter's hydraulic system, combined with how control inputs were applied, led to the March 2016 loss of control and collision with terrain involving a helicopter near Smithers, British Columbia.
On 16 March 2016, an Airbus Helicopter AS 350 FX2 operated by TRK Helicopters Ltd., departed from the base of a ski run approximately 82 nautical miles northwest of Smithers, on a day visual flight rules flight to the base camp, with the pilot and six passengers onboard. Soon after takeoff, while operating at low altitude, the pilot initiated a descent into a ravine. During the descent, the helicopter's airspeed increased rapidly. Moments later, the helicopter abruptly rolled to the right, pitched up, and collided with terrain on a steep snow-covered slope. There were no injuries, and all seven occupants exited the helicopter, which was substantially damaged. There was no post-impact fire and the emergency locator transmitter did not activate.
The investigation highlighted a well-known design characteristic of the AS 350 hydraulic system, called servo transparency. This phenomenon occurs when the aerodynamic forces on the main-rotor system, due to a combination of environmental and operational factors, exceed the capability of the hydraulic system and cause the aircraft to pitch up and roll to the right. The investigation found that prior to the crash, the pilot placed the helicopter in a flight regime that resulted in servo transparency. Although the self-correcting tendency of the aircraft allowed the pilot to regain hydraulic system assistance, the altitude was too low for the pilot to recover before impact.
The helicopter was not equipped with a flight data recorder or a cockpit voice recorder, nor were these required by regulation. However, there was a Global Positioning System (GPS) onboard that incorporated a data recording capability. The flight was also captured on two personal in-flight videos. The GPS and videos provided investigators with vital information about airspeed and other key variables in the last seconds of the flight. The Board has recommended in the past that Transport Canada work with industry to implement flight data monitoring and lightweight flight recorders in commercial aircraft (Recommendation A13-01). Although the recommendation was supported by the regulator, few concrete actions have been taken to date.
The investigation also found that the emergency locator transmitter failed because of undetected wear over time. If manufacturers do not follow recommended inspection and/or replacement schedules provided by sub-component suppliers, there is an increased risk that the emergency locator transmitter will fail.
Following the occurrence, TRK Helicopters Ltd. amended its training curriculum to emphasize emergency procedures related to hydraulic system failures and the conditions that increase the risk of servo transparency. Airbus Helicopters has begun developing flight data monitoring systems and has undertaken to revise its training syllabus, with the possible inclusion of a video on servo transparency.
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SOURCE Transportation Safety Board of Canada
For further information: Transportation Safety Board of Canada, Media Relations, 819-994-8053, [email protected]
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