What happened
On July 1, 2007, a Eurocopter AS 350 B2 helicopter, registration C-FLUK, was performing a ferry flight from a fuel cache to Points North Landing, Saskatchewan. The aircraft was carrying a pilot and one passenger. After completing a survey flight earlier that day, the crew departed the fuel cache, sending messages indicating an expected arrival time of 1905 central standard time. When the aircraft failed to arrive, emergency procedures were initiated by the survey company.
Search efforts located debris on Bernick Lake the following day. An underwater search later recovered the wreckage at a depth of 69 feet. The helicopter had sustained extensive damage upon hitting the water. Both occupants sustained serious injuries during the impact but subsequently drowned as the aircraft sank.
The investigation
The investigation focused on the mechanical state of the engine and the flight dynamics during the emergency. Investigators examined the Honeywell LTS101-700D-2 engine and found that the number three power turbine shaft bearing had failed. This failure caused the power turbine shaft to move rearward, cutting the engine's Py line. This triggered a design feature that automatically reduced fuel flow to a minimum level, dropping engine speed to a ground idle setting insufficient to maintain flight.
Technical analysis of the engine revealed corrosion pitting on the bearings, likely caused by improper storage procedures during a period when the engine was not maintained according to manufacturer specifications. The investigation also looked into the pilot's response to the power loss, the aircraft's flight path, and the impact conditions.
Findings
- The failure of the number three power turbine shaft bearing caused an automatic reduction in engine power to ground idle, necessitating an immediate autorotation.
- The bearing failure was likely preceded by corrosion pitting due to the engine not being stored in accordance with required procedures.
- The pilot likely conducted a forced landing into the lake because the altitude was too low to reach the shore, or because the pilot was distracted by the engine's changing parameters while attempting to maneuver toward the shoreline.
- The pilot likely misjudged the height above the water, initiating the flare prematurely, which depleted the kinetic energy of the main rotor blades and prevented a controlled landing.
- The severity of the water impact likely prevented the occupants from escaping the sinking aircraft.