Summary
On a day visual flight rules flight, a Eurocopter AS 350 B2 (registration C-GOGN, serial number 2834) departed Sault Ste. Marie, Ontario, with a pilot and three passengers from the Ministry of Natural Resources. The mission was to conduct a moose survey approximately 45 nautical miles northeast of Sault Ste. Marie. During the survey, at 1143 eastern standard time, the pilot reported a hydraulic failure and intended to land at a logging site at Mekatina. While maneuvering for landing, the helicopter entered a left turn, lost control, and crashed in wooded terrain east of the logging site. The aircraft came to rest inverted, and all four occupants sustained fatal injuries. There was no post-crash fire.
Accident Narrative
The helicopter departed the Ministry of Natural Resources ramp at Sault Ste. Marie Airport at 0910 and landed at a slipway to board two resource technicians and one conservation officer. It departed the slipway at 0926 with an estimated 15-minute transit to the survey block. During the survey, the pilot communicated a hydraulic failure and proceeded toward the Mekatina logging site. Workers observed the helicopter fly north, enter a left turn, and then crash while returning toward the logging operation.
Investigation Findings
Hydraulic System Failure
The investigation determined that the hydraulic pump drive belt likely failed in flight, causing the hydraulic failure. Examination of the failed belt and similar belts from other aircraft revealed extensive cracking at the same location, indicating a potential design issue. The hydraulic circuit breaker (CB) was likely tripped in flight for undetermined reasons, rendering the hydraulic CUTOFF and HYD TEST switches inoperative. This resulted in asymmetric depletion of hydraulic pressure from the main-rotor servos, preventing a smooth transition to manual controls. The pilot may have moved the HYD TEST switch to the test position in flight, an action not recommended and not in accordance with the Aircraft Flight Manual.
Pilot Actions and Loss of Control
After the hydraulic failure, the pilot flew for about three minutes to reach the logging site. He did not slow the helicopter to the recommended speed range (40–60 knots) for a hydraulic failure emergency. At low altitude during a left turn, the forces encountered may have been too extreme for the pilot to overcome, leading to loss of control. The reason for the departure from controlled flight could not be determined. There was no pre-existing condition found in the servo controls or main-rotor components that would have prevented normal operation.
Other Findings
Hydraulic fluid water content was within limits. The pilot's decision to land at the logging site may have been influenced by snow depth on a nearby lake and the availability of personnel. Transport Canada issued Airworthiness Directives (CF-2003-15 and CF-2004-10) mandating improved drive belts and pre-flight checks.
Probable Cause
After experiencing a hydraulic system failure, the helicopter departed controlled flight and crashed while maneuvering for landing. The reason for the departure from controlled flight could not be determined. It is likely that the hydraulic pump drive belt failed in flight, precipitating the hydraulic failure, and that the hydraulic circuit breaker was tripped, leading to asymmetric hydraulic depletion.