What happened
On 04 October 2021, a Kaman K-1200 helicopter, registered as C-FZVM and operated by Black Tusk Helicopter Inc., was performing logging operations near Killam Bay in Jervis Inlet, British Columbia. The pilot was transporting logs from a cut block to an ocean log pen when the aircraft began a rapid descent. Approximately 75 seconds after releasing a load of logs, the helicopter entered a steep dive and struck the water within the log pen, sinking immediately.
Although the aircraft was equipped with a 406 MHz emergency locator transmitter (ELT), the device was submerged upon impact, and no signal reached search and rescue agencies. The operator, which had been in radio contact with the pilot, initiated a search that led to the recovery of main rotor blade fragments. The helicopter was located via sonar eight days later. The pilot sustained fatal injuries.
The investigation
Investigators determined that the aircraft suffered an in-flight breakup of its twin rotor system prior to hitting the water. Laboratory analysis of recovered rotor blade components revealed that a structural failure occurred on one of the main rotor blades. Specifically, the separation of a servo flap afterbody created an out-of-track condition. This imbalance triggered intense vibrations and flutter across the remaining rotor blades, eventually causing the failure of the left-pylon structure. This failure led to a mid-air collision between the blades of the left and right rotors.
Technical testing indicated that a fatigue crack likely formed in the servo flap skin, originating from a fracture in the bond joint between the inboard closeout and the afterbody. The investigation noted that inconsistent bond quality in these components could compromise the structural integrity of the servo flap under aerodynamic loads.
Additionally, the investigation highlighted that the lack of a flight data recorder or cockpit voice recorder prevented investigators from determining the exact maneuvers performed by the pilot in the final seconds before impact. The investigation also noted that the submerged ELT prevented immediate distress signaling, though the pilot's regular radio contact with the company facilitated a timely search.
Findings
- The primary cause of the accident was the separation of the servo flap afterbody on a main rotor blade, which induced a catastrophic imbalance and rotor system breakup.
- A fatigue crack in the servo flap skin, initiated by a failure in the bond joint, led to the structural separation.
- The inability of the ELT to transmit a signal was due to its submersion following the impact.
- The absence of flight recording equipment limited the ability to reconstruct the final moments of the flight.