Accident Summary
A Kananaskis Mountain Helicopters Ltd. Bell 206B Jet Ranger helicopter (registration C-GFQZ, serial number 2436) was on final approach to the Cline River heliport (CCR5) over Abraham Lake, Alberta, at approximately 1420 mountain daylight time when the Rolls-Royce/Allison 250-C20B engine decelerated and flamed out. The pilot entered autorotation, and the helicopter descended into the lake, rolled onto its right side, and sank near shore. The pilot and the left cabin seat passenger evacuated the wreckage without assistance. The right cabin seat passenger required the pilot's assistance to release the lap belt and exit after the cabin became submerged. All three occupants sustained minor injuries. The helicopter was substantially damaged, and there was no post-impact fire.
Weather and Environment
Visual meteorological conditions with unlimited visibility prevailed at Cline River at the time of the accident. Surface winds were from the south at an estimated speed of 15 to 20 mph. Abraham Lake is a large man-made glacial lake formed by the Bighorn Dam on the upper North Saskatchewan River. The water temperature was low, increasing physiological risks associated with cold water immersion.
Operator Information
Kananaskis Mountain Helicopters Ltd. operated one Bell 206 L-3 and two Bell 206B helicopters under Canadian Aviation Regulations (CARs) Sections 702 and 703. The operator conducted high-frequency, short-duration tourist sightseeing flights over glaciers in the Cline River area. The operation was seasonal, with most flying activities from April through October.
Cline River Heliport
The heliport was located approximately 200 m inland from the west shore of Abraham Lake. The shoreline near the helipad was oriented north-south. In strong south winds, final approaches were typically crosswind heading east to west due to terrain-induced mechanical turbulence to the north and west. A noise abatement restriction prohibited flight over a resort area to the northeast, requiring approaches from the east to be over Abraham Lake for a brief period.
Accident Flight
The helicopter was chartered by two European tourists for a 25-minute glacier sightseeing trip west of Cline River. On final descent to the heliport at about 250 feet above Abraham Lake, the engine slowly decelerated. The engine-out warning horn and light activated, and the pilot observed low rotor rpm. He entered autorotation and turned about 90 degrees left to avoid steep shoreline. Seconds later, the helicopter ditched into wind, parallel to the water's edge, about 20 feet from shore. It rolled onto the right side and sank in about eight feet of water.
Wreckage Examination
The helicopter was recovered two days after the accident and transported to the TSB Western Region facility in Edmonton for examination. Damage to the lower fuselage indicated high rate of descent upon water contact. The battery switch was ON; the engine auto relight switch was OFF, but it was not determined if it was off before impact or displaced by forces. The boost pump circuit breakers were engaged, and the collective twist grip was in ground idle. The engine was examined in situ; water immersion precluded a test cell run due to concerns about rapid cooling of turbine wheels. No visual external or internal mechanical damage was noted. Engine controls showed no discontinuity; N1 and N2 turned freely by hand; accessory drives had no discontinuity. No metallic contamination was found in the engine oil filter. The compressor, combustion, turbine, and accessory gearbox assemblies were not disassembled.
The engine had a Bendix fuel control system. The power turbine governor (PTG), fuel control unit (FCU), engine-driven fuel pump, fuel nozzle, fuel line check valve, and bleed valve were removed and bench tested. A fuel nozzle replaced approximately nine hours before the accident was also tested. No anomalies likely preventing normal operation were identified. The fuel check valve assembly leaked internally at 0.6 psig, while it required zero leakage at 17 psig. Minute amounts of unidentified solid contamination were found in the FCU, the installed fuel nozzle screen, the replaced nozzle screen, and the fuel system check valve. The FCU bypass valve stem was worn undersize, and there was a small perforation in the bleed valve diaphragm.
Maintenance Irregularities Found
Several maintenance irregularities were identified:
- The engine data plate was missing; it had not been transferred after an accessory gearbox change.
- No current engine technical record meeting CARs requirements was available.
- The installed PTG (part number 23070101) was designed for Rolls-Royce/Allison 250 C30 series engines, not the C20B.
- A small air leak was found in the compressor discharge pressure (Pc) tube at the "B" nut on the PTG tee-fitting. The leak may have been due to solid contamination between the cone and flare. Torque paint on the "B" nut showed no continuation on the adjacent surface; old paint had not been removed and fresh paint applied per maintenance manual.
- A crack was found in the end flare on the main fuel line in the fuel cell, at the attachment to the reducer tee-fitting on the aft boost pump. The flare likely failed initially due to overtorquing, and the crack propagated by stress corrosion cracking.
- The PTG had been replaced approximately 36 flight hours before the accident. The company AME verbally ordered a PTG from Eagle Copters Ltd., which shipped a newer version inadvertently from the wrong part number. The AME noted visual differences but attributed them to a newer version; part number verification was not completed. A C30 series PTG operates through a different Pc pressure range than a C20 series. Bench testing showed the C30 PTG met C30 calibration parameters; while incorrect, its installation would not likely have contributed to power loss.
- A fuel control system pneumatic leak check had not been accomplished after the PTG change. Although a Pc leak was found, communication with the engine manufacturer indicated the leak rate was likely insufficient to have contributed to the power loss given the tube was not broken, the flare not cracked, and the "B" nut not loose.