History of the Flight
The pilot of a Bell 206B JetRanger was conducting charter flights for Saskatchewan Environment and Resource Management near Hudson Bay, Saskatchewan, to locate and tag Trumpeter swans. At an altitude of about 3,000 feet above sea level, the pilot and three passengers heard a high-pitched buzz from the engine compartment. The pilot noted the power turbine rpm decaying and advised passengers to prepare for an emergency landing. The pilot autorotated into a swampy area directly ahead. Despite significant rotor energy required to avoid high trees, the helicopter landed heavily. The helicopter sustained substantial damage; however, the pilot and passengers were uninjured. The pilot radioed the operating base, and a second helicopter arrived within an hour. The accident occurred at 1740 central standard time, in daylight, about 19 miles south of Porcupine Plain, Saskatchewan.
Injuries to Persons
There were no injuries. The pilot and three passengers had no injuries.
Damage to Aircraft
The helicopter was substantially damaged during the hard landing. The high skid gear was bent outward and rearward, and the chin bubble glass was broken. The transmission tilted forward, damaging the upper deck, control linkages, and main beams. The main rotor did not contact the tail boom or cabin; the helicopter remained intact.
Aircraft and Engine Information
The aircraft was a Bell 206B, year of manufacture 1980, serial number 2994, with a total airframe time of 7,709.6 hours. It was powered by one Allison 250-C20B engine (serial number 830813). The aircraft was equipped with an externally mounted cargo rack on the right-hand cross tubes, approved by Transport Canada. A review of records indicated the aircraft was certified, equipped, and maintained in accordance with existing regulations.
Pilot Information
The pilot, aged 37, held a Commercial Pilot Licence and had 2,600 total flying hours, with 2,000 hours on type. The pilot was certified and qualified for the flight.
Meteorological Information
Weather was clear, with light southwesterly winds and a temperature of 27 °C.
Engine Malfunction Indications
The pilot heard a high-pitched whine from the engine compartment and observed decreasing power turbine rpm. No warning lights or horns were noted. The turbine outlet temperature (TOT) was approximately 650 °C and maintained until landing. The pilot did not close the throttle during autorotation but did so after landing, after which TOT decreased. The pilot then radioed for assistance and turned off the battery switch. The pilot believed the warning light circuit breaker was reset before take-off.
Wreckage and Engine Examination
The helicopter landed in a swamp and remained upright. The skids sank, and the helicopter was later moved. Post-occurrence examination of flight controls, fuel, and electrical systems revealed no pre-impact unserviceabilities. Warning lights and horns tested normally. External engine examination showed damage to trailing edges of the fourth stage turbine blades and guide vanes, and dents on the exhaust collector with silver-grey material.
Engine teardown revealed that a blade from the second stage gas producer turbine wheel had failed near the base. The fracture surface showed a flat, darkened section through approximately 65% of the cross section, with the remaining 35% bright. The adjacent blade was bent and contacting the second stage nozzle, restricting rotation. The TOT probe at the nine o'clock position was sheared off. The failed blade and severed thermocouple traveled downstream, causing extensive foreign object damage to the third and fourth stage turbine nozzles and blades. Cracking in second stage nozzle guide vanes was deemed normal wear, but the outer band of the number two nozzle assembly had a circumferential crack extending about 120° adjacent to a previous braze repair.
Laboratory Examination
The fracture surface of the second stage turbine blade was examined by the TSB Engineering Branch. Scanning electron microscopy confirmed fatigue originating from the convex side of the blade at the crown, typical of high cycle fatigue cracking likely driven by engine vibratory stresses. The source of the engine-induced stresses or excitation was not determined. Metallographic examination showed no evidence of overtemperature exposure. The wheel material met engineering specifications.
Medical Information
No evidence of incapacitation or physiological factors affecting pilot performance.
Survival Aspects
A canoe loaded on the right-side cargo rack prevented egress through the right front and rear doors. The canoe was 18 feet long.