Accident Overview
On a daylight visual meteorological conditions flight, a Bell Helicopter Textron Canada Ltd. 206L helicopter (registration C-GDQH, serial number 45046) operated by Sunrise Helicopters Inc. departed Kapuskasing, Ontario. The aircraft was chartered by a forestry company for a local timber survey flight to the south. On board were two passengers and one pilot. At approximately 1048 Eastern Daylight Time, about 15 nautical miles south of Kapuskasing, an in-flight separation of one of the helicopter’s main rotor blades occurred. The helicopter subsequently struck terrain. All occupants received fatal injuries, and the helicopter was destroyed. There was no post-impact fire. The emergency locator transmitter activated upon impact, and a search and rescue team was deployed; however, a civilian helicopter located the wreckage before the team's arrival.
History of the Flight
After departure, the helicopter flew southbound, performing an aerial survey of pre-selected areas. The flight was conducted at low altitudes, with periods of slow and hovering flight. The final recorded GPS data at 1047 indicated an altitude of 917 feet above sea level (82 feet above ground level), a ground speed of 5 knots, and a track of approximately 270° magnetic. The wreckage was located at 49°10′1.46″ N, 082°27′50.14″ W, at an elevation of 825 feet asl, on an old logging road approximately 25 feet west of the last GPS position. The helicopter struck the ground at approximately a 40° nose-down angle and a 52° left-bank angle. The main rotor system, including the transmission and top of the fuselage, separated in flight and came to rest about 140 feet west of the main wreckage. The engine also separated and came to rest 170 feet north. Both main rotor blades remained attached to the hub; one blade was significantly damaged but not fractured, while the other blade was fractured with approximately 8 feet of the outboard end missing. An extensive search for the missing section was unsuccessful.
Aircraft and Crew Information
The helicopter was a Bell 206L with a two-blade semi-rigid rotor system. At the time of the accident, it was equipped with main rotor blades part number 206-015-001-115, serial numbers A-4705 and A-4753. The blades had a designated lifespan of 3600 hours and were installed on the helicopter on May 12, 2011, with 3367.8 hours. At the accident, the blades had accumulated 3592.1 hours total time. The pilot held valid certifications and qualifications, with 1206 total flight hours, including 585 hours on Bell 206 type helicopters. The pilot had worked the day before but was off duty the preceding four days; no physiological factors degraded performance.
Investigation Findings
The fractured blade (serial A-4705) exhibited a complete chord-wise fracture approximately 100 inches from the tip. Examination revealed that the fracture initiated in the blade leading edge spar due to fatigue cracks. The blade had manufacturing defects including a void in the adhesive and residual stress in the spar, conditions previously identified in Alert Service Bulletin (ASB) 206L-09-159. Numerous fatigue cracks originated from the inner surface of the spar at the void location. One crack progressed until the blade separated. Corrosion was present in the void, likely from moisture ingress through micro-cracks, but was not the main cause. The mating blade also had large adhesive voids but no cracks or corrosion. The investigation determined that after a similar 2008 occurrence, Bell Helicopter implemented a damage tolerance approach based on the ASB, but the inspection criteria proved inadequate as the crack was not detected. Wipe checks performed by the operator did not detect the crack, and two checks were performed slightly outside the prescribed 60-cycle interval (at 65 and 62 cycles). Additionally, some wipe checks were performed by non-qualified personnel (pilots rather than licensed aircraft maintenance engineers), which increased the risk of missed defects.
Safety Actions Taken
Following the accident, Transport Canada (TC) released Civil Aviation Safety Alert (CASA) 2011-08 on November 17, 2011, noting that the first main rotor blade failure in 2008 was considered isolated and the ASB was not mandated by an airworthiness directive (AD). TC stated it was considering corrective action and emphasized that the wipe check with blue food coloring solution is not an elementary task under Canadian Aviation Regulations. TC strongly recommended radiographic inspection (X-ray) of affected blades per Part III of ASB 206L-09-159 (Rev "A"). On November 29, 2011, TC released Emergency Airworthiness Directive CF-2011-44 (revised February 1, 2012), mandating blade spar radiography.