Accident Summary
On July 3, 2013, at approximately 1648 eastern daylight time, a Schweizer 269C helicopter, registration N888ZW, operated by Point of View Helicopter Services, LLC, collided with terrain near Burnham, Maine. The flight was conducted under 14 CFR Part 91 as an aerial observation flight for bear spotting, originating from Waterville Robert LaFleur Airport (WVL) at about 1544. Visual meteorological conditions prevailed, and no flight plan was filed. The helicopter sustained substantial damage; the commercial pilot suffered serious injuries, and the passenger sustained minor injuries.
Flight History
The pilot reported that earlier that day, he flew the helicopter from Auburn/Lewiston Municipal Airport to WVL without incident. After landing, he disengaged the main rotor but kept the engine running while fueling, adding 13.5 gallons. He did not check the fuel tanks or strainer for contamination, stating that there was inadequate time for contaminants to settle and that he had drained the fuel before departure from Auburn/Lewiston. He had previously fueled at WVL without issues.
Before departure, the pilot briefed the passenger on safety and operational aspects, including engine instruments and controls. He recalled showing her the needle split but did not conduct a magneto check since the engine was already running. Weather conditions included calm wind and high overcast clouds.
During the flight to the study area northeast of WVL, the pilot showed the passenger bald eagles and nests he monitored. They then began tracking bears. Initially flying at 1,000 to 2,000 feet for a grid search, they descended upon receiving radio collar signals. While flying about 50 feet above treetops at 10 to 20 knots with calm wind, the pilot initiated a "fading right turn" with left anti-torque pedal input while slowing.
Approximately two seconds into the turn, the helicopter entered a spin consistent with sudden loss of tail rotor authority. As it descended, the passenger asked, "what's going on?" and the pilot replied, "I don't know" before pulling up the collective to ease tree contact. The helicopter was in the trees within about two seconds of spin initiation. The pilot blacked out upon impact and believed he was unconscious for 40 minutes. The passenger helped him out of the helicopter and summoned help from a passing motorist. Emergency responders arrived approximately 45 minutes to an hour later, and the pilot was transported to a hospital.
The passenger reported hearing an unusual sound before the helicopter turned counterclockwise (contrary to the pilot's account of clockwise rotation). She asked the pilot what happened, and he said he did not know. After impact, she noticed fuel leaking and heard a buzzing sound, then helped the pilot away from the helicopter before walking to a road for assistance.
Investigation Findings
Post-accident inspections of the airframe, engine, and drive system by manufacturer representatives and an FAA inspector revealed no evidence of preimpact failure or malfunction. The fuel strainer contained fuel without contamination. The on-board Electronics International MUX-8A was downloaded, showing 157 data points in one-minute increments. Exhaust gas temperatures remained above 1,350°F after takeoff, and cylinder head temperatures fluctuated between 290 and 330°F until about 1632, then increased until recording ended.
FAA Advisory Circular 90-95 on Unanticipated Right Yaw in Helicopters notes that loss of tail rotor effectiveness (LTE) is a low-speed aerodynamic characteristic that can cause an uncommanded yaw, particularly during right turns at low airspeed. Recommended recovery technique includes applying full left pedal and moving cyclic forward to increase speed, and reducing power if altitude permits.
Probable Cause
The investigation did not identify a specific probable cause.