History of Flight
On January 5, 2010, at 1209 Pacific standard time, a Bell 206B helicopter, registration N5016U, collided with power lines near Auberry, California. The helicopter was registered to Palm Springs Aviation, Inc., d.b.a. Landells Aviation, and operated by the California Department of Fish and Game (CDFG) as a public-use deer surveying flight. The certificated commercial pilot and three passengers were killed. The helicopter was substantially damaged by post-crash fire. The flight departed Trimmer Heliport, Trimmer, California, at 1007. Visual meteorological conditions prevailed, and a company flight plan had been filed.
Two witnesses, law enforcement officers for the United States Forest Service, observed the helicopter emerge from a valley to the north, flying southbound along Willow Creek toward power transmission lines spanning the valley. As the helicopter approached the lines, it reared back and then began an immediate descent, colliding with the ground. The officers noted the engine sounded normal and smooth prior to the accident.
Personnel Information
The 70-year-old pilot held a commercial pilot certificate with ratings for airplane single-engine land, rotorcraft-helicopter, instrument airplane, and helicopter, and a flight instructor rating. He held a second-class medical certificate issued May 12, 2009, with a limitation for near vision glasses. According to Landells Aviation records, as of December 2009, the pilot had accumulated 16,864 total flight hours, with 13,560 in helicopters and 3,369 in the Bell 206 series. He had 47 years of flying experience including helicopter emergency medical services, search and rescue, aerial survey, photography, mapping, and animal capture. In 2009, he flew 95.4 hours. His most recent flight prior to the accident was a deer survey mission on December 23, 2009.
Two CDFG employees who had flown with the pilot about one month prior reported that he did not perform his usual pre-flight briefing but gave an abbreviated briefing with a reminder to watch for obstructions. During one mission, they noted the pilot appeared to be "trying too hard" to observe deer and admonished him during the flight.
Aircraft Information
The helicopter, serial number 2634, manufactured in 1979, was equipped with a Rolls-Royce/Allison 250-C20J gas turbine engine. Maintenance logbooks showed the last 100-hour inspection on October 30, 2009, at 15,339.6 flight hours, when the engine was replaced. The replacement engine had 6,675 hours since new. The last maintenance entry was for battery service the day before the accident at 15,376.4 hours. The helicopter flew about 2.5 hours after that to Trimmer.
The helicopter was equipped with a wire strike protection system (Bristol Aerospace Limited, supplemental type certificate SH4083SW), consisting of upper and lower fuselage deflector/cutter and a serrated windshield center post deflector channel. It also had a Trimble TNL 1000 GPS receiver (destroyed by fire) and dual pedal controls with single right-seat pilot controls for cyclic and collective.
Meteorological Information
The nearest aviation weather observation station was Fresno Yosemite International Airport, 27 miles southwest of the accident site. An 1153 report indicated winds calm, visibility 2 miles with mist, 600 feet overcast, temperature 6°C, dew point 4°C, altimeter 30.22 inHg. The USFS officers reported clear skies with high scattered clouds and light north winds at the accident site, which was above the lower cloud layer in Fresno. The sun's altitude at 1210 was 30.7 degrees, azimuth 181.4 degrees.
Wreckage and Impact Information
The main wreckage came to rest in the Sierra National Forest, on a heavily-wooded valley floor 50 feet east of Willow Creek at about 1,200 feet msl. Valley peaks east and west were about 2,500 feet. Two sets of intersecting power transmission lines crossed diagonally over Willow Creek near the wreckage. The upper lines, owned by Southern California Edison, consisted of two steel skylines and three 220,000-volt conductor lines strung between towers 81 and 95 feet tall. The lower set of five cables on 40-foot wooden towers was about 200 feet below. Neither set had spherical visibility markers. Examination showed the skyline was about 0.5 inches thick, composed of 7 strands of high-strength steel; conductor lines were 0.994 inches thick.
The main wreckage (cabin, tailboom, tail rotor) came to rest inverted 100 feet south of the upper lines' midspan, with the cabin consumed by fire. The debris field included forward cowling, air filter, pilot door, and Plexiglas segments. The main transmission gearbox and mast were 300 feet north; main rotor components were found nearby. A 4-foot outboard section of a main rotor blade was found 1,100 feet south. Two days after the accident, from a vantage point matching the helicopter's elevation, the skyline appeared partially obscured by the sun at the accident time.
All major sections were accounted for.
Medical and Pathological Information
An autopsy of the pilot reported the cause of death as right hemothorax and lacerations of heart, aorta, and pulmonary artery. Toxicological tests by the FAA detected doxylamine in blood and liver, and hydrocodone in liver. No carbon monoxide, cyanide, or ethanol were found. The pilot had not reported doxylamine or hydrocodone on his most recent medical application, but reported Celebrex, Prevacid, and Simvastatin. His FAA records showed a prior DUI conviction in 1982 and a second in 1992, after which a medical certificate was issued contingent on abstinence. In 2001, his application was denied due to intermittent Luvox use for obsessive-compulsive disorder, but after evaluation he was deemed not to have OCD and was issued a medical certificate in September 2001.
Tests and Research
Engine and airframe were examined. The engine sustained thermal damage; many components were consumed. The compressor case was bent about 10 degrees, impinging on axial compressor wheels with blades bent opposite rotation. Six first-stage blades were liberated. Turbine section showed soot and light sooting on fuel nozzles. Airframe exhibited heavy crush and thermal damage; flight controls were consumed. Main rotor blades had serrated leading edge gouges and striations consistent with the skyline. The wire strike protection system showed no evidence of cable contact. No pre-accident failure or malfunction was found.
Additional Information
Deer survey procedures: A CDFG employee explained that mission profiles are predefined by a specialist using transect lines. Typically, two spotters sit in the rear, pilot and navigator in front. The pilot sees and avoids obstructions; navigator assists with transect and spotting obstructions. When deer are observed, the helicopter diverts from the transect. A 200-meter-wide window is used for observation. The pilot typically gives a preflight briefing including safety and obstruction reporting.
CDFG employees reported no formal safety or operational training for survey missions; they learned on the job. The CDFG contract with Landells Aviation described low-level flying, intricate maneuvers in mountainous terrain, and surveys requiring altitudes generally 20 to 200 feet above ground. Federal Aviation Regulations Part 77 define obstruction criteria; the power lines (installed in 1951) were not filed with the FAA, as the rule was adopted in 1968. The San Francisco Sectional Aeronautical Chart depicted the power lines at the accident location. A map from the debris field showed transect line SJ7A/sJ7B crossing the power line, with the accident site about 200 feet west of the transect.