N5016UBell 206B

On January 5, 2010, at 1209 Pacific standard time, a Bell 206B, 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 local flight departed Trimmer Heliport, Trimmer, California, at 1007. Visual meteorological conditions prevailed at the accident site, and a company flight plan had been filed.

The mechanic assigned to the helicopter drove up from Landells Aviation the afternoon prior to the accident. He stated that the pilot departed Landells in the helicopter about 1300, and arrived at Trimmer at 1545. The mechanic then drove with the pilot for an hour to their hotel. They then had dinner and the pilot retired to his room about 2000. The mechanic reported that the following morning they met in the hotel lobby at 0700; the pilot appeared well rested, in a good mood, and his "normal self." They then drove to Trimmer, arriving at 0900, and were greeted by the three CDFG passengers. The mechanic then serviced the helicopter with the addition of 38 gallons of fuel, for a total of 75 gallons. He then checked the helicopter fluids, and removed the aft doors. The mechanic stated that he observed the pilot then perform a preflight inspection, followed by a briefing with the three passengers.

At the time of the accident, two witnesses, who were law enforcement officers for the United States Forest Service (USFS), were located on a north facing ridge at the confluence of Willow Creek and the San Joaquin River. Both officers observed the helicopter emerge from a valley to the north, and fly southbound along Willow Creek and directly towards them. A set of power transmission lines spanned the valley from the east to west. The officers reported that the helicopter continued through the valley, on a trajectory towards the power lines. As the helicopter came within the immediate vicinity of the lines it reared back, and then began an immediate descent, colliding with the ground. The officers noted that prior to the accident, the helicopter was flying straight and level, with the engine sounding, "normal and smooth."

A review of Federal Aviation Administration (FAA) airman records revealed that the 70-year-old pilot held a commercial pilot certificate with ratings for airplane single-engine land, land, rotorcraft-helicopter, instrument airplane, and helicopter. He additionally held a flight instructor rating for airplane single and multi engine, and instrument airplane. The pilot held a second-class medical certificate issued on May 12, 2009, with limitations that he have glasses available for near vision.

According to records provided by the Landells Aviation, as of December 2009, the pilot had accumulated a total flight time in all aircraft of 16,864 hours, of which 13,560 was in helicopters, with 3,369 in the Bell 206 series. The records also indicated that the pilot had 47 years of flying experience, which included helicopter emergency medical services (HEMS), search and rescue, aerial survey, photography, mapping, and animal capture.

The pilot's total flight time for 2009 was 95.4 hours, and was comprised of HEMS, fire suppression, sling, and survey missions, all of which were flown in either the Bell 206 or Bell 222U. His most recent flight prior to the accident was a deer survey mission, which took place on December 23, 2009.

Two CFDG employees, who had last flown with the accident pilot on deer surveying missions about 1 month prior to the accident both reported that the pilot did not perform his usual pre-flight briefing, but rather an abbreviated briefing followed by a reminder to watch for obstructions in-flight. Additionally, during one mission they noted that the pilot appeared to be, "trying too hard" to observe deer. They became alarmed, and admonished the pilot during the flight.

The helicopter, serial number 2634, was manufactured in 1979 and equipped with a Rolls-Royce/Allison 250-C20J gas turbine engine.

A review of the helicopter's maintenance logbooks revealed that the last inspection was for a 100-hour engine and airframe exam dated October 30, 2009, at a total airframe time of 15,339.6 flight hours. At that time, the engine was replaced. According to the maintenance records, the replacement engine had a total time since new of 6,675 hours. The last maintenance entry was for battery service, and occurred the day before the accident at a total airframe time of 15,376.4 hours. Later that day, the helicopter flew for approximately 2.5 hours to Trimmer.

The helicopter was equipped with a wire strike protection system. FAA records indicated that the system was manufactured by Bristol Aerospace Limited, under supplemental type certificate number SH4083SW. The wire strike protection kit was comprised of an upper and lower fuselage deflector/cutter, and a serrated windshield center post deflector channel.

The helicopter's equipment list referenced the installation of a Trimble TNL 1000 Global Positioning System (GPS) receiver. The GPS unit was destroyed by post-accident fire.

The helicopter was equipped with dual pedal controls, and single right seat pilot controls for the cyclic and collective.

The closest aviation weather observation station was Fresno Yosemite International Airport, Fresno, California, located 27 miles southwest of the accident site, at an elevation of 336 feet mean sea level (msl). An aviation routine weather report was recorded at 1153, and stated: winds calm; visibility 2 miles with mist; skies 600 feet overcast; temperature 6 degrees C; dew point 4 degrees C; altimeter 30.22 inches of mercury.

The USFS officers reported the weather conditions at the accident site to be clear skies with a few high scattered clouds, and light winds out of the north. They stated that the accident site elevation was above the lower cloud layer in Fresno.

According to the United States Naval Observatory Astronomical Applications Department, the altitude and azimuth of the sun in Fresno at 1210 were 30.7 degrees and 181.4 degrees, respectively.

The helicopter was equipped with an Automated Flight Following (AFF) system. According to Landells, the system was not required per the CDFG contract, and was not being used at the time of the accident.

An impact damaged Garmin III global positioning systems receiver (GPS) was recovered from the accident site. The unit was sent to the National Transportation Safety Board Office of Research and Engineering for data extraction. Due to the damage sustained during the accident sequence, flight track data could not be extracted.

The main wreckage came to rest in the Sierra National Forest, within a heavily-wooded valley floor, 50 feet east of Willow Creek at an approximate elevation of 1,200 feet msl. The elevation of the valley peaks directly to the east and west of the creek were about 2,500 feet.

The valley was spanned by two separate sets of intersecting electrical power transmission lines, crossing diagonally over Willow Creek adjacent to the main wreckage.

The first set of lines were on a southwest-northeast orientation, and strung between two metal towers separated by a span of about 2,900 feet. The tower to the east was 81-feet-tall, with the tower to the west 95 feet. The base of the east tower was located at an elevation of about 1,570 feet, with the west tower at 1,680 feet. The cables strung between the towers consisted of two parallel steel 'skylines' at the top, and three 220,000 volt power conductor lines mounted about 20 feet below. The power lines and skylines exhibited differing degrees of droop such that their vertical separation was about 70 feet at the midspan point. The skyline to the south had severed approximately midspan, subsequently becoming entangled in the remaining lower conductor lines.

The second set of lines consisted of a group of 5 cables spanned by two, 40-foot-tall wooden towers. The lines followed a southeast-northwest orientation about 200 feet below the first set of power transmission lines.

Neither of the sets of power lines were equipped with spherical visibility markers, or similar identification devices.

The upper power lines were owned by Southern California Edison (SCE). Examination of the severed skyline at the accident site revealed it to be about 0.5 inches thick. According to a SCE representative, the skylines were comprised of 7 strands of high-strength steel wire. The conductor lines were 0.994 inches thick, and comprised of 30 strands of aluminum, wrapped around 19 strands of steel.

The main wreckage, which consisted of the cabin, tailboom, and tail rotor, came to rest inverted, 100 feet south of the upper power transmission lines' midspan point. The entire cabin area had been consumed by fire.

The debris field continued to the north and consisted of the forward cowling, air filter assembly, pilot door, and segments of Plexiglas.

The main transmission gearbox and mast were located about 300 feet north of the main wreckage. The main rotor assembly, consisting of the 'red' blade, hub assembly, and inboard section of the 'white' blade, came to rest on the adjacent banks of Willow Creek, about 90 feet northwest of the main wreckage. A 4-foot-long outboard section of the white main rotor blade was located 1,100 feet south of the main wreckage on a rocky outcropping beyond the banks of the San Joaquin River.

The sun's position was reviewed 2 days following the accident from a south-facing vantage point within the valley. The vantage point closely matched the helicopter elevation noted by the witnesses. At the accident time of day, the skyline appeared partially obscured by the sun.

All major sections of the helicopter were accounted for at the accident site.

An autopsy of the pilot was conducted by Pathology Associates of Clovis, for the Madera County Sheriff's Department. The cause of death was reported as right hemothorax, and lacerations of heart, aorta, and pulmonary artery.

Toxicological tests on specimens from the pilot were performed by the FAA Civil Aeromedical Institute. Analysis revealed no findings for carbon monoxide, cyanide or ethanol. The results contained the findings for doxylamine detected in the blood and liver, and hydrocodone detected in liver. Refer to the toxicology report included in the public docket for specific test parameters and results.

The pilot had not reported the use of doxylamine or hydrocodone on his most recent application for an airman medical certificate. He did report the use of Celebrex, Prevacid, and Simvastatin.

FAA medical records revealed a prior conviction for driving under the influence of alcohol (DUI) in 1982, which the pilot did not report on his medical certificate application until 1992, when he was subsequently convicted for a second DUI offense. In August 1992, he was issued a second-class medical certificate contingent upon total abstinence from alcohol or mood altering chemicals.

In July 2001, the pilot's medical certificate application was denied based on his intermittent use of Luvox to control Obsessive Compulsive Disorder (OCD). The pilot was subsequently psychiatrically evaluated, and it was determined that he did not have OCD, but rather manifested a, "life-long pattern of compulsive traits and perfectionist tendencies." The pilot then discontinued the use of Luvox, and was issued a second-class medical certificate in September 2001.

The engine and airframe were recovered from the accident site to a remote storage facility for further examination.

Engine

The engine sustained thermal damage during the post accident fire, and as such, most ancillary components were consumed. Fire damage prevented examination of all fuel lines, the fuel controller, fuel pump, bleed valve, and power turbine governor.

The accessory gearbox had become fire consumed, with only white ash case remnants remaining. The associated gears remained in the general vicinity of the gearbox. The gears exhibited thermal distortion; the teeth for all observed gears remained intact.

Both exhaust outlets and the combustor case exhibited malleable crush damage, and were free of internal dents. The compressor case exhibited crush damage, and appeared bent about 10 degrees from the centerline. The case appeared to impinge on the first and second stage axial compressor wheels, the blades of which were noted bent opposite the direction of travel. Six blades from the first stage wheel had become liberated at the root.

Circumferential rub marks were noted to the seal of the sixth stage compressor wheel, consistent with component rotation during impact.

Examination of the turbine section revealed the fourth stage wheel to be soot-covered and intact. The first stage wheel was examined utilizing a borescope; the blades appeared intact and no damage was noted. The fuel nozzle orifices appeared clear, and displayed light sooting.

Airframe

The entire cabin area including the flight controls and cockpit instruments sustained heavy crush damage and subsequent thermal exposure. The flight control servos, and their associated control rods, had become fire consumed.

The main transmission gearbox remained attached to its mounts, which had become separated from the fuselage assembly. The main rotor mast remained attached to the gearbox, and had separated at the hub. The fracture surface was on a 45-degree plane around the mast circumference, and displayed granular features. Rotation of the mast by hand resulted in rotation of the gearbox input shaft.

Both main rotor blade roots remained attached at the hub, with the blades separated into five sections. The pitch link tubes remained attached at the blade horns, but had become twisted and separated about midspan. Examination of the blades revealed serrated leading edge gouges, with upper and lower skin striations consistent in appearance with the severed skyline.

The tail had become separated into two sections consisting of tail rotor and gearbox assembly, and the center tailboom. The remaining sections of the tail through to the fuselage had been consumed by fire. The tail rotor assembly remained intact and attached to the gearbox; rotation of the tail rotor by hand resulted in rotation of the gearbox input shaft.

The air filter assembly appeared clear and free of obstructions.

Examination of the airframe and engine did not reveal any evidence of pre-accident failure or malfunction.

Wire Strike Protection System

The upper and lower wire cutter assemblies had sustained varying degrees of thermal damage. Examination of the blade and cutting surfaces revealed them to be free of scratches, nicks, abrasions or any indication of cable contact.

Deer Survey Flight Procedures

A CDFG employee explained the general procedures for conducting deer survey flights. He stated that the mission profile is defined prior to the flight by a specialist who creates a route based on the area of study. The area is bisected by a set of parallel 'transect lines', which are then followed by the helicopter crew.

A helicopter survey mission typically includes two 'spotters' in the rear of the helicopter, with the pilot and a navigator in the front seats. The pilot's responsibility is to fly the helicopter, and see and avoid obstructions. The navigator's duties include assisting the pilot with following the correct transect lines, as well as spotting obstructions. When deer are observed, the spotters call the position relative to the helicopter; the pilot then turns the helicopter towards the deer while they are counted. Typically a 200-meter-wide 'window' is defined along the transect line for deer observation. The helicopter will divert from the transect to observe deer within this window. Once the deer are documented, the helicopter returns to the original diversion point.

The CDFG employee reported that typically the pilot gives a preflight briefing prior to the flights. The briefing includes helicopter safety, and procedures for spotting and reporting aerial obstructions.

A CDFG employee who had flown on previous deer surveying missions revealed that she did not receive any formal safety or operational training with regards to surveying missions, and that she learned through, "on the job training." Another employee reported that he was not aware of any formal surveying guidelines explaining the duties of each person on board the helicopter, and that no formal training regarding surveying flights was provided by the CDFG.

The CDFG contract with Landells Aviation makes reference to the type of flying maneuvers required. In particular, the specifications for helicopter services states, "Pilots and their helicopters must routinely perform extremely low level and intricate flying maneuvers. The work includes, but is not limited to…flying close to the ground at variable speeds in mountainous terrain…negotiating abrupt sharp turns in response to animal movements…" With respect to survey and census services, the contract further states, "Oftentimes, this requires approaching the animal to within several feet and becomes even more difficult when the animal is attempting to flee in an erratic manner in mostly steep, mountainous terrain…Surveys require the pilot to navigate the helicopter to a precise set of coordinates, fly in a prescribed direction or pattern (transect) to a predetermined location or distance while maintaining an altitude generally 20 to 200 feet above the surface in through variable terrain."

Federal Aviation Regulations

Title 14 Code of Federal Regulations (CFR) Part 77, Section 23, defines what constitutes "Objects Affecting Navigable Airspace." Generally, only those objects greater than a height of 500 feet above ground level (agl), or greater than a height of 200 feet agl within 3 nautical miles of an airport, are considered to be obstructions to navigable airspace.

Title 14 CFR Part 77, Section 13, covers "Construction or alteration requiring notice," and defines reporting requirements for proposed construction, or alterations exceeding 200 feet, irrespective of location. The regulation requires that the planned construction of such structures be filed with the FAA. Based on the filing, the FAA performs an obstruction evaluation study, the results of which could include the addition of obstruction marking devices.

Review of the FAA archives revealed that no filing had been made regarding the installation of the power lines at the accident site. Title 14 CFR Part 77, Section 13, was adopted in 1968. According to a representative from SCE, the towers were installed in 1951.

Maps and Charts

The accident site was located within the area covered by the FAA San Francisco Sectional Aeronautical Chart. Examination of the chart revealed that the power lines were depicted at the accident location. Additionally, a printed map was located in the debris field. The map appeared to depict the transect lines for the accident flight. Further examination revealed that the transect line SJ7A/sJ7B crossed over the power line. The accident location was located about 200 feet west of the transect line.