History of Flight
On February 5, 2010, at approximately 1920 mountain standard time, an Aerospatiale AS350/B2 helicopter, registration N157BC, was substantially damaged after impacting terrain while maneuvering in the McGregor Military Range, 23 miles northeast of El Paso, Texas. A postaccident fire ensued. The commercial pilot and two paramedics received fatal injuries. The helicopter was owned and operated by Enchantment Aviation Inc., doing business as Southwest Med Evac, under 14 CFR Part 135 as a practice emergency medical services flight. Night visual meteorological conditions prevailed, and the flight operated without a flight plan. It departed El Paso International Airport at approximately 1825.
The flight was conducted under a U.S. Army contract to simulate picking up injured personnel. The crew was using night vision goggles (NVGs), with standard company practice for the pilot and the left aft seat paramedic to wear NVGs.
Army personnel on the ground using night vision devices reported that the helicopter arrived south of the accident site and made two right-turn orbits. During these orbits, the helicopter was seen turning on and panning its white spotlight. Ground personnel attempted radio contact without success and waved chemical light sticks. The helicopter then made a wider third orbit, during which it banked approximately 45 degrees and entered a steep nose-down attitude before impacting the ground. No avoidance maneuver was reported.
Personnel Information
The 63-year-old pilot held commercial pilot certificates for airplane single-engine land, helicopter, and instrument helicopter, plus an airline transport pilot certificate with type ratings for Boeing 707, 720, 737, 757, 767, and Lockheed L-1011. He had logged over 17,610 total flight hours, including 5,142 rotorcraft hours and 3,351 night hours.
On July 10, 2009, he was issued a first-class medical certificate with restrictions for corrective lenses. He had authorizations for special issuance due to a history of vitreous exchange, retinal detachment, scleral buckle, cataract surgery, hyperopia, and glaucoma. FAA records noted cataract surgery with intraocular lens implants in both eyes (1998 left, 2005 right); a 2004 bilateral vitreous exchange; a 2005 right retinal detachment treated with scleral buckle and cryotherapy; glaucoma treated with eye drops; minor arcuate field loss in the right eye; and an episode of cystoid macular edema in 2005. On September 18, 2008, he received a 6-year Authorization for Special Issuance for glaucoma, with restrictions to report adverse changes and prohibit flight if new symptoms or medication side effects occur. His most recent application (July 10, 2009) showed corrected visual acuity of 20/15 distance, 20/20 near, and 20/25 intermediate. Visual field testing in 2008 and 2009 demonstrated a small fixed peripheral right upper quadrant deficit. On November 13, 2009, the FAA continued his authorization with the same restrictions. Records from his optometrist and ophthalmologist revealed two additional episodes of cystoid macular edema (May 2008 and August 2009) not in FAA records, with complete resolution after topical treatment. Laser surgery on the left eye for glaucoma occurred on November 6, 2009, with a follow-up on December 31, 2009, noting stable vision.
The pilot completed Part 135 competency checks on December 22, 2009, with satisfactory grades. He also completed night vision training on January 29, 2010. He had been hired by Enchantment Aviation in late November 2009 and completed initial pilot-in-command training on December 22, 2009, and NVG training on January 29, 2010. At the time of the accident, he had 22.3 hours in AS350 B3s, 1.4 hours in AS350 B2s, and 7.5 hours with NVGs. The accident flight was his second non-training flight and first non-training NVG flight. He had not previously operated in the McGregor Military Range. According to his spouse, he felt comfortable flying helicopters and did not express concerns about training or NVGs.
Aircraft Information
The single-engine helicopter, N157BC, serial number 2418, was manufactured in 1991. It was powered by a 732-shaft horsepower Turbomeca Arriel 1D1 engine, serial number 9098. The last continuous airworthiness inspection was on October 29, 2009, at 8,583.9 airframe hours and 8,512.5 engine hours. On the accident morning, the aircraft had 8,594.7 airframe hours and 8,523.3 engine hours. On January 5, 2009, the helicopter was modified via Supplemental Type Certificate for NVG-compatible interior lighting.
Meteorological Information
At 1951, an automated weather station at El Paso International Airport (23 nautical miles southwest) reported wind calm, visibility 10 miles, clear skies, temperature 46°F, dew point 28°F, and barometric pressure 30.13 inHg. Astronomic data showed zero moon illumination at accident time; the moon did not rise until 0111 on February 6, 2010. Dark, rolling terrain prevailed, with ambient starlight, distant city lights, chemical light sticks, and infrared strobes as the only lighting for NVG amplification.
Communications
Enchantment Aviation had been acquired by Omniflight Helicopter Inc. Omniflight's Mesa Communication Center in Mesa, Arizona, monitored flight operations. During the flight, the aircrew communicated via GPS phone with the center. Around 1805, McGregor Range contacted Mesa to dispatch a helicopter for training. The pilot was notified of the flight and landing zone coordinates. At 1833, the pilot reported airborne. At 1847, an Army officer reported the helicopter was about 500 meters away but direct communications were not established. At 1854, the crew reported being over the coordinates but unable to locate the landing zone. At 1900, new coordinates were given. Mesa relayed them. Shortly after, McGregor Range reported the helicopter flying in the wrong direction. Mesa informed the crew, who acknowledged turning around. At 1923, the crew reported the landing zone in sight and would conduct reconnaissance. At 1927, McGregor Range reported a crash. Mesa placed another helicopter on standby and launched it to the last known position.
Wreckage and Impact Information
The helicopter collided with relatively level terrain with low-lying desert vegetation, free of obstacles. The impact crater was 18 inches deep at 4,830 feet mean sea level. Impact direction was magnetic 300 degrees. The wreckage was fragmented; major components were accounted for. A postimpact fire consumed most cockpit instrumentation. The gearbox transmission showed shearing at the drive shaft. Two of three main rotor blades remained attached, displaying signatures consistent with impact under power. The blue blade sleeve separated in overload, with the blade found about 100 yards away. The tail boom separated; tail rotor drive shaft continuity was confirmed, with power-on impact signatures. One tail rotor blade showed broom straw fracture; the other was bent and deformed, both with thermal damage. The right skid toe was fractured and embedded, indicating an impact angle of 42 degrees nose low and 35 degrees right bank.
Engine and component examinations revealed no pre-impact anomalies. Hydraulic pump, control servo, and tail rotor actuator showed no anomalies. Engine examination showed misalignment of reduction gearbox index marks consistent with power applied at sudden blade stoppage. Soil and rocks in diffuser and combustion chamber indicated engine continued operating after impact.
Medical and Pathological Information
An autopsy performed by the Office of the Armed Forces Medical Examiner classified the pilot's death as accidental. Forensic toxicology detected ethanol in muscle (18 mg/dL) but not in liver, consistent with postmortem production. Tests for carbon monoxide, cyanide, volatiles, and drugs were negative.
Additional Information
The operator used Generation III ANVIS 9 NVGs with a 40-degree nominal field of view. Both sets of goggles were found at the accident site, damaged, but consistent with being worn and in the down position at impact. The pilot completed NVG training on January 25-29, 2010, with flights near Las Cruces, New Mexico, under moon illumination of 83-100%. The accident flight was the pilot's first non-training NVG flight. SkyConnect data showed the helicopter's flight path; the final plot at 1919:45 was at 6,155 feet MSL (about 1,200 feet AGL) traveling at 92 knots.