History of Flight
On March 25, 2010, about 0600 central daylight time, a Eurocopter AS350 B3, registration N855HW, impacted terrain near Brownsville, Tennessee. The helicopter was operated by Memphis Medical Center Air Ambulance Service, doing business as Hospital Wing, under 14 CFR Part 91 as a positioning flight. Night visual meteorological conditions prevailed, and a visual flight rules flight plan was filed. The flight originated from Jackson-Madison County General Hospital Heliport (TN05) in Jackson, Tennessee, at about 0551 and was en route to Haywood County EMS Heliport (99TN) in Brownsville. According to satellite tracking and witness interviews, the helicopter had earlier departed its home base (99TN) at about 0426 to pick up a patient in Parsons, Tennessee, arriving there about 0450. It departed Parsons about 0517, dropped the patient at TN05 about 0534, and then departed TN05 about 0551. The last satellite contact occurred near the accident site about 0600, indicating an altitude of 752 feet mean sea level (about 350 feet agl) and 105 mph. An oncoming shift pilot who started duty about 0530 reported that it was dark, cloudy, and lightly raining when he arrived at 99TN. He noticed the helicopter was gone and called MedCom to locate it. The accident pilot called him and asked about the weather, stating he wanted to get the helicopter out. The two pilots discussed weather; the oncoming pilot noted from radar that a front was coming from the Memphis area about 65 miles southwest at an estimated 25 mph, with radar depicting red over Memphis and yellow extending about 10 miles out. The accident pilot believed he had about 18 minutes to beat the storm. He asked the oncoming pilot to call the two flight nurses, who were not yet on board, to advise they would be picked up later by car. The oncoming pilot tried to call one nurse, but her phone was left at base; the other nurse said they had already returned to the helicopter and were 7 minutes out. The oncoming pilot raised the hangar door and checked radar again, seeing the thunderstorm line had just touched the southwest corner of the county, about 18 miles from base. He saw a blinking light on a radio tower 6 miles away, indicating good visibility. He told the nurse she had the weather beat. At that time, it was raining lightly, wind picked up to about 20 knots. He then heard a loud clap of thunder and saw lightning; he looked out, saw no helicopter, and tried to call the nurse without success. He contacted MedCom and ran to an ambulance service. The helicopter was found in a field about 1,500 feet southwest of the last satellite target, about 2.5 miles east of home base.
Personnel Information
The pilot, age 58, held a commercial pilot certificate with airplane single-engine and multiengine land, rotorcraft helicopter, instrument airplane, and instrument helicopter ratings. He was hired by Hospital Wing on May 10, 2005, with about 2,200 hours helicopter flight time, and had accrued about 415 additional hours since then. His latest Part 135 competency check was on August 26, 2009; his latest instrument competency check on February 14, 2010; and his initial and only night vision goggles (NVG) training on July 27, 2009. His FAA second class medical certificate was issued on March 15, 2009, with a restriction for glasses. He reported 4,008 total flight hours. His duty history before the accident included time off and varied flight hours; his wife reported he seemed normal and did not complain of fatigue.
Aircraft Information
The accident helicopter was a Eurocopter AS350 B3, manufactured in 2008, with a three-blade main rotor, two-blade tail rotor, and a 747 shp Turbomeca Arriel 2B1 engine. It was delivered to Hospital Wing in May 2009, equipped with high-skid landing gear, NVG-compatible lighting, vehicle engine multifunction display (VEMD), autopilot, and enhanced ground proximity warning system (EGPWS). Aftermarket installations included a medical interior. The most recent 200-hour and annual inspections were on March 1, 2010, at 199.6 hours total time since new (TTSN); at accident, it had about 248 hours TTSN with no outstanding discrepancies.
Meteorological Information
At about 0553, McKeller-Sipes Regional Airport (MKL), about 17 miles east, reported winds from 160 degrees true at 5 knots, visibility >10 miles, few clouds at 2,000 feet, broken at 2,700 feet, overcast at 3,700 feet, temperature 16°C, dew point 12°C, altimeter 29.77 inHg, distant lightning to southwest. About 0609 (9 minutes after accident), MKL reported winds from 220 degrees at 15 knots gusting to 19 knots, visibility 9 miles, thunderstorms in vicinity, broken ceiling at 1,800 feet, overcast at 2,700 feet, temperature 15°C, dew point 12°C, altimeter 29.84 inHg. Remarks noted distant lightning and thunderstorm beginning about 0603. Radar images showed a mesoscale convective system (line of thunderstorms) moving southwest to northeast at about 61 knots, with a bow echo including localized IMC, heavy rain, lightning, and wind gusts up to 20 knots. Infrared satellite imagery showed extensive cloud cover with tops at 30,000 feet. Lightning detection within 15 miles of accident site: one cloud-to-ground strike at 0602:08; between 0545-0615, WeatherBug detected 6 cloud-to-ground and 12 intercloud strikes, but none within 90 seconds of accident time. Three witnesses near the site reported lightning and thunder; one stated it was very windy, another that heavy rain bands were passing.
Wreckage and Impact Information
The wreckage was in an open wheat field about 2.5 miles from 99TN, at 35°36.44' N, 089°11.70' W. Main debris field was about 250 feet long and 150 feet wide, oriented toward 180° magnetic. Initial ground scars contained main rotor blade fragments, left landing gear skid parts, and belly pieces, consistent with impact in a near nose-level, 33-degree left bank attitude. The main wreckage (cabin and cockpit) came to rest about 112 feet south and was mostly destroyed by postimpact fire. The radar altimeter indicated 75 feet, altitude bug set at 200 feet, Kollsman setting at 29.78. Examination revealed no preimpact failures or malfunctions of engine, drive train, rotors, or structure; no in-flight fire. Main rotor blades remained attached; two exhibited composite broomstrawing. Blade bonding braids showed no lightning strike damage. The red blade outboard tip (about 18 inches) was found 300 feet northwest of initial impact crater. Tail boom separated about 3 feet aft of fuselage attach point; flex coupling exhibited torsional separation; tail rotor strike indicators bent, flapping damage on blades, and damage to right side of tail boom consistent with rotating tail rotor contact. Flight controls showed overload fractures. Engine partial disassembly showed evidence of power at impact: foreign object damage to eight axial compressor blades and blade tip curling on two; power shaft had torsional damage; internal bearings showed no lightning strike damage. A nearby irrigation system had no evidence of lightning strikes.
Medical and Pathological Information
An autopsy on the pilot at the Shelby County Medical Examiner's Office listed cause of death as multiple blunt force injuries. Toxicological testing at CAMI was negative for ethanol, cyanide, carbon monoxide, and drugs.
Tests and Research
Examination of the EGPWS computer revealed severe thermal damage; no data recovered. The VEMD had recoverable nonvolatile memory; data showed no recorded faults for the accident flight. The Digital Electronic Control Unit (DECU) had extensive heat damage to memory chips; no data recovered. The Avidyne Multifunction Display (MFD) recorded power-on times and weather product timestamps but not flight data. NEXRAD weather data from XM satellite weather service indicated that during the accident flight, the only update received was at 05:56:20, showing the leading edge of weather (light rain) just crossed 99TN, with moderate rain about 7 miles southwest. Overall latency of that product was about 5 minutes 21 seconds. The MFD displayed an age indicator of 1 minute.
Organizational and Management Information
Hospital Wing began operations in 1986; at accident time, it operated five AS350 B3 helicopters with 16 pilots at three bases. It had a formal safety program with a safety officer. The Director of Operations participated in NTSB hearings on HEMS safety. The company employed a full-time training officer; after the accident, it purchased an AS350 B3 flight simulator. Hospital Wing had a formal risk assessment program; a risk assessment form was completed at the start of the pilot's duty shift on March 24, 2010, at about 1725. The form evaluated static and dynamic risks, with a total score of 3 (including deductions for high pilot experience and NVG use), which was below the no-go threshold of 14.