Accident Overview
On June 8, 2008, at approximately 0248 central daylight time, a Bell 407 helicopter registered as N416PH and operated by PHI Inc. as Med 12 was destroyed after impacting heavily forested terrain in the Sam Houston National Forest, south of Huntsville, Texas. The flight was an emergency medical services (EMS) air ambulance operating under Title 14 Code of Federal Regulations Part 135 on a company visual flight rules (VFR) flight plan. The aircraft had departed Huntsville Memorial Hospital Heliport at 0246 en route to John S. Dunn Helistop at Herman Memorial Hospital in Houston, Texas. All four occupants—the pilot, flight nurse, flight paramedic, and a patient—sustained fatal injuries.
Flight Details
The helicopter was equipped with a Global Positioning System (GPS) flight tracking system called Outerlink. According to Outerlink data, the helicopter powered up at 0244:11 and departed at 0246:56. The last recorded data point at 0247 showed an altitude of 1,016 feet mean sea level (approximately 600 feet above ground level), a groundspeed of 106 knots, and a track of 170 degrees. The flight to the destination was 68.7 nautical miles on a magnetic bearing of 168.1 degrees. Med 12's first required position report was due at 0300. At 0259, the Air Force Rescue Coordination Center notified PHI's Communications Center of an emergency locator transmitter signal from N416PH. Search efforts began immediately and the wreckage was located at 0830 using the 406 MHz ELT, approximately 2.5 miles southwest of the last known coordinates.
Aircraft Information
The accident helicopter, a Bell 407 (serial number 53276), was manufactured in 1998 and held a standard airworthiness certificate. It was equipped with a Rolls-Royce turbo shaft C-47B engine rated at 650 shaft horsepower. The helicopter had been fitted with an Aviation Night Vision Imaging System (NVIS)-compatible cockpit lighting system in April 2008 and had a Free Flight radar altimeter installed. It was not equipped with a Helicopter Terrain Awareness Warning System (HTAWS). Maintenance was conducted under an Approved Inspection Program (AAIP) by PHI out of Bryan, Texas. The last inspection, an AAIP event two, was completed on April 16, 2008, at an airframe total time of 6,141 hours and 8 minutes. The accident occurred at a total airframe time of 6,233 hours and 19 minutes, approximately 92 hours after the last inspection.
Crew Information
The pilot, aged 63, held an airline transport pilot certificate with a rotorcraft helicopter rating and a second-class medical certificate issued March 13, 2008, with the limitation that corrective lenses must be worn. He was hired by PHI in January 1976 and had logged no less than 20,537 hours of rotorcraft flight time, with 200 hours in the Bell 407 and 224 hours at night. He had been flying EMS operations for PHI for 18 months, accumulating 205.5 hours, including 36 hours in the previous 90 days and 5.4 hours at night. His most recent competency/proficiency check under 14 CFR 135.293 and 135.299 was completed on November 17, 2007, in daylight conditions. He had not been trained for NVIS use.
Weather Conditions
Dark night visual meteorological conditions prevailed at the time of the accident. The pilot of another EMS helicopter that had declined the same patient transfer earlier reported encountering low clouds and reduced visibility near Huntsville. He stated that while en route at 1,400 feet he encountered wispy clouds, descended to 1,200 feet where more clouds were present, and eventually descended to 800 feet where visibility decreased rapidly; he aborted the flight. Official weather observations from nearby stations did not report such conditions: the 0235 METAR at Huntsville Municipal Airport (6 nm north) reported 10 miles visibility, scattered clouds at 1,200 feet; the 0240 METAR at Lone Star Executive Airport (18 nm southeast) reported 10 miles visibility, few clouds at 1,700 feet. The moon had set at 0015, and the moon was a waxing crescent with 30% illumination.
Communications
Recordings of telephone conversations between PHI dispatch and the pilot were reviewed. At about 0120, Huntsville Memorial Hospital contacted PHI dispatch requesting a patient transfer after the previous EMS flight had aborted due to clouds or fog. The pilot performed a weather check and discussed the situation with PHI's Enhanced Operational Control Center (EOCC). Both concluded that official weather stations showed no restrictions. The pilot contacted EOCC again after arriving at Huntsville, reporting no issues and weather as forecast.
Flight Recorder Data
The helicopter was equipped with a full authority digital engine control unit (FADEC). The unit separated during the crash and was recovered 10-15 feet west of the main wreckage. Data extraction revealed two full lines and one partial line of data. The first line recorded a torque exceedance at 110 percent; the second line recorded a main rotor droop at 90 percent, which according to Rolls-Royce is consistent with a sudden stoppage. The limited data was attributed to electrical power loss during impact.
Wreckage and Impact Examination
The accident site was in densely forested terrain at an elevation of 344 feet msl. The helicopter impacted on a magnetic heading of 180 degrees. The initial impact point consisted of several trees 80-100 feet tall, with tops and branches exhibiting torn and cut separation features. The main wreckage was spread over a debris path approximately 629 feet long. The main rotor blades separated from the mast, with all four composite yoke flexures showing broomstraw fractures. The tail boom separated, with the aft portion including the tail rotor and gearbox located 50 feet west of the separated transmission and mast assembly. The engine assembly remained partially attached to the aft fuselage; continuity checks showed rotation of both N1 and N2 spools. The skids exhibited light surface scratching but no deformation or dirt on the toes, indicating no ground contact prior to impact. Examination of cockpit instruments revealed the horizontal situation indicator course set to 166 degrees and an airspeed indicator needle slap mark at 64 knots. The Kollsman window was set to 29.96 inches. Caution and warning panel bulbs showed no remarkable anomalies.
Medical and Pathological Information
An autopsy performed on the pilot on June 9, 2008, listed the cause of death as blunt force injuries. Toxicological testing by the FAA's Civil Aerospace Medical Institute was negative for carbon monoxide, cyanide, and ethanol. Diphenhydramine was detected in the urine but not in the blood.
Additional Information
PHI Inc. began air ambulance operations in 1981 and at the time operated 68 bases in 16 states. The accident crew was based in Bryan, Texas. The pilot met the Commission on Accreditation of Medical Transport Systems (CAMTS) training and experience requirements at the time of his initial air medical assignment.
Probable Cause
Not determined or not stated in the source.