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On January 8, 2001, at 1420 central standard time, a Bell 206B, single-engine helicopter, N152AL, was destroyed when it struck trees and terrain during a forced landing following a loss of engine power near Mineral Wells, Texas. The helicopter was owned and operated by S-TEC Corporation of Mineral Wells. The airline transport pilot, sole occupant, sustained fatal injuries. Visual meteorological conditions prevailed, and a company visual flight rules (VFR) flight plan was filed for the 14 Code of Federal Regulations Part 91 business flight. The local flight originated from the Mineral Wells Airport at 1410.
According to a witness, who was loading topsoil into a truck with a Caterpillar loader, he noticed a shadow pass overhead and "heard the noise of rotor blades." He turned around and observed the helicopter impact the ground, nose over, and come to rest inverted about 30 feet from his location. The witness stated that he "did not hear the engine running." The witness also stated that the pilot asked for assistance in getting out of the helicopter since he was getting wet with the fuel draining from the ruptured fuel tank.
The operator reported that the helicopter was being used for the development of a helicopter autopilot system, which contained rotary and linear servos. One of the servos had been removed and reinstalled during the previous 30 days, during which time the pilot had not flown the helicopter. On the day of the accident, the pilot was to fly the helicopter in the local area.
According to FAA records, the pilot was issued an airline transport certificate on September 14, 1996, for multiengine land airplanes. He held a flight engineer certificate and a commercial certificate for airplane single-engine land and rotorcraft-helicopter. The pilot also held a flight instructor certificate for airplane single and multiengine land, instrument airplane, and rotorcraft-helicopter. The pilot held a second class medical certificate, which was issued on August 25, 2000. The medical certificate stipulated a limitation to have corrective lenses available for near vision while operating an aircraft.
A review of the pilot's flight logbooks revealed that on July 24, 2000, he completed a biennial flight review in a Bell 206 helicopter. The logbook also revealed that as of January 5, 2001 (last entry in logbook), the pilot had logged a total flight time of 8,176.79 hours and 156.7 hours in helicopters, of which 73.1 hours were in the Bell 206 helicopter.
The 1975-model Bell 206B helicopter (S/N 1703) had a two-bladed main rotor system, and was powered by an Allison 250-C20 turboshaft engine (S/N CAE 821746) rated at 400 horsepower. The helicopter was issued an experimental airworthiness certificate on April 15, 1999.
A review of the maintenance records revealed that the helicopter underwent its most recent annual inspection on July 13, 2000, at a total airframe time of 15,599.2 hours, and engine total time of 14,700.0 hours. At the time of the accident, the airframe had accumulated a total of 15,627.0 flight hours and the engine a total of 14,728.0 hours . No evidence of uncorrected maintenance discrepancies was noted in the records.
WRECKAGE IMPACT INFORMATION
The accident site was located using a global positioning satellite (GPS) receiver at 32 degrees 45.486 minutes north latitude and 098 degrees 05.357 minutes west longitude, about 2.34 miles southwest of the Mineral Wells Airport. The accident site was in an area of relatively level terrain with mesquite trees.
An examination of the accident site revealed that a 20-foot tree, located at the beginning of the energy path, exhibited broken and sheared branches near its top. The right horizontal stabilizer was found at the base of this tree. The helicopter came to rest inverted on its right side on a measured magnetic heading of 198 degrees, 68 feet 8 inches from the initial tree strike. Ground scars on a measured magnetic heading of 080 degrees were found 30 feet past the initial tree strike. The ground scars were consistent with the shape of the left and right landing skids, and the rear of the fuselage. The left and right skid tubes joined by the aft cross tube were separated from the fuselage. The skids were found straddling a tree located adjacent to the main wreckage. An 8-inch diameter portion of this tree was found embedded in the cockpit area of the fuselage. The fuel filler cap was found open and there was the odor of fuel around and within the wreckage.
The main rotor hub remained attached to the mast. The top of the mast was bent below the main rotor static stop contact area. Both main rotor blades remained attached to the hub. One of the blades was fractured 2 feet from the blade grip. The other blade had damage on the trailing edge near the tip. Both blades exhibited smudges and dents consistent with having struck trees while rotating. The main transmission remained attached to the pylon links. The transmission rotated freely when the power input was rotated by hand. The K-flex main drive shaft was intact and remained connected to the engine and transmission.
The tail boom was separated from the fuselage at Boom Station 45. The left horizontal stabilizer and tail boom displayed impact signatures consistent with a main rotor blade strike. The left horizontal stabilizer was separated and found on the ground next to the vertical stabilizer. The tail rotor 90-degree gearbox was attached to a partially separated portion of the separated tail boom and it rotated freely. The tail rotor hub and blade assembly was found attached to the 90-degree gearbox. One of the tail rotor blades was bent over 90 degrees outboard of the attachment point and it displayed a dent in the leading edge near the tip. The other tail rotor blade exhibited some bending, but remained intact.
Continuity was established from the cyclic, collective, and anti-torque pedals to their respective flight controls.
The engine was intact and mounted to the engine deck. The power turbine governor case was fractured at the power lever entry point. The compressor inlet screen was intact and remained in place. Both the compressor and power turbine turned freely and smooth when rotated by hand. The fire shield to fuel nozzle fuel supply line contained fuel. Both the engine and airframe fuel filters were clean and full of fuel. The fuel was clear and no evidence of contamination was noted.
The helicopter wreckage was recovered to Air Salvage of Dallas, Lancaster, Texas. The engine was removed from the wreckage and transported to the Dallas Airmotive facility, Dallas, Texas, for further examination.
MEDICAL AND PATHOLOGICAL INFORMATION
The pilot succumbed to his injuries while being treated in a hospital, therefore an autopsy was not performed.
The FAA Civil Aeromedical Institute toxicology laboratory noted 0.295 (mg/dl, mg/hg) morphine detected in liver and 0.878 (mg/dl, mg/hg) morphine detected in kidney. Atropine was present in blood and detected in liver, and quinine was detected in blood. These medications were most likely administered to the pilot following the accident.
TESTS AND RESEARCH
An examination and test run of the helicopter's engine was conducted under the supervision of the NTSB investigator-in-charge (IIC) on February 17, 2001, at Dallas Airmotive, Dallas, Texas. The air pressure lines for the engine were pneumatically tested and no leaks were noted. Prior to the engine test run, the damaged power turbine governor was replaced with a slave governor. The engine was test run for about 47 minutes through various power settings and no anomalies were noted. The NTSB IIC took possession of the power turbine governor and main fuel control for further examination and testing.
Functional testing of the main fuel control (S/N 320195) and a disassembly examination of the power turbine governor (S/N 26748) were conducted under supervision of the NTSB IIC on February 22, 2001, at the Honeywell facility, South Bend, Indiana. Due to damage, functional testing of the power turbine governor was not possible; however, a low pressure Pc test was conducted. The results of the low pressure Pc input tests were consistent with a "normally" functioning Py pneumatic circuit. No anomalies were noted during the disassembly examination of the governor. No anomalies were noted during the functional testing of the main fuel control that would have prevented it from operating "normally."
The retained parts of the aircraft wreckage were returned, and a final wreckage release was issued to the owner's representative on April 4, 2001.