FRENCHVILLE, PA, USA
N52AG
Bell UH-1H
The helicopter was on its fourth spray mission of the day, and the pilot's 51st spray mission for the season, when the accident occurred. The helicopter returned from the third mission, was refueled, reloaded, and departed. The helicopter then crashed a couple of minutes after takeoff in a wooded area. The weather was clear at the time of the accident. Main-rotor blade, and tail-rotor blade damage was consistent with low rotor rpm at impact. Examination of the transmission revealed no preimpact failures or malfunctions. Examination of the engine revealed that the compressor and turbine sections of the engine had been exposed to a large amount of aluminum from an unknown source prior to impacting the trees.
HISTORY OF FLIGHT On May 16, 2000, about 1900 Eastern Daylight Time, a former military, Bell UH-1H, N52AG, was substantially damaged when it impacted a hill near Frenchville, Pennsylvania, while spraying a non-toxic agent. The certificated commercial pilot was fatally injured. Visual meteorological conditions prevailed, and a company flight log was used to track the helicopter while spraying. The flight was conducted under 14 CFR Part 137, and originated from a remote landing zone (LZ) approximately 2.6 miles from the accident site. According to witnesses, The helicopter was on its fourth gypsy moth spray mission of the day, and the pilot's 51st spray mission for the season, when the accident occurred. According to a witness, the pilot got a "good night's rest" got up, and then flew from Tallman West Airport, Dauphin, Pennsylvania, to the Clearfield-Lawrence Airport, Clearfield, Pennsylvania, arriving between 1000 and 1030. Plans were then developed for the spray missions scheduled for that afternoon and early evening. About 1615, the pilot flew to the planned LZ, and waited for support personnel, who arrived, about 1645. A forester was then sent to the spray area to check weather. He reported that conditions were suitable for spraying, and the helicopter departed on the first mission, at 1707. The helicopter returned from the first mission, was refueled, and 300 gallons of spray was loaded. It departed on the second mission, at 1750. The helicopter returned from the second mission, was refueled again, and loaded with another 300 gallons of spray before departing on the third mission, at 1823. At 1853, the helicopter returned to the LZ. It was refueled, loaded again with 300 gallons of spray, and departed on the forth mission, at 1858. By 1944, the helicopter had not returned. A ground and air search was initiated, and at 2005, the helicopter was found at the eastern boundary of the spray area about 2.56 miles northeast of the LZ. The accident occurred during the hours of daylight. The wreckage was located 41 degrees, 10.810 minutes north latitude, 78 degrees, 17.225 minutes west longitude, and about 870 feet elevation. PERSONNEL INFORMATION The pilot held a commercial pilot certificate with ratings for airplane single engine land, helicopter, and instrument airplane and helicopter. In addition, he held a flight instructor certificate for helicopters. His last FAA second class medical certificate was dated February 14, 2000, and listed no restrictions. On his last application for a medical certificate, the pilot indicated a total of 4,000 hours of flight experience. According to company records, the pilot had 4,714.8 hours of total flight experience, of which 4,441.8 hours were in helicopters, with 150.8 hours of that in make and model. METEOROLOGICAL INFORMATION Approximately 13 minutes before the accident, an automated weather station located approximately 29 miles southeast of the accident site, recorded the wind as 240 degrees at 4 knots, visibility 20 miles, few clouds at 9,000 feet, an overcast layer at 15,000 feet, temperature 64 degrees Fahrenheit, dew point 36 degrees Fahrenheit, and an altimeter setting of 30.07 inches of mercury. WRECKAGE AND IMPACT INFORMATION The helicopter came to rest inverted, on the side of a tree covered hill, on a magnetic heading of 355 degrees. Trees in the area averaged 70 feet in height and 2 feet in diameter. Approximately 200 feet to the southwest of the main wreckage were several tree tops with freshly broken branches. In and below the tree tops were components from the spray system. At the main wreckage, the tree tops also had broken branches, with several displaying intermittent scrape mark to the ground. The majority of impact damage was from the nose of the helicopter to a point approximately 6 feet aft. After this point, impact damage diminished rapidly. The spray tank was compromised and the dump valves were closed. The engine cowling had only minor impact damage. The anti-collision beacon located on the top of the helicopter, over the engine exhaust, was not damaged. The tailboom was connected to the fuselage, and displayed a compression wrinkle below the engine exhaust. In addition, the outboard 2 feet of the left-synchronized elevator, and the bottom left side of the vertical fin were damaged. The left, top, and right engine plenum screens were intact and partially separated from the airframe. The sand and dust separator was severely fragmented and only a portion of it was recovered. The engine was intact with the inlet section resting approximately 1 foot from the leaf-covered ground. No impact damage to the engine was observed except to the output shaft. Two of the engine mounts were broken, and the fracture surfaces were consistent with overload. Examination of the engine compressor, via the intake, revealed no missing compressor blades. In addition, no dirt or leaves were identified in the intake. Approximately six of the compressor blades displayed damage consistent with foreign object damage on their trailing edge. Examination of the turbine section, via the engine exhaust pipe, revealed no damaged to any of the turbine blades. The engine-chip detector was removed and found absent of debris. In the cockpit, the main fuel switch was on, and the engine-governor switch was in the "GOV AUTO" position. The transmission separated from the airframe and was located underneath the main wreckage. The transmission-chip detector was removed and found absent of debris. When a clockwise rotational force was applied to the input quill, the mast rotated, along with all the accessory output drives. When a counter-clockwise rotational force was applied to the input quill, the unit rotated freely, and the mast remained stationary. The K-Flex coupling had separated from the transmission and engine. It was in two pieces, both within 5 feet of the transmission. Both main rotor blades were attached to the main-rotor hub. Both blades were missing the majority of the honeycomb material aft of the blade spar. The bottom side of the honeycomb material from both blades had chordwise gouges. The leading edge on one of the blades had only minor impact damage, and 30 degree up bend approximately 10 feet from the hub. The other blade spar was also intact, and displayed a slight downward and then upward bend from the hub outward. Both tailrotor blades were attached to the tailrotor hub assembly. One of the blades displayed no visible damage. The outboard 6 inches of the other blade showed signs of impact damage, and had a reddish paint smeared across it. The paint was similar in color to the paint on the vertical fin. In addition, damage on the vertical fin was approximately the same size as the tailrotor blade damage. The wreckage was recovered on May 16, 2000, and transported to a hangar at the Clearfield Airport for further examination. Once at the hangar, flight control continuity was verified from the pilot and copilot stations to the main rotor assembly, tail rotor assembly, and synchronized elevator. Power train continuity was also verified from the engine to the transmission, and to the tailrotor. The helicopter was equipped with a crash-worthy fuel system, and approximately 1,000 pounds of fuel remained onboard after the accident. The airframe mounted fuel filter was opened. It was full of fuel, and less than 1 percent of the filter had fungus on it. The fuel line from the filter to the engine was then drained, no fungus or water was observed, but five small pieces (each about the size of a grain of sand) of inorganic materiel were identified. Approximately 1 quart of fuel was drained from the tank used to refuel the helicopter at the LZ. The fuel was absent of water, and one small pieces of inorganic materiel was observed. TEST AND RESEARCH On June 12, 2000, the transmission input quill was examined by the manufacturer under the supervision of the FAA and direction of the Safety Board. During the examination no preimpact failures or malfunctions were observed. On September 26, 2000, at one of the engine manufacturer's facilities in Phoenix, Arizona, the engine was removed from its shipping container, and a pre-run inspection was preformed under the supervision of the Safety Board. During the inspection it was determined the engine could not be run. The engine was then placed back into its shipping container, and shipped to another location for teardown. On September 27 and 28, 2000, the engine was examined at one of the manufacturer's other facilities in Phoenix, under the supervision of the Safety Board. During the examination, the inlet section gearbox, compressor section, and turbine section of the engine were examined. In addition, the N2 and N1 accessory gearboxes were examined along with their respective accessories. The K-Flex coupling adapter had separated from the engine-output shaft. The fracture surface was grayish in color, and consistent with overload. The majority of the engine side and transmission side flexors were broken on the coupling. The fracture surfaces for the broken flexors were grayish in color and also consistent with overload. The drive shaft located between the engine flexors and the transmission flexors was intact. The inlet reduction gearbox was removed, and a rotational force was applied by hand to the output shaft. The planetary gears rotated freely with some occasional resistance. The output drive shaft was then removed, and damage consistent with impact was observed on some of the splines. The forward power shaft support bearing was intact and rotated freely, along with all the other bearings in the compressor and turbine section of the engine. All the inlet variable guide vanes were present, and no impact damage was observed on the leading edge of the vanes. The middle section, along with the trailing edge of the vanes had multiple impact marks consistent with foreign object damage (FOD). All of the compressor blades were present. The first stage compressor blades had damage to both their leading and trailing edges. Damage to the compressor blades became less after the first stage, with the last axial flow blades displaying the least amount of damage. The radial flow section of the compressor was intact, along with its shroud, except for several nicks in the shroud. In both the inner and outer thermal liners, soot and small metal fragments were observed. On the entire circumference of the diffuser, spaced approximately 2 inches apart, were streaks of melted aluminum, each approximately 4 inches long. In the gas producer section, melted aluminum was observed on the No. 1 nozzle, No. 1 turbine, No. 2 nozzle, and No. 2 turbine. In the power turbine section, melted aluminum was observed on the No. 1 nozzle, No. 1 turbine, No. 2 nozzle, and No. 2 turbine. The distribution of melted aluminum was not symmetrical through the combustion section. The No. 1 nozzle for the gas producer had the most melted aluminum, with each component after that having less then the component upstream. Initially the turbine section could not be rotated by hand. The turbine section was then disassembled. During the disassembly, the No. 1 power turbine nozzle and then the No. 1 power turbine rotor were removed. The turbine section along with its support bearing then rotated free by hand. N1 accessory drive pads for the N1 tachometer generator, starter generator, fuel control, and engine oil pump all rotated when the gas producer drive shaft was rotated by hand. The N2 accessory drive pads for the N2 tachometer generator, and the fuel control's N2 input, all rotated when the power turbine drive shaft was rotated by hand. The variable guide vane actuator and support systems were examined and no preimpact failures were identified. The bleed band actuator was examined and no preimpact failures were identified. The fuel control was tested at a Pueblo Airmotive in Tucson, Arizona, on September 29, 2000, under the supervision of the Safety Board. The governor, emergency governor, and engine drive fuel pump were all evaluated, and no anomalies were identified. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy was preformed on the pilot, May 18, 2000, at the Medical Examiners Office in Altoona, Pennsylvania. A toxicological test was performed on the pilot by the FAA Toxicology and Accident Research Laboratory, Oklahoma City, Oklahoma, on June 7, 2000. ADDITIONAL INFORMATION The helicopter was equipped with a digital spray log. The log was recovered after the accident and downloaded to a computer for examination. The log contained spray information and track information that were based on a Differential Global Positioning System installed on the helicopter. According to the log, the helicopter departed the LZ on the fourth mission at 18:57:42 and proceeded to the northeast back towards the last spray track. At 18:59:14 and 1.90 miles northeast of the LZ, the log stopped. The helicopter was located 2.56 miles northeast of the LZ. The majority of the wreckage was released on May 19, 2000, to the owner's representative. The engine, K-Flex coupling, and transmission clutch assembly were released on February 27, 2001, to the owner's representative.
Foreign object damage to the compressor and turbine sections of the engine, which resulted in a loss of power.
Source: NTSB Aviation Accident Database
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