Ardmore, OK, USA
N1774
Bell Shelby Aero 47G2
After completing a precision instrument landing approach (ILS), the pilot of the accident helicopter requested a clearance for another ILS approach. Prior to the outer marker, the pilot broke off the ILS approach and proceeded to execute a very high frequency omni range (VOR) approach at the departure airport. After completion of the VOR approach, the helicopter over flew the airport and departed the area to the south. Shortly thereafter, a pilot reported that he heard a radio transmission from the pilot of the helicopter that they were having "throttle linkage problems and were trying to make it back to the airport." A few minutes later the witness heard the pilot state "they were in the pattern and for all aircraft to clear the way", no further radio transmissions were received. Another witness, who was fishing approximately one mile east of the accident site, reported that as the helicopter flew by him in a level attitude, he heard "3 bangs," and then "the engine became silent." The witness stated that the main rotor blades were turning, and the helicopter started descending at a "slight angle." The witness lost site of the helicopter when it descended below a tree line. A third witness located approximately one half north of the accident site reported observing the helicopter descending through approximately 200 feet, "really fast nose first." He stated "all he could hear was the [rotor]blades like they were trying to catch air." No structural or mechanical anomalies were observed during the examination of the helicopter.
HISTORY OF FLIGHT On May 6, 2003, at 1915 central daylight time, a Bell Shelby Aero 47G2 helicopter, N1774, was destroyed when it impacted terrain during a forced landing following a loss of throttle control near Ardmore, Oklahoma. The helicopter was registered to Versatile Aviation Inc., and operated by Versatile Helicopter Inc., of Ardmore. The designated pilot examiner (DPE) and the commercial pilot were fatally injured. Visual meteorological conditions prevailed, and a flight plan was not filed for the 14 Code of Federal Regulations Part 91 instructional flight. The instrument rating flight check flight originated from the Ardmore Downtown Executive Airport (1F0), approximately one hour prior to the accident. According to the air traffic control tower controller at the Ardmore Municipal Airport (ADM), after completing a precision instrument landing approach (ILS), the pilot of the accident helicopter requested a clearance for another ILS approach. Prior to the outer marker, the pilot broke off the ILS approach and proceeded to execute a very high frequency omni range (VOR) approach at 1F0. After completion of the VOR approach, the helicopter over flew the airport and departed the area to the south. A pilot who recently departed 1F0, reported that he heard a radio call from the pilot of the helicopter that they were having "throttle linkage problems and were trying to make it back to the airport." A few minutes later the witness heard the pilot state "they were in the pattern and for all aircraft to clear the way." No further radio transmission calls were received. Another witness, who was fishing at the north ramp of Lake Murray, approximately one mile east of the accident site, reported that as the helicopter flew by him in a level attitude, he heard "3 bangs," and then "the engine became silent." The witness stated that the main rotor blades were turning, and the helicopter started descending at a "slight angle." The witness lost site of the helicopter when it descended below a tree line. A third witness, located approximately one half mile north of the accident site, reported observing the helicopter descending through approximately 200 feet, "really fast nose first." He stated "all he could hear was the [rotor]blades like they were trying to catch air." PERSONNEL INFORMATION The pilot being examined held a commercial airplane single-engine land pilot certificate with an instrument rating, and a commercial rotorcraft helicopter certificate. A review of the pilots logbook revealed he had accumulated a total of 2,029.9 hours of flight time, of which 1,210.3 were in helicopters. Further review indicated he had accumulated a total of 18.1 hours in the accident make/model helicopter. The pilot was issued a second-class medical certificate on April 15, 2003 with no limitations or restrictions. The pilot most recent biannual flight review was conducted on January 8, 2002. The pilot conducting the examination held an airline transport pilot certificate for airplane-multiengine land and rotorcraft helicopter; a commercial pilot certificate for airplane single-engine land with an instrument rating; flight instructor for airplane single-engine, airplane multiengine, and rotorcraft. The pilot's flight instructor certificate was last renewed on October 28, 2002. The pilot was issued a second-class medical certificate on March 18, 2003 with no limitations and reported on his last medical application that he had accumulated a total of 8,800 hours, with 50 hours within the previous 6 months. The pilot reported on an Airman Certificate and/or Rating Application on November 11, 2001, that he had accumulated 4,800 hours in fixed wing aircraft, 3,000 hours in helicopters, and 2.1 hours in the accident make/model helicopter. Previous experience in the accident type or non-turbine helicopter is unknown. The pilot's logbooks were not located, despite multiple attempts. At the time of the accident, the pilot was currently employed for the United States Department of Homeland Security, National Aviation Center, as a fixed wing standardization pilot. AIRCRAFT INFORMATION The three-seat Bell Shelby Aero 47G-2 helicopter was built from spare and/or surplus parts on July 25, 1969 in Shelby, North Carolina, and was powered by a Lycoming V0-435-A1D engine. A review of the aircraft maintenance logs revealed that the helicopter underwent its most recent annual inspection on December 8, 2002 with an approximate airframe total time of 10,000 hours. The most recent inspection of the helicopter was a 100-hour inspection, conducted on n April 23, 2003. The airframe had accumulated a total of 10,206 hours of flight time, and the engine had accumulated a total of 200 hours since major overhaul at the time of this inspection. METEOROLOGICAL INFORMATION At 1910, the automated weather observation system at 1F0 reported the wind from 350 degrees at 6 knots, visibility 10 statue miles, sky clear, temperature 31 degrees Celsius, dew point 11 degrees Celsius, and an altimeter setting of 29.71 inches of Mercury. WRECKAGE AND IMPACT INFORMATION The helicopter impacted a soft grass field, approximately one half mile from the approach end of runway 35 at 1F0. The wreckage energy path was measured on a magnetic heading of 240 degrees, approximately 288 feet in length. The helicopter came to rest inverted on a magnetic heading of 266 degrees at an elevation of 805 feet, approximately 82 feet from the first ground scar. Examination of the wreckage revealed the tubular structure fuselage remained intact. The bubble canopy was shattered and spread throughout the wreckage debris path. The main cabin area was destroyed. The tailboom was separated from the fuselage, and severed into four pieces. The furthest piece extended 206 feet beyond the main wreckage. The engine was separated from its respective mounts, but remained attached to the fuselage by various cables and hoses. The main rotor hub and blade assembly were located adjacent the fuselage. Both main rotor blades were destroyed. Both pitch change tubes were fractured at the clevis. The collective was found wedged in the full down position. The control tube from the collective jackshaft through the cabin wall was fractured at the jackshaft connection. The vertical collective tube behind the wall was fractured. The small link that attaches the collective lever assembly was also fractured at the threads at the bottom of the link. No pre-impact anomalies were observed in the collective control system. The right seat cyclic was fractured at its base. The fracture progressed toward the right. On the fore and aft cyclic system, the control tubes from each cyclic stick to the cyclic jackshaft were flattened. The left seat left anti-torque pedal was fractured. The quadrant assembly that delivers anti-torque movements via cables to the tail rotor was found fractured throughout the web structure in the center of the quadrant. The centrifugal clutch and freewheeling units were examined with no anomalies noted. Flight control continuity was established throughout the flight control system from fracture to fracture. Rotational continuity of the engine was established after removing the camshaft gear. Valve continuity was established. The left magneto was destroyed. The right magneto was separated from its mount, and would not spark when rotated by hand. Fuel was observed in the gascolator and the carburetor float bowl. A borescope inspection revealed that all cylinders were free of anomalies. The engine throttle control cable was removed from the aircraft for further examination at a later date. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy was performed on the examinee by the Office of the Chief Medical Examiner, of Oklahoma City, Oklahoma. No evidence was found of any preexisting disease that could have contributed to the accident A toxicology test was performed by the Federal Aviation Administration's Civil Aeromedical Institute (CAMI) in Oklahoma City, Oklahoma, for carbon monoxide, cyanide, volatiles, and drugs. The toxicology test was negative for all tests. An autopsy was performed on the DPE by the Office of the Chief Medical Examiner, of Oklahoma City, Oklahoma. No evidence was found of any preexisting disease that could have contributed to the accident A toxicology test was performed by the Federal Aviation Administration's Civil Aeromedical Institute (CAMI) in Oklahoma City, Oklahoma, for carbon monoxide, cyanide, volatiles, and drugs. The toxicology test was negative for all tests. TESTS AND RESEARCH On June 20th, 2003, the engine throttle cable and tube were examined under the supervision of the NTSB investigator-in-charge at the engineering laboratories at Bell Helicopter, of Hurst, Texas. The cable was separated from the carburetor attach point rod, and lock plug. The inner strands of the cable were fractured approximately 39.81 inches from the carburetor end of the cable. At the inner strand fracture location, the outer thicker single strand of coiled wire was stretched but not fractured. All of the fractured wires from the inner strands fractured were typical of overload as evidence by cup-cone tensile features. Wear and mechanical damage was noted on the outside of the tube. Impact damage was noted on the tube adjacent to the cable inner strands fracture. Examination of the carburetor end of the cable revealed approximately .25 inches of the center bundle of wires was retracted from the carburetor end of the cable outer strands. The outer single strand of the coiled wire and internal strands were stretched out of their original coiled and meshed condition. Scrapes were found on the outer cable wrap in the direction of the end of the cable from scraping against the lock plug. The cable would go into the lock plug .210 inches. The lock plug nut was tight with the head bottomed out on the sliding end body. No anomalies were noted that would have prevented normal operation prior to the accident. ADDITIONAL INFORMATION On May 9, 2003, the wreckage was released to the operator's representative.
The pilot's failure to control the rate of descent, which resulted in an improper touchdown of the helicopter. A contributing factor was the loss of throttle control for undetermined reasons.
Source: NTSB Aviation Accident Database
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