EAST BERNSTADT, KY, USA
N9609F
HUGHES 269C
THE HELICOPTER WAS ON A LOW ALTITUDE POWERLINE PATROL WHEN IT DESCENDED AND COLLIDED WITH UPSLOPING TERRAIN. THE INVESTIGATION REVEALED THE CLUTCH SPRING ASSEMBLY WAS FRACTURED, INVOLVING THE ASSEMBLY RETAINER END WHICH SEPARATED. THE RETAINER WALL WAS SEVERELY WORN WHERE THE SEPARATION OCCURRED. THE ASSEMBLY FUNCTIONS TO ENGAGE THE BELT DRIVE SYSTEM WHICH IN TURNS TRANSMITS ENGINE POWER TO THE MAIN TRANSMISSION. THE HELICOPTER HAD OVER 11,000 HOUR OF TOTAL TIME. THE LAST INSPECTION OF THE ASSEMBLY WAS ABOUT A MONTH EARLIER, DURING A 100 HOUR INSPECTION. A REVIEW OF MAINTENANCE RECORDS REVEALED NO PREVIOUS REPLACEMENT OF THE ASSEMBLY.
History of the Flight On September 25, 1992 at about 1215 hours eastern daylight time, N9609F, a Hughes 269C helicopter, a powerline patrol flight, operated by Helicopters, Inc. crashed at East Bernstadt, Kentucky. Visual meteorological conditions existed. The pilot and passenger were fatally injured. The helicopter was destroyed. The local flight was conducted under 14 CFR 91 and originated at Winchester, Kentucky. The pilot was on the fifth day of patrol flight, according to the operator of the helicopter. The passenger was aboard as an observer. A witness said he saw the helicopter flying low over the powerline before the accident occurred. He first saw the helicopter flying west and then about five minutes it was headed north. Suddenly he heard the sound of the helicopter stop, followed by the sound of a crash. Pilot Information The pilot held a commercial pilot certificate. According to the pilot's logbook, he had 21,386 hours of total time. According to Helicopter Inc., he had over 11,000 hours in type. Aircraft Information The 1971 year model helicopter, serial no. 700017, was equipped with a Lycoming HIO 360 D1A engine. According to maintenance records, as of September 24, 1992, the helicopter had 11,092 hours of total time and it was operated 35 hours since the last progressive inspection, which was done on September 15, 1992. Meteorological Information The September 25, 1992 1150 hour surface weather observation for East Bernstadt, Kentucky, located about 8 miles from the accident site, was the following: sky and ceiling, clear; visibility, 20 miles; temperature, 69 degrees F; wind, 140 degrees at 5 knots; altimeter setting, 30.23 inches hg. Wreckage and Impact Information The helicopter crashed on the upslope (11 degrees) of a hill, about 100 feet south of powerlines. The helicopter struck and became partially embedded in the ground, and it was oriented on a 70 degree magnetic heading. The landing skid and tail section separated on impact. Inspection of the helicopter revealed the clutch spring assembly was fractured. Examination of the assembly revealed the retainer section sustained separation of the retainer end. The wall of the retainer where the separation occurred was worn completely through. Also noted was wear on the assembly housing, approximately in a location adjacent to where the retainer separation occurred. The assembly was submitted to the NTSB Material Laboratory for examaination. Details of the visual and metallurgical examinations are an attachment to this report. Medical and Pathological Information An autopsy of the pilot was done by Kentucky State Medical Examiner Office. According to the autopsy report, the pilot died as a result of injuries incurred from the accident. Toxicological test were negative for alcohol, drugs, and carbon monoxide. Additional Information System Description: Power Train According to the Schweizer (the current manufacturer) Model 269 Series Basic Handbook of Maintenance Information (HMI): "The power train system consists of a bell drive transmission, belt drive clutch control, main rotor drive shaft, tail rotor drive shaft, tail rotor transmission and related miscelllaneous components. Engine output is coupled through the bell drive transmission and associated pulleys to the tail rotor and the main transmission which drives the main motor." Clutch Control According to the HMI: "The belt drive control installation consists of a linear actuator, electrical connections to a Clutch control switch and to warning light on the instrument panel, and a vcable and pulley to interconnect the linear actuator to the clutch spring on the belt drive transmission. Wnen the Clutch control switch on the instrument panel is at the Engage position, the linear actuator retracts, applying tension to the idler pulley. The idler pulley moves outboard and applieds tension to the main rotor drive V belt to transfer power from the engine to the main transmission and the tail rotor."
INADEQUATE MAINTENANCE INSPECTION INVOLVING FAILURE TO DETECT WEAR OF THE CLUTCH SPRING ASSEMBLY, RESULTING IN THE UNCOUPLING OF ENGINE POWER TO THE MAIN TRANSMISSION.
Source: NTSB Aviation Accident Database
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