Valparaiso, IN, USA
N250AD
Fairchild Hiller FH-1100
During cruise flight the main rotor mast fractured and the main rotor separated from the helicopter. Witnesses to the accident reported seeing the helicopter falling to the ground in multiple sections. The aft 7.5 feet of tailboom, including the tail rotor gearbox, was located 220 feet from the main wreckage. The main rotor hub and blades were located 146 feet from the main wreckage. The main rotor blades remained attached to the rotor hub assembly. The main rotor mast was fractured approximately 6 inches below the rotor hub assembly. The fracture was transverse to the longitudinal direction of the mast. The interior diameter of the main rotor mast was corroded and had several areas of surface pitting. According to the NTSB Materials Laboratory Factual Report, the main rotor mast contained a "flat" crack that contained crack arrest features indicative of fatigue cracking. The report states, "The crack arrest features in the flat fracture region emanated from corrosion pits on the inside diameter surface of the mast. The entire inside diameter surface had been affected by this corrosion in the area of the flat fracture region."
HISTORY OF FLIGHT On August 19, 2000, at 1324 central daylight time, a Fairchild Hiller FH-1100, N250AD, piloted by a private pilot, was destroyed during an in-flight failure of the main rotor mast and subsequent collision with the terrain near Valparaiso, Indiana. Visual meteorological conditions prevailed at the time of the accident. The personal flight was operating under the provisions of 14 CFR Part 91 without a flight plan. The pilot, the sole occupant, was fatally injured. The flight departed the Porter County Municipal Airport (VPZ), Valparaiso, Indiana, at 1320 for the local flight. A witness to the accident reported, "I looked up and watched the helicopter flip over, break apart and crash. The helicopter's [main] rotor separated from the fuselage, and the tail rotor left [with] part of the fuselage." Another witness reported, "I looked up and heard a loud 'pop' and as helicopter was falling straight down in pieces... ." Copies of the written witness statements are appended to this factual report. PERSONNEL INFORMATION The pilot held a private pilot certificate with ratings for helicopter, single engine land airplanes, multi-engine land airplanes, and instrument airplane operations. The pilot's last medical examination was conducted on November 10, 1998, and he was issued a second-class medical certificate with the limitation, "Must wear corrective lenses for near and distant vision." According to the pilot's flight logbooks, he had a total flight time of 1,584.9 hours, of which 715.2 hours were in helicopters, 705.4 hours were in single engine airplanes, and 159.2 hours were in multi-engine airplanes. The pilot's last flight review, as required by Federal Aviation Regulation (FAR) 61.56, was completed on December 13, 1998. The pilot had logged 20.2 hours during the last 90 days, of which 4.3 were in helicopters and 15.9 hours were in single engine airplanes. The pilot had logged 8.2 hours in the last 60 days, of which 1.2 hours were in helicopters and 7.0 hours were in single engine airplanes. The pilot had logged 1.9 hours in the last 30 days, of which 0.7 hours were in helicopters and 1.2 hours were in single engine airplanes. There were no flight logbook entries within 24 hours of the accident. AIRCRAFT INFORMATION The helicopter was a Fairchild-Hiller FH-1100, serial number 162. The FH-1100 has a two-bladed rotor system and is powered by a single turbo shaft engine. The FH-1100 has a maximum gross weight of 2,750 lbs and can be configured to accommodate a pilot and three passengers. According to Federal Aviation Administration (FAA) records, the helicopter was issued a FAA standard airworthiness certificate on June 12, 1969, and was certified for normal category operations. At the time of the accident, the helicopter had accumulated a total airframe time of 4,624.4 hours. The last annual inspection was completed on May 1, 2000, and the helicopter had accumulated 31.1 hours since the inspection. The last 100-hour and 300-hour inspection was completed during the last annual inspection. The engine was a 317 horsepower Allison 250-C18B, serial number CAE800950B. According to the engine logbooks, the engine had accumulated a total time of 4,459.36 hours. The last engine inspection was completed on May 1, 2000, and the engine had accumulated 31.1 hours since the inspection. METEOROLOGICAL INFORMATION A weather observation station, located at VPZ, about 3.2 nautical miles (nm) from the accident site on a 093 degrees magnetic heading, recorded the weather approximately 6 minutes after the accident as: Observation Time: 1330 cdt Wind: 010 degrees magnetic at 8 knots Visibility: 10 statute miles Sky Condition: Sky Clear Temperature: 21 degrees Celsius Dew Point: 13 degrees Celsius Pressure: 30.27 inches of mercury WRECKAGE AND IMPACT INFORMATION The helicopter impacted an open, level, agricultural field. A GPS receiver recorded the position of the main wreckage as 41-degrees 27-minutes 13.8-seconds north latitude, 87-degrees 04-minutes 36.8-seconds west longitude. There was a wreckage debris field that was approximately 550 feet in length oriented on a 283-degree magnetic heading. The aft 7.5 feet of tailboom, including the tail rotor gearbox, was located 220 feet from the main wreckage on a 084-degree magnetic heading. The main rotor hub and blades were located 146 feet from the main wreckage on a 180-degree magnetic heading. All major airframe components were located within the wreckage debris field. The main rotor blades remained attached to the rotor hub assembly. The main rotor mast was fractured approximately 6 inches below the rotor hub assembly. The fracture was transverse to the longitudinal direction of the mast. The interior diameter of the main rotor mast was corroded and had several areas of surface pitting. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy was performed on the pilot by the Porter Memorial Hospital - Department of Pathology, Valparaiso, Indiana, on August 20, 2000. A Forensic Toxicology Fatal Accident Report was prepared by the FAA Civil Aeromedical Institute, Oklahoma City, Oklahoma. The toxicology results for the pilot were: * No Carbon Monoxide detected in Blood * No Cyanide detected in Blood * No Ethanol detected in Urine * No drugs detected in Blood TESTS AND RESEARCH The fractured main rotor mast was sent to the National Transportation Safety Board Materials Laboratory Division for examination. According to the Materials Laboratory Factual Report, the main rotor mast contained a "flat" crack that contained crack arrest features indicative of fatigue cracking. The report states, "The crack arrest features in the flat fracture region emanated from corrosion pits on the inside diameter surface of the mast. The entire inside diameter surface had been affected by this corrosion in the area of the flat fracture region." The report states, "The deepest corrosion pit ... extended 0.032 inch below the inside diameter surface and was about 0.046 inch wide. A second severe pit ... was 0.027 inch deep." The report states, "Areas of corrosion damage on the inside diameter surface of the mast were contiguous from the upper end of the mast to a position slightly above the transition from the taper to the larger diameter portion of the mast. On the upper piece of the mast this corrosion damage had affected more than 80 percent of the surface. An additional area of corrosion damage was noted on the inside diameter surface adjacent to the cut location on the lower piece of the mast." The main rotor mast is a part of the main rotor transmission assembly, part number 24-23000-41. According to the helicopter's maintenance information, main rotor transmission, serial number 1136, was installed on the accident helicopter in June 1993 during a major rebuild of the helicopter. Main rotor transmission, serial number 1130, was installed in the helicopter at the time of the accident. There were no logbook entries or component cards that indicated that the main rotor transmission had been replaced subsequent to June 1993. An accurate component history for the main rotor transmission, including the main rotor mast, was not possible due to the inaccurate maintenance logbook information. Several airframe and engine components were found whose serial numbers did not correspond to the serial numbers listed in the maintenance records. The maintenance history for those components could not be determined. ADDITIONAL INFORMATION Parties to the investigation included the FAA, Rolls-Royce, and the FH-1100 Manufacturing Corporation.
The in-flight fracture of the main rotor mast and the separation of the main rotor. Factors to the accident were the corroded main rotor mast that resulted in fatigue.
Source: NTSB Aviation Accident Database
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