HURRICANE, WV, USA
N9070F
Robinson R-22
A witness observed the helicopter at approximately 200 feet above ground level (AGL) and then descend to approximately 60 feet AGL. The witness stated that the helicopter was making a 'popping noise,' and wobbling back and forth, and side to side for about 30 seconds. The witness also stated that he could see the helicopter's main rotor blades slowing down. The helicopter then 'nose dived' towards the ground. The helicopter impacted in a dry creek bed and came to rest on it's left side. One main rotor bladed was found curved upward and contained blue and white paint transfer. It should be noted that the helicopter tail boom is painted blue and white. A 12,000 volt electrical wire system was located approximately 37 feet above the main wreckage and one of the wires had been severed. The helicopter had been operated for about 1 hour since an annual inspection had been performed 5 days prior to the accident; about 70 hours since December 1994; and about 2,070 hours since it was last overhauled in 1992. The helicopter was fueled with automotive gasoline. A supplemental type certificate (STC) for the use of automotive gasoline for the accident helicopter was available; however, examination of the helicopter's maintenance records did not reveal that an STC had been obtained for the use of automotive gasoline. The engine was test run and it operated satisfactorily. Examination of the wreckage did not reveal any pre-impact malfunctions of the airframe or engine. Review of the FAA 'Carburetor Icing Probability Chart' placed the reported temperature and dewpoint in the 'serious icing at glide power' area. Additionally, examination of the engine low oil pressure light bulb filament from the annunciator panel revealed some elongation of the filament.
HISTORY OF FLIGHT On June 23, 1999, about 1935 Eastern Daylight Time, a Robinson R-22, a helicopter, N9070F, was substantially damaged when it descended and impacted terrain in Hurricane, West Virginia. The certificated private pilot was fatally injured. Visual meteorological conditions prevailed and no flight plan had been filled for the local flight which departed from a field at the pilot's home, about 1925. The personal flight was conducted under 14 CFR Part 91. Witnesses observed the helicopter above a local carnival. One witness, who also knew the pilot, stated the helicopter made a pass overhead and momentarily rolled from side to side, which was the pilot's way of "waving" to the crowd. The helicopter made a right turn, came around for another pass, and then departed the area. Less than 2 minutes after observing the helicopter, he heard a radio call that a helicopter had crashed. He further stated that he had witnessed the helicopter on several previous occasions, and it seemed to be operating normally. In a telephone interview, a second witness who lived about 1/4 miles from the accident site stated he was working in a garden when he observed the helicopter make a circle overhead. He noticed the helicopter was making a "crackling and popping" noise, and "didn't sound right." The helicopter made another circle and disappeared beyond his field of view. He then noticed that all was quite. A third witness, who lived about 300 feet from the accident site stated he observed the helicopter flying straight and level, about 100 feet above his house, when it began to make a "popping noise." After a few moments the noise stopped. The helicopter then climbed and departed from his field of view. About one minute later, he observed the helicopter about 200 feet above the ground, heading south. The helicopter made a "U turn," and descended to about 60 feet above the ground. At that time, he heard the popping noise again, and the helicopter was wobbling back and forth, and side to side, for about 30 seconds. He could see the helicopter's main rotor blades slowing down, and thought it might have climbed slightly. The helicopter slowly approached the road and all noise then stopped. The helicopter then "instantly took a nose dive" down towards the ground. The accident occurred during the hours of daylight approximately 38 degrees, 26 minutes north latitude, and 82 degrees, 2 minutes west longitude. PERSONNEL INFORMATION The pilot held a private pilot certificate with ratings for rotorcraft and airplane single engine land. He reported 1,900 hours of total flight experience on his most recent Federal Aviation Administration (FAA) third class medical certificate, which was issued on January 8, 1999. According to the pilot's wife, the pilot had owned the helicopter for about 3 years and regularly flew short 10 to 15 minute flights. She stated that the helicopter's insurance policy had lapsed between April 18 and June 18, and except for a short 5-minute flight, the pilot's most recent flight prior to the accident was "sometime before April 18." According to the pilot's logbook, the pilot's last flight in the helicopter was on March 5, 1999. During the 12 months prior to the accident, the pilot flew about 40 flights in the helicopter, and each flight averaged about 15 minutes in duration. AIRCRAFT INFORMATION According to maintenance records, the helicopter's last annual inspection was performed 5 days prior to the accident, at a "Hobbs" time of 2,481 hours. Examination of the helicopter's Hobbs meter at the accident site revealed about 8/10 of an hour had elapsed since the annual inspection. Both the helicopter and engine were overhauled on December 4, 1992. On August 4, 1994, at a Hobbs time of 1,589 hours, the helicopter's Hobbs meter was replaced with another Hobbs meter which read 2,000 hours. Examination of the helicopter's airframe logbook revealed the helicopter had been operated for about 70 hours since January 1996. Additionally, the following entry was made by maintenance personnel on December 12, 1994: "Hobbs [time] 2,410 [hours]. Aircraft total time since last overhaul is 2,000 hours. [Aircraft] not to be run-up or flown because of 2,000 hour TBO items. Aircraft needs repair." The next entry in the airframe logbook was for an annual inspection, which was performed on April 20, 1996, at a Hobbs time of 2,413 hours. In an interview with a Federal Aviation Administration (FAA) Inspector, maintenance personnel who performed the helicopter's most recent annual inspection stated that the helicopter was using automotive gasoline. A supplemental type certificate (STC) for the use of automotive gasoline for the accident helicopter was available; however, examination of the helicopter's maintenance records did not reveal that an STC had been obtained for the use of automotive gasoline. The STC requires the use of premium automotive gasoline (a minimum of 93 octane). METEOROLOGICAL INFORMATION The weather reported at an airport about 24 miles east-southeast of the accident site, at 1954, was: Winds calm, Visibility 8 statue miles with clear skies, Temperature 84 degrees F, Dewpoint 59 degrees F, Altimeter 29.98 inches HG. Review of an FAA "Carburetor Icing Probability Chart," placed the reported temperature and dewpoint in the "serious icing at glide power" area. WRECKAGE AND IMPACT INFORMATION Examination of wreckage revealed the helicopter impacted in a dry creek bed, adjacent to a road, and came to rest on it's left side, oriented on a magnetic course of 290 degrees. On the other side of the road, and across from the wreckage was a grass area lined with trees. The grass area was irregularly shaped; however, the portion across from the accident site measured about 350 feet by 125 feet, at it's widest point. A 12,000 volt electrical wire system was located approximately 37 feet above the main wreckage. According to the power company, one of the wires had been severed, and at 1938, a phone call was received from a local resident who reported a loss of electrical power. All major components of the helicopter were accounted for at the accident site. The main wreckage consisted of the fuselage, and about two-thirds of the helicopter's tail boom. A 29 inch portion of the tail boom, which included the tail rotor, was found about 66 feet, north-northwest of the main wreckage, and a 26 inch portion of the tail boom was found about 28 feet, west of the main wreckage. Examination of the separated portions of the tail boom revealed that the left side of each portion contained a 15 inch-long diagonally crushed area, which when viewed from left to right, sloped in a downward direction. The tail boom was painted white and blue. Examination of the tail rotor assembly revealed that one blade had separated near it's attach point. The separated portion of the tail rotor blade contained a 3 inch diagonal cut with striations emitting from the cut surface in a fan shaped pattern. Additionally, scratches with dark discoloration consistent with electrical arching was observed on the tail rotor pitch change links, and on the tip of one of the tail rotor blades. Visual inspection of the main rotor blades at the accident site revealed that both main rotor blades were intact and curved downward; however, further examination revealed that the swash plate ear from one of the blades was broken, and the pitch change link was missing. The blade had rotated 180 degrees and when the blade was rotated to its normal position, it was curved upward. Additionally, blue paint transfer was observed on the blade. The swash plate ear and pitch change link of the other blade was not damaged. The helicopter's flight controls were actuated by push/pull or torque tubes. The "mixing area" where the torque tubes were connected and routed to the main rotor system was pushed aft into the firewall. Two of the cyclic control tubes were broken forward of the mixing area. Collective and cyclic control continuity was confirmed from the torque tube breaks in the cockpit area to the pitch change link of one of the main rotor blades, and to the point of the missing pitch change link on the other blade. Tail rotor flight control continuity was confirmed from the cockpit area and the tail rotor, to the point of the tail boom separation. The helicopter's "V-belts" remained in place, and drive train continuity was confirmed to the main rotor system. Tail rotor drive system continuity was established from the tail rotor to the point of the tail boom separation. The helicopter's engine was removed, and rotated via the crankshaft. Thumb compression was confirmed on all cylinders, and valve action was noted on the number one cylinder. All spark plugs were removed. The spark plug electrodes were intact and exhibited a dark, sooty appearance. The left magneto was removed, and produced spark on all towers when rotated. The engine cooling fan was undamaged and no evidence of rotation was observed on the cooling shroud. The engine was retained for further examination. Prior to the Safety Board Investigator's arrival at the accident site, the carburetor was removed and dissembled by FAA personnel. During disassembly, the carburetor's main discharge nozzle was damaged. Fuel was found in the carburetor bowl, and in the fuel strainer. The fuel, which was consistent with automotive gasoline, was absent of contamination. Additionally, the main and tail rotor magnetic chip detectors were removed and found to be absent of debris. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy was performed on the pilot, on June 24, 1999, by the Office of the Chief Medical Examiner, Charleston, West Virginia. The toxicological testing report from the FAA Toxicology Accident Research Laboratory, Oklahoma City, Oklahoma, was negative for drugs and alcohol for the pilot. TESTS AND RESEARCH The engine was test run on August 18, 1999, at Textron Lycoming, Williamsport, Pennsylvania. After the installation of some "slave" parts, which included a carburetor main discharge nozzle, the engine was started. No pre-impact discrepancies were observed which would have precluded normal engine operation. The helicopter's low rotor and low oil pressure annunciator lights were removed and forwarded to the Safety Board's Materials Laboratory for examination. Examination of the filaments from both lamps revealed no evidence of "hot stretching" in the filament from the low rotor rpm lamp; however, the filament from the low oil pressure lamp was distorted and contained some elongation of the filament coil. ADDITIONAL INFORMATION Overhaul Requirements At the time of the accident, the Robinson R-22 Maintenance Manual, Section 3 "Life Limited Components", stated in part: "The complete helicopter airframe, including rotor systems, drive system, control system, and fuselage must be overhauled by Robinson Helicopter Company (RHC), by a RHC authorized overhaul facility, or as authorized by Section 1.004, when any of the following occur: a) When the helicopter has been operated for 2,000 hours since new or since last overhaul." The manufacturer recommended time between overhaul (TBO) for the helicopter's engine was 2,000 hours. Carburetor Precision Airmotive Corporation (PAC) Mandatory Service Bulletin MSA-1, required the replacement of composite floats with metal floats in the Marvel Schebler (MA) line of carburetors. It also stated: "Previous reports from the field indicate that composite floats may be absorbing fluid and sinking....A sinking float may result in disruption of fuel flow to the engine, Precision Airmotive therefore considers the replacement of composite floats with metal floats mandatory..." Additionally, the Service Bulletin stated that carburetors with a "black" Precision Airmotive data plate should already contain a metal float. The carburetor installed on the engine at the time of the accident was an MA-4SPA, serial number 75023906, with a "black" data plate, manufactured by PAC on July 20, 1993. According to PAC, the carburetor was assembled and shipped with a metal float; however, composite floats were found installed in the carburetor when it was disassembled at the accident site. After the engine was overhauled in 1992, the engine was shipped with a MA-4SPA model carburetor, serial number 75013713. Engine maintenance records revealed that on July 8, 1993, a MA-4SPA, serial number 7500220, carburetor was installed on the engine. There were no further maintenance entries regarding the replacement of the carburetor which was installed in July 1993. Automotive Gasoline According to FAA Advisory Circular AC 91-33A, Use Of Alternate Grades Of Aviation Gasoline For 80/87 and Use Of Automotive Gasoline. "...Since 1982, Supplemental Type Certificates (STCs) have been issued for the use of specified automotive gasolines in certain aircraft engines and aircraft and provide an additional source of fuel for several piston engine models that were originally rated for Grade 80 or lower octane aviation gasoline. The STCs were issued after each different airplane and engine combination was evaluated to assure compliance with applicable FARs and that the airplane was safe for continued operation on automotive gasoline. Owners and operators are cautioned that only airplanes that have been modified in accordance with the STC are eligible to be operated on automotive gasoline...." According to Textron Lycoming, "automotive fuels should never be used as a substitute for aviation fuel in aircraft engines." According to a representative of PAC, PAC does not have any written policy regarding the use of automotive gasoline in its carburetors; however, in December of 1999, PAC revised its carburetor warranties to indicate that the use of non-aviation grade fuel voided all warranties. Wreckage Release The helicopter wreckage was released on March 15, 2000, to the pilot's wife.
A loss of engine power for undetermined reasons. Contributing to the accident was the pilot's failure to maintain rotor rpm and the transmission wires.
Source: NTSB Aviation Accident Database
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