Meeker, CO, USA
N131AL
HUGHES 369D
While conducting deer capture operations,the crew felt a shudder or jolt through the helicopter and collective. The first jolt was immediately followed by a bang, at which time the helicopter started to rotate to the right. The helicopter pitched nose down with forward movement as it rotated to the right, impacting the ground. The pilot estimated that he was 40 feet above the trees and that the airspeed was between 25 and 30 knots when the shudder or jolt occurred. The empennage was located 70 feet to the east of where the helicopter came to rest. Examination of the helicopter, engine, and related systems revealed no mechanical anomalies. Metallurgical examination revealed features consistent with overstress separations on all fractures in the tail boom and the driveshaft. The damage and mode of separation of the empennage was consistent with an impact from a main rotor blade. The manufacturer noted that main rotor contact with the fuselage is only possible with a low rotor rpm state or with flight outside of the approved operational envelope. However, the pilot indicated that there were no bells, horns, or warnings prior to the bang and that he did not receive a low rotor warning or a chip light; the investigation was unable to conclude that low rotor rpm or flight outside of the approved operational envelope led to the separation of the tail boom.
HISTORY OF FLIGHT On March 8, 2011, at 1305 mountain standard time, a Hughes 369D, N131AL, was substantially damaged when it impacted terrain near Meeker, Colorado. The commercial pilot was not injured and the passenger sustained minor injuries. The helicopter was registered to and operated by Quicksilver Air, Inc. The deer netting flight was being conducted as a public use flight for the Colorado Division of Wildlife. Marginal visual meteorological conditions prevailed at the time of the accident which operated without a flight plan. The local flight departed approximately 1200, from Meeker, Colorado (KEEO). The pilot reported that they were conducting their seventh deer capture of the day. He stated that they were herding a dear towards the road to aid in a clear capture area. The pilot reported that they were 40 feet above the trees and he utilized forward cyclic, while lowering the collective, to descend towards the deer for the capture. He estimated his airspeed was between 25 and 30 knots. At this time, a shudder or jolt was felt through the helicopter and collective. The first jolt was immediately followed by a "bang" at which time the helicopter started to rotate to the right and the nose pitched down. The passenger reported that the helicopter leveled just prior to impact, then bounced as it hit the ground. He stated that he did not recall any violent maneuvers prior to the loud bang and that they were "fairly slow and controlled" while preparing to capture the deer. PERSONNEL INFORMATION The pilot, age 31, held a commercial pilot certificate with an airplane single engine land, and helicopter ratings. He was issued a second class airman medical certificate without limitations on June 24, 2010. The pilot reported that he had logged 7,600 hours total time; 2,420 hours were logged in the make and model of the accident helicopter. The pilot had successfully completed the requirements of a flight review on November 29, 2010. AIRCRAFT INFORMATION The accident helicopter, a Hughes 369D (serial number 1107230D), was manufactured in 1977. It was registered with the Federal Aviation Administration (FAA) on a standard airworthiness certificate for normal operations. A Rolls-Royce 250-C20B turbo-shaft engine rated at 375 horsepower powered the helicopter. The engine powered five main rotor blades and the tail rotor through a main gearbox. The helicopter was registered to and operated by Quicksilver Air, Inc., and was maintained under a continuous airworthiness inspection program. A review of the maintenance records indicated that a 100-hour inspection had been completed on February 24, 2011, at an airframe total time of 16,414.7 hours, by Flight Ready Aviation, LLC. The helicopter had flown approximately 26.2 hours between the last inspection and the accident and had a total airframe time of 16,440.9 hours. METEOROLOGICAL INFORMATION The closest official weather observation station was Meeker Airport (KEEO), Meeker, Colorado, located 25 nautical miles (nm) east of the accident site. The elevation of the weather observation station was 6,426 feet mean sea level (msl). The routine aviation weather report (METAR) for KEEO, issued at 1306, reported wind 230 degrees at 3 knots, visibility 2 miles in light snow, sky condition broken at 1,400 feet, temperature minus 1 degree Celsius (C), dew point minus 4 degrees C, altimeter 30.00 inches. WRECKAGE AND IMPACT INFORMATION The accident site was located in terrain vegetated with Juniper trees, just off of a dirt road. The accident site was at an elevation of 6,785 feet msl . The Rio Blanco County Sheriff's Department stated that the helicopter came to rest on the west side of the dirt road and the tail boom came to rest 70 feet from the helicopter, on the east side of the dirt road. TESTS AND RESEARCH Wreckage Examination The helicopter was recovered by the Rio Blanco County Sheriff's Department and relocated to their impound lot in Meeker, Colorado. Investigators from the National Transportation Safety Board (NTSB), The Boeing Company, and MD Helicopters, Inc. (MDHI), an FAA inspector, and a representative from Quicksilver Air, Inc., examined the wreckage. The main wreckage consisted of the fuselage, cabin, main rotor, engine, transmission, instrument panel, and the forward and aft bench seats. The right side landing skid separated from the airframe. The left side landing skid was bowed out and partially separated at the front skid leg. Battery power was applied to the instrument panel to verify correct light sequence. A press to test, functional check of the trim actuators, and functional check of the power governor "beep" switch revealed no anomalies. Cyclic and collective continuity were confirmed from the control stick through to the main rotor hub. Both chip detectors on the engine were free from contaminants. All five main rotor blades were removed for inspection purposes. The yellow blade exhibited a 4.5 inch tear on the trailing edge of the blade, 18 inches inboard from the blade tip. The tear originated from the bottom of the blade and the metal in the area of the tear was bent up. The blade was bowed down and wrinkled. A second partial tear was observed 5.5 inches inboard from the blade tip. A scratch, 2.5 inches in length, was observed 15 inches inboard from the blade hub, on the bottom of the blade. The scratch penetrated through to the blade metal and contained white paint transfer on the outer edges of the scratch. Blue paint transfer was noted on the outboard leading edge of the blade. In addition several dents, consistent in size and shape with rivets, were noted adjacent the blue paint transfer. The blue blade exhibited wrinkling along the entire trailing edge span of the blade. The blade was bowed up slightly approximately 3 feet inboard from the blade tip. The white blade was bowed up and wrinkled along the entire span of the blade. A white paint transfer/scratch was observed 15 inches outboard from the blade hub on the bottom of the blade. The red blade was wrinkled slightly along the trailing edge of the blade. White paint transfer 3 inches long in the center of the blade was documented 37 inches outboard from the blade hub. The blade was otherwise unremarkable. The green blade was wrinkled along the entire span of the trailing edge of the blade. Three areas of white paint transfer were documented 37 inches outboard from the blade hub. The portion of the tail boom which remained attached to the fuselage exhibited torn, bent, and crushed metal. The upper portion of the separation point, along the rivet line, exhibited a large scratch mark and the paint was missing. The upper portion was crushed down slightly. The tail rotor drive shaft and the inner portion of the skin at that point exhibited rotational scoring around the circumference of both the tail rotor drive shaft and the inner portion of the tail boom skin. The separated portion of the tail boom consisted of the aft portion of the tail rotor driveshaft, the tail rotor, horizontal, and vertical stabilizer, and the tail rotor gearbox. The vertical stabilizer was unremarkable. The right side of the horizontal stabilizer was bent down 20 inches inboard of the outboard edge of the surface. The tail rotor was rotated by hand. The driveshaft rotated without hesitation or binding. The leading outboard edge of both blades had dirt streaks, but was otherwise unremarkable. The inboard edge of the tail boom, at the separation point was jagged and torn. The driveshaft stuck out 2.5 to 8 inches from the outer structure of the tail boom. The driveshaft illustrated rotational scoring/scratching along the circumference of the shaft. The skin on the tail boom, at the separation point was rolled in and exhibited scratching similar to that observed on the portion connected to the fuselage. Tail rotor continuity was confirmed aside from the point of separation at the tail boom. Laboratory Examination Several pieces of the tail boom, the tail rotor driveshaft, and the outboard portion of the yellow main rotor blade were shipped to the NTSB Materials Laboratory in Washington, DC, for further examination. The materials laboratory factual report is available with the docket for this accident report. Microscopic examinations of the tail boom and tail rotor driveshaft found features consistent with overstress separations on all fractures in the tail boom and the driveshaft. The tail boom was significantly deformed in the area of the top lap joint with a sharp demarcation at the aft end of the deformation area. Further, the top blue paint and much of the underlying primer paint were missing from the upper left quadrant of the boom in the deformation area. Circumferential smears of blue paint were noted on the exterior surfaces adjacent to the top lap joint. Additionally blue paint was smeared onto the interior surface of the mid-sized pieces of sheet metal. The upper surface of the yellow blade's leading edge abrasion strip had blue paint smeared onto its outer 6 inches. The blue paint visually mated in color to that seen in the smeared areas of the tail boom. Additionally, the leading edge abrasion strip displayed a line of 6 indentations. The rounded dents approximated the spacing and configuration of the rivets in the top lap joint of the tail boom. The damage and deformation patterns visible on the tail boom and rotor blade along with the paint smearing were consistent with the end of the yellow main rotor blade impacting the tail boom just to the left of the top lap joint rivet line. Further, the sharp demarcation in deformation, at the aft end of the separation area, in addition to paint transfer and paint smearing found on the inside of the mid-sized piece of sheet metal, indicated that the tip of the rotor passed under the top rivet line while further aft the indentations on the blade indicated that the blade passed directly through the rivet line. ADDITIONAL INFORMATION According to MDHI/Boeing, flight tests on all airframes and main rotor configurations have indicated that low rpm is required to allow blade flexing low enough to contact the tail boom during normal flight operations. MDHI/Boeing stated further that historically, main rotor blade contact with the fuselage and tail boom has been achieved only with main rotor rpm in a low rotor state below normal operating range or in flight outside of the approved operational envelope of the helicopter.
Main rotor contact with the tail boom resulting in tail boom separation.
Source: NTSB Aviation Accident Database
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