Vinson, OK, USA
N9008H
Brantly Helicopter B-2B
After the helicopter leveled off at 2,500 feet, scattered clouds began moving in. The pilot climbed to 4,500 feet where clouds were now above and below him, preventing the pilot from locating his next checkpoint until there were breaks in the clouds. Approximately 56 miles into the flight and with the clouds thinning, the helicopter broke into a right turn. After turning back on course the helicopter began gaining altitude, then nosed over quickly, dropping approximately 1,000 feet. After leveling off back on course, the helicopter began gaining altitude again to 5,000 feet and began a smooth left-hand descending turn into a canyon. All attempted control inputs by the pilot were unresponsive. The helicopter was now traveling at a high rate of speed through the canyon, eventually coming to a quick stop to the right on a hill at the end of the canyon. As rotor rpm bled off the pilot attempted another control input by applying aft cyclic and left rudder pedal; however, the helicopter would not respond. The helicopter impacted terrain in a rapid spin to the left, coming to rest on its left side. Post-accident examination of the helicopter's flight controls revealed no anomalies which would have prevented normal operations. Approximately two hours prior to departure, a warm front was moving into the area of intended flight. At the time of the accident, weather observation facilities in the region reported winds gusting up to 31 knots with multilayered clouds.
On October 12, 2002, approximately 0945 central daylight time, a Brantly B-2B single-engine helicopter, N9008H, was substantially damaged after impacting terrain following a loss of control near Vinson, Oklahoma. The non-instrument rated private pilot and his passenger were not injured. The aircraft was registered to and operated by Brantly International Inc., of Vernon, Texas. Visual meteorological conditions prevailed, and a flight plan was not filed for the 14 CFR Part 91 personal flight. The cross-country flight originated from the Wilbarger County Airport, Vernon, Texas at 0850, destined for the Hemphill County Airport, Canadian, Texas. In a written statement provided to the NTSB investigator-in-charge (IIC), the pilot reported that after departing on the cross-country flight and leveling off at 2,500 feet mean sea level (MSL) at 90 miles per hour (MPH), "scattered clouds began moving in." The pilot stated that he climbed to 4,500 feet MSL and "there were clouds above and below and a tailwind. We were flying on course and could not get a visual on our next checkpoint until we found a break in the clouds." The pilot reported that he eventually got a visual of a river and main highway that was on his map. The pilot further stated that approximately 56 miles into his flight "the clouds were thinning and we broke into a right turn heading southwest into the sun." The pilot reported there was a sudden change in the temperature from cool to very warm, then back to cool again, at which time he turned back on course. The pilot stated that the helicopter began gaining altitude and "it took a nose over quickly, dropping approximately 1,000 feet at a speed of 145 MPH, exceeding the helicopter's rotor engine limitations." The pilot reported that after he leveled off and was back on course, the helicopter began gaining altitude again to 5,000 feet MSL, then began a smooth left-hand descending turn heading into a canyon. The pilot stated "I had the controls in my hand and watching gauges, and no corrections I tried to make would respond." The pilot reported that they were going very fast through the canyon, just above the tree tops, and came to a quick stop to the right on a hill at the end of the canyon. The pilot reported "the RPM bled off -- I attempted to correct by applying aft cyclic and left rudder pedal, but the helicopter would not respond. Then we went into a rapid spin to the left and crashed on our left side, heading northeast." The pilot secured the engine and egressed the helicopter with his passenger, both of whom were not injured. There was no post-crash fire. In a written statement provided to the NTSB IIC, the passenger reported that as they passed through the clouds they looked for checkpoints and made a right turn facing the sun. The passenger stated ".....very warm air came into the cabin. We both noticed it and then it was replaced with cooler air. We were heading back in the direction of our flight plan and started climbing. I could see the ground all around me, was watching the gauges, and it was getting cooler." The passenger further reported ".....suddenly we did a nose over, and then right back as suddenly. There were no vibrations, no strange noises, and no problems with the gauges. He [the pilot] was making moves to correct with no response, then we began to gain altitude and then made a left descending turn heading straight for a canyon very fast." She reported the helicopter made a quick stop to the right, hovered, and then started spinning to the left before it impacted the terrain. A Federal Aviation Administration (FAA) inspector, who traveled to the accident site, reported that the tail section had been severed, the canopy was destroyed, and the outer blades had separated. The helicopter came to rest on its left side with the rotor head touching the ground. A subsequent inspection by a member of the FAA's Rotorcraft Directorate Southwest Regional office, Fort Worth, Texas, reported finding no anomalies with the helicopter which would have prevented normal operations. The 0700 surface analysis chart depicted a warm front extending from Amarillo, Texas, to the northeast through western Oklahoma moving easterly approaching the intended route of the flight. At the time of the accident weather reporting facilities in close proximity to the accident site reported winds gusting up to 31 knots, with cloud ceilings from 1,200 feet to 2,400 feet. At 0953, the weather observation facility at the Hobart Municipal Airport (HBR), Hobart, Texas, (located 44 nautical miles east-northeast of the accident site) reported wind 360 degrees at 17 knots, visibility 10 statute miles, scattered clouds at 1,900 feet, temperature 20 degrees C, dew point 17 degrees C, and an altimeter setting of 30.07 inches of Mercury. At 0953, the weather observation facility at the Clinton-Sherman Airport (CSM), Clinton, Oklahoma, (located 65 nautical miles northeast of the accident site) reported wind 010 degrees at 26 knots, gust 31 knots, visibility 10 statute miles, overcast clouds at 1,200 feet, temperature 18 degrees C, dew point 16 degrees C, and an altimeter setting of 30.09 inches of Mercury. At 0953, the weather observation facility at the Frederick Municipal Airport, Frederick, Oklahoma, (located 59 nautical miles southeast of the accident site) reported wind 350 degrees at 9 knots, visibility 6 statute miles, mist, overcast clouds at 600 feet, temperature 18 degrees C, dew point 17 degrees C, and an altimeter setting of 30.01 inches of Mercury. At 0953, the weather observation facility at the Childress Municipal Airport, Childress, Texas, (located 38 nautical miles southwest of the accident site) reported wind 350 degrees at 17 knots, gust to 25 knots, visibility 10 statute miles, overcast clouds at 2,400 feet, temperature 19 degrees C, dew point 16 degrees C, and an altimeter setting of 30.12 inches of Mercury. Peak wind reported of 340 degrees at 26 knots.
The pilot's inadvertent flight into adverse weather conditions during cruise resulting in his failure to maintain control of the helicopter, and his failure to maintain rotor rpm. Contributing factors relating to the accident included the frontal activity associated with the adverse weather condition and the variable wind.
Source: NTSB Aviation Accident Database
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