BORGER, TX, USA
N111JA
BELL 206-L3
ACCORDING TO THE PILOT, HE NOTICED THUNDERSTORMS 'DEVELOPING RAPIDLY' TO THE LEFT OF HIS FLIGHT PATH; HOWEVER, 'THEY APPEARED TO BE AT A SAFE DISTANCE.' HE FURTHER REPORTED THAT, HE NOTICED DUST PICKING UP ON THE GROUND, ALONG WITH SOME DEBRIS, ABOUT 1/2 MILE AHEAD, AND TO THE LEFT OF HIS FLIGHT PATH. AFTER INITIATING A TURN TO THE RIGHT, AWAY FROM THE STORM AREA, HE 'COULD NOT CONTROL THE HELICOPTER', AND DOES NOT RECALL THE ENSUING GROUND IMPACT. DOPPLER RADAR IMAGES, FOR THE TIME AND AREA OF THE ACCIDENT, SHOW RAPIDLY DEVELOPING WEATHER ECHOES IN THE VICINITY OF THE ACCIDENT SITE. ALSO, BASE VELOCITY DATA, AT THE APPROXIMATE TIME OF THE ACCIDENT, SHOW A SIGNIFICANT THUNDERSTORM OUTFLOW BOUNDARY LOCATED JUST NORTHWEST OF THE ACCIDENT SITE. SEVERAL WITNESSES, IN THE VICINITY OF THE ACCIDENT SITE, REPORTED HIGH WINDS AND TURBULENT CONDITIONS. ALL STRUCTURAL COMPONENTS, TAIL AND MAIN ROTOR DRIVE SYSTEMS, ENGINE COMPONENTS, AND FLIGHT CONTROLS, THAT WERE NOT DESTROYED BY IMPACT FORCES AND POSTIMPACT FIRE, DID NOT REVEAL EVIDENCE OF FAILURE PRIOR TO IMPACT.
HISTORY OF FLIGHT On July 22, 1995, approximately 1837 central daylight time, a Bell 206-L3 helicopter, N111JA, was destroyed upon impacting terrain near Borger, Texas. The private pilot sustained serious injuries and one passenger was fatally injured. The helicopter, owned by the pilot's company, was being operated under Title 14 CFR Part 91 when the accident occurred. The personal flight originated at Amarillo Tradewind Airport, Amarillo, Texas, at 1821, and was en route to a private ranch home approximately 60 miles northeast of the airport. No flight plan was filed and visual meteorological conditions prevailed during the flight. According to Amarillo Approach Control, the pilot requested visual flight rules (VFR) radar service after departing the airport. Radar contact was established at 1822, and the helicopter proceeded on a 025 degree bearing toward it's destination at an altitude of approximately 4,100 feet mean sea level (MSL). At 1825, the pilot requested information from Approach regarding the movement of convective "cells" located to the north and west of the helicopter's course. Approach then informed the pilot that, a developing area of thunderstorms was moving from two eight zero degrees at twenty five knots. The pilot acknowledged the information and radar service was terminated at 1826. Subsequently, the pilot switched the transponder to VFR code 1200. No further voice communications from helicopter were reported. In a written statement (the pilot's best memory at the time of this report), the pilot stated that, he departed the airport heading about 025 degrees en route to the Turkey Track Ranch to spend the weekend with family. During the flight, he noticed dust "picking up" on the ground, along with some debris, approximately 1/2 mile ahead and to the left of his flight path. He further stated that, some thunderstorms appeared to be "developing rapidly" to the left (northwest) of his flight path; however, they "appeared to be at a safe distance" and didn't "unduly concern" him. He remembers starting a turn to the right (southeast), away from the storm area. At this point, the pilot's memory is "hazy", but he remembers his passenger asking, "what's happening? What are we doing?" He recalls that he said something to the effect that, "I was just trying to keep the ship level." The next thing that the pilot recalls was that, he was "sitting on the ground, with no helicopter around" him. Subsequently, an oil field worker, who had observed the smoke from a distance, found the pilot and coordinated emergency assistance. In an interview, the oil field worker stated that, the pilot "looked like he was in shock and was badly burned." PERSONNEL INFORMATION According to several close associates, the pilot had flown the route between Amarillo and the ranch home many times in the past, and was familiar with the weather tendencies during the summer months. According to Federal Aviation Administration (FAA) records, the pilot had approximately 3,300 hours in rotary wing aircraft, and more than 1,400 hours of flight time in the Bell 206. Additionally, the pilot completed Bell 206 training from the manufacturer. AIRCRAFT INFORMATION Examination of the engine and airframe maintenance records did not reveal any evidence of anomalies or uncorrected defects. METEOROLOGICAL INFORMATION Convective SIGMET 86C, issued at 1755 was in effect at the time of the accident. The accident site was about 28 nautical miles southeast of the southeastern extent of this Convective SIGMET when it was first issued (see attachment 19 in the Meteorological Factual Report). The movement of the developing area of thunderstorms was 280 degrees at 25 knots. Therefore, at about 1835, the area of thunderstorms noted in the SIGMET moved to near the accident site (see attachment 20 in the Meteorological Factual Report). The information contained in this SIGMET was provided to the pilot at about 1826, by the controller working the Amarillo West Radar Position. Convective SIGMET 86C issued July 22 at 1755 and valid until July 23 at 1955: Developing area of thunderstorms moving from 280 degrees at 25 knots. Tops to 42,000 feet. Hail to 1 inch...Wind gusts to 50 knots possible. Additionally, the following Center Weather Advisory (CWA) was in effect (the accident site was located on the southeastern edge of this CWA): Area of severe thunderstorms developing with tops to Flight Level 50,000 feet. Thunderstorms moving from 290 degrees at 20 knots with large hail and high winds possible. Geostationary Operational Environmental Satellite (GEOS) 8 data were reviewed on the Safety Board's McIDAS Workstation. The visible image for 1832 showed that the approximate location of the accident was on the edge of a convective cloud mass. The 1745 visible image showed the accident location in an area of convection. Sequential looping of the images (see attachments 12-14 in the Meteorological Factual Report), for 1802, 1815, 1832, and 1845 showed an increase in convective activity in the area of the accident. Significant and rapidly developing weather echoes (doppler weather radar, NEXRAD/WSR-88D, images 1833 and 1838), are seen about 8 nautical miles west of the accident site. The 1833 image showed an area of vertical axis horizontal rotation about 1 1/2 miles northeast of the accident site. Although the initial doppler radar signatures of this phenomena were inconclusive, a doppler radar specialist (statement is attached to this report), reported that, it would be unlikely that a "dust devil" could be detected by the radar unless "it was a very large dust devil with many reflectors and shears." Additionally, enhanced spectrum width image data, at 1833, for accident area, showed shears consistent with an area of rotation. These data are consistent with the pilot's observation of "dust and debris" picking up to the left of his flight path, in addition to, "dust devils" that were observed by several weather condition witnesses in the vicinity of the accident site. Additionally, the 1833 doppler radar data show evidence of weak divergent winds in the vicinity of the accident site, indicating a down flow of air spreading out as it approached the ground. Base Velocity data show a significant outflow boundary located about 10 nautical miles northwest of the accident site at 1833, and about 7 nautical miles northwest of the site at 1838 (translation speed = about 36 knots). Additionally, at 1900, microbursts were observed by the Amarillo Tower, approximately 24 nautical miles southeast of the accident site. This information is consistent with the movement and boundary of the storm system in the vicinity of the accident site. In addition to weather radar data, several witnesses who observed the local weather before, during, and after the accident, reported that the storm system moved "rapidly" and had "high winds" associated with it. An individual, located about 2 miles west of the accident site, reported that, at about 1830, he observed what looked like "a wall of water coming toward him. He further reported that, at 1855 it started to rain. He noted that, the storm was an "unusually narrow wall of heavy rain accompanied by high winds", and it seemed "to appear out of nowhere." Another eyewitness, located near the accident site, noted the thunderstorm buildup, with very remarkable lightning activity. He noted a "very heavy wind out of the northwest." A detailed Meteorological Factual Report is attached to this document. COMMUNICATIONS/ATC Although there were no reported sightings of the helicopter en route, or it's impact with terrain, detailed radar track data provided by the National Track Analysis Center (NTAP), show the aircraft's flight path and altitude from 1822 to 1833. These radar data show the helicopter heading approximately 025 degrees, at an altitude of approximately 4,200 feet MSL. According to the radar data, the helicopter travelled approximately 25 nautical miles from the departure airport, to a point approximately 2 1/2 miles northwest of the accident site. This information is consistent with the pilot's report of initiating a right turn to the southeast, away from the storm area. According to ATC records, the pilot did not make any distress calls prior to the accident and all previous communications were normal. An official transcript between the pilot and Amarillo Approach Control is attached to this report. WRECKAGE AND IMPACT INFORMATION Wreckage distribution was plotted utilizing straight line distances radiating outward on magnetic bearings from the main wreckage center point. The center of the main wreckage was located approximately, latitude 35 degrees 30 minutes 28 seconds north and longitude 101 degrees 31 minutes 52 seconds west, at an elevation of approximately 3,400 MSL. Total wreckage distribution, including ground scars, encompassed a circular area around the main wreckage center point, radiating outward to a maximum radial distance of 480 feet. Wreckage debris of the cabin structure and skid assembly were found resting adjacent to the initial ground scars, on a measured heading of 020 degrees magnetic. The helicopter was destroyed by impact forces and consumed by a postcrash fire. Two initial ground scars, correlating to the skid assembly, and impact damage to the landing gear skid assembly, indicate that the helicopter initially impacted the ground vertically, heading approximately 220 degrees. The forward cross tube of the skid assembly was found fractured due to overload. Additionally, the aft cross tube exhibited upward bending (approximately 12 inches of skid spread) outside of the attaching points, and the left rear cross tube mount was found fractured (see skid damage sketch attached to this report). The widespread radial distribution of helicopter's dynamic components outward from the main wreckage area is documented in the wreckage diagram attached to this report. The tailboom, was severed approximately 8 inches forward of the synchronized elevators. The 90 degree gear box, still attached to the tail rotor hub and blade assembly, was found 296 feet northeast of the main wreckage. The bottom of the 90 degree gear box case was found fractured, exposing the internal ring gear which displayed impact damage. The #1 shaft exhibited bending and was fractured in overload. The #2 hanger bearing exhibited rotational scars adjacent to the corresponding drive shaft coupling, and indicated shaft bending of approximately 50 degrees up. Additionally, the top 2 feet of the elevator winglets and the vertical fin exhibited multiple cuts corresponding to main rotor blade strikes. The main transmission, still attached to the roof pylon main beam, along with the main rotor hub assembly, and rotating mast, were found torn from the airframe. The mast exhibited bending near the yoke, and the rotating swashplate was fractured. The static stops on the main rotor hub assembly exhibited rotational gouges corresponding to the yoke and the rotating mast. The following main rotor blade damage was documented: One blade (#1) was sharply bent upward approximately 15 degrees, 3 feet from the root. This blade displayed several episodes of paint transfers corresponding to main cabin structure and tail fin areas. The other blade (#2), exhibited two leading edge spar fractures correlating to separations at 6 feet and 12 feet outward from the root. Approximately 48 inches of the #2 blade's fractured spar was found 300 feet west of the main wreckage. Another 57 inches of the #2 blade's spar was found 480 feet northwest of the main wreckage, with gear teeth impressions in the leading edge, adjacent to the spar's fracture point. These gear teeth impressions correspond to the ring gear in the 90 degree gear box. The engine was damaged by the postcrash fire; however, a detailed examination of the engine was accomplished on August 2-3, 1995. The following observations were made during the engine examination: Both N1 and N2 curvic couplings were intact, and both N1 and N2 rotors rotated freely. Continuity was established throughout the gas producer and power turbine sections. The compressor shroud housing exhibited rubbing from the impeller. Ash and soot deposits were observed to be centrifuged outward against the blade shrouds of the third and fourth stage power turbine wheels. Additionally, both third and fourth stage power turbine wheels exhibited rub scars corresponding to the fourth stage nozzle. A detailed engine examination report from the manufacturer is attached to this document. In summary, all structural components, tail and main rotor drive systems, engine components, and flight control components that were not destroyed by impact forces and postcrash fire, did not reveal evidence of failure prior to impact. MEDICAL AND PATHOLOGICAL INFORMATION The passenger received fatal injuries. The pilot sustained serious traumatic injuries in addition to 2nd and 3rd degree burns. Toxicology tests on the pilot were not requested. FIRE Fire patterns within and adjacent to the wreckage area were postimpact. Examination of the wreckage did not reveal any evidence of an in-flight fire. Although the postimpact fire was intense, and the grassy terrain dry at the time of the accident, the fire did not spread far. It was extinguished almost immediately after the impact, from the onset of heavy rain. The fire pattern indicated a strong wind from approximately 340 degrees. This is consistent with the "rapidly moving" storm system through the accident area. TESTS AND RESEARCH Analysis of material deposits found in the first stage turbine wheel blades, the first stage nozzle, and the nozzle shield was found to have similar properties as the material of the compressor shroud housing coating. As stated earlier in this report, there were signatures of impeller rub against the compressor shroud housing. The material deposit composition, as well as the physical evidence of rubbing, is consistent with engine rotation at the time of impact. A full material analysis report is attached to this document. ADDITIONAL DATA The wreckage was released to the owner's representative on November 27, 1995.
THE PILOT'S LOSS OF CONTROL DUE TO AN ENCOUNTER WITH A DUST DEVIL/WHIRLWIND AND THE TURBULENCE AND HIGH WIND ASSOCIATED WITH THUNDERSTORM OUTFLOW.
Source: NTSB Aviation Accident Database
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