New Athens, IL, USA
N9263Y
BELL OH-58C
The helicopter was being used for agricultural spraying of a wheat field. It had just taken off from a support truck for another spraying circuit when the support truck workers heard a noise, looked in the direction of the helicopter, and saw the helicopter spinning without its tail boom attached. The terrain in the area of the accident site consisted of rolling hills. At the top of a hill along the route of flight, several spray nozzles from the helicopter’s spray boom were found on the ground. The main wreckage of the helicopter was located about 250 feet further along the route of flight. The tail rotor and the aft section of the tail boom were found between the spray nozzles and the main wreckage. Examination of the wreckage revealed evidence that the main rotor blade had struck the tail boom severing it from the helicopter. Further examination found no preimpact defects of the helicopter, its engine, control system, or drive system. Data downloaded from an on-board global positioning system (GPS) showed that the helicopter took off from the support truck and headed in a westerly direction and accelerated to about 52 miles per hour. The GPS track passed over the location where the spray nozzles were found. The recorded altitude from the GPS was below the elevation of the surrounding terrain. Therefore, the altitude information from the GPS was not accurate enough to use for flight analysis. Based on the available information, it is likely that the pilot inadvertently flew the helicopter into the rising terrain, which resulted in the main rotor blades flexing downward and severing the tail boom. Once the tail boom was severed, the pilot would not have had any anti-torque control and would not have been able to prevent the helicopter from spinning uncontrollably.
HISTORY OF FLIGHT On May 12, 2011, about 1517 central daylight time, a Bell OH-58C, N9263Y, impacted terrain during an aerial application flight near New Athens, Illinois. The commercial pilot, who was the sole occupant, received fatal injuries. The helicopter sustained substantial damage including separation of the aft tail boom/tail rotor assembly and crushing of the forward fuselage. The helicopter was registered to and operated by Couch Helicopter Service, Inc., Walcott, Arkansas, under the provisions of 14 Code of Federal Regulations Part 137 as an aerial application flight. Visual meteorological conditions prevailed for the flight, which operated without a flight plan. The flight originated from New Athens, Illinois, at an unconfirmed time. The helicopter was being used to spray fungicide on a wheat field. The operator reported that the helicopter pilot would land the helicopter on the platform of a support truck positioned in the farm field. Another employee would then fill the chemical hopper and add fuel as required while the pilot remained in the running helicopter. Once filled, the pilot would then proceed back to the field and continue the spray operation. This process would continue until spraying of the field was complete. According to the operator, the pilot had completed twelve of these cycles and was proceeding back to the field when the accident occurred. Two employees of the operator were present at the support truck when the accident occurred. One of the employees reported that he was standing on the end of the support truck when the helicopter lifted off of the truck platform. He stated that the takeoff appeared normal and the helicopter accelerated and began to climb as it traveled west. The helicopter then went over a rise in the terrain that obstructed the employee’s view. He heard a loud noise which drew his attention back to the helicopter and he saw the tail rotor separated from the main fuselage and the remainder of the helicopter spinning about the axis of the rotor shaft. He stated that the helicopter had pitched up and the top of the main rotor was visible from his position. The helicopter then went behind another rise and he heard the impact with the ground. The other employee stated that he had loaded the helicopter with 100 gallons of chemical for spraying and that no fuel was taken on during this cycle as fuel had been added on the previous cycle. This employee stated that the helicopter took off normally and he also heard a sound that drew his attention back to the helicopter. He stated that when he looked back at the helicopter, the tail boom was gone and the helicopter was spinning. He said that it spun at least 5 times before it went behind a rise in the terrain that obstructed his view. Both witnesses immediately responded to the accident scene where they used a chain to pull the helicopter into an upright position in order to extricate the pilot. The pilot had no vital signs and the witnesses began cardiopulmonary resuscitation until emergency medical services arrived. PERSONNEL INFORMATION The pilot held a commercial pilot certificate with single and multiengine land, helicopter, and instrument ratings. He was issued a second-class airman medical certificate on June 9, 2010, with no restrictions. The pilot’s flight logbook was not recovered during the investigation; however, he reported having 23,000 hours of flight experience on his most recent medical certificate application. AIRCRAFT INFORMATION The helicopter was originally manufactured by Bell Helicopters for the United States military as a OH-58C helicopter, serial number 69-16239. At the time of the accident the helicopter was operating under the provisions of Rotorcraft Development Corporation Type Certificate R00006DE, which allowed operation as a restricted category military surplus helicopter. It was a single main rotor design with an anti-torque tail rotor mounted on an aft boom. The helicopter was powered by a 420 horsepower Rolls-Royce T63-A720 engine, serial number AE-405191. Maintenance records indicated that the helicopter had undergone an annual inspection on June 14, 2010, and subsequently a 100-hour inspection on April 28, 2011. As of the date of the 100-hour inspection, the helicopter accumulated 12,630.3 hours total time in service, at a recording hour meter reading of 9,467.7. The recording hour meter read 9,532.0 at the accident scene. The calculated total time in service at the time of the accident was 12,694.6. The helicopter was equipped with a spray boom system and chemical hopper for agricultural spraying. METEOROLOGICAL INFORMATION The weather observation facility located at the Scott Air Force Base/Mid America Airport, about 13 nautical miles north of the accident site recorded the weather condition at 1455 as: wind from 220 degrees at 10 knots, visibility 10 miles, clear sky condition, temperature 30 degrees Celsius, dew point 15 degrees Celsius, and altimeter 29.85 inches of mercury. WRECKAGE AND IMPACT INFORMATION The helicopter came to rest in a rolling wheat field. Also present in the field was the support truck used during the spray operation. The main wreckage was sitting upright on the back side of a hill as viewed from the location of the support truck. At the top of the hill was a depression in the wheat and located in the depression were several nozzles from the spray boom. The main wreckage was about 250 west of this location. Between the location of these nozzles and the main wreckage was the tail rotor and aft section of the tail boom. The tail rotor blades were intact and the tail rotor shaft rotated freely when the tail rotor driveshaft was turned by hand. The pitch change function also operated freely when actuated by hand. There was a portion of the cover that goes over the tail rotor driveshaft that had an angular impact on the left side that corresponded to main rotor blade contact. A portion of the aluminum tail boom skin that was still attached to the main wreckage also showed evidence of main rotor blade impact. One main rotor blade showed chordwise scuffing and scratching and black paint transfer on its leading edge which was consistent with the black colored tail boom. This blade was fractured and bent over about 3 feet from the mast centerline. The other blade was relatively straight and intact with several spots of buckling on the trailing edge. The tip cover on this blade was found in a “cut” in the ground near the helicopters resting position. The helicopter fuselage was broken almost in two. The break was located in the rear passenger door area of the helicopter. The main rotor gearbox remained attached to the helicopter and was rolled forward on its mounts. The engine drive input to the gearbox was seen to move when the main rotors were turned. The pitch change links from the swashplate to the blades were separated but showed evidence of overload failure. Other linkages from the flight controls to the swashplate showed similar overload failures. The collective control handle was broken at its base bracket, but the collective operated the pushrod in the vertical tunnel when the cockpit control base bracket was actuated. The helicopter had significant crushing of its nose. The fuselage and tail boom aft of the passenger cabin remained intact except for the separated portion of tail boom mentioned earlier. The tail rotor driveshaft was separated except for the first portion aft of the engine. This portion rotated freely by hand. The chemical pod was separated and located about 75 feet from the main wreckage. There was an unknown quantity of fuel still remaining in the fuel tank. The helicopter had an Ag-Nav GPS navigation system used for spray operation. The unit was downloaded in the field with the assistance of the helicopter operator. The helicopter was removed from the accident scene and transported to a facility where further examination could be performed. On May 19, 2011, a second examination of the helicopter was conducted. The engine was intact and exhibited no external evidence of operational failure, fire or malfunction. The aircraft engine was removed from the airframe and non-engine related components removed. The engine compressor and power turbine rotors could not be rotated by hand. During removal from the airframe, evidence of rotation of the engine output shaft (witness marks) were observed on the bottom side of the main rotor gearbox, and on a pad mounted to the airframe that was located below the drive coupling. No disassembly of the main engine was performed during this examination except for removal of non-essential components for shipping. The engine was then inserted into a shipping container supplied by Rolls Royce for shipment to the Rolls Royce facility for an examination of the engine. The helicopter spray boom assembly was laid out on the floor with the individual pieces placed in their respective locations. The center boom between the skids, and the outboard booms had been cut using an abrasive saw to facilitate transport from the accident site. Other than these cuts, the booms were continuous with bending due to impact. The “brace bars” that attached to the boom and airframe to prevent the folding outboard booms from rotating rearward were continuous. The boom end mounts for these bars were present on each bar but no means of attachment to the actual boom was found. There was no evidence noted that was consistent with the booms having impacted the main rotor system of the helicopter. The tail rotor driveshaft pieces were gathered and laid out in their respective locations. It was determined that all components of the driveshaft were present and accounted for. All breaks in the driveshaft system were consistent with damage due to an impact from the main rotor blade system. The tail boom was laid out and components of the tail rotor driveshaft cover were placed in their respective positions on the tail boom. A piece of the cover had a diagonal impact mark consistent with main rotor blade impact. The diagonal mark was on the left side of the cover and the diagonal line was at an angle that would continue forward to the top of the rotor mast. The location of this mark was consistent with the tail rotor driveshaft damage mentioned earlier. Control continuity was checked. The collective control handle was broken off at its base but movement of the pushrod for the collective control was noted in the “broom closet” when a tool inserted into the socket was used to manipulate the collective control. The cyclic control, when moved fore and aft, would move a pushrod in the “broom closet” when moved by hand. Movement side to side of the cyclic control yielded no movement of the pushrods in the broom closet; however, there was extensive damage to the fuselage in the cockpit area. The tail rotor pedals were crushed rearward and no determination of continuity within the cockpit was established for the tail rotor controls. The tail rotor pushrod at the separated portion of the tail boom would actuate the tail rotor blades when moved by hand. All of the damage to the airframe, and spray boom assembly was consistent with impact damage. No evidence of a preimpact deficiency with regard to the airframe or control system was noted. The separation of the tail boom and associated damage was consistent with main rotor blade impact. On August 9, 2011, the helicopter engine was disassembled and examined at the Rolls Royce facility near Indianapolis, Indiana, under the supervision of a Federal Aviation Administration (FAA) Inspector. Disassembly revealed a substantial amount of carbon had dislodged, consistent with impact, and had become wedged in various labyrinth air seals on both turbine modules, causing the engine compressor and power turbine rotors to lock. Rotational scoring was evident in the compressor section of the engine. Bright silver metal splatter was found within the combustion section of the engine which was consistent with engine operation at the time of impact. The engine examination revealed no preimpact defects. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy of the pilot was performed on behalf of the St. Clair County Coroner's Office, Belleville, Illinois, on May 13, 2011. The pilot's death was attributed to blunt trauma to the chest which was received in the accident. Toxicology testing was performed by the FAA Civil Aerospace Medical Institute. Testing results listed the following findings: 217.6 (ug/ml, ug/g) Acetaminophen detected in Urine TESTS AND RESEARCH The data downloaded from the Ag-Nav GPS receiver showed that on the last flight segment, the helicopter took off from the support truck and travelled in a westbound direction and accelerated to about 52 miles per hour. The last flight segment was approximately 22.6 seconds in duration and the flight track passed over the location where the spray nozzles were found. Using the GPS altitude data from the beginning of the last flight segment, when the helicopter would have been on the support truck, the helicopter remained at approximately the same altitude during the entire 22.6 seconds of the data with the altitude only varying by 6 feet. The GPS altitude when the helicopter left the support truck was recorded as 331 feet and the lowest recorded altitude was 325 feet. Topographic data of the area indicated that the ground elevation was between 410 and 420 feet.
The pilot’s failure to attain sufficient altitude to clear terrain while maneuvering.
Source: NTSB Aviation Accident Database
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