DEN03FA099

Fatigue of the tail rotor trunnion resulting in complete trunnion failure and subsequent tail rotor separation from the helicopter. Factors contributing to the accident were the low altitude, low airspeed, excessive tail rotor loading, and the worn tail-rotor blade grip bushings.

The helicopter flight crew had just finished rescuing a lost hiker and was preparing to return to their home base. The pilot informed the flight nurse that dispatch wanted them to proceed home because the helicopter was due its 25-hour inspection. The pilot mentioned that he first needed to return to the location where they picked up the hiker so he could get an altitude reading. Before taking off, search and rescue personnel warned the pilot of paragliders in the area. The flight nurse said the pilot acknowledged them, and then took off and proceeded southbound. The flight nurse said they were climbing out when she heard a loud noise. She said it seemed to come from beneath the helicopter. She said she heard the pilot say, "Oh no" and then the helicopter began spinning clockwise out of control. The flight nurse said she was being tossed around, but was trying to get into a position for the crash. Then the helicopter impacted the ground. The flight nurse said she got out through the front of the helicopter. She said she checked the paramedic and the pilot, and then went for the radio to call for help. She said that the engines were still running and she smelled fuel. At that point she noticed the tail rotor was missing. Several witnesses on the ground heard and saw the helicopter. The witnesses recalled the helicopter took off and made a right turn to proceed south. Some of the witnesses said they heard a loud bang. Most of the witnesses described the helicopter as doing a 360-degree counter clockwise turn, then the nose of the helicopter pitched up, the tail rotor came off, and the helicopter continued to spin and descend until it impacted the hillside. An examination of the helicopter's broken tail rotor trunnion showed four separate fatigue areas originating from the inner splines. The exam also showed that the fatigue occurred due to stresses that exceeded the design spectrum. Excessive heating was noted due to friction between the trunnion and blade grip bushings. The tail rotor trunnion had a published service life of 2,700 hours. At the accident, the trunnion had 698.0 total hours.

HISTORY OF FLIGHT On June 7, 2003, at 2012 mountain daylight time, an Agusta A109K2 helicopter, N123RX, owned by IHC Hospitals, Incorporated, and operated as IHC Life Flight was destroyed when it impacted a hillside 13.7 miles southeast of the Salt Lake International Airport (SLC), Salt Lake City, Utah. Visual meteorological conditions prevailed at the time of the accident. The positioning flight was being conducted under the provisions of Title 14 CFR Part 91. A company visual flight rules flight plan was on file. The airline transport pilot piloting the helicopter was fatally injured. A paramedic on board sustained minor injuries. A flight nurse on board reported no injuries. The local flight originated from a southeast Salt Lake City residential area at 2011, and was en route to SLC. The flight nurse reported they had just finished rescuing a lost hiker and were preparing to return to their home base. The pilot informed her that dispatch wanted them to proceed home because the helicopter was due for a 25-hour inspection. The pilot told the flight nurse that he would drop her off at the hospital where she was picked up earlier, on his way back to SLC. The pilot mentioned that he needed to return to the location where they picked up the hiker so he could get an altitude reading. Before taking off, search and rescue personnel warned the pilot of paragliders in the area. The flight nurse said the pilot acknowledged them, and then took off and proceeded southbound. The flight nurse said they were climbing out when she heard a loud noise. She said it seemed to come from beneath the helicopter. She said she heard the pilot say, "Oh no," and then the helicopter began spinning clockwise out of control. The flight nurse said she was being tossed around, but was trying to get into a position for the crash. Then the helicopter impacted the ground. The flight nurse said she got out through the front of the helicopter. She said she checked the paramedic who was strapped in the left seat and determined he was unconscious. She then checked the pilot and determined he was fatally injured. The flight nurse said she then went for the radio to call for help. She said that the engines were still running and she smelled fuel. At this point she then noticed the tail rotor was missing. Several witnesses on the ground heard and saw the helicopter. The witnesses recalled the helicopter took off and made a right turn to proceed south. Several witnesses said they heard a loud bang. Most of the witnesses described the helicopter as doing a 360-degree counter clockwise turn, then the nose of the helicopter pitched up, the tail rotor came off, and the helicopter continued to spin and descend until it impacted the hillside. Radar data obtained from the Federal Aviation Administration (FAA) SLC Air Traffic Control Tower (ATCT) showed the helicopter lift off at 2011:16, make a 180 degree right turn to a heading of 179 degrees, and begin a climb from 4,800 feet mean sea level (msl). At 2011:43, the helicopter began a left turn to a heading of 089 degrees. The helicopter's speed was recorded as 57 knots, and the helicopter's altitude was 5,000 feet msl. At 2011:57, the helicopter was tracking on a 089-degree heading and was at an altitude of 5,400 feet msl. Its speed was 60 knots. At 2012:02, ATCT radar showed the helicopter on a heading of 045 and in a descent. The helicopter's altitude was 5,200 feet msl and its speed was 58 knots. The last radar contact with the helicopter was at 2012:07. The helicopter's altitude was not recorded. Its heading was 114 degrees and its speed was 58 knots. PERSONNEL INFORMATION The pilot held an airline transport pilot certificate with rotorcraft-helicopter and instrument ratings. The certificate was issued on September 26, 1996. According to the operating company, IHC Life Flight, the pilot had been employed with them for approximately 6 years. Company flight records showed the pilot had 6,381.6 total flying hours and 959.4 hours in the A109K2. The pilot had successfully completed a proficiency check flight with the company's chief pilot on June 6, 2003. The pilot had a second class medical certificate dated July 25, 2002. The certificate listed the following in the limitations section: "Must possess lenses for near vision. Not valid for any class after July 31, 2003." AIRCRAFT INFORMATION The helicopter, serial number 10018, was owned and operated by IHC Hospitals, Incorporated, and doing business as IHC Life Flight. It was used for air ambulance and rescue operations. The registration certificate was issued on April 20, 1994. The helicopter was being maintained under the manufacturer's recommended continuous maintenance program. A 2,400-hour inspection was conducted on April 3, 2003. The airframe time at the time of the inspection was 4,683.1 hours. The airframe time recorded at the accident scene was 4,833.3 hours. WRECKAGE AND IMPACT INFORMATION The National Transportation Safety Board on-scene investigation began on June 8, 2003, at 1125. The accident site was located at a residential horse corral on a mountainside approximately 250 feet northeast of Wasatch Road, a north south running 2-lane paved road. The site was at geographical coordinates 40 degrees, 43.26 minutes north latitude, and 111 degrees, 43.14 minutes west longitude. The accident site was at an elevation of 5,000 feet msl. The main wreckage was located on the east edge of the corral at the base of a continuing 60-degree sloping hill. The main wreckage consisted of the remaining cockpit area, the cabin section, the engine deck, both engines, control rods, fuel tank, and baggage area, the transmission, main rotor mast and rotor head, the tail boom, tail rotor drive shaft, tail rotor gear box, horizontal stabilators, and vertical fin. The helicopter was resting on its left side against several fence posts at an 85-degree angle from vertical. The fuselage was oriented on a 003-degree magnetic heading. An impact scar preceded the main wreckage. It began 75 feet northeast of the main wreckage and ran down slope along a 220-degree magnetic heading to the main wreckage. The impact scar was approximately 5 feet wide north to south, and 14 inches at its deepest point at the start of the scar. Pieces of broken Plexiglas, red paint chips, antennae pieces, honeycomb structure pieces, a fuel line, and several flight publications were located along the scar. A second ground scar, consistent with a main rotor blade strike, was located approximately 25 feet south of the impact scar. The second ground scar ran west to east, was approximately 4 feet long, and 18 inches wide. The helicopter's nose section was crushed aft and broken open. The cockpit area was broken free aft of the pilot seats. The cockpit floor was crushed upward. The left and right windscreens, eyebrow and chin windows, window frames, and cabin ceiling were broken aft and fragmented. The right cockpit door was broken out with portions of the doorframe crushed inward. The right side glareshield and instrument panel were crushed downward. The overhead circuit breaker panel was broken and canted to the right. The nose gear was bent forward and crushed upward. The cabin area was intact. The right side fuselage skin at the cabin was wrinkled. The right side sliding door was closed and locked. The skin was wrinkled. The left side fuselage skin was crushed and broken inward where the helicopter struck a fence post. The left side sliding door was closed and locked. The skin was crushed inward and wrinkled. The Plexiglas window was cracked. The bottom skin of the helicopter fuselage was crushed upward and wrinkled. Both of the main landing gears were broken outward and aft. The main landing gears were together and found resting 4 feet east of the main wreckage. The top of the hoist was broken aft longi