HISTORY OF FLIGHT On February 19, 1996, at 1455 central standard time, a Hughes 369D, N5141Y, registered to D Bar O Aviation, Inc., of Red Lodge, Montana, and piloted by a commercial helicopter pilot, impacted a transmission tower, while engaged in construction work on the tower. The accident occurred 2 miles north of Dweese, Nebraska. The helicopter was destroyed during the impact with the tower and the terrain. The pilot sustained fatal injuries. One worker on the tower received fatal injuries. The 14 CFR Part 133 operation was operating in visual meteorological conditions. No flight plan was on file. The local flight had departed on this mission at 1450. The purpose of the flight was to place two workers and rigging on the top of a transmission tower so that the workers could set the rigging in order to pull transmission cables. The pilot was working for the first day on this type of endeavor. He had placed workers on two other transmission towers on the day of the accident. This was to be the third such operation. The pilot was trained by an individual who had been in this type of activity for a number of years. The individual giving the instruction had been along on previous flights that day. In an interview with the "instructor," he stated that he had told the pilot that landing on the top of the tower, on the "bridge" was not a recommended procedure. He stated that during the previous two operations the pilot had let the workers off on the outside of the tower on the "goats peaks." He said that the pilot's execution of the operation was excellent and he had decided to allow him to work alone and for that reason was no on the helicopter at the time of the accident. (Depiction of the tower are attached to this report). Witnesses to the accident stated that the pilot held a "tailgate" instruction session prior to the flight to tell the workers to expect some windy conditions, but that the flight should go as the two previously had and that he would let the workers and their rigging off on the "goats peaks." The helicopter was loaded with rigging, the two workers, and the pilot. They said that the helicopter then lifted off and let the first worker out on the north "goats peak" with his equipment. Then instead of flying around to the south goats peak the helicopter approached the "bridge" and sat down facing west northwest to allow the second worker to get out with his rigging. Witnesses said that after the worker and his rigging were let out on the "bridge," they then observed the helicopter back off the bridge. The rotor system was seen to drop and contact the north "goats peak." The helicopter then spun around three times prior to impacting the terrain on the east side of the tower. Witnesses stated that the wind was from the southwest at about 15 knots at the surface. (Witness statements are attached to this report). INJURIES TO PERSONS The pilot sustained fatal injuries. A worker on the tower received fatal injuries when the main rotor blades came in contact with the portion of the tower where he was working. PERSONAL INFORMATION The pilot was born February 11, 1949. He was the holder of a commercial certificate for helicopter and single engine land airplanes. He held a second class medical certificate issued June 27, 1995, with the restriction for possessing correcting lenses for near vision, while exercising the privileges of his airman certificate. He received a biennial flight review in the same make and model of helicopter on August 31, 1995. At the time of the accident he had a total flight experience of over 6,000 hours with 515 hours in the make and model of the helicopter involved in the accident. AIRCRAFT INFORMATION The helicopter was a Hughes 369D, N5141Y, serial number 1114D. The helicopter had accumulated 11,640 hours time in service. It received an annual inspection on January 4, 1996, and had accumulated 35 hours since that time. WRECKAGE AND IMPACT INFORMATION The helicopter wreckage was headed north on the east side of the tower. The main rotor system exhibited impact damage. Portions of the main rotor blades were located on the southwest side of the tower. Damage to the tower was slight and confined to the east side and on the north "goats peak." The fuselage of the helicopter remained upright. A continuity check of the helicopter verified flight and engine controls. Nothing was found during the on-scene investigation to indicate pre-accident anomalies. The turbine section rotated. Witnesses stated that the engine sounds were like previous flights prior to the impact sequence. They stated that they noted nothing unusual about the flight of the helicopter or pilot on this particular flight, prior to the collision with the tower. MEDICAL AND PATHOLOGICAL INFORMATION A post mortem examination of the pilot was conducted by the Douglas County (NE) Morgue, on February 20, 1996. No pathological anomalies were found during the examination. Specimens from the pilot were tested for toxicology and found negative for the drugs screened. FIRE There was a small post-crash fire which was extinguished by ground personnel. There was some scorching due to the fire, but no other damage. TESTS AND RESEARCH The trim switch was checked for continuity at the accident site and the operation verified. The trim actuators were taken from the accident site and further tested and found to operate within specifications. ADDITIONAL INFORMATION Parties to the investigation were the Federal Aviation Administration, Flight Standards District Office, Lincoln, Nebraska, and McDonnell Douglas Helicopter, Mesa, Arizona. The wreckage was released to representatives of the owner on February 20, 1996.