WPR15FA051

The pilot/mechanic's failure to properly secure the pitch link hardware of one main rotor blade to the rotating swash plate, which resulted in the pitch link separating in flight and a subsequent loss of control.

Before the accident flight, the commercial helicopter pilot, who was also a mechanic, had re-installed the main rotor blades, which had just been reworked, on the helicopter. The accident flight was a test flight to adjust the track and balance of the rotor blades. A mechanic, who spoke with the pilot a few weeks before the accident, stated that they had a discussion about an elongated pitch change link attachment hole on the accident helicopter and how to address it. On the night before the accident flight, they spoke again; the pilot was having trouble tracking the blades on the accident helicopter. The pilot stated that he could not get the blades to track any better, and that he was trying to change the track with the trim tabs. Witnesses in the area of the accident site heard "popping" or "banging" sounds, then saw the main rotor and empennage separate from the helicopter. Several of the witnesses then saw the helicopter tumble in flight and impact the roof of a building. The main rotor and empennage came to rest on the ground a few hundred feet from the building. Witness statements and wreckage documentation were consistent with a main rotor blade striking the tail and subsequently, a mast bump, which resulted in the helicopter descending uncontrollably. The damage observed on the components of the main rotor system was consistent with an in-flight separation of the pitch change link for the red blade, with separation occurring at the location where the pitch change link attached to the swashplate. The swashplate was free of contact marks corresponding to contact with the red pitch change link, which contrasted with the area around the blue blade pitch change link attachment, where multiple contact marks corresponding to contact with the blue pitch change link were observed. Also, the red pitch change link was intact and relatively straight, indicating that separation occurred under loads less than that required to buckle or fracture the pitch change link. The slight bending in the red pitch change links was likely secondary to the separation of the attachment at the lower end as evidenced by the location of the corresponding thread contact marks on the pitch horn. Finally, a series of impressions corresponding to contact with threads on the red blade pitch change link attachment bolt were observed on the attachment hole bore through the swashplate in an area that should have only contacted the grip portion of the bolt. Thus, it is likely that the intact bolt separated from the attachment due to loss of the lock nut and palnut. Torque measurements were obtained on the locknuts installed on the three recovered pitch change link attachment bolts. All measured torque values were lower than that specified in the helicopter's maintenance manual, indicating that the fasteners were improperly torqued before the accident. While torque for the missing attachment bolt could not be measured, the torque measured on the remaining pitch change link attachment bolts and witness marks on the attachment hole bore in the swashplate suggest that the bolt likely separated due to insufficient torque applied at the time of installation, which led to the loss of the locknut and palnut due to vibrational loads under normal operation.

HISTORY OF FLIGHT On December 2, 2014, about 1400 mountain standard time, a Robinson R44 II helicopter, N3234U, impacted a two-story building while maneuvering near Skypark Airport (BTF), Bountiful, Utah. The commercial pilot/mechanic and passenger were fatally injured, and the helicopter was substantially damaged. The helicopter was registered to Native Range Capture Services, Inc., Elko, Nevada, and operated by Native Range, Inc, Ventura, California. Visual meteorological conditions prevailed for the area, and no flight plan was filed for the local, post-maintenance test flight, which was conducted under the provisions of 14 Code of Federal Regulations Part 91. The flight departed from BTF shortly before the accident. According to the owner of the helicopter, the pilot/mechanic was performing maintenance on the main rotor assembly and the purpose of the post-maintenance flight was part of the procedure to "track and balance" the main rotor blades. This maintenance spanned over several days. Several witnesses in the area of the accident site heard "popping" or "banging" sounds then saw the main rotor and empennage separate from the helicopter. Some of the witnesses then saw the helicopter tumble in flight and impact the top of a building. The main rotor and empennage came to rest on the ground a few hundred feet from the impacted building. Security camera video footage from a nearby business captured the helicopter in the air shortly after the separation of the main rotor and empennage. PERSONNEL INFORMATION The pilot, age 65, held a commercial pilot certificate with rotorcraft, airplane single-engine land, multi-engine land, and instrument ratings. The pilot held a Federal Aviation Administration (FAA) second-class medical certificate, which was issued on April 1, 2014, with no limitations. The pilot reported on his most recent medical certificate application that he had accumulated 5,500 total hours of flight experience. The pilot was issued a mechanic certificate on August 17, 2012, with ratings for airframe and powerplant. He attended the Robinson Helicopter Company's maintenance course in December 2008. The passenger, age 63, held a private pilot certificate with a rating for airplane single-engine land. He held an FAA third-class medical certificate, issued on October 26, 2006, with the limitations that he must have available glasses for near vision, and not valid for any class after. The pilot reported on his most recent medical certificate application that he had accumulated 250 total hours of flight experience. He was issued a mechanic certificate on September 9, 2008, with ratings for airframe and powerplant. He had not attended the Robinson Helicopter Company's maintenance course. AIRCRAFT INFORMATION The four-seat helicopter was manufactured in February 2007. It was powered by a Lycoming IO-540-AE1A5 reciprocating engine rated at 205 horsepower. The helicopter's owner stated that, during a flight in the accident helicopter the month before the accident, the helicopter "had a bit of a vertical [vertical vibrations]". The blades also had noticeable slop and movement in the pitch change link bolt attachment to the swashplate. During a 100-hour inspection, on November 2, 2014, at 582 hours of helicopter total time, the owner and pilot/mechanic recommended sending the blades out for rework. According to airframe records, the [red] main rotor blade pitch horn was replaced, and the pilot-rated mechanic declined repainting of the blades. When the blades returned, the owner hired the pilot-rated mechanic to install the blades and track them in a heavier configuration. According to a mechanic who spoke with the pilot a few weeks before the accident, they discussed an elongated pitch change link attachment hole on the accident helicopter and how to address it. On the night before the accident flight, they spoke again, and the pilot said he was having trouble tracking the blades on the accident helicopter. He reported that the blades could not track any better than a 1/2-inch separation, and that he was using the trim tabs to change the track. The mechanic suggested that the pilot use the fine adjustments on the pitch change links, then fly through all flight regimes, and fine tune with the trim tabs. He recommended to the pilot to look at the entire rotor system and thought that something was amiss. Review of the helicopter's maintenance records showed that on September 12, 2007, at 87.3 hours total time, the hub and blades were rebuilt by Robinson Helicopter Company. The spindles, which include the pitch horns, were reused during the rebuild. METEOROLOGICAL INFORMATION The 1353 weather observation at Salt Lake City International Airport (SLC), Salt Lake City, Utah, located 5 miles south of the accident site, reported wind from 320 degrees at 3 knots, visibility 10 statute miles, scattered clouds at 15,000 feet above ground level, broken clouds at 19,000 above ground level, temperature 8 degrees C, dew point 2 degrees C, and an altimeter setting of 30.05 inches of mercury. WRECKAGE AND IMPACT INFORMATION Examination of the accident site by the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) revealed a wreckage debris field about 880 ft in length, about 400 ft in width, and oriented on a 277° magnetic heading. The main rotor and empennage separated from the main wreckage before impact and were found within the wreckage debris field. The main rotor assembly was found near a parking lot about 188 ft from the main wreckage. The empennage separated from the main wreckage and was found near a parking lot about 430 ft from the main wreckage. Several sections of the tail rotor drive shaft were found throughout the debris field. A large section of the tail rotor drive shaft pierced the roof about 90 ft from where the fuselage entered the roof. Both pitch change links and transmission housing material were found throughout the debris field. Plexiglas sections were found throughout the debris field. A 4-ft section of the main rotor blade tip was found in a retention pond and was furthest from the main wreckage. The main wreckage impacted and penetrated the roof of a two-story building about 2,000 ft southwest of the approach end of runway 34 at BTF. A postimpact fire occurred; however, the building's sprinkler system was activated, and an overhead sprinkler pressure line was separated near the main wreckage, releasing water and limiting the postimpact fire to the main wreckage. The main wreckage displayed impact damage and was partially damaged by the fire. The wreckage was recovered to a secure facility for further examination. The main wreckage, consisting of the cabin area and a 5-ft section of the tailboom, exhibited impact and thermal damage. The left side of the cabin was crushed inward towards the center, and the right side near the firewall was crushed inward. The rear seat area had minor thermal damage. The cabin area was crushed and distorted. Both forward seat structures were crushed inward and slightly forward. The front of the fuselage was crushed inward and the windshield was shattered. First responders cut the left forward seat belts. The right forward seat belts were unbuckled. The top side of the airframe had several disconnects and separations, and was bent to the right side. The tail cone separated aft of the number seven bay, and bay numbers 4, 5 and 6 separated into several sections, consistent with a main rotor strike. The left side of the number 1, 2 and 3 tail cone bays were flattened inward. The flight controls had several disconnects between the cyclic/collective and swashplate. All fractures exhibited signatures consistent with overload. The tail rotor flight controls had several disconnects from the pedals to the tail rotor, and all separations exhibited overload signatures. The fuel tanks remained attached to the airframe. The crossover h