WPR16LA155

The commercial pilot of the scheduled cargo flight reported that, during cruise flight about 8,000 ft indicated altitude, he heard a small impact noise and believed that the airplane was struck by a bird. There was no loss of directional control, change in control configuration, or impact shudder. He continued the flight and subsequently landed without further incident. After exiting the airplane, the pilot noticed that about 12 inches of the top of the vertical stabilizer was missing, and that there was substantial damage to the rudder. The separated top of the vertical stabilizer section was not recovered. The fracture surface of the upper section of the remaining vertical stabilizer was in a nearly horizontal plane. The skin was deformed adjacent to the fracture into curled rolls turning downward and aft. Some areas were crushed, consistent with the vertical stabilizer moving forward relative to another object. Sliding contact marks were observed at the leading edges, vertical spars, and deformed faces of the skin panel adjacent to the fracture. No evidence of any biological or manufactured foreign material transfer was observed associated with any of the fracture surfaces either visually or under optical magnification. Closer examination identified deposits of particles consistent with aluminum alloy 2024 and similar metallic element peaks. Other particles had spectra consistent with a low alloy steel, stainless steel, brass, and a nickel-base alloy with iron and chromium. The curling deformation to the skin and the deformation through the airplane structure was consistent with contact with a stationary object, such as a suspended cable. Given the diameter of the impact deformation and the materials found, it is likely that the airplane impacted overhead power transmission lines during a portion of the flight that was conducted at an altitude much lower than reported.

On August 1, 2016, about 1850 mountain daylight time, a twin-engine turboprop Beech C-99 airplane, N234AV, collided with an object while in-flight near Spanish Fork, Utah. The commercial pilot was not injured. The airplane sustained substantial damage to the vertical stabilizer and rudder. The airplane was registered to UAS Trans Services and operated as AMF1843 by Ameriflight, LLC as a Title 14 Code of Federal Regulations Part 135 scheduled cargo flight. Visual meteorological conditions were reported at the time of the accident, and company flight following procedures were in effect. The flight originated from Carbon County Regional Airport (PUC), Price, Utah about 1830 and was destined for Salt Lake City, Utah. The pilot reported that while about 8,000 - 8,500 ft indicated altitude, he heard a small impact noise and believed that the airplane was struck by a bird. There was no loss of directional control, change in control configuration, or impact shudder. He continued the flight and subsequently landed without further incident. After exiting the airplane, the pilot noticed about 12 inches of the top of the vertical stabilizer was missing, and there was substantial damage to the rudder. The separated top of the vertical stabilizer section was not recovered. A section of the remaining upper area of the vertical stabilizer, rudder and the rudder trim were removed from the airplane and sent to the National Transportation Safety Board Materials Laboratory, Washington DC for examination. The materials engineer reported that the pieces were fractured in a nearly horizontal plane at the upper ends of the submitted pieces. The skin on the vertical stabilizer and rudder were deformed adjacent to the fracture into curled rolls turning downward and aft. Some areas were crushed consistent with the vertical stabilizer moving forward relative to another object. Sliding contact marks were observed at the leading edges, vertical spars, and deformed faces of the skin panel adjacent to the fracture. No evidence of any biological or manufactured foreign material transfer was observed associated with any of the fracture surfaces as observed visually and under optical magnification. Closer examination using a scanning electron microscope (SEM) with energy dispersive x-ray spectroscopy (EDS) identified deposits of particles consistent with aluminum alloy 2024, and similar metallic element peaks. Other particles had spectra consistent with a low alloy steel, stainless steel, brass, and a nickel-base alloy with iron and chromium.