Incident Overview
On August 27, 2015, at approximately 1110 central daylight time, a Piper PA-23-250, registration N900AM, sustained minor damage when it was struck by an unknown object while in cruise flight. The aircraft was at 2,500 ft above mean sea level (1,920 ft above ground level) about 4 nautical miles north of Joliet Regional Airport (JOT), Joliet, Illinois. The commercial pilot was not injured. The airplane was registered to and operated by Aerial Imaging Inc. under 14 Code of Federal Regulations Part 91 as a positioning flight. Visual meteorological conditions prevailed, and no flight plan was filed. The airplane had departed Aurora Municipal Airport (AAR), Aurora, Illinois, about 1100 and landed without incident at South Bend International Airport (SBN), South Bend, Indiana.
Pilot Report
The pilot reported hearing a "bang" and feeling a jolt in the flight controls while completing the cruise checklist. He did not see any objects before the noise and observed no damage to the airplane. The engines operated normally, flight controls felt normal, landing gear indicated up and locked, and the cargo did not appear to have shifted. He continued the flight to SBN, noting no abnormal flight characteristics.
Damage Description
After landing, damage to the leading edge of the left horizontal stabilizer was observed. The damage included about four dents spanning approximately 13 inches from left to right, with the inboard dent piercing the aluminum skin. The damage also included multiple scratches and cuts in the deicing boot covering the leading edge.
Examination Findings
The damaged section of the deicing boot was removed and examined at the National Transportation Safety Board's Materials Laboratory. Ultraviolet light examination indicated insect impacts on the boot but no widespread area of fluorescence consistent with exposure to larger volumes of biological materials. Tears in the boot exhibited features consistent with failure from overstress. Subsequently, the boot was examined at the Feather Identification Laboratory, Division of Birds, Smithsonian Institution National Museum of Natural History. Several feather barbs removed from the tears during microscopic examinations were consistent with remnants from the Columbidae bird family (doves and pigeons).