N155NRMd Helicopters 369E · 2015

On June 17, 2016 about 1400 central daylight time (CDT), an MD Helicopters Inc., 369E, N155NR, sustained a windscreen failure in flight, 20 miles south of Brainerd Lakes Regional Airport, Minnesota. The helicopter was registered to the State of Minnesota Department of Natural Resources Enforcement Division and operated as a visual flight rules (VFR) public use local flight under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed for the flight, and company VFR flight following was in effect.

The commercial pilot reported that he conducted the aerial observation flight near known thunderstorms and that both the passenger and pilot doors had been removed from the helicopter. He reported that, about 20 miles south of his destination, he decreased the helicopter's airspeed to about 110 mph because, "it began to feel a little bumpy." The pilot added that, "suddenly with no warning," the right center windscreen shattered. The helicopter's nose dropped immediately, and the pilot lowered the collective. After slowing the helicopter to maintain control, the pilot conducted a precautionary landing without further incident. The pilot reported that he did not see anything strike the windscreen and found no evidence of a bird strike. Two of the helicopter's main rotor blades and the horizontal stabilizer sustained substantial damage. The pilot sustained facial lacerations, and the observer on board did not sustain any injury.

According to the Federal Aviation Administration Inspector who responded to the accident, the right front windscreen failed in cruise flight for unknown reasons. A post-accident examination of the helicopter by the inspector revealed that debris from the windscreen had made gouges in the main rotor blades and the horizontal stabilizer. A significant portion of the windscreen was not recovered.

Examination of the recovered windscreen pieces revealed evidence of cracking that originated on the external surface of the center of the windscreen and then propagated outward.

DNA samples taken from portions of the windscreen were sent to the Smithsonian Feather Identification Laboratory in Washington, DC. Microscopic examination of one of the samples revealed evidence of feathers. The DNA from the feathers matched the Western Kingbird (Tyrannus verticalis), which is a very small bird.