The National Transportation Safety Board today released the final report in its investigation into the 2018 crash of an Air Medical plane northwest of Bismarck.
Its conclusion as to the probable cause of the accident: Pilot error resulting in an overload on the wings, causing the plane to break up in flight.
The Bismarck Air Medical Cessna turboprop was en route to Williston from Bismarck around 10:40 p.m., November 18, 2018, when, according to the NTSB, the plane apparently broke up in flight and came down near Harmon, about 20 miles northwest of Bismarck.
The crash killed all three people aboard: pilot Todd Lasky, nurse Bonnie Cook and paramedic Chris Iverson.
The NTSB reports radar data showed the airplane climbed to 14,000 feet mean sea level after it departed Bismarck at 10:31 p.m., and proceeded directly toward the destination airport.
While en route, around 10:39 p.m., the plane began an unexplained right descending turn, losing 7,800 feet of altitude over the span of 30 seconds. At some point, the NTSB reported, the pilot attempted a pull-up maneuver to recover from the descent. The NTSB said the stress on the plane from that action caused the part of the wing that passed through the center of the airplane to compress, buckle and fracture. That led to the separation of the left wing and right wing engine and the subsequent breakup and crash of the plane.
The NTSB said, “the descending right turn was inconsistent with the intended flight track and
ATC-provided clearance. However, there was insufficient information to determine how it was initiated and when the pilot became aware of the airplane’s state in the dark night IMC conditions. Yet, the absence of a distress call or communication with ATC about the airplane’s deviation suggests that the pilot was not initially aware of the change in state. The structural failure signatures on the airplane were indicative of the wings failing in positive overload, which was consistent with the pilot initiating a pull-up maneuver that exceeded the airplane spars’ structural integrity during an attempted recovery from the spiral dive.”
The NTSB also noted, “there was no evidence of any pre-existing conditions that would have degraded the strength of the airplane structure at the fracture locations. “Flight control continuity was confirmed. An examination of the engines, propellers, and available systems showed no mechanical malfunctions or failure that could have contributed to the accident.”