Background
The U.S. Department of Agriculture's Animal Plant Health Inspection Service (APHIS) Wildlife Services aviation program conducted aerial hunting operations using a public-use airplane. The flight crew consisted of a rear seat instructor-gunner and a front seat trainee-pilot. Their mission required the trainee to maneuver at slow airspeed and low altitude while the instructor shot coyotes. The instructor was also responsible for monitoring the trainee's flying skills and providing instruction as needed.
On previous flights, the instructor observed that the trainee had difficulty maintaining altitude during turns and opined that she lacked the strength to fully extend the wing flaps. To compensate, the trainee placed two seat cushions behind her back to position herself closer to the flight controls and instrument panel. The instructor did not report these observations to management.
Accident Sequence
Following a coyote shoot during the accident flight, the trainee entered a low-altitude, slow-airspeed, medium-bank turn to reverse course. During the turn, the instructor's attention was diverted as he searched the cabin floor for an ejected live shotgun shell. When he looked outside, the left wing was already impacting the level terrain in a nose-low attitude.
Maintenance and Harness Attachment
The USDA operated the airplane and directed the instructor to have it maintained by contract mechanics in accordance with FAA regulations. Contrary to the manufacturer's FAA type certificate, the front seat shoulder harness—with its associated inertial reel—was erroneously connected to the back of the front seat instead of the prescribed overhead airframe hardpoint. Additionally, the shoulder harness webbing was routed beneath the seatback material. The airplane had undergone four 100-hour inspections and one annual inspection with the harness incorrectly attached.
Analysis
An engineering analysis determined that anchoring the harness to the seat structure rather than the airframe hardpoint, combined with the nose-low ground impact trajectory, increased inertial crash loads on the seat beyond its designed strength. The improper harness attachment, together with compressive fuselage buckling, caused the seat to yield in a forward bending direction. Consequently, the trainee's head impacted the instrument panel, resulting in fatal injuries.