What happened
During a local flight intended for testing purposes, the crew was operating near Lukhovitsy-Tretyakovo Airport. While executing the third turn of an approach sequence, the crew engaged the feathering mechanism on the second engine. Shortly after this action, at an altitude ranging between 80 and 100 meters, the aircraft experienced a left bank accompanied by a reduction in both airspeed and altitude. The aircraft subsequently entered a stall and collided with the terrain.
Upon hitting the ground, the landing gear was sheared from the airframe. The wreckage slid for several dozen yards before coming to a stop, at which point the left wing sustained structural failure. There were no fatalities among the six crew members, though all survived the impact. The aircraft sustained damage that rendered it a total loss.
Findings
Investigations into the accident determined that the aircraft suffered a loss of control during its final approach. This was primarily due to a loss of thrust on engine number one following the propeller entering an autorotation state, which generated negative thrust.