The Antonov 2R biplane operated on aero-chemical flight over the Yenisei Forest in Russia. On the fortieth minute of the flight along the route there appeared smoke of the cockpit of medium intensity. The captain decided to terminate the task and return. After 30 km of flight the smoke intensity increased significantly. The crew heard blows in the area of the engine, after which vibrations were felt, accompanied by a loss of power. Oil was seen flowing onto the windows and wings. The engine did not respond to the propeller pitch and thrust movement. The captain then decided to make a forced landing in the forest. During the landing, the aircraft collided with trees and the ground surface, resulting in significant damage to the aircraft. The crew members suffered minor injuries. Conclusion (translated from Russian): The cause of the aviation accident with the AN-2 RA-33036 aircraft was the decrease of power of the ASh-62 IR engine due to fatigue failure of cylinder No. 5. Fatigue failure of the cylinder occurred due to a manufacturing defect – no blunting of sharp edges at the ? 12 mm bore for the stud bolt of the sleeve to the crankcase in the most loaded zone. Probable factor contributing to the failure could be the irregularity of the cylinder flanges and engine crankcase in the specified area.