CEN16FA172 · Cessna 310F

The commercial pilot was conducting a checkride in the multi-engine airplane with an airline transport pilot-certificated designated pilot examiner. The pilot reported that, during the initial climb after takeoff, the left engine experienced a partial loss of power. At this time, the airplane was climbing at its single-engine best rate-of-climb speed (Vyse). The pilot reported that he was able to maintain control of the airplane with partial right rudder and right aileron inputs, and chose not to shut down and secure the engine because it was still providing "positive thrust." The examiner reportedly agreed with the decision to keep the engine running and to make left turns in the traffic pattern due to the increased number of landing options in that direction. The left turns, toward the partially running left engine, would have decreased the directional control of the airplane. While on the downwind leg of the traffic pattern, the left engine lost further power, and the pilot then attempted to feather the left propeller. Although he moved the left propeller control full aft, the propeller did not feather. Radar data indicated a continual loss of airspeed as the airplane turned from the upwind to downwind leg and from the downwind leg toward the airport. The airplane reached a maximum altitude about 255 ft above ground level on the downwind leg. As it turned toward the airport, the airplane collided with terrain in a 45° left bank and slight nose-down pitch attitude and was subsequently destroyed by a postcrash fire.

The postaccident airframe, engine, and propeller examinations did not reveal any evidence of a mechanical malfunction that would have prevented normal operation; however, the airplane sustained significant postimpact fire damage, which prevented a full assessment of the fuel system and its configuration at the time of the accident. Examination of left propeller determined it was not in a feathered position at the time of impact, and that both blades appeared to be at or near the start lock position.

The propeller was equipped with start locks that engaged below 800 rpm to prevent feathering of the blades during engine shutdown on the ground. In the event of an in-flight engine shutdown, the propeller must be feathered before engine speed decays to 800 rpm. It is likely that the pilot allowed the left engine rpm to decay below the start lock engagement speed, which prevented the propeller from feathering and, instead, remain windmilling. This would have resulted in a large amount of parasitic drag and a significant decrease of the airplane's single-engine climb performance. Due to the windmilling propeller, it is likely that the airplane would not have been able to maintain altitude even if the pilot had maintained Vyse; however, the pilot should have maintained this speed to minimize altitude loss and maintain controllability of the airplane. As the pilot maneuvered the airplane back toward the airport, he allowed the airspeed to decay such that the airplane no longer had the flight control authority to counteract the yaw and roll produced by the operating right engine, which resulted in a loss of control at a low altitude.

Verbatim NTSB analysis and probable cause from the NTSB dataset