What happened
On January 21, 2019, a Douglas DC-3C, registration N467KS, was performing a positioning flight from Stoltzfus Airfield (OH22) to Akron Canton Regional Airport (CAK) in Kidron, Ohio. The aircraft was being used as a prototype for an engine upgrade project involving newer Pratt and Whitney Canada PT6A series engines. The aircraft was loaded to its maximum gross weight with fuel and ballast.
During the takeoff roll, the captain bypassed certain checklist items, specifically the auto-feather system and overspeed governor tests, due to snow-packed conditions on the taxiway and runway. At 0-911:13 EST, the first officer called for takeoff power. Shortly after liftoff, the left engine experienced a sudden loss of power. Witnesses reported seeing white smoke exiting the left engine exhaust, followed by the aircraft banking and yawing to the left.
Automated data indicated that left engine torque, fuel flow, and gas generator speed decreased rapidly. While the propeller began to auto-feather, the process was interrupted. The aircraft subsequently struck power lines and trees before impacting the terrain. The accident resulted in 2 fatal injuries for the two pilots on board.
The investigation
Investigators examined the wreckage and the aircraft's automated data acquisition system (ADAS). The left engine showed signs of a flameout, though the specific cause of the flameout could not be determined. The examination of the left engine's fuel control unit, fuel pump, and propeller governor revealed damage from the impact but no pre-impact anomalies that would have prevented normal operation.
Regarding the propeller, the left engine propeller blades were fractured near their roots. The investigation found that while the auto-feather system was operational, the propeller stopped feathering approximately three seconds after the initial power loss.
Analysis of the aircraft's minimum control airspeed (Vmc) indicated that the required airspeed to maintain control during the engine failure was estimated between 97 and 107 knots. However, the aircraft's airspeed at the time of the engine failure was approximately 86 knots, and it reached a maximum of only 91 knots before the impact.
Findings
- The left engine experienced an engine flameout during the takeoff climb.
- The auto-feather system was interrupted, preventing the propeller from reaching the full feather position.
- The aircraft was operating at an airspeed below the minimum controllable airspeed (Vmc) required to maintain lateral control following the engine failure.
- The critical, time-sensitive nature of the engine failure at low altitude challenged the crew's ability to recognize the problem and manually feather the propeller.