What happened
During the takeoff roll, a mechanic had noted that one of the engines was producing an irregular sound. According to air traffic control records, the Cessna 421C utilized approximately 4,500 feet of the runway before becoming airborne. Roughly one minute after receiving takeoff clearance, the pilot notified the controller that the right engine had failed. Witnesses and air traffic controllers observed the aircraft level off, experience lateral oscillations, and begin a descent. The pilot indicated that the aircraft would be unable to maintain flight, and the plane subsequently disappeared behind a treeline.
Following the accident, an inspection of the aircraft's engines, propellers, flight controls, and structural components revealed no evidence of mechanical malfunctions or failures that would have hindered the operation of the aircraft prior to the crash. The investigation noted that the landing gear and wing flaps were in the retracted position. Additionally, both propellers were found in a low blade angle configuration with comparable damage levels.
Findings
An analysis of NTSB audio from air traffic control communications revealed differing propeller speeds at the time the pilot reported the emergency; one propeller was rotating at 1,29MU rpm while the other was at 2,160 rpm. While the Pilot Operating Handbook for this aircraft specifies that the engine inoperative procedure requires closing the throttle, setting the mixture to idle cut-off, and feathering the propeller, the propellers were found in a non-feathered state. Under the specific conditions present during the accident, the aircraft typically required only 2,000 feet of runway for takeoff, yet this flight used significantly more distance before liftoff.