Cessna 421C N297DB accident near Lake Worth, Florida

Probable cause

The pilot's failure to follow established engine-out procedures and to maintain a proper airspeed after the total loss of engine power on one of the airplane’s two engines during the initial climb. Contributing to the accident was the total loss of engine power due to a loss of torque on the crankcase bolts for reasons that could not be determined because of impact- and fire-related damage to the engine.

NTSB analysis

The twin-engine airplane was released to the owner after an annual inspection and repainting of the airplane had been completed. The pilot/owner had completed a post-maintenance test flight with the mechanic/proprietor of the maintenance facility, and minor discrepancies noted during the flight were corrected prior to final release of the airplane. The pilot performed a ground run of the airplane for several minutes before taxiing to the approach end of the departure runway. The airplane lifted off about halfway down the runway and climbed at a normal rate. The mechanic then observed the airplane suddenly yaw to the left for a second or two and the airplane's nose continued to pitch up before rolling left and descending vertically, nose-down, until it disappeared from view. Several witnesses provided similar accounts of the accident sequence. One witness, a certificated flight instructor said, "The airplane just kept pitching up, and then it looked like a VMC roll."

Examination of the No. 1 (left) engine revealed signatures consistent with contact made between the piston domes and the valves. The crankcase halves were separated and the No. 1 main bearing was rotated, and damaged and distorted severely, with bearing fragments located in the oil sump. Bearing material was extruded from its steel backing. The No. 3 cylinder main bearing displayed signatures consistent with accelerated wear and wiping of the Babbitt material. Damage and signatures consistent with excessive heat due to oil starvation were displayed on the No. 1 and No. 3 main bearing journals, as well as the No. 1 and No. 2 connecting rod journals. The camshaft gear was damaged, with five gear teeth found sheared from the gear. A review of engine maintenance records revealed no maintenance was performed on the engine that would have required breaking of crankcase thru-bolt torques (such as cylinder removal) since overhaul.

Examination of the wreckage revealed that the landing gear was in the down and locked position, the left propeller blades were in the feathered position, and the left fuel selector valve was in the off position. Examination of the manufacturer's Pilot Operating Handbook revealed that if properly configured, with the landing gear retracted, the airplane was capable of a 500 feet-per-minute rate of climb on the day of the accident. As found, the airplane was not configured in accordance with the after-takeoff checklist or either engine failure after takeoff checklist.

Text from the NTSB. Open the NTSB docket for ERA13FA082 for the full record.