Accident Overview
A twin-engine airplane sustained substantial damage during an in-flight collision with terrain after a loss of control in the airport traffic pattern. The accident occurred approximately one-quarter mile south of the runway, in the side yard of a residence adjacent to airport property.
Sequence of Events
Approximately 20 minutes before the accident, the pilot transmitted a mayday call reporting single engine problems. Radar track data showed the aircraft at 3,500 feet mean sea level on a northwest course. Shortly after the pilot reported the engine failure, the track data indicated the aircraft entered a descending left turn, losing 1,000 feet and reaching a south heading 24 seconds later. The pilot regained control, and air traffic control provided guidance to the nearest airport. The pilot subsequently established the aircraft on approach and stated he intended to circle the airport to the left and hand pump the landing gear down. The aircraft then impacted terrain in the side yard of a residence. A line of trees about 40 feet in height was located approximately 19 feet west of the accident site, but no evidence of a tree strike was observed.
Aircraft Damage and Position
Upon impact, the airplane came to rest on its nose and wings. The empennage was oriented vertically, at approximately 65 degrees relative to the terrain. The landing gear was found extended.
Engine Examination
Examination of the left engine revealed a separation of the No. 4 cylinder head. The cylinder head had separated between the second and third cooling fin. Metallurgical examination determined that the fracture was consistent with fatigue cracking. The left propeller and propeller governor showed no anomalies that would prevent normal operation of the feathering mechanism. However, observations during the left propeller teardown were consistent with the propeller not being in the feathered position at the time of the accident.
Maintenance and Systems
Maintenance records indicated that approximately 345 hours had accumulated on both engines since overhaul. No other anomalies were observed. According to the aircraft manufacturer's documentation, the hydraulic system was powered by an engine-driven hydraulic pump mounted on the left engine. Hydraulic pressure was used to control the retractable landing gear and flaps. In the event the left engine loses power, the hydraulic pump is not powered, and emergency gear extension must be used.