What happened
While operating under the direction of the Denver Air Route Traffic Control Center, the pilot of the aircraft reported an oil leak in the left engine and requested permission to divert to the nearest available airfield. Controllers directed the pilot toward Akron (AKO), where the pilot was subsequently cleared to land. After the pilot confirmed the airport was in sight, radar services were terminated, and the pilot was instructed to transition to an advisory frequency.
Roughly 17 minutes after the last contact, air traffic control contacted Flight Service to verify the aircraft's arrival at Akron, but the pilot had not checked in. A search was initiated, and approximately 13 minutes later, the local sheriff located the wreckage positioned off the airport grounds. Ground witnesses observed the aircraft traveling in a westbound direction before it suddenly pitched nose down, entered a two-turn spiral, and crashed. The impact resulted in an explosion and a subsequent fire that consumed the wreckage.
Findings
Investigation of the left engine revealed that the number 2 and 3 rods had fractured at the journals, accompanied by heavy spalling on the number 2 and 3 pistons. The engine case halves exhibited fretting at the seam and through bolts, and all six cylinders showed fretting between the bases and the case. Evidence of heat and oil discoloration was present on the exterior of the engine case. The right engine also showed similar fretting at the cylinder bases and case halves, along with oil seepage around the seals and heat-related discoloration.
Analysis of the propellers indicated that both were at or near a low pitch setting during the accident. While the right propeller was operating under power at the moment of impact, the left propeller was operating under low or no power. According to the manufacturer, if an engine undergoes a sudden seizure, the propeller speed remains below the threshold required for the propeller lock latch to allow feathering. Maintenance records indicated the aircraft had a history of left engine oil leaks, including one instance where a crack in a case half bolt was addressed using an unapproved resin instead of standard repair procedures.