What happened
The pilot was conducting an instrument approach to Waukegan Airport when he reported an oil leak in the right engine to air traffic control. Several minutes later, the pilot informed controllers that he had lost visual contact with the airport and experienced a loss of power in the right engine. Consequently, the pilot elected to perform a forced landing in a plowed field adjacent to the airport. Upon impact, the aircraft's landing gear collapsed.
The investigation
A post-accident examination of the right engine focused on the oil scavenger pump. Investigators discovered that the drive gear had fractured into five distinct pieces. Analysis of the fracture surfaces revealed that four of the five breaks exhibited characteristics consistent with an overload-type failure. However, one specific fracture surface was determined to have been a pre-existing fatigue crack.
Findings
The mechanical failure of the right engine's oil scavenger pump drive gear was the primary factor in the loss of power. The presence of a pre-existing fatigue crack on one of the gear teeth initiated the failure sequence, which ultimately led to the complete separation of the gear components and subsequent engine malfunction.