Incident
A pilot observed smoke in the cockpit and shortly afterward noted that the oil pressure gauge indicated zero. Radar vectors were provided to the nearest airport, but the pilot was unable to reach it. During the subsequent forced landing, the aircraft collided with trees and a powerline.
Examination
Post-incident examination revealed that an oil cooler line had ruptured, allowing the engine oil supply to be pumped overboard. The line was found to be in a very brittle condition. There was no evidence of chafing on the line.
Maintenance History
The last annual inspection was conducted on July 11, 1983. The ruptured oil cooler line had accumulated 794 hours of time in service and had been installed for almost seven years. The aircraft manufacturer recommends replacement of these lines every 1,000 hours; however, the manufacturer of the lines specifies a shelf life of five years.