Accident Details
At 1247 hours during cruise flight, the pilot informed the radar controller of a minor oil leak on the windshield. The leak intensified, and within five minutes, oil had covered the front windshield, obstructing visibility. One minute later, the pilot declared a total loss of oil pressure. Attempting a forced landing on an interstate freeway, the airplane impacted three automobiles during flare, cartwheeled, and came to rest upside down.
Preceding Events
Three days before the accident, the pilot flew from Torrance, California, to Bullhead City, Arizona. During that flight, an engine oil leak became apparent, hindering visibility through the front windshield. The pilot suspected that engine oil was leaking past the engine's crankcase nose seal, aft of the propeller, and believed replacing the seal would resolve the issue. (Seepage in that area had been documented during the last annual inspection, completed 21 engine operational hours prior.)
The pilot then flew 16 miles to near Needles, California, where repair services were available. Upon arrival, oil was dripping from the engine. An engine shop advised the pilot to have the engine removed and repaired, but the pilot declined due to insufficient funds. Instead, he purchased the nose seal parts from the shop and hired a local independent mechanic to install them.
After the maintenance was completed, the mechanic requested a ground run-up to check for leaks. The pilot declined and departed. The accident occurred approximately 40 minutes later, 92 miles from Needles.
Maintenance History
About 537 engine operational hours prior to the accident, in 1986, the airplane's landing gear collapsed, damaging the propeller. The crankcase was found cracked on its front, right side, and the engine was overhauled. According to maintenance records, the case was repaired. During the last annual inspection, oil seepage was noted on the front, right side of the case.
Investigation Findings
During the accident investigation, a weld was observed on the front, right side of the crankcase. Electrical arc marks were found approximately 2.3 inches inside the crankshaft bore. The crankshaft had fractured, with the fracture originating at the site of the arc marks, which had created a stress riser. As the fracture progressed, it provided a path for oil to escape from the crankshaft and propagate through the nose seal.