ERA12LA343 · Cessna 195A

The pilot stated that, during cruise flight, he noticed that the engine rpm began fluctuating and that, about 20 seconds later, the rpm dropped. The pilot immediately looked at the oil pressure gauge and observed that it was "reading zero." He then declared an emergency with air traffic control, and a controller informed him that the nearest airport was 15 miles south of his location. He brought the engine back to idle to keep it from seizing in case power would be needed later to avoid terrain, which was primarily mountain ridges with hills and narrow valleys, and set the propeller to low rpm. The pilot realized that he could not make it to the nearest airport and chose to land on a road in an industrial park. The landing was uneventful, but, during the landing roll, the airplane was substantially damaged when the left wing struck a standpipe and the airplane subsequently nosed over.

Examination of the engine revealed that a 1/2-inch metal oil line had fractured at the rocker's scavenge oil tube adjacent to the coupling sleeve and nut. Further examination revealed that the metal oil line had failed in fatigue in the manufactured bend adjacent to the coupling sleeve, that it was at least 34 years old, and that it had probably been reused many times. The oil tube assembly also displayed a distinctive bend and compression at the bead end and a slight bend at the nut end that were not specified on the manufacturer's drawings and were consistent with the oil tube assembly being significantly bent to fit on the engine. The manufactured bends also displayed oval cross-sections not specified in the drawings. The oval cross-sections may have been produced by the original manufacturing process but were likely produced by bending at each reuse, which would have initiated bending fatigue. Cracks propagating from the fracture face at the centerline of the tube were also present. Hardness testing revealed that the tubing at the fractured bend was harder than a sample of tubing that had not been subjected to any bending and that it exceeded the specified maximum hardness. This testing indicated that the increased hardness of the tubing in the bend had been produced by the original manufacturing process and/or by subsequent work hardening (that is, the undesirable strengthening of a metal such as copper by plastic deformation).

Verbatim NTSB analysis and probable cause from the NTSB dataset