Accident Overview
On April 4, 2024, about 2000 Pacific time, an experimental amateur-built Kitfox Series 5, registration N743JT, was substantially damaged during a precautionary landing near Yucca Grove, California. The airplane was operated as a personal flight under 14 Code of Federal Regulations Part 91.
Flight Details
The pilot, relocating the airplane from California to Colorado, departed Cable Airport (CCB) in Upland, California, with a planned destination of Henderson, Nevada. This was the first leg of the trip. While en route at an altitude of 9,500 ft mean sea level, the pilot noticed a slight reduction in engine oil pressure. No increase in oil temperature or other engine warnings were observed, so he decided to continue while monitoring engine parameters.
Oil Pressure Issue
Shortly thereafter, the oil pressure began to drop at a faster rate. Concerned about continuing towards inhospitable terrain as the sun set, the pilot opted to perform a precautionary landing. He shut down the engine and configured the airplane for landing on a highway service road.
Landing and Damage
During approach, the pilot observed light poles obstructing the intended landing area. He maneuvered towards an adjacent dirt field. However, the terrain proved rougher than anticipated. After striking scrub brush, the airplane nosed over during rollout. The airplane sustained damage to both wings and the vertical stabilizer. Post-accident examination revealed the belly was completely covered in engine oil.
Post-Accident Examination
The airplane was equipped with a Continental C90 engine fitted with a steel “kidney” style oil sump. Inspection of the engine compartment showed the oil sump and surrounding components, including the back of the carburetor, coated in oil. No anomalies were found in the engine oil system lines, filter, or cooler. The oil drain plug was secure. One quart of oil was drained from the sump; the oil was brown and free of visible debris.
A 3-inch-wide bead of grey filler had been applied to the forward neck of the oil sump mounting flange. When the sump was pushed by hand, the filler was not properly bonded and appeared to cover a crack. The filler was easily pried off, revealing a 4-inch-long crack at the weld joining the sump to the mounting flange. The crack extended beyond the filler contact area. Abrasive marks consistent with bonding preparation were evident in the area where the filler had been installed, but most of the paint remained.
Pilot's Repair
The pilot, an FAA-certified airframe and powerplant mechanic with inspection authorization, later confirmed that the crack had been present since December 2023. He described the leak as a nuisance but not significant, with total oil consumption of about 1 quart every 4-6 hours. He repaired the crack with “Steelstik” epoxy putty, manufactured by J-B Weld. After the repair, he performed multiple engine ground test runs. The accident flight was the first flight since the repair was made.
Data from the airplane’s engine monitor recorded a gradual loss of oil pressure consistent with the pilot’s description.