CEN24FA212 · Beech V35A

The pilot reported that shortly after takeoff he noticed a slight drop in engine manifold pressure, but the airplane was still able to climb. He chose to divert to a nearby airport, and shortly thereafter, noticed that the oil pressure caution light had illuminated and oil pressure was rapidly decreasing. The engine subsequently lost total power. The pilot performed a forced landing on a residential street, during which the airplane impacted a tree and a parked pickup truck. The airplane was consumed by a postimpact fire. Examination of the airplane after it was recovered from the accident site revealed one missing bolt and three loose bolts associated with the oil line adapter fittings on the engine turbocharger. Police photos confirmed that the missing bolt was missing from the top oil line fitting at the accident site before the wreckage was moved. Three witnesses along the route of flight saw smoke emanating from the airplane, consistent with leaking oil contacting hot exhaust components during the flight. An engine examination revealed signatures consistent with an oil starvation event. The No. 5 connecting rod separated from the crankshaft, and the No. 5 connecting rod journal exhibited lubrication distress and smeared bearing material. The other connecting rod journals and main bearing journals showed varying degrees of discoloration from heat and lubrication distress. The engine oil and filter were replaced in the days before the accident. Additionally, the maintenance technician also replaced exhaust/muffler hardware in the vicinity of the missing and loose oil line fitting bolts; however, this would not have required loosening the oil line fitting bolts. The technician stated that there were no fluid leaks identified during a post-maintenance engine run and leak check. The pilot reported that when he retrieved the airplane after maintenance, he checked the oil and performed a thorough preflight inspection before takeoff and did not observe any discrepancies during a 50-mile flight the day before the accident. Based on the available evidence, the engine lost total power due to an oil starvation event as a result of the loose turbocharger oil line fittings, which allowed for an oil leak. Although the engine had undergone recent maintenance in the vicinity of the loose oil line fittings, the associated maintenance tasks did not require the those fittings to be loosened or removed. As such, the investigation could not conclusively determine how and when the oil line fittings became loose.

Verbatim NTSB analysis and probable cause from the NTSB dataset