CEN24FA212

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.

On June 7, 2024, about 0930 mountain daylight time, a Beech V35A airplane, N150WR, was destroyed when it was involved in an accident near Arvada, Colorado. The pilot was not injured. Two passengers sustained serious injuries, and a third passenger was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that he and the passengers intended to fly from Centennial Airport (APA), Englewood, Colorado, to Northern Colorado Regional Airport (FNL), Fort Collins, Colorado, which was located about 53 nautical miles (nm) north of APA. A preflight inspection and engine runup revealed no anomalies. Recorded ADS-B flight track data indicated that the airplane departed about 0915. The pilot stated that the takeoff and climb were uneventful until reaching an altitude of 7,000 ft, where he noted a “slight drop in manifold pressure”; however, the airplane was still able to climb. About 0927, the pilot sent a text message to his mechanic, who was based at FNL, stating, “…I’m in air headed home and I’m only getting 20” manifold pressure at full throttle. Can you guys look at it when I land.” The pilot chose to divert to Rocky Mountain Metro Airport (BJC), Broomfield, Colorado, about 24 nm northeast of APA. The pilot contacted the tower controller about 0928 and reported that his “oil light” was on and that he was losing oil pressure. The controller instructed the pilot to make a straight-in approach to runway 30R, which the pilot acknowledged. The pilot then informed the controller that the airplane was “losing power quickly” and that he “might have to put it down somewhere.” When the controller asked the pilot if he had located a safe landing site, the pilot indicated that he was “trying to find a field or a park” and that he had “something in sight.” The pilot stated that he selected a residential street as a forced landing site and chose not to extend the landing gear to avoid hitting obstructions. The airplane impacted the pavement “fairly hard.” The pilot stated that a fire immediately started on the left wing, and spread quickly to the right wing. Three eyewitnesses near the flight path of the airplane described an airplane traveling past their residences trailing smoke. One witness said the smoke was white. Each witness described the engine sound differently, but their statements were consistent with the engine being in distress. Examination of the accident site revealed that the airplane impacted a tree before landing on a street with the landing gear retracted. The airplane struck a parked truck and came to rest in the front yard of a residence about 500 ft from the tree. The majority of the airplane was consumed by a postimpact fire. A postaccident examination of the engine revealed that the oil line adapter fitting to the turbocharger was missing one bolt and that the other was loose, as shown in figure 1. Figure 1. Oil supply line fitting with one bolt missing and the other wasloose. Both bolts that normally secure the adapter fitting for the oil return line to the engine on the turbocharger were also found loose. No other anomalies other than the missing and loose bolts were noted. A review of police photos confirmed that one bolt was missing from the top oil line fitting at the accident site before the wreckage was moved. as shown in figures 2-3. Figure 2. Police photo of the left side of the engine. Oil supply line fitting location is circled in blue. Figure 3. Previous police photo zoomed in and exposure adjustments made for clarity. Attachment bolt is missing from the oil line fitting before aircraft wreckage recovery. An engine teardown examination revealed that the No. 5 connecting rod separated from the crankshaft. 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 consistent with heat and lubrication distress. Review of maintenance documentation revealed no logbook entries related to the oil line fittings on the turbocharger during the previous five years. The most recent annual inspection was completed August 1, 2023, at a tachometer time of 6,091.2 hours. Maintenance personnel reported that the pilot had dropped off the airplane for an oil change three days before the accident. A statement from the individual who performed the work indicated that he removed and inspected the oil filter, replaced 4 bolts, washers, and nuts on the front muffler clamp, and torqued as required. Some of the hardware the technician replaced was in the vicinity of the oil line fittings on the turbocharger. Replacement of the exhaust hardware would not have required the technician to loosen the bolts on the oil line fittings. According to the technician, there were no observed fluid leaks during a post-maintenance engine run and leak check. The pilot retrieved the airplane from his maintenance provider at FNL the day before the accident. He performed a lengthy preflight and completed one touch-and-go takeoff and landing before departing to APA. According to the pilot, the airplane performed well during the flight.