Grayslake, IL, USA
N5300A
CESSNA T210N
While en route on an instrument flight rules cross-country flight, the pilot noticed that the engine oil pressure had decreased; the oil pressure gauge was indicating in the yellow range, but the other engine instruments were showing normal indications. During the descent to landing, when the airplane was about 2,500 ft mean sea level, the pilot heard a "loud bang" from the engine, and smoke filled the cockpit. After declaring an emergency and requesting vectors from air traffic control to the nearest airport, the pilot executed an emergency landing just short of the runway in a wet, grassy area; the airplane slid, came to rest upright on the runway, and sustained substantial damage. A postaccident examination of the engine revealed two large holes in the crankcase and mechanical damage on the inside of both crankcase halves. The No. 4 connecting rod, which exhibited thermal damage signatures, had separated from the crankshaft and thus punctured the holes in the crankcase. The No. 4 connecting rod bearings were significantly damaged consistent with lack of lubrication, and all of the connecting rod bearings displayed smear-type signatures consistent with lubrication distress. Gouging was found inside the oil pump consistent with the passage of hard particles during engine operation; it is likely that the metal pieces from the damaged engine passed through the oil pump and created the gouges. The turbocharger's oil scavenge check valve spring was found broken, which resulted in the check valve not closing automatically; it would not restrict oil traveling from the turbo to the scavenge pump. The pilot reported a normal oil level before the flight and no signs of oil leaking. Further, according to the engine manufacturer, an open check valve would not have any effect on oil consumption during engine operation; thus, it was not a factor in this accident. The reason for the lack of lubrication could not be determined.
HISTORY OF FLIGHTOn November 12, 2017, about 1730 central standard time, a Cessna T210N airplane, N5300A, experienced a loss of engine power and landed short of runway 9 at Campbell Airport (C81), Grayslake, Illinois. The commercial rated pilot, who was the sole occupant, was not injured, and the airplane sustained substantial damage. The airplane was registered to and operated by Runzel Brothers Aviation LLC under the provisions of Title 14 Code of Federal Regulations Part 91 as a business flight. Night instrument meteorological conditions prevailed at the time of the accident, and the flight was operated on an instrument flight rules (IFR) flight plan. The airplane departed Pierre Regional Airport, Pierre, South Dakota, about 1435, and was en route to Chicago Executive Airport (PWK), Wheeling, Illinois. The pilot reported that during the en route portion of the IFR flight, the engine indications were all normal. About 1715, he noticed the oil pressure had decreased into the yellow arc, but all other instruments were still showing normal indications. Shortly after ,the air traffic controller instructed the pilot to descend to 2,500 ft mean sea level (msl). When the airplane reached 2,500 ft, the pilot heard a "loud bang" from the engine, and the cockpit filled with smoke. He decleared an emergency and requested vectors to the nearest airport, C81. About 700 ft above ground level (agl), he descended out of the cloud layer and identified the runway lights. The pilot was very familiar with C81 and planned to land in a wetland area short of runway 9 since he could not glide the airplane all the way to the runway. He left the landing gear retracted and landed in the wetland area, slid across a flat wooden bridge as seen in figure 1, and came to rest on runway 9. Figure 1 – Ground scars in the dirt and across a bridge AIRCRAFT INFORMATIONThe airplane was powered by a six-cylinder Continental Motors IO-550-P6B engine, serial number 1005420. The engine was modified via Vitatoe Supplemental Type Certificate (STC) SA02918CH, which converted the engine to a turbo-normalized induction system. According to the maintenance records, the modified engine was installed on the accident airplane on April 2, 2012. The last maintenance logbook entry was on noted on July 27, 2017, at a tachometer time of 1,010.1 hours. The entry indicated compliance with airworthiness directive AD 71-09-07R1, which was an exhaust system inspection. The entry also noted a new fuel injector and a new cylinder head temperature probe were installed. The last oil change was performed on June 29, 2017, at a tachometer time of 1,001.73. The last 100-hour engine inspection was performed on November 1, 2016, at the same time the engine was reinstalled after a top overhaul. The pilot stated that he couldn't remember the exact oil level and didn't recall anything out of the ordinary during the preflight inspection. He also did not recall any oil on the ramp underneath the airplane or any white smoke upon engine start up. AIRPORT INFORMATIONThe airplane was powered by a six-cylinder Continental Motors IO-550-P6B engine, serial number 1005420. The engine was modified via Vitatoe Supplemental Type Certificate (STC) SA02918CH, which converted the engine to a turbo-normalized induction system. According to the maintenance records, the modified engine was installed on the accident airplane on April 2, 2012. The last maintenance logbook entry was on noted on July 27, 2017, at a tachometer time of 1,010.1 hours. The entry indicated compliance with airworthiness directive AD 71-09-07R1, which was an exhaust system inspection. The entry also noted a new fuel injector and a new cylinder head temperature probe were installed. The last oil change was performed on June 29, 2017, at a tachometer time of 1,001.73. The last 100-hour engine inspection was performed on November 1, 2016, at the same time the engine was reinstalled after a top overhaul. The pilot stated that he couldn't remember the exact oil level and didn't recall anything out of the ordinary during the preflight inspection. He also did not recall any oil on the ramp underneath the airplane or any white smoke upon engine start up. WRECKAGE AND IMPACT INFORMATIONThe airplane landed in a field about 300 ft west of the runway 9 threshold. During the landing, the airplane sustained damage to the fuselage and elevator. The pilot stated that after the accident he recalled oil covering the bottom fuselage and on the runway where the airplane came to rest. After the accident, the engine was removed from the airframe and shipped to the manufacturer's facility for a detailed examination, which was conducted under the supervision of a National Transportation Safety Board investigator. The examination revealed no evidence of ground impact or fire damage. The crankcase exhibited two large holes; one was located near the No. 4 cylinder and the other was in between the Nos. 3 and 5 cylinders. All six cylinders remained attached to the crankcase with the No. 4 cylinder displaying mechanical damage to the cylinder skirt and two of the attachment studs had broken free from the crankcase. The inside of both the crankcase halves displayed mechanical damage with the most damage concentrated near the two holes. The No. 4 connecting rod had separated from the crankshaft and displayed thermal damage signatures. All of the connecting rod bearings exhibited smear type signatures on the bearing surfaces; the No. 4 bearings were significantly damaged as seen in figure 2. Figure 2 – Damaged No. 4 connecting rod and bearings There were no signs of fretting on the bearing supports or evidence of a bearing shift. The oil galleys did not reveal any blockages. The oil sump and the oil pickup tube and screen all remained intact, undamaged, and contained a significant amount of metallic debris. The oil pump remained intact, undamaged, and internally contained a few metallic flakes and a small amount of gouging along the oil pump housing. The oil filter remained attached to the oil filter adapter with no anomalies noted. The oil filter pleats contained a significant amount of metallic debris. The oil cooler remained intact with no signs of an oil leak and no anomalies noted. There were no blockages noted in any of the oil lines. Since the oil lines had been removed for shipping, the b-nuts could not be checked for tightness. The turbocharger oil scavenge check valve spring was found broken, and the flapper valve would not close automatically. No other anomalies were noted with the engine. ADDITIONAL INFORMATIONEngine Data An AuRACLE CRM 2100 engine monitor was installed on the airplane. The extracted data revealed that the oil pressure remained steady for about the first 2 hours of the flight; after 2 hours, the oil pressure began to decrease. The oil pressure decreased steadily from 51 psi to a low of about 13 psi over the course of about 42 minutes. When the oil pressure decreased below 30 psi, the oil temperature began to increase steadily until the total loss of engine power. Turbocharger Oil Scavenge Check Valve According to the STC owner and the turbocharger manufacturer, the broken check valve spring that wouldn't allow the flapper valve close automatically, would allow oil to enter the turbo after engine shutdown. The oil could leak into the compressor/induction and turbine/exhaust areas and small batches would get consumed during each subsequent engine start. Typical signs of this issue include oil leaking from the exhaust pipe and pooling under the airplane and white smoke during engine start. The broken spring would not have caused a restriction from oil going from the turbo to the scavenge pump. According to the engine manufacturer, usually when a scavenge check valve isn't closing properly, while the airplane is sitting on the ground, the oil that is in the line is allowed to pool in the turbocharger. This would be a small amount of oil that gets lost while the airplane is sitting. However, during engine operation, an open check valve would not have any effect on oil consumption.
The failure of the No. 4 connecting rod due to inadequate oil lubrication for reasons that could not be determined because the postaccident engine examination did not reveal any anomalies that would have caused a lack of lubrication.
Source: NTSB Aviation Accident Database
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