Llano, CA, USA
N6109R
CESSNA T210F
The pilot had flown the airplane uneventfully on the outbound leg of a cross-country flight. On the return leg, the pilot noticed that he was unable to achieve full manifold pressure and that the engine was "running roughly." He stopped at an interim airport, where an aircraft mechanic examined the airplane but was unable to find any problems with the airplane or engine. The pilot subsequently departed to continue the trip home. While in cruise flight, he noticed that the oil pressure had dropped to 0 psi. The pilot retarded the throttle, declared an emergency with air traffic control, and diverted toward a nearby airport. The engine then lost total power. The airplane was unable to reach the diversion airport and sustained substantial damage to the fuselage during the forced landing. Preliminary examination of the wreckage revealed that the engine was devoid of oil; no obvious leaks or other failures were apparent. Further examination of the engine revealed that the No. 1 connecting rod bearing and cap assembly had failed catastrophically due to oil starvation and that the liberated or partially liberated components caused significant internal damage to the engine. In addition, many internal engine components exhibited thermal distress signatures due to oil starvation. Detailed examination of the turbocharger revealed significant damage to the compressor and turbine blades, grossly excessive axial and radial freeplay of the compressor and turbine rotors, and fracture separation of the two rotors from one another. In addition, the turbocharger bearing housing, turbine outlet case, and turbine blades displayed coked oily/dirty residue. This evidence indicated that the engine oil was depleted by leaking and/or burning via the turbocharger. The turbocharger manufacturer guidance specified certain inspections and that the turbocharger overhaul interval should coincide with, but not exceed, the time between overhaul (TBO) (hours in service) published by the engine manufacturer. The engine manufacturer's published TBO was 1,400 hours. However, the engine manufacturer guidance explicitly excluded engines with parts not supplied by the engine manufacturer, which was the case for this engine. The airplane maintenance records showed that the turbocharger was overhauled 13 years before the accident and had accumulated about 1,974 hours since that overhaul. The records did not document any relevant maintenance actions or inspections of the turbocharger since its overhaul. Given this information, it is likely that the turbocharger failure was the result of improper and/or incomplete maintenance and inspection. The turbocharger failure completely depleted the engine oil during the accident flight, and the oil depletion resulted in a catastrophic internal failure of the engine and a complete loss of engine power. There was insufficient evidence to determine when the oil depletion began or how long that process took.
HISTORY OF FLIGHTOn July 31, 2017, about 1745 Pacific daylight time, a Cessna T210F airplane, N6109R, was substantially damaged during a forced landing near Crystal Airport (46CN), Llano, California. The private pilot and passenger were not injured. The airplane was registered to and operated by the pilot as a Title 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions prevailed at the accident site and no flight plan was filed for the cross-country flight that departed from Modesto, California at 1530, and was destined for Hemet, California. The pilot reported that he flew the airplane uneventfully to northern California. On the return leg, he noticed that he was unable to achieve full manifold pressure, and that the engine was "running roughly." He stopped at an interim airport, where an aircraft mechanic examined the airplane. The mechanic was unable to find any problems with the airplane or engine. The pilot and passenger departed in the airplane to continue their trip home. While in cruise, the pilot noticed that the oil pressure had dropped to 0 psi. The pilot retarded the throttle, declared an emergency with air traffic control, and diverted towards 46CN. The engine was no longer able to develop any power, and near the end of the descent, the pilot recognized that the airplane would not be able to reach the diversion airport, forcing him to land in the desert. At an unspecified but low altitude, the pilot determined that the terrain appeared suitable for a landing gear down landing, and he selected the landing gear handle to the extended position. The airplane touched down while the landing gear was still in transit. The airplane came to rest upright, but with the landing gear deformed and collapsed. PERSONNEL INFORMATIONThe pilot held a private pilot certificate with an airplane single engine land rating. The pilot reported that he had a total flight experience of about 1,323 hours, including about 938 hours in the accident airplane make and model. His most recent flight review was completed in December 2015, and his most recent Federal Aviation Administration (FAA) third-class medical certificate was issued in August 2015. AIRCRAFT INFORMATIONThe airplane was manufactured in 1965, and was equipped with a Continental TSIO-520 series engine. The pilot had purchased the airplane in the spring of 2011. According to the pilot, the airframe had a total time (TT) in service of about 3,534 hours, and the engine had a TT of about 1,974 hrs. The most recent annual inspection was completed in July 2017. The airplane was equipped with a JPI brand EDM-700 engine monitor. That device was sent to the NTSB Recorders Laboratory in Washington DC for data download. METEOROLOGICAL INFORMATIONThe 1755 automated weather observation at Gray Butte Field Airport, Palmdale, California located about 8 miles northeast of the accident site, included wind from 020o at 10 knots, visibility 10 miles, scattered clouds at 16,000 ft, temperature 39oC, dew point 0oC, and an altimeter setting of 29.93 inches of mercury. AIRPORT INFORMATIONThe airplane was manufactured in 1965, and was equipped with a Continental TSIO-520 series engine. The pilot had purchased the airplane in the spring of 2011. According to the pilot, the airframe had a total time (TT) in service of about 3,534 hours, and the engine had a TT of about 1,974 hrs. The most recent annual inspection was completed in July 2017. The airplane was equipped with a JPI brand EDM-700 engine monitor. That device was sent to the NTSB Recorders Laboratory in Washington DC for data download. WRECKAGE AND IMPACT INFORMATIONThe touchdown location was flat, sparsely vegetated desert terrain. All three landing gear had collapsed during touchdown. The lower cowl, fuselage underside, and fuselage aft of the cabin all sustained crush, buckling, or scraping damage. The wings and empennage were undamaged, and the cockpit/cabin remained intact. Law enforcement personnel and two FAA inspectors responded to the accident site later that same day. The inspectors reported that there was sufficient fuel in the fuel tanks for continued operation, but that the engine oil sump was devoid of oil. Visual examination of the engine compartment and airplane exterior did not reveal any indications of significant oil leaks or venting/dumping, or any pre-impact failures that could account for an oil loss. The pilot reported that the engine had just completed a top-overhaul about 11 hours prior to the accident, and that the oil quantity was checked and verified full prior to the departure on the accident leg. The airplane was recovered to a secure facility for detailed examination. The airframe and engine were examined by representatives of Continental Motors (CMI) and the NTSB at the recovery facility on August 9-10, 2017. The wings, vertical stabilizer and elevator had been removed by the recovery crew. The engine, propeller and engine cowlings remained intact and in place. An examination of the external fuselage, including the belly, revealed the presence of oil and/or grease on some of the surfaces, which had then resulted in an accumulation of dust. The pilot reported that he personally last cleaned the airplane underside ("belly") on July 30, 2017, the day prior to the accident. The oil/grease was generally consistent with normal in-service levels, particularly on the fuselage sides, but not consistent with a recent, thorough cleaning. The belly accumulation was slightly heavy, with several localized accumulations, but did not appear consistent with an oil leak or overboard venting that would account for the complete loss of engine oil. No oil was dripping from the fuselage. Recovery personnel stated that there was no oil staining on the ground at the accident site, and that no oil had leaked or dripped onto the trailer used to recover the airplane. There was some evidence of possible oil on the exterior cowling near the cooling air inlets, and its source was not obvious, nor was it consistent with the complete loss of oil. No oil residue was observed on the wings, horizontal stabilizers, or elevators. There were no obvious indications of any catastrophic failure of the engine or any of its components, nor were any holes observed in the crankcase. With the exception of the right cowl flap and right lower cowling area, there were no indications of excessive oil presence in the engine compartment. The source of the oil stains was not positively determined, but it was directly below the No. 1 cylinder rocker assembly, which leaked oil when the rocker cover was removed. It was also approximately below the turbocharger and externally-mounted oil filter. There were no indications of any separation failure or disconnection of any electrical or fluid lines in the engine compartment. The electronic "Horizon" brand tachometer indicated that the "Tachometer Time" was 3,534 hours (no decimal point). The engine dataplate indicated the following: Model: TSIO-520-C (overstamped with a "C" and an "M") Serial: 140012-5-C. Continental Motors records indicate that the engine serial number was shipped new to Cessna in May 1965 as a model TSIO-520C. The "C" overstamp denotes a "field conversion" (modified by other than CMI) of the engine, and the "M" denotes the resulting (new) engine model. The CMI-manufactured TSIO-520C engine is rated at 285 hp at 2700 rpm. The CMI-manufactured TSIO-520M engine is rated at 310 hp for takeoff (5 minutes maximum) at 2700 RPM, 285 hp continuous operation, and 230 hp recommended cruise. The accident airplane data plate was not modified to show these (or any) changes to the power rating. The airplane had "RAM T210" decals on the cowling. RAM Aircraft is a known converter of CMI engines and T210 airplanes. A 10/22/04 maintenance record entry by "Corona Cylinder and Engine Overhaul, Inc" for an engine overhaul cited "Ram STC #SA2689SW" at the top. According to a representative of RAM Aircraft, "RAM did sell STC SA2689SW to N6109R in November 2004. The STC was sent to a company in Henderson, Nevada. SA2689SW is an airframe STC which allows the installation of the later 310hp TSIO-520-M or R engine" in place of the C model of the same engine. A maintenance records entry dated 11/7/04 contained the text "installed new TSIO-520 engine serial no. 1400125C." An FAA Form 337 for this airplane dated 12/27/05 stated "Installed Teledyne Continental engine- TSIO – 520 – M, SN = 140012-5-C with RAM modification under STC# SA2689SW…" This 337 was accompanied by seven other 337s for other items; all carried the same date (12/27/05) and all were signed by the same technician. Review of the airframe log revealed that a corresponding entry for those seven items was present in the airframe log, and that the only other entry between the 11/7/04 and 12/27/05 entries was for an annual inspection, with a date of 12/2/05. The investigation was unable to determine why the engine installation 337 was dated a year after the engine was installed. With all spark plugs still installed, the engine was free to rotate smoothly when the propeller was manually rotated in its normal rotation direction, and appeared to provide less resistance than normal. Both magnetos remained installed and intact, and their impulse couplings audibly snapped (consistent with normal functioning) when the engine was manually rotated in its operational rotation direction. The top spark plugs were removed and inspected. When compared to a Champion Spark Plug "Check A Plug" chart, all top spark plugs appeared to have normal wear, with a slightly dark coloration. All spark plugs had an odor of fuel present. The porcelain insulator of the No. 1 cylinder top spark plug was found fracture-separated. When the engine was manually rotated, thumb compressions were achieved on all cylinders except No. 1. A borescope inspection showed that when the engine was manually rotated, the piston did not move in the cylinder, the exhaust valve was fixed in the open position, and the intake valve was fixed in the closed position. Crankshaft continuity was confirmed by rotation of the starter adapter drive on the rear of the engine. The No. 1 cylinder rocker box cover was removed. Both rocker arms were intact. The exhaust valve rocker arm was depressing the valve, and the spring tension was not relieved when the engine was rotated. The intake valve pushrod could be seen inside its pushrod tube, but the pushrod did not extend to the rocker arm; there was an approximate ¾ inch gap between the two. The cause was not able to be determined by observation. The three-blade constant speed propeller remained attached to the engine crankshaft propeller flange. All three propeller blades exhibited smooth rearward bending at about their 2/3 span points, consistent with ground contact with little or no engine power. No torsional twisting of the blades was observed. All three propeller blades were free to rotate within the propeller hub. The engine was then removed from the airplane, and shipped to Continental Motors in Mobile, Alabama for detailed examination. Continental Motors Examination The engine was uncrated and stripped of most external components in preparation for accessing the engine case interior. No significant non-impact anomalies were noted. All fuel system components were free of pre-impact damage or evidence of any malfunctions. The external housing for the oil quantity indication rod was observed to have 3 segments of flexible tubing/sheathing, whereas the manufacturer's version is a single-piece aluminum tube with a single flexible fitting/sheath at its base, where it installs into the crankcase. The overall length of the as-found housing assembly was about 15.5 inches, while the design length of the manufacturer's housing was about 13.1 inches. The as-found housing excess length would result in an erroneously low oil quantity reading. Continental representatives reported that there were no known adverse effects of slightly overfilling the oil sump. The oil filter was cut open. The filter element had trapped numerous metallic particles and fragments. The oil pump assembly was removed and partially disassembled. The assembly included two pumps; the scavenge pump and the main pump. Both pumps were gear-type pumps, and both were intact and rotated freely. No gears displayed any damage. The chamber walls of the main pump displayed significant rotational scoring, consistent with the passage of small metallic particles that were harder than the aluminum chamber walls. The pump did not exhibit any signs of leakage or damage other than that described. None of the accessory gears exhibited any damage, and all were properly safetied. The oil sump was removed, and the case halves were separated. The lower cap for the No. 1 connecting rod was found separated in the oil sump. The cap was blackened, consistent with thermal distress, and severely damaged. One of the two cap bolt/nut assemblies was found in the oil sump. The bolt was fractured in two, and retained its cotter-pin safetied nut. The bolt was also blackened, and exhibited severe elongation and necking. The No. 1 connecting rod remained attached to its piston pin and plug assembly (commonly referred to as the wrist pin) and piston. The rod moved freely on the wrist pin. The crankcase bores for the two hydraulic lifters for the No. 1 cylinder were partially fractured, with their liberated sections found in the oil sump The pushrods remained in place. The crankcase interior in the vicinity of the No. 1 connecting rod exhibited gouges and scrapes. This mechanical damage was consistent with the flailing of the failed connecting rod end. The crankshaft journal for the No. 1 connecting rod was blackened and scored, gouged, and peened. Its bearing was not located/identified. The oil sump contained a significant amount of metal flakes/chips of at least three colors: black, brownish-copper, and silver-gray. These fragments were consistent with remnants of the No. 1 bearing cited above. The other 5 connecting rods showed varying indications of minor thermal distress. The connecting rod bearings displayed varying indications of wear and distress. The two aft cylinder skirts (No. 1 & No. 2) exhibited some impact and scoring damage, consistent with mechanical damage from the liberated No. 1 connecting rod components. All pistons were intact, with no signs of distress. All observed engine internal damage was consistent with oil starvation or exhaustion, or its consequent results, but no obvious reasons for that condition were observed. There was insufficient evidence to determine the rate or duration of the oil depletion. The cockpit instrumentation included an oil temperature gauge, but its pre-accident functionality and accuracy were not determined. Review of the recorded accident flight engine oil temperature data from a system separate from the cockpit oil temperature gauge did not reveal any abnormal temperature behaviors that would have alerted the pilot to the oil depletion problem. Engine TBO Information According to the April 2016 edition of the Continental Motors Standard Practice Maintenance Manual, "Continental Motors (CM) provides operational limitations and instructions…along with the requirements for continued airworthiness as specified in the engine Operator Manuals, Maintenance Manuals, Overhaul Manuals, and Service Documents. The Time Between Engine Overhaul provided in this document applies only to engines that have been operated and maintained in accordance with these instructions. Engine mounted components and accessories require overhaul at the same hourly and calendar intervals as the engine, unless otherwise specified by the component or accessory manufacturer." For TSIO-520 C and M model engines, the manual specified a TBO of 1,400 hours in service or 12 years, whichever occurs first. The manual also stated that "Continental Motors does not provide a TBO for engines that have been…Assembled with parts not supplied by Continental Motors." The airplane maintenance records indicated that in April 2009, all six cylinders were replaced with Superior Air Parts part number SA52006-A22P cylinders, which were not supplied by Continental Motors. Thus,
A failure of the turbocharger that resulted in complete depletion of the engine oil and catastrophic internal failure of the engine. Contributing to the accident was improper and/or incomplete maintenance and inspection of the turbocharger.
Source: NTSB Aviation Accident Database
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