WPR17LA172

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.

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.

The 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. The 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. The 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 en