YORBA LINDA, CA, USA
N6377G
Cessna 150K
The student was descending toward the destination airport when the engine began to run rough, then it quit altogether. The CFI took over and attempts to remedy the engine power loss were unsuccessful. During the subsequent forced landing on a city street, the aircraft collided with ground obstructions. Disassembly and examination of the engine revealed a shop rag inside the accessory case in the upper right quadrant just under the starter motor cover plate and entwined in the accessory gears. The oil suction screen was collapsed and heavily contaminated with cloth and lint fragments. The oil sump suction tube inlet was found completely plugged by rag fragments. Typical oil starvation failure signatures were noted to the internal crankshaft pins, rod ends, and bearings. The last entry in the engine logbook was dated July 16, 1998, 7 hours prior to the accident, and listed the removal and replacement of the starter.
On July 28, 1998, at 1953 hours Pacific daylight time, a Cessna 150K, N6377G, collided with ground obstructions during a forced landing on a city street in Yorba Linda, California. The forced landing was precipitated by a loss of engine power as the aircraft was descending toward the Fullerton, California, airport. Visual meteorological conditions prevailed at the time and no flight plan was filed for the operation, which was conducted under 14 CFR Part 91 of the Federal Aviation Regulations. The aircraft, owned and operated by the flight instructor, sustained substantial damage. The commercial pilot/flight instructor and the dual primary student were not injured. The flight originated from the Fullerton airport at 1830 for a local area dual instructional flight. In a telephone interview conducted on July 29, 1998, the instructor reported that the flight departed the Fullerton airport and proceeded to Riverside, California, for touch-and-go landing practice. He stated that the aircraft was at 1,800 feet agl en route back to Fullerton when carburetor ice symptoms began, which included a minor loss of rpm accompanied by engine roughness. The instructor applied carburetor heat and leaned the mixture, which momentarily improved the power output. Shortly thereafter, the engine quit altogether with a great deal of roughness and the instructor landed the aircraft on a city street. During the landing rollout, the aircraft collided with a light pole, a tree, and a concrete block wall. The Safety Board examined the engine and airframe on August 5, 1998, at the facilities of Aircraft Recovery Services, Compton, California, following recovery of the aircraft. The carburetor/induction air box was crushed, with the carburetor heat butterfly found trapped in the ON position. The Bracket air filter was clean and remained in its bracket. The carburetor was broken from the crankcase mounting pad. The mixture arm was separated from its shaft, with an impact mark noted on the side of the arm. No foreign deposits were found in the bowl. The metal floats and one-piece venturi were intact. Both magnetos were tight in their clamps and produced sparks at the ignition lead spark plug cap ends in firing order with hand rotation of the propeller. Electrical continuity was established for the magneto switch, and, between the switch and magnetos. The top and bottom spark plugs exhibited moderate ovaling signatures, with gaps about 0.017 inches. In comparison to the Champion Check-A-Plug chart, the plugs from cylinders 1, 3, and 4 displayed normal combustion coloration; heavy soot deposits were noted on the No. 2 cylinder top and bottom plugs. Hand rotation of the crankshaft yielded accessory gear train continuity. Equal lift was observed on the valve stems for cylinders 2, 3, and 4. The No. 1 cylinder exhaust valve was stuck in the full open position. Compression was noted in cylinders 3 and 4. Very weak compression was obtained for cylinder 2 and none for cylinder 1. Visual examination through the spark plug holes of the No. 1 cylinder head revealed that the piston would not move. The oil sump was removed from the case and drained through a screen mesh filter. The following items were recovered from the sump: 1) bent, distorted and mechanically damaged rod end cap; 2) about 1/2 of a rod end cap bolt, which was elongated and necked; 3) fragments of ring(s); 4) oil wiper spring fragments; and 5) rag fragments. The magnetos were removed from the accessory case. An oil shop rag was visible inside the accessory case at the 2 o'clock position, just under the upper right quadrant of the starter motor cover plate, intertwined in the accessory gears (see photos). The oil suction screen was collapsed and heavily contaminated with cloth and lint fragments. The oil sump suction tube inlet was found completely plugged by rag fragments. No metal particles or scoring was noted during an internal examination of the oil pump rotors and housing; however, rag fragments were found inside. The remainder of the engine was completely disassembled for internal examination. The No. 1 rod was liberated from the crankshaft but remained secured to the piston. The crankshaft end was peened and mechanically damaged. The No. 1 rod crank pin on the crankshaft exhibited scoring and heat distress. In comparison to No.1, the No's. 2 and 3 crank pins displayed minor scoring and heat exposure. The No. 4 crank pin was heavily scored and heat distressed, with bearing material extruding between the rod and the crankshaft cheeks. The crankcase rear main bearing saddle exhibited heat distress. The cylinder skirts for the No's. 1 and 2 cylinders were peened over, with displaced case material found jamming the No. 1 cylinder exhaust lifter in the OPEN position. The maintenance records were reviewed in detail, with pertinent page copies appended to this report. The Continental O-200A engine, serial number 205634-70A, had accrued a total time in service of 3,757 hours. The last major overhaul was accomplished on July 25, 1997, 353 hours prior to the accident. The last entry in the engine logbook was dated July 16, 1998, 7 hours prior to the accident, and listed the removal and replacement of the starter. There were no entries in the logbook between the major overhaul and the starter replacement detailing either the removal of accessories from the accessory case or entry into the accessory case.
An oil starvation failure of the engine due to the mechanic's inadequate maintenance installation and quality control procedures, which resulted in a shop rag being inadvertently left inside the accessory case when the starter was changed 7 hours prior to the accident.
Source: NTSB Aviation Accident Database
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