KERRVILLE, TX, USA
N761FM
Cessna T210M
The airplane was on its climb to cruise when the engine lost power. The pilot performed a forced landing short of the runway in rough and uneven terrain. An examination of the engine revealed that the #1 cylinder piston was seized in the cylinder, the piston rings were broken, the piston head was deteriorated around the edge down to the top compression ring with a portion of the ring missing, metal was deposited on the intake valve seat, and the intake valve was stuck in the open position. The #1 cylinder dome was damaged and scaring was noted on the cylinder walls. Aluminum particles were found in the #1 cylinder spark plugs and embedded in the #1 cylinder combustion chamber and internal components of the engine. According to the manufacturer, no discrepancies were found with the engine components that 'would have caused detonation/preignition to [the] number 1 cylinder.' The cylinder met the SAE chemistry requirements. The manufacturer's metallurgist stated that 'the burning of the piston crown most likely is the result of either detonation or pre-ignition.'
On July 2, 1996, at 1430 central daylight time, a Cessna T210M, N761FM, operated by a private individual under Title 14 CFR Part 91, impacted terrain following a power loss during the cruise climb from the Kerrville Municipal Airport, Kerrville, Texas. The private pilot and the three passengers were not injured and the airplane sustained substantial damage. Visual meteorological conditions prevailed for the cross country flight and a flight plan was not filed. The flight originated from Kerrville about 5 minutes before the accident. During personal interviews, conducted by the investigator-in-charge (IIC), and on the Pilot/Operator Aircraft Accident Report, the pilot reported that the airplane was topped with 31 gallons of 100LL fuel prior to the flight. Power indications were within limits during the taxi, run up, and the full power takeoff from runway 20. During the downwind departure, as the airplane climbed through 2,500 feet MSL, there was a transient drop in the power and fluctuations in the fuel flow and manifold pressure. The pilot performed the emergency checklist; however, the fuel flow and manifold pressure continued to decrease. The pilot initiated a 180 degree turn toward runway 30. During the final approach at 500 feet AGL, the pilot realized that the airplane would not make the runway. There was no suitable terrain for an emergency landing, and the pilot decided to land the airplane with the gear retracted. The airplane landed approximately 150 feet short of the threshold and skidded onto the runway where it slid approximately 300 feet before coming to a stop. The pilot and passengers exited the airplane through the cockpit doors. In retrospect, one of the passengers noted the engine "didn't sound like she was use[d] to hearing" during the climb. The pilot was wearing a noise-attenuating headset and did not "appreciate any abnormality." The FAA inspector examined the airplane and found structural damage to the wing spars and fuselage. An examination of the engine revealed that the #1 cylinder intake valve was stuck in the open position, the piston rings were broken, the piston head was deformed, and metal was deposited on the intake valve seat. The #1 cylinder and fuel injection lines were removed for examination. Continuity was confirmed to the other cylinders. Four airplanes were fueled from the same fuel truck and no discrepancies have been reported with those aircraft. On July 10, 1997, at Kerrville, Texas, the engine and airframe manufacturer's representatives examined the airplane under the surveillance of the FAA inspector. The #1 cylinder piston was seized in the cylinder and the intake valve was stuck in the open position with the cylinder dome damaged and scaring on the cylinder barrel. There was a metal buildup around the intake valve stem. The piston was deteriorated around the edge down to the top compression ring with a portion of the ring missing, and the #1 cylinder connecting rod was bent. The oil pump was intact and the gears, which were free to rotate, were coated with oil and contained metal particles. Both magnetos sparked at all their terminals during hand rotation. The #1 cylinder spark plugs contained metal particles. The drive coupling on the fuel pump was free to rotate, and the throttle and mixture controls were connected at the fuel control assembly. The fuel manifold valve was disassembled, and the diaphragm and spring were not damaged and the fuel screen was free of debris. The turbocharger shaft rotated and the edges of the compressor inlet vanes were found to be nicked. Flight control continuity was confirmed. No pre-impact anomalies were found with the airframe. On August 30, 1997, at Mobile, Alabama, the engine was examined by the manufacturer under the surveillance of the FAA. The #1 cylinder exhibited aluminum embedded in the upper portion of the cylinder, and the cylinder walls exhibited scoring. The heat pattern on the #1 cylinder piston progressed from the upper portion of the piston down the side of the piston and eroded the steel insert. Aluminum particles were embedded in the combustion chamber, and internal components of the engine were contaminated with aluminum. The manufacturer stated that no discrepancies were found with the engine that "would have caused detonation/preignition to [the] number 1 cylinder." The #1 cylinder was examined by Teledyne Continental Motor's metallurgist and was determined to met the Society of Automotive Engineers (SAE) chemistry requirements. The metallurgist stated that "the burning of the piston crown most likely is the result of either detonation or pre-ignition." A standard airworthiness certificate was issued to the aircraft on September 13, 1997. The rebuilt engine, model TSIO-520-R9B, serial #245658R, was installed on May 24, 1985, at a total airframe time of 652.7 hours. On June 2, 1995, at an engine time of 712.3 hours, the engine cylinders were chromed and reassembled with new rings, and serviceable pistons and valves (except for 1 new valve). The engine was reinstalled on the airframe. On March 11, 1997, at the last annual inspection, the tachometer time was 1424.0 hours. The tachometer reading at the accident site was 1442.7 hours. During a personal interview, conducted by the IIC, the mechanic stated that work performed on the engine in June 1995 was not a major overhaul. He further stated that the "the pistons and valves met the serviceable limits." He did not recall the cylinder in which the new valve was installed.
The disintegration of the #1 cylinder piston resulting from a detonation/pre-ignition condition due to an unknown reason. A factor was the lack of suitable terrain for the forced landing.
Source: NTSB Aviation Accident Database
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