History of Flight
On June 21, 2010, at approximately 1257 eastern daylight time, a Cessna T210L, registration N30266, operated under contract by the USDA Forest Service, struck a light stanchion and collided with terrain during a forced landing near William T. Piper Memorial Airport (LHV) in Lock Haven, Pennsylvania. The flight had departed Clarion County Airport (AXQ) around 1035 on a public-use aerial observation mission to survey tree defoliation. According to Automated Flight Following data, the aircraft was about 14 miles west of LHV at 2,500 feet mean sea level around 1250. Witnesses reported hearing engine sputtering and a loud noise before the engine ceased operating temporarily, then coughed and sputtered. The airplane was observed trailing smoke and struggling to maintain altitude. The pilot had communicated with other traffic about fuel availability but did not declare an emergency.
Personnel Information
The pilot held an airline transport pilot certificate with single- and multi-engine land ratings, as well as a flight instructor certificate. According to USDA Forest Service records, he had logged 8,280 total flight hours, including 1,775 hours in the accident aircraft make and model. His most recent FAA second-class medical certificate was issued on December 29, 2009.
Aircraft Information
The 1973 Cessna T210L was equipped with a Teledyne Continental Motors TSIO-520-H engine. The most recent engine overhaul was completed on May 7, 2004, at 4,276 total aircraft hours. An annual inspection on March 9, 2010, at 5,000 hours recorded satisfactory compression checks and oil filter examination. The aircraft had accumulated about 45 additional hours since that inspection.
Meteorological Information
Weather recorded at LHV at 1300 included visibility 10 statute miles, temperature 21°C, dewpoint 16°C, and an altimeter setting of 30.10 inches of mercury. Winds were from 250 degrees at 6 knots.
Wreckage and Impact Information
The accident site was on a residential street about 1,300 feet west of the runway 9 threshold. Initial impact occurred when the left horizontal stabilizer struck a wooden street light stanchion. The wreckage path extended about 260 feet, striking a residence porch and three parked cars. The cockpit and cabin were substantially damaged and partially consumed by post-impact fire. The throttle was found full aft, mixture full rich, propeller full forward, and fuel selector on the right tank. The main landing gear was up, and the flaps were retracted.
Medical and Pathological Information
Autopsies performed on the pilot and the front seat passenger listed the cause of death as inhalation of smoke with thermal injury. Toxicological testing was negative for cyanide, ethanol, and drugs; the pilot showed a 10% carboxyhemoglobin saturation.
Tests and Research
Examination of the engine revealed extensive mechanical damage, particularly to the number 2 cylinder. The exhaust valve for the number 2 cylinder had fractured due to fatigue cracking, with ratchet marks and multiple origins. The exhaust valve guide was also fractured. The measured clearance between the valve stem and guide far exceeded the service limit of 0.0070 inches, averaging over 0.0300 inches. The oil sump contained only about half a quart of oil with metallic particles and debris. The fuel system screens showed light-brown and white particulate contamination. The number 2 connecting rod and cap were severely damaged, and piston fragments were found in the oil sump.
Probable Cause
The NTSB report did not explicitly state a probable cause. However, the investigation identified fatigue cracking of the number 2 cylinder exhaust valve, excessive valve-to-guide clearance, and subsequent mechanical failure of the engine.