Lock Haven, PA, USA
N30266
CESSNA T210L
The aerial observation flight was conducted by a 14 CFR Part 135 certificated on-demand air carrier under contract to the U.S. Forest Service. As the flight neared its destination airport, the pilot reported via the airport's common traffic advisory frequency his intent to land. Witnesses reported that, as the airplane overflew them on approach to the airport, it appeared to be in distress, trailing black smoke with the engine "sputtering." The airplane subsequently impacted a light stanchion about 1,300 feet short of the intended landing runway. Before coming to rest, the airplane struck a house and several parked cars, and it was nearly consumed during a post-impact fire. Postaccident examination revealed a catastrophic failure of the airplane's engine, which originated with a fatigue failure of the number 2 cylinder exhaust valve. The fatigue failure was likely due to abnormal loading associated with excessive valve-to-valve guide clearance resulting from valve guide wear. Typically, valve guide wear results from either overall elevated engine operating temperatures or individually elevated valve temperatures due to improper valve seating. The normal wear pattern observed on the number 2 exhaust valve seat suggested that improper valve seating was not an issue in this case. Significant exhaust valve guide wear was observed on all cylinders, with the valve guides of the generally cooler cylinders near the front of the engine showing less wear than those of the generally hotter cylinders near the rear of the engine. This overall pattern suggested a persistent elevated temperature problem, which could have resulted from either improper engine operation or an undiagnosed maintenance issue. The investigation revealed that, when performing engine cylinder differential pressure tests during required routine inspections of the airplane’s engine, the contract operator utilized gauges that had not been calibrated since their purchase and did not perform the tests in accordance with the engine manufacturer's recommendations. Also, the engine manufacturer recommended that cylinder borescope inspections be accomplished in conjunction with the differential pressure tests, and there were no notations in the engine maintenance records of any visual borescope inspections of the interior of the cylinders. Further, there was no notation in the records that the fuel injection system had been inspected and adjusted per the engine manufacturer’s recommendations. If properly performed, differential pressure tests and borescope inspections may have detected valve guide wear and prevented the exhaust valve failure, and fuel injection system inspections may have detected and corrected incorrect adjustment of the engine fuel system, which can result in elevated engine cylinder temperatures and lead to valve guide wear. These and other instances of non-compliance with manufacturer service recommendations discovered during the investigation indicated that the contract operator was not maintaining the airplane in a manner consistent with its "Operator's Manual," which dictated that inspections of time-limited components were to be conducted in accordance with the applicable manufacturers' recommendations.
HISTORY OF FLIGHT On June 21, 2010, at 1257 eastern daylight time, a Cessna T210L, N30266, registered to Sterling Airways, Inc., and operated under contract by the United States Department of Agriculture (USDA) Forest Service, was substantially damaged when it struck a light stanchion and collided with terrain while maneuvering for a forced landing following a total loss of engine power near William T. Piper Memorial Airport (LHV), Lock Haven, Pennsylvania. The certificated airline transport pilot and two USDA Forest Service mission specialists were fatally injured. Visual meteorological conditions prevailed, and a company visual flight rules (VFR) flight plan was filed for the public use aerial observation flight, which departed Clarion Country Airport (AXQ), Clarion, Pennsylvania, about 1035. According to a representative of USDA Forest Service, the purpose of the flight was to conduct an aerial survey of tree defoliation in southwestern Pennsylvania. A review of fueling records revealed that the pilot serviced the airplane with 49 gallons of fuel on the evening of June 20, 2010. Automated Flight Following (AFF) data provided by the USDA Forest Service indicated that, on the morning of the accident, the pilot repositioned the airplane from its base at Hornell Municipal Airport (4G6), Hornell, New York, to AQX where the two USDA Forest Service mission specialists boarded it about 1030. The flight from AQX was scheduled to arrive at LHV about 1300 to refuel the airplane, before continuing with the survey. About 1250, AFF data indicated that the airplane was about 14 miles west of LHV, at an altitude of 2,500 feet msl (about 1,000 feet agl). Subsequent data indicated that the airplane tracked generally northeast over the next 6 minutes, toward the town of Lock Haven. The airplane's final indicated position was about 3 miles west of the LHV runway 9 threshold, at an altitude of 1,519 feet msl (about 1,000 feet agl). According to a certificated flight instructor (CFI) who was flying in the traffic pattern at LHV for runway 27, he heard the accident pilot announce over the LHV Common Traffic Advisory Frequency (CTAF) that he was 8 miles southwest of the airport. The CFI also heard the accident pilot ask if fuel was available at the airport. About 2 minutes later, the CFI heard the accident pilot report that he was 5 miles southwest of the airport. The CFI heard no further transmissions by the accident pilot. The CFI also stated there was no tone of urgency in the accident pilot's voice nor did he declare an emergency at any point. A Piper PA-24 subsequently taxied onto runway 27, and the pilot announced his position via the CTAF before departing to the west. Shortly after that airplane departed, when the CFI had turned his airplane onto the base leg of the traffic pattern, an unknown person announced on the CTAF that there had been an explosion off the departure end of the runway, which the CFI later learned was the accident airplane. Two witnesses, who worked at Lock Haven University, about 1.5 nautical miles northwest of the accident site, observed the accident airplane as it overflew university property. Both of the witnesses stated that the airplane was flying lower when compared to the other airplanes that they would normally see landing at the airport. Shortly after first observing the airplane, it began trailing smoke. The smoke trail then stopped, and they both heard a loud noise, similar to a "gun blast." Both witnesses stated that after the initial loud noise, the engine ceased operating for several seconds, and then it started to "cough and sputter." Both of the witnesses reported hearing a second loud noise while the engine continued to sputter. Numerous other individuals witnessed the accident airplane as it approached LHV over the town of Lock Haven, and their statements were generally consistent. Six of the witnesses described that the airplane’s engine was "sputtering" as it flew over them, and several remarked about how loud the engine was. One witness commented that "it sounded like a connecting rod problem with the engine due to the noise it was making." Six of the witnesses also commented that the airplane appeared to be "struggling" to maintain altitude, or that it was lower than normal as it overflew them. Several witnesses commented that they thought it unusual that the airplane's landing gear was retracted as it overflew them. PERSONNEL INFORMATION The pilot, who was an employee of Sterling Airways Inc., held an airline transport pilot certificate with ratings for airplane single and multiengine land. He also held a flight instructor certificate with ratings for airplane single engine and instrument airplane. His most recent Federal Aviation Administration (FAA) second-class medical certificate was issued on December 29, 2009. The pilot’s logbooks were not recovered, but according to USDA Forest Service records, the pilot had logged 8,280 total hours of flight experience as of March 16, 2010, with 1,775 hours in the accident airplane make and model. AIRCRAFT INFORMATION According to FAA records, the airplane was manufactured in 1973. The airplane was equipped with a Teledyne Continental Motors TSIO-520-H engine. The most recent engine overhaul was completed by Sterling Airways Inc. on May 7, 2004, and on that date the airplane had accumulated 4,276 total hours of operation. According to maintenance records, the engine was "…overhauled [in accordance with] TSIO-520 sandcast series [overhaul manual]," and all hardware was replaced in accordance with Teledyne Continental Motors Service Bulletin (SB) SB97-6. All six cylinders and their respective exhaust and intake valves were replaced with new Teledyne Continental Motors parts. The following logbook entry documented a post-maintenance flight check conducted by the accident pilot. The pilot entered a remark of "fuel flow low," which was addressed in the following log entry, "Adjusted fuel flow pressure per overhaul manual. (Cessna) Ground run check good." An engine logbook entry dated June 7, 2007, at 4,710 total aircraft hours, documented an annual inspection. The entry also noted, "Removed #3 & 6 cyl for valve (exh) & valve guides both cyl. Cylinders re-installed with new gaskets." No additional details regarding the cylinder work performed during this inspection were documented in the engine maintenance log. An airframe maintenance logbook entry dated January 18, 2008, documented the completion of an annual inspection and the flight of the airplane for a period of about 6 hours under 14 CFR Part 91. The entry noted that airworthiness directives (ADs) were complied with prior to departure and that an airworthiness conforming validation check was performed during the annual inspection. All time limited components were checked, and the airplane was cleared to return to 14 CFR Part 135 service. No further entries removing or reinstating the airplane to 14 CFR Part 135 service were noted. The airplane's most recent annual inspection was completed on March 9, 2010, at 5,000 total aircraft hours. The engine logbook entry for the inspection noted a replacement of the engine oil and filter with an accompanying check of the oil and oil filter contents. The magnetos, timing, and compression checks were satisfactory, with a note describing the cylinder differential pressure test values as 75, 68, 72, 74, 77, and 70 psi for cylinders 1 through 6, respectively. The spark plugs were cleaned, gapped, tested, and reinstalled. The oil filter adapter was repositioned and the engine was washed. The entry noted that no applicable ADs were required to be complied with at the time, and a ground run of the engine was satisfactory. The airplane had accumulated about 45 additional hours of operation between the time of the annual inspection and the date of the accident flight. Detailed inspection of the airplane's maintenance records from the time that the engine was overhauled in 2004 until the time of the accident showed that guidance used for conducting annual inspections varied. For the annual inspections completed in 2004 and 2005, the entries specified using the guidance provided by "Cessna 210 maint. man. insp. form." For annual inspections in 2006 and 2007, the entries specified using the guidance provided by, "FAR 43 Appendix D." An annual inspection completed in 2008 cited using "FAR 43 Appendix D & Cessna insp. sheet" as guidance, while entries for inspections in 2009 and 2010 again cited "FAR 43 Appendix D." A detailed comparison of the scope of guidance provided by each of the above listed inspections can be found in the public docket for this case. Neither the engine nor the airframe maintenance logbooks explicitly detailed compliance with any manufacturer's service bulletins, service information directives, or service information letters following the entries detailing the engine overhaul in May 2004. METEOROLOGICAL INFORMATION Weather, recorded at LHV at 1300, included no ceiling information, visibility 10 statute miles, temperature 21 degrees C, dewpoint 16 degrees C, and an altimeter setting of 30.10 inches of mercury. The winds were from 250 degrees true at 6 knots. WRECKAGE AND IMPACT INFORMATION The airplane was examined at the accident site on June 21, 2010. The accident site was located on a residential street, about 1,300 feet west of the runway 9 threshold at LHV, at an elevation of 556 feet. The initial impact point was located about 7.5 feet below the top of a wooden street light stanchion, where the outboard section of the left horizontal stabilizer impacted the pole. The wreckage path was oriented about 120 degrees magnetic. The airplane struck the front porch of a residence and three parked cars before coming to rest about 260 feet from the initial impact point, headed about 250 degrees magnetic. Small parts of the airplane were strewn along the wreckage path, and all flight control surfaces were accounted for at the accident scene. The cockpit and cabin were substantially impact-damaged and partially consumed by a post-impact fire. The instrument panel was severely burned, and none of the flight instruments contained any legible information. The throttle was found in the full aft position, the mixture control was found in the full rich position, and the propeller control was found in the full forward position. The fuel selector valve was selected to the right fuel tank. Flight control continuity to the ailerons was traced through a single separation, consistent with overload, to the control column. Flight control continuity was confirmed from the rudder, elevator, and elevator trim tab to the cockpit area. Measurement of the elevator trim tab actuator correlated to between a 10- and 15-degree tab trailing-edge-up position. Measurement of the flap actuator jackscrew correlated to the flaps up position. The main landing gear was in the up position, although both were dislodged out of the up-locking mechanism. The nose gear was in the up and locked position. All three propeller blades remained attached to the hub, which remained attached to the engine. One of the three propeller blades was bent aft at a point about 1/3 of its span, and had rotated 180 degrees in the propeller hub. The remaining two propeller blades exhibited minor scratching, and were relatively undamaged. The engine exhibited impact and thermal-related damage, and a large portion of the engine was covered by dark black soot. The crankcase exhibited a protruding hole extending from the number 1 cylinder deck area over to the number 2 cylinder deck area extending forward to the number 4 cylinder deck area. The oil sump exhibited a puncture hole on the aft side of the sump. The oil sump drain was intact and secure with no safety wire present. The safety wire installed on the oil filter was oriented in a direction as to apply a loosening force to the filter; however, the oil filter was securely in place. The left and right magnetos turned freely with impulse coupling engagement. Their outer cases exhibited impact related damage. The magnetos were installed and tested on the test bench and produced a blue spark across a 7 mm gap through the full range of test bench rpm. The number 2 top and number 2 bottom spark plugs exhibited mechanical damage. The numbers 1, 3, and 5 top and bottom sparkplugs exhibited worn signatures in accordance with the Champion Aviation check-a-plug comparison chart, while the numbers 4 and 6 top and bottom spark plugs exhibited normal wear signatures in accordance with the chart. The oil sump was drained of oil, and the amount was measured to be approximately a half a quart. The oil was dark in color and contained metallic particles. Once the oil sump was removed there were numerous internal engine components located in the bottom of the oil sump. The oil pick-up tube was undamaged, and the oil suction screen was unrestricted. The oil filter housing was cut open and the filter element was cut from the canister to allow examination. The oil filter element was examined and contained an abundance of metallic flakes and slivers. The fuel control exhibited a dark colored soot and thermal related damage. The throttle body valve was found in the full open position. The link rod and levers did not move freely by hand. The fuel pump turned freely and the fuel pump drive was intact and undamaged. The fuel nozzles were unrestricted and exhibited normal operating signatures, with the exception of the number 6, which exhibited a light amount of impact related damage on the upper portion of the nozzle. A fine, particle-type contamination was found within the fuel control finger screen, fuel pump, and fuel manifold valve. Samples of the contaminate were forwarded to the NTSB Materials Laboratory for further examination. The turbocharger turbine wheel rotated freely by hand, and exhibited a normal amount of shaft end play. The camshaft exhibited mechanical damage from the number one to number four cylinder locations. With the exception of the mechanical damage to the camshaft the camshaft lobes exhibited normal operating signatures. The crankshaft and counterweight assembly exhibited mechanical damage concentrated at the number two, three and four connecting rod journals. The crankshaft main bearing journals were intact, undamaged and exhibited normal operating signatures. The number 1, 5, and 6 connecting rod journals were intact, undamaged and did not exhibit any signs of lubrication distress. The number 2, 3, and 4 connecting rod journals exhibited mechanical damage. The oil transfer passages were open and unrestricted, and the oil transfer collar was intact and undamaged. The crankshaft main bearings remained intact, and exhibited normal operating and lubrication signatures, with no signs of lubrication distress. The number 1, 5, and 6 connecting rods were intact and undamaged. Their respective bushing and bearings exhibited normal operating and lubrication signatures. The number 2, 3, and 4 connecting rods exhibited extreme mechanical damage and had separated from their respective connecting rod caps. Fragments of the connecting rod caps exhibited mechanical damage. Fragments of the connecting rod bolts and nuts were fractured through and exhibited mechanical damage and signatures consistent with overload. The number 2, 3, and 4 connecting rod bearings could not be distinguished from the bearings found in the oil sump, though each of the six connecting rod bearings recovered from the oil sump exhibited extensive mechanical damage. All of the pistons displayed normal combustion deposits and varying levels of damage, with the exception of the number 2 piston, which was absent from its respective bore. Numerous piston fragments were recovered from the oil sump. Each of the cylinders was removed from the crankcase and examined in detail. Cylinder numbers 1, 3, 4, 5, and 6 generally displayed similar signatures. The cylinder combustion chambers exhibited normal combustion deposits with bore conditions that were free of scoring and undamaged. Hone marks were visible in the cylinder bore ring travel areas, and the intake and exhaust valve heads exhibited normal deposits. An oil residue was present in the rocke
The total loss of engine power resulting from the fatigue failure of the engine's number 2 cylinder exhaust valve. The fatigue failure was due to valve guide wear that led to excessive clearance between the valve and valve guide. Contributing to the accident was the contract operator’s lack of compliance with its own maintenance procedures, which, if followed, would have prevented the accident.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
