GROVELAND, CA, USA
N761LX
Cessna T210M
The airplane collided with multiple trees during an attempted forced landing in mountainous terrain following a catastrophic engine failure in cruise. The flight was obtaining VFR flight following from air route traffic control center (ARTCC) when the facility lost radar and radio contact. The airplane came to rest near the edge of an elliptical meadow, which was about 1 mile long by 1/4 mile wide, with the long axis oriented east and west. The meadow was in mountainous terrain and surrounded by trees over 100 feet tall. The debris path was along the eastern edge of the meadow on a magnetic bearing of 210 degrees. Multiple large trees were observed with broken branches and major impact marks on their trunks. The crankcase had a 3-inch diameter hole in it above cylinder number 3. Examination of the engine found that the crankshaft fractured and separated at the rear of the number 4 cheek. The fracture was at the forward radius of the number 2 main bearing journal. Smeared metal was on the fracture surfaces. A metallurgical examination determined that a large portion of the fracture surface exhibited smooth crack arrest markings typical of fatigue propagation. Failure of the crankshaft was caused by a fatigue crack in the cheek between the number 3 rod journal and the number 2 main bearing journal. The fracture of the crankshaft caused the additional damage to the engine, including the separation of the numbers 3 and 4 connecting rods from their respective journals, and would have led to a complete loss of engine power. The origin of the fatigue fracture was in the transition between the number 2 main bearing journal surface and the forward fillet radius, approximately 0.036 inches below the surface of the journal. No metallurgical anomalies or manufacturing process errors were found to explain the fatigue initiation. This failure is very similar to a number of others investigated by the Safety Board's Materials Laboratory in the past, with a fatigue crack initiating just below the hardened case layer. As with many of those previous events, there were no material or microstructural defects that could be identified as the root cause of the fatigue initiation. The crankshaft met design material specifications.
HISTORY OF FLIGHT On May 13, 2002, at 1355 Pacific daylight time, a Cessna T210M, N761LX, collided with trees during a forced landing in mountainous terrain near Groveland, California. The forced landing was precipitated by a catastrophic engine failure in cruise. The owner was operating the airplane under the provisions of 14 CFR Part 91. The airline transport pilot and one passenger sustained fatal injuries. The airplane was destroyed by the collision sequence and post crash fire. The personal cross-country flight departed Fullerton, California, about 1130, en route to the airplane's home base in Carson City, Nevada. Visual meteorological conditions prevailed, and no flight plan had been filed. The primary wreckage was at 37 degrees 50.358 minutes north latitude and 119 degrees 51.484 minutes west longitude at an estimated elevation of 4,595 feet. The airplane became the subject of an alert notice (ALNOT) when Oakland (ZOA) Air Route Traffic Control Center (ARTCC) lost radar and radio contact at 1356. ZOA lost contact 50 miles northeast of Linden, California, at 12,500 feet. Local authorities responded about 1430 to a report of a fire, and discovered the airplane's wreckage. The National Transportation Safety Board investigator-in-charge (IIC) reviewed recorded radio transmissions by the pilot and air traffic control. The IIC converted all times to Pacific daylight time. The pilot contacted Oakland Center at 1311, and reported level at 12,500 feet en route to Carson City. The pilot made a couple of frequency changes as the airplane changed radar sectors. At 1354, the pilot reported level at 12,500 feet, and several transmission exchanges followed. The last transmission was at 1355:16. The pilot verified that he was proceeding to Carson City via Placerville, California, and then would cut across the Sierra Mountains near Lake Tahoe, California. At 1356:35, the controller tried to inform the pilot that he had lost radar contact, but received no reply. After several attempts, the controller asked an airliner in the vicinity to try and contact the pilot; there was no response. A review of a plot of recorded radar data provided by the airframe manufacturer showed a target that departed Fullerton at 1217:41. The target proceeded in a northerly direction, and climbed to a mode C reported altitude of 12,500 feet. It reached 12,500 feet near Palmdale, California. The target maintained that altitude on a relatively straight track. The last target was at 1355:21, at a mode C altitude of 12,500 feet. The coordinates were 37 degrees 51 minutes 15 seconds north latitude and 119 degrees 49 minutes 10 seconds west longitude. The plot showed a primary target at 1355:40, at 37 degrees 52 minutes 01 seconds north latitude and 119 degrees 49 minutes 09 seconds west longitude. PERSONNEL INFORMATION A review of Federal Aviation Administration (FAA) airman records revealed that the pilot held an airline transport pilot certificate with an airplane multiengine land rating, and a commercial pilot certificate with an airplane single engine land rating. The pilot held a second-class medical certificate issued on April 30, 2001; it had no limitations or waivers. The Safety Board IIC was unable to locate personal flight records for the pilot. The IIC obtained the aeronautical experience listed in this report from a review of the FAA airmen medical records on file in the Airman and Medical Records Center located in Oklahoma City, Oklahoma. The pilot reported on his medical application that he had a total time of 7,200 hours with 300 hours logged in the last 6 months. AIRCRAFT INFORMATION The airplane was a Cessna T210M, serial number 21062351. A maintenance shop had recently completed a pitot/static transponder check on the airplane. They routinely placed the logbooks in the airplane following any work. The owner could not find the logbooks, and assumed that they were still in the airplane. The owner stated that he owned the airplane for 12 to 14 years. When he purchased the airplane, it had 710 hours on it. Shortly after his purchase, he had one or two cylinders top overhauled. His company flew the airplane about 500 hours before they had camshaft problems and overhauled the engine. Therefore, he estimated that the airframe and engine had about 1,200 hours at the time of engine overhaul. He had work done on one or two cylinders about 200 hours prior to the accident. He estimated that the airframe had about 1,920 hours total time. The maintenance shop provided work orders for the airframe. The shop completed an annual inspection on July 16, 2001. Total time on the airframe was 1,841 hours. The last work order indicated that they removed and sent the transponder and encoding altimeter to other shops for bench testing. Upon the units' return, the shop installed them in the airplane and completed a pitot/static and transponder test. On April 18, 2002, they noted a total time of 1,897 hours. The engine was a Teledyne Continental Motors TSIO-520R, serial number 512516. METEOROLOGICAL INFORMATION A routine aviation weather report (METAR) for Modesto, California (240 degrees at 55 miles), was issued at 1353. It stated: skies clear; visibility 10 miles; winds from 330 degrees at 13 knots; temperature 81 degrees Fahrenheit; dew point 31 degrees Fahrenheit; altimeter 30.06 inches of mercury. COMMUNICATIONS The airplane had established radio contact with Oakland Center, and was on frequency 126.85. WRECKAGE AND IMPACT INFORMATION The Safety Board IIC and representatives from the FAA, Cessna Aircraft Company, and Teledyne Continental Motors (TCM) examined the wreckage on scene. The airplane came to rest near the edge of an elliptical meadow, which was about 1 mile long by 1/4 mile wide, with the long axis oriented east and west. The meadow was in mountainous terrain and surrounded by trees over 100 feet tall. The debris path was along the eastern edge of the meadow on a magnetic bearing of 210 degrees. The airplane came to rest about 245 feet from the first identified point of contact (FIPC), which was a 4-inch diameter tree with the trunk broken about 10 feet above the ground. All measurements in this section are looking from the FIPC along the debris path centerline and left or right of the centerline. The coordinates for the FIPC were 37 degrees 50.388 minutes north latitude and 119 degrees 51.449 minutes west longitude at an estimated altitude of 4,550 feet. Ten feet right of the FIPC was a 15-foot-tall tree that did not have any scrape marks or broken branches. Thirty-six feet from the FIPC and 14 feet left, was a 100-foot-tall tree with scarred branches about 30 feet up from its base. At 144 feet and 14 feet left, was another 100-foot-tall tree with a 2-foot diameter trunk. About 25 feet up the trunk was a round 2-foot scarred area that had no bark covering about 20 percent of the tree's circumference. Thirty-two feet left of this tree was a piece of aluminum skin whose fracture surfaces mated to the fracture surfaces of the left wing. The inverted left wing, which separated, was 177 feet from the FIPC on the centerline of the debris path. The left wing exhibited cylindrical crush damage that was about 2 feet in diameter. A piece of red lens remained in its fitting on the left wing tip, and shards of red lens were within 10 feet of the wing. The tree line began about 190 feet from the FIPC. Numerous trees in the debris path had broken limbs from 5 to 10 feet above ground level. One flap section, which was about a foot long, was at 204 feet and 10 feet left, and another similar sized piece was at 213 feet and 3 feet left. The left wing and pieces of the airplane that were not in burned areas were not oily, sooty, or scorched. Several Plexiglas shards that the airplane manufacturer's representative identified as windscreen components lay outside of the burned area. These pieces were not oily, sooty, charred, or melted on either side. Fire consumed the majority of the aluminum structure and skins. The main wreckage consisted of the propeller, engine, fuselage, empennage, and right wing. Green lens fragment were near the right wing tip, which separated and lay about 2 feet from and parallel to the leading edge of the right wing. The burned rotating beacon and tail navigation light, whose installed location was on top of the vertical stabilizer, were in the middle of the main wreckage. Fire consumed the fuel selector valve. The left side entry door was about 20 feet right of the main wreckage. The door's locking pins were extended. Section 3 of the Pilot's Operating Handbook (POH) articulates the procedures for a forced landing. It instructs the flight crew to unlatch all doors prior to landing. Investigators established control continuity from the right aileron, the rudder, and the elevators to the cockpit. The cables on the separated left wing broomstrawed, and one cable sawed into the wing skin. The left elevator and rudder had a blob of molten metal at the location of the balance weights. Fire consumed the forward portion of the right elevator balance weight horn, but the outboard hinge and aft half of the balance weight horn area were present. Investigators identified four seat belt buckles. One front seat belt buckle was latched, and the shoulder harness was attached. The other front seat belt buckle was not latched, and the shoulder harness was not latched. One rear seat belt buckle was latched, and the other was unlatched. All three of the propeller blades bent aft, and the outboard half of the blade closest to the burn area was missing. The blades did not exhibit any gouges or scrape marks. The engine and nose of the airplane angled to the right and exhibited thermal damage. The right side was more damaged than the left side. The engine cowling and cylinder valve covers on the left side were scorched, but not destroyed. Fire partially consumed the valve covers for cylinders number 1 and number 3. The ignition harness and magnetos were scorched. The oil cap was dangling by its safety chain next to the filler tube. The crankcase had a 3-inch diameter hole in it above cylinder number 3. Looking in the hole, investigators observed a fractured connecting rod piece. After recovery, investigators inverted the engine, and hooked it on a hoist. Most of the bottom of the oil pan was missing. Looking into the case, investigators noted that one crankshaft journal was bare. MEDICAL AND PATHOLOGICAL INFORMATION The Mono County Coroner completed an autopsy. TESTS AND RESEARCH TCM personnel examined the engine under the supervision of the Safety Board at the factory in Mobile, Alabama, on June 20, 2002. TCM submitted a written report, and the Safety Board investigator who observed the inspection concurred with the facts in the report. The report noted that the spark plugs were oval. Both magnetos exhibited fire damage. The left magneto rotated, but the right one did not. The right side (1, 3, and 5) fuel injector nozzles were not obstructed. The left side nozzles (2, 4, and 6) were clogged. All nozzles exhibited fire damage. The throttle body/fuel metering unit exhibited fire damage. The fuel pump sustained severe fire damage, and the pump had seized. The drive coupling was intact. The oil pump cavity was dry; TCM attributed this to the heat of the post-crash fire. They reported that the cavity and gears looked normal except for rust on the gears from lack of oil residue. The oil pump drive was intact. The oil pickup tube screen was unobstructed. The forward portion of the sump contained some aluminum and steel particles. They noted no excess oil on the filler neck or crankcase. They reported that the crankcase only exhibited char from the post accident fire. Cylinders number 3, 4, and 5 exhibited damage to the lower skirt areas. All cylinder bores were dry and slightly rusty; TCM attributed this to the heat of the post-crash fire. TCM visually inspected the valves and noted normal signatures. All of the valve springs were intact and oily. The number 3 piston fractured at the piston pin boss area. All other pistons exhibited dryness and darkened skirts. All rings were free in their respective grooves. All piston pins were intact, as were the extruded aluminum pin plugs. The numbers 3 and 4 connecting rods were off their respective crankshaft journals. Both connecting rods exhibited heat discoloration and baked oil. TCM felt that this was the result of lubrication distress. The number 4 connecting rod had one bolt intact. Its rod cap was attached, but open so that the rod escaped the journal. A bearing from the number 4 connecting rod was in the oil sump. This bearing exhibited stripping of the surface. TCM attributed this to lubrication distress. A rod bearing from the number 3 connecting rod was in the oil sump; it burned. One bearing from the number 4 connecting rod was in the sump; it bent up, and the bearing surface was smeared. The camshaft was dry. It was bent, and stuck at the center at the number 3 and 4 intake lobes. TCM noted that all of the lobes exhibited normal operational signatures. All lifters were dry, and their faces exhibited normal operational signatures. The numbers 2 and 3 main bearings exhibited lubrication distress. Number 2 was dark in color and stripped. Number 3 was loose in the crankcase bearing saddle. TCM felt that this was the result of the hot fire making the bearing lose its free length. TCM noted that all other main bearings appeared normal. The lower thru bolt in the nose was packed with red silicone sealant. A piece of cutout gasket material was on the side of the thru bolt with silicon smeared around it. The crankshaft fractured and separated at the rear of the number 4 cheek. The fracture was at the forward radius of the number 2 main bearing journal. Smeared metal was on the fracture surfaces, and TCM felt that this occurred when the front part of the engine continued to rotate after separation. TCM cut the fractured section from the remainder of the crankshaft, and sent the fractured section the Safety Board Materials Laboratory in Washington, D. C., for further analysis. All counterweights moved freely. Materials Laboratory A Safety Board Materials Laboratory specialist examined the fractured piece and prepared a factual report. A summary of the report follows, and the complete report is attached. A large portion of the fracture surface exhibited smooth crack arrest markings typical of fatigue propagation. The origin of the fatigue fracture was in the transition between the number 2 main bearing journal surface and the forward fillet radius, approximately 0.036 inches below the surface of the journal. The fracture initiated on a plane with a normal at approximately 35° to the crankshaft axis, and then progressed to lie on a plane with a normal nearly perpendicular to the crankshaft axis. The fatigue fracture extended through approximately 90 percent of the area of the crank cheek. Nearly circular crack propagation marks could be seen around the origin. Some of the surrounding surface was smeared or rubbed smooth during fracture. By contrast, the origin area had a slightly rougher texture. X-ray energy dispersive spectroscopy (EDS) of the fracture surface revealed a major peak for iron and minor peaks for nickel, chromium and manganese, consistent with the 4340 steel specified for the crankshaft. The specialist found no significant difference for EDS spectra taken in the origin area when compared to EDS spectra from the surrounding fracture surface. The specialist took a metallurgical section near the fatigue origin; he ground and polished the section to the position of the origin. Etching of the section revealed a microstructure of tempered martensite typical for this application. The etching also revealed a darker layer adjacent to the journal surface consistent with the nitrided layer specified for this part. He visually estimated that the depth of the nitrided layer was approximately 0.027 inches. He also noted a very thin white layer (approximately 0.0003 inches thick) at the journa
a catastrophic engine failure due to the fatigue fracture and failure of the crankshaft. A factor contributing to the accident was the unsuitable nature of the mountainous terrain for a successful forced landing. The precipitating cause of the fatigue fracture could not be determined.
Source: NTSB Aviation Accident Database
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