ARVIN, CA, USA
N738VE
CESSNA 172N
WHILE IN CRUISE FLIGHT AT 10,000 FEET MEAN SEA LEVEL, THE ENGINE SUDDENLY QUIT. THE PILOT DECLARED AN EMERGENCY AND RECEIVED VECTORS TO A SMALL AIRSTRIP. THE PILOT COULD NOT LOCATE THE AIRSTRIP AND ELECTED TO LAND ON A ROAD; HOWEVER, POWER LINES PREVENTED ITS USE. THE PILOT LANDED IN AN ADJACENT FIELD AND THE AIRPLANE NOSED OVER IN SOFT TERRAIN. AN EXAMINATION OF THE ENGINE REVEALED THAT THE CRANKSHAFT GEAR TEETH HAD FAILED DUE TO FATIGUE. INTERNAL ENGINE GEARS MATING TO THE CRANKSHAFT GEAR WERE NOT DAMAGED. THE CRANKSHAFT WAS INSTALLED IN THE ACCIDENT ENGINE 644 HOURS PRIOR TO THE ACCIDENT AFTER BEING MAGNAFLUXED AND NITRIDE. NO RECORDS OF THE CRANKSHAFT MAINTENANCE HISTORY, PRIOR TO INSTALLATION IN THE ACCIDENT ENGINE, WERE LOCATED.
On May 16, 1994, about 1124 hours Pacific daylight time, a Cessna 172N, N738VE, nosed over during a forced landing about 3 miles south of Arvin, California. The airplane was on an instrument flight rules (IFR) cross-country business flight to San Jose, California, when the accident occurred. The airplane, operated by AV Aviation, Lancaster, California, sustained substantial damage. The certificated private pilot, the sole occupant, received minor injuries. Visual meteorological conditions prevailed. The flight originated at General William J. Fox Airfield, Lancaster, California, about 1020 hours. The pilot reported that at 1110 hours while in cruise flight at 10,000 feet mean sea level (msl), the engine suddenly quit. The pilot noted that although the propeller was windmilling, the vacuum and rpm gauges were at zero. He completed the emergency procedures checklist and the engine would not restart. The pilot declared an emergency and was given vectors to a small airstrip by the Bakersfield, California, Air Traffic Control Tower (ATCT). The pilot could not locate the airstrip and he selected a road for landing. While on final approach, the pilot noted power lines across the road and selected a soft field adjacent to the road. During the landing roll, the nose wheel dug into the soft dirt and separated. The airplane nosed over and received damage to the right wing, landing gear, and vertical stabilizer. A Federal Aviation Administration (FAA) airworthiness inspector, Fresno Flight Standards District Office (FSDO), examined the aircraft. He reported that the airplane received damage to the wings and spar. The fuel tanks contained fuel. One propeller blade was bent aft 15 degrees and the other blade was not damaged. Rotation of the propeller did not produce any rotation of the valves or accessory gears. After recovery, the engine was examined on June 1, 1994. The inspection revealed that metal particles were found throughout the engine. The crankshaft gear is pressed, not bolted, onto the aft end of the crankshaft. The gear teeth had sheared and disintegrated at the root of the teeth around the circumference of the crankshaft. The separated surfaces were battered and spalled. The adjoining mating gear teeth from the camshaft, idler gear, oil pump, and magneto drive gears did not appear to be damaged. All of the mating gear teeth could be rotated by hand. The airplane had accumulated a total time in service of about 2,643 flight hours. Examination of the maintenance records revealed that the most recent annual inspection was accomplished on April 1, 1994, 59 flight hours before the accident. The engine in the accident aircraft had previously been installed in N117AB, with an engine serial number of L-3254-76. Examination of the engine logbook revealed that on September 12, 1989, the engine had accrued a total time in service of 5,742.2 hours of operation. The next entry reflected a total time in service of 4,756.2 hours. On December 11, 1991, the logbook indicated that the engine was removed from N117AB due to a damaged case, and the total accumulated time on the engine was 4,969.7 hours. The next entry in the engine logbook was May 12, 1993. It reflected that the engine was overhauled by a company in Pembroke Pines, Florida. The operator had considered utilizing the aircraft for 14 CFR Part 135 operations. During a review of the engine logbook, an FAA inspector, Fresno FSDO, did not find any documentation of an engine overhaul. A mechanic with an Inspection Authorization (IA) provided the inspector with a statement that the engine was overhauled in accordance with the Lycoming overhaul manual. Engine serial number L-3254-76 was replaced with an overhauled engine case, serial number L-5869-76. The overhaul included the engine case, an overhauled crankshaft, an overhauled camshaft, cylinders, and various other parts. No accessories were installed and the engine was not test run. The engine was installed in the accident aircraft on September 30, 1993. The same accumulated hours of operation listed for engine L-3254-76 (4,969.7 hours) was utilized for L-5869-76. According to the engine logbook, at the time of the accident the engine had accrued 5,614.3 hours of operation, 644.6 hours since being overhauled. The crankshaft, serial number P-46, had previously been installed in engine serial number L-4796-75. Prior to its installation in L-5869-76, the crankshaft was overhauled by a company in Lake Alfred, Florida. The FAA's principle maintenance inspector for the company reported that the overhaul included magnaflux, grinding of the main bearings, nitride treatment, and polishing. No maintenance history was located for engine L-4796-75 or the crankshaft. The crankshaft was examined by the Safety Board's Materials Laboratory on October 19, 1994. Optical examination revealed that all of the crankshaft gear teeth had separated slightly outboard from the root radii. The fracture surfaces were almost completely obliterated by severe battering from postseparation mechanical damage. One small area of an original fracture surface was found and examined by scanning electron microscope. The fracture surface displayed multiple ratchet marks and microfissuring indicating high stress fatigue propagation from the flank of the gear tooth at the root radius. A metallographic inspection of the gear revealed microstructure typical of a quench and tempered alloy steel and included a carburized case adjacent to the root radii of the gear teeth. The energy dispersive spectra was consistent with an alloy steel containing small amounts of manganese and chromium. Safety Board investigators requested maintenance information about engine L-4796-75 from the engine overhaul facility in Pembroke Pines, Florida. Correspondence was addressed by registered mail to the company and to the IA who performed the work. Both letters were returned unclaimed. A third attempt to verify engine information was addressed to the IA by regular mail. Safety Board investigators received correspondence from the IA on August 19, 1994. The IA indicated that the company has ceased operation. He reported that the gear backlash measurements on engine L-5869-76 were within the overhaul limits. The Safety Board retained the engine crankshaft until its release to the owner's representatives on November 9, 1994. No other parts or components were retained by the Safety Board.
a fatigue failure of the crankshaft gear teeth.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
