Rock Springs, WY, USA
N323JC
CESSNA T207A
The commercial pilot reported that, during the business flight, while about 9,500 ft mean sea level, the engine lost all power. The pilot was unable to restart the engine and realized that the airplane would not be able to reach the airport, so he initiated a forced landing in a nearby clearing. Examination of the engine revealed that the No. 2 main bearing had separated from the bearing support. The No. 2 main bearing support exhibited evidence of bearing shift. The No. 2 main bearing support mating surfaces displayed fretting damage, consistent with the application of insufficient torque on the cylinder through bolts. Further, the breakaway torque on the Nos. 1 and 2 cylinder through bolts were below specifications. It is likely that the insufficient torque on the Nos. 1 and 2 through bolts resulted in the fretting damage, the No. 2 main bearing shifting, and the subsequent separation of the crankshaft. Further examination of the engine revealed that the No. 2 cylinder piston was labeled as a piston for a naturally aspirated engine, whereas the other pistons were labeled for a turbocharged engine, which the airplane was equipped with. No additional anomalies were observed with the airframe and engine that would have precluded normal operation. A review of maintenance records revealed that the No. 1 cylinder was replaced 94.5 hours before the accident, which would have required the removal and installation of the Nos. 1 and 2 cylinder through bolts. It is likely that maintenance personnel applied insufficient torque on the Nos. 1 and 2 cylinder through bolts during the reinstallation of the No. 1 cylinder.
On May 5, 2014, about 1330 mountain daylight time, a Cessna T207A, N323JC, sustained substantial damage during a forced landing following a reported loss of engine power, near the Rock Springs-Sweetwater County Airport (RKS) Rock Springs, Wyoming. The airplane was registered and operated by Aero-Graphics Inc., under the provisions of Title 14 Code of Federal Regulations Part 91. The commercial pilot and passenger were not injured. Visual meteorological conditions prevailed and no flight plan was filed for the business flight. The flight originated from Evanston-Uinta County Airport-Burns Field, Evanston, Wyoming, at 1200, with a destination of RKS. The pilot reported that during cruise flight, about 9,500 feet mean sea level (msl), the engine stopped, and he was unable to restart the engine. The pilot stated that when he realized that he would not be able to make the airport, he initiated a forced landing to a nearby clearing. The airplane came to rest in an upright position, in a field about 15 miles north from RKS. Initial examination of the airplane by a Federal Aviation Administration (FAA) inspector revealed that the engine firewall sustained substantial damage. The airplane was recovered to a local storage facility for further examination. A certified Airframe and Powerplant (A&P) mechanic examined the engine under the oversight of the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), and an FAA inspector. Examination of the engine revealed that it was intact and all accessories remained attached. The rocker covers and spark plugs were removed and the cylinder overhead components were lubricated and undamaged. The engine was unable to be rotated by hand. The engine oil filter was removed and examined. The filter was contaminated with metal particles. The cylinders were removed from the engine during the examination. The break-away through bolt torque during disassembly indicated that the cylinder number 1 and 2 through bolts were improperly torqued. The number two cylinder piston was observed to be labeled as an IO-550 piston, for a naturally aspirated engine, while all the other pistons were labeled appropriately for the turbocharged engine that was installed. The engine was further disassembled and the interior surfaces were covered in oil and metal particles. The disassembly revealed the crankshaft separation of the number 2 cheek, aft of the number 2 main bearing journal. The engine exhibited substantial internal damage in the area of the number 2 main bearing. The number 2 main bearing separated from its bearing support. The main support mating surfaces for the number 2 bearing revealed fretting signatures. The number 2 cylinder bay had mechanical damage. The number 2 main bearing support aft facing surface revealed metal deformation consistent with the bearing shedding from the bearing support. The bearing support lock tab showed lateral movement and lock slot elongation. Further, the bearing support also showed metal deformation along the edges. A review of the maintenance records revealed the engine was overhauled on February 17, 2011, at an engine total time of 4,985 hours. The number 2 cylinder was removed and replaced on October 25, 2012. Top overhaul was accomplished on May 23, 2013. The number 3 cylinder was removed and replaced on July 11, 2013. The number 1 cylinder was removed and replaced on January 17, 2014. At this time, the connecting rod was also removed and repaired and furthermore the nose seal was replaced. The airplane had logged 94.5 hours since the number 1 cylinder removal and replacement.
Maintenance personnel’s application of insufficient torque to the engine cylinder through bolts during replacement of the No. 1 cylinder, which resulted in the displacement of the No. 2 main bearing, the bearing shifting, and a catastrophic engine failure.
Source: NTSB Aviation Accident Database
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