Pilot Debrief

CESSNA T207A near Rock Springs, WY — 2014-05-05

Final reportWPR14LA240
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Date
2014-05-05
Location
Rock Springs, WY, USA
Airport
RKS
Aircraft
CESSNA T207A
Registration
N323JC
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Cruise

Probable cause

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.

NTSB narrative

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.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Proper engine maintenance could have prevented the power loss.

NTSB coding

Evidence available

  • 5 docket documents
View NTSB final reportView NTSB docket

Docket documents5

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