NTSB Identification: FTW01LA210.
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Accident occurred Thursday, September 27, 2001 in Aiken, TX
Probable Cause Approval Date: 08/26/2002
Aircraft: Cessna T188C, registration: N4629J
Injuries: 1 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The pilot was maneuvering the agricultural airplane to enter a field and commence spraying, when at 120 feet agl, the engine lost power. The pilot attempted to restart the engine; however, the engine did not restart. During the ensuing forced landing, the airplane contacted circular rows of cotton, before coming to rest upright. The engine was examined at the manufacturer's facility and silicon sealant was observed on the base flanges of the #1, #2, #4, and #6 cylinders and on the crankcase mating surfaces. Fretting was observed on the base flanges of the cylinders, on the mating surface of the crankcase halves, and on the main bearing bosses. The #2 main bearing was observed fragmented and the bearing's bore was cracked and damaged. Additionally, it was observed that the crankshaft was fractured between the #2 main bearing and #3 crankshaft cheek. According to a TCM metallurgist, the fatigue fracture's origin was determined to be at the aft radius of the #2 main bearing. The silicon sealant prevented proper torqueing of the bolts that mate the crankcase halves and led to vibration at the crankcase mating surfaces. The #2 main bearing then shifted and failed, resulting in a loss of engine power.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

the application of silicon sealant to the crankcase mating surfaces by maintenance personnel, which resulted in improper torque on the bolts which mate the crankcase halves, vibration, and the subsequent failure of the #2 main crankshaft bearing. A factor was the lack of suitable terrain for the forced landing.

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