NTSB Identification: FTW98FA307.
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Accident occurred Saturday, July 11, 1998 in LINCOLN, TX
Probable Cause Approval Date: 03/30/2000
Aircraft: Cessna 172N, registration: N5632E
Injuries: 3 Serious.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

Witnesses observed the airplane maneuvering at a low altitude with black smoke coming from the engine. During landing toward the southwest on State Highway 21, at the intersection of Farm Road 1624, the airplane went under the power lines which span State Highway 21 striking the lower wire, and continued under the flashing traffic signal lights which also span State Highway 21. The airplane's right wing tip impacted a stop sign. The airplane touched down and bounced, veered to the right, and then impacted a convenience store's gasoline pumps. The airplane exploded into flames and was consumed by the post crash fire. Examination of the engine revealed that the #3 cylinder exhaust valve rocker arm fulcrum was displaced, and the rocker arm retaining stud could be turned by hand. The tapped hole in the cylinder head for the exhaust rocker arm retaining stud did not conform to blueprint specifications. There was also evidence which indicated a probable recent maintenance activity on the #3 cylinder. The aircraft's operator could not locate the airplane's airframe and engine logbooks.

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

The #3 cylinder exhaust valve rocker arm fulcrum retaining stud backing out of its stud-tapped hole due to the improper tapping of the stud hole by unknown maintenance personnel. Contributing factors were the transmission wire, sign and gasoline pump.

Full narrative available

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