On July 11, 1998, a Cessna 172N (registration N5632E) was involved in an aviation accident near Lincoln, TX. Investigators recorded the probable cause as: 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. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 1 related events involving the same aircraft type or operator are linked below.
During an emergency landing, an airplane with black smoke from its engine struck power lines, a stop sign, and gasoline pumps, leading to a post-crash fire. Investigators found a displaced rocker arm fulcrum and a non-conforming cylinder head thread.
Accident Sequence
Witnesses reported seeing the airplane maneuvering at a low altitude while emitting black smoke from its engine. The aircraft was landing toward the southwest on State Highway 21, at the intersection of Farm Road 1624. During the landing approach, the airplane passed under power lines that cross Highway 21 and struck the lower wire. It continued under flashing traffic signal lights also spanning the highway. The right wing tip of the aircraft then impacted a stop sign. After touchdown, the airplane bounced, veered to the right, and collided with a convenience store's gasoline pumps. The aircraft subsequently exploded into flames and was consumed by the post-crash fire.
Examination Findings
An examination of the engine revealed that the #3 cylinder exhaust valve rocker arm fulcrum was displaced. The rocker arm retaining stud could be turned by hand. Further inspection indicated that the tapped hole in the cylinder head for the exhaust rocker arm retaining stud did not conform to blueprint specifications. Additionally, there was evidence suggesting a probable recent maintenance activity on the #3 cylinder.
Logbook Status
The aircraft's operator was unable to locate the airplane's airframe and engine logbooks.
What happened in the 11 Jul 1998 Cessna 172N accident near Lincoln, TX?
During an emergency landing, an airplane with black smoke from its engine struck power lines, a stop sign, and gasoline pumps, leading to a post-crash fire. Investigators found a displaced rocker arm fulcrum and a non-conforming cylinder head thread.
What aircraft was involved and where did it happen?
The accident on 11 Jul 1998 involved a Cessna 172N, registration N5632E, at Lincoln, TX.
What was the probable cause of the accident?
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.
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