On September 11, 1991, a Cessna 172P (registration N97564) operated by Mohave Aviation Inc. was involved in an aviation accident near Hesperia, CA. Investigators recorded the probable cause as: The loss of engine power was caused by a stuck exhaust valve in the number 2 cylinder due to carbon buildup. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During initial climb, a pilot experienced a loss of engine power. After unsuccessful attempts to restore power, he executed a forced landing in unsuitable terrain, resulting in the aircraft nosing over. Investigation identified a stuck exhaust valve due to carbon buildup.
Accident Narrative
During the initial climb following takeoff, the pilot reported a sudden loss of engine power. The aircraft was unable to continue climbing or maintain altitude. The pilot attempted corrective actions by switching fuel tanks and adjusting the mixture control, but these measures did not restore power. With limited options, the pilot performed a forced landing straight ahead into terrain that was unsuitable for a normal landing. During the landing, the aircraft nosed over.
Investigation Findings
Subsequent investigation determined that the loss of engine power resulted from a stuck exhaust valve in the number 2 cylinder. The valve had become stuck open due to carbon buildup. The investigation also revealed that a manufacturer's service bulletin addressing this potential issue had not been accomplished at the recommended time. Additionally, other items of in-service inspection or information regarding valve sticking were not addressed according to the available records.
Probable cause
The loss of engine power was caused by a stuck exhaust valve in the number 2 cylinder due to carbon buildup.
What happened in the 11 Sept 1991 Cessna 172P accident near Hesperia, CA?
During initial climb, a pilot experienced a loss of engine power. After unsuccessful attempts to restore power, he executed a forced landing in unsuitable terrain, resulting in the aircraft nosing over. Investigation identified a stuck exhaust valve due to carbon buildup.
What aircraft was involved and where did it happen?
The accident on 11 Sept 1991 involved a Cessna 172P, registration N97564, operated by Mohave Aviation Inc., at Hesperia, CA.
What was the probable cause of the accident?
The loss of engine power was caused by a stuck exhaust valve in the number 2 cylinder due to carbon buildup.
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