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ASN Wikibase Occurrence # 165781
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Type:Silhouette image of generic FDCT model; specific model in this crash may look slightly different    
Flight Design CTLS
Registration: N106SF
MSN: F-09-10-13
Fatalities:Fatalities: 0 / Occupants: 2
Aircraft damage: Substantial
Location:SportsPark, NW of Majors Airport (KGVT), Greenville, Texas -   United States of America
Phase: Landing
Departure airport:Gilmer, TX (JXI)
Destination airport:Denton, TX (DTO)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
The private pilot reported that a routine maintenance inspection had been completed earlier on the day of the accident. During the initial personal flight after the inspection, the engine exhaust gas temperatures (EGT) differed by up to 150 degrees, although they remained within the specified operating limitations. The pilot chose to divert to an intermediate airport to investigate any mechanical issue with the engine. The pilot reported that a mechanic informed him that the EGT difference was not unusual for that particular engine. No significant engine issues were identified, and two subsequent run-ups were normal. A third run-up and subsequent takeoff were also normal. As the flight progressed, the EGT indications were within limitations, and, after 25 minutes, they had equalized. About 5 minutes later, the engine and propeller “stopped abruptly.” The pilot’s attempts to restore engine power were unsuccessful. He subsequently executed a forced landing to an athletic field. During the landing, the nose landing gear separated, and the airplane nosed over.
A postaccident engine examination revealed that the No. 4 cylinder exhaust valve had failed near the valve head due to bending fatigue. The No. 4 cylinder, piston, and exhaust valve head exhibited extensive gouging, scraping, and deformation consistent with secondary damage due to the failed exhaust valve. Further examination revealed that the No. 4 cylinder exhaust train tappet exhibited severe wear, which had significantly reduced the height of the exhaust tappet compared to the height of the intake tappet. The resulting gap in the exhaust valve train due to the shortened tappet likely caused excessive impact loads between the exhaust valve and the cylinder valve seat during engine operation, which resulted in the valve’s failure. The subsequent secondary damage due to the separated valve head ultimately caused the catastrophic engine failure.

Probable Cause: The fatigue failure of the No. 4 cylinder exhaust valve due to excessive wear of the corresponding train tappet, which resulted in a total loss of engine power.


FAA register:

Accident investigation:
Investigating agency: NTSB
Status: Investigation completed
Download report: Final report

Revision history:

26-Apr-2014 05:26 Geno Added
02-May-2014 22:07 Geno Updated [Nature, Departure airport, Source, Narrative]
21-Dec-2016 19:28 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
29-Nov-2017 14:03 ASN Update Bot Updated [Other fatalities, Departure airport, Destination airport, Source, Narrative]

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