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ASN Wikibase Occurrence # 174017
Last updated: 8 October 2020
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Type:Silhouette image of generic C170 model; specific model in this crash may look slightly different
Cessna 170B
Registration: N2502C
C/n / msn: 26146
Fatalities:Fatalities: 0 / Occupants: 1
Other fatalities:0
Aircraft damage: Substantial
Location:Santa Rosa, CA -   United States of America
Phase: Landing
Departure airport:Santa Rosa, CA (STS)
Destination airport:
Investigating agency: NTSB
The engine lost power and the airplane nosed over during a forced landing in a field. Post accident examination revealed that the number 2 cylinder separated from the engine. The engine had accumulated 900 hours since its last major overhaul 13 years prior to the accident; the cylinder had accumulated 1,212 hours since replacement in 1986. The hours on the cylinder prior to that time could not be determined. A metallurgical examination found that the barrel failed due to a fatigue crack. The barrel fractured circumferentially between the 11th and 13th fin from the head. The fracture initiated approximately 1.8 inches below the head and started from the inner diameter below a plated region. The initiation area was a small, flat, thumbnail-shaped region approximately 0.5-inch wide through the wall thickness, with signatures indicative of fatigue. Multiple crack initiation sites were observed in the origin area. From the initiation point, the fracture continued propagating in the circumferential direction with coarse arrest marks over approximately 45 percent of the barrel circumference. No material, manufacture, or plating defects were found. The metallurgical examination could not determine why the cracking occurred at the given location; however, it occurred below the chrome plating. From this, it is possible that the barrel exhausted the available fatigue life at that location, which was lowered by the presence of plating.

Probable Cause: the failure of the number 2 cylinder barrel due to fatigue. The lack of suitable landing terrain was a factor in the accident.



Revision history:

21-Feb-2015 18:27 Noro Added
21-Dec-2016 19:28 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
07-Dec-2017 17:34 ASN Update Bot Updated [Total occupants, Other fatalities, Departure airport, Destination airport, Source, Narrative]

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