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ASN Wikibase Occurrence # 44609
Last updated: 27 December 2019
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Type:Silhouette image of generic BE35 model; specific model in this crash may look slightly different
Beechcraft S35 Bonanza
Registration: N5631K
C/n / msn: D-7389
Fatalities:Fatalities: 2 / Occupants: 2
Other fatalities:0
Aircraft damage: Substantial
Location:Herman, WI -   United States of America
Phase: Landing
Departure airport:Manitowoc, WI (MTW)
Destination airport:Romeoville, IL (LOT)
Investigating agency: NTSB
The airplane collided with trees and terrain during a forced landing following a loss of engine power. Approximately 8 minutes after taking off, the pilot reported to air traffic control that the cabin of his airplane was filling with smoke and he was diverting to a near-by airport. The airplane contacted 30 to 40 foot tall trees which bordered an open field. The airplane then contacted the terrain and a post impact fire ensued. Inspection of the engine revealed two holes in the crankcase near the number four cylinder with the number four piston rod separated from the crankshaft. Teardown of the engine revealed five cylinder deck stud nuts were missing and the number five cylinder seventh stud had sheared. The crankshaft, counterweights, and rod bearings exhibited thermal damage which was most prominent at the number four cylinder connecting rod journal. Material from the number four connecting rod bearing was fused to the crankshaft journal displacing the oil tube toward the number three main journal. The cylinders had been removed and overhauled approximately 380 hours prior to the accident. The cylinder base packings on all of the cylinders were flattened and extruded between the base of the cylinders and the crankcase. The cross section diameter of the packings was larger than a sample packing, part number 641066, which is used on IO-520-BA engines. The cross section diameter of the base packings that were removed from the engine were similar in diameter to those used on the O-470 series engines.
Probable Cause: The installation of the improper cylinder base packing seals by maintenance personnel resulting in the loss of lubriation and subsequent failure of the number four connecting rod/bearing. A factor associated with the accident was the trees that the airplane contacted during the forced landing.



Revision history:

28-Oct-2008 00:45 ASN archive Added
21-Dec-2016 19:24 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
07-Dec-2017 18:34 ASN Update Bot Updated [Source, Narrative]

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