ASN Wikibase Occurrence # 44609
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| Date: | Saturday 25 December 2004 |
| Time: | 10:21 |
| Type: |  Beechcraft S35 Bonanza |
| Owner/operator: | Private |
| Registration: | N5631K |
| MSN: | D-7389 |
| Year of manufacture: | 1964 |
| Total airframe hrs: | 5616 hours |
| Engine model: | Continental IO-520-BA6B |
| Fatalities: | Fatalities: 2 / Occupants: 2 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Herman, WI -
 United States of America
|
| Phase: | Landing |
| Nature: | Private |
| Departure airport: | Manitowoc/Newton Municipal Airport, WI (MTW/KMTW) |
| Lockport-Lewis Lockport Airport, IL (LOT/KLOT) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
On December 25, 2004, at 1021 central standard time, a Beech S35, N5631K, collided with trees and the terrain in Herman, Wisconsin, following a loss of engine power during flight. The airline transport pilot and a passenger were fatally injured. The airplane was substantially damaged by impact with the terrain and a post impact fire. The 14 CFR Part 91 personal flight was operating in visual meteorological conditions on an instrument flight rules (IFR) flight plan. The airplane departed the Manitowoc County Airport (MTW), Manitowoc, Wisconsin, at 1010, en route to the Lewis University Airport (LOT), Romeoville, Illinois. The pilot was attempting to divert to the Sheboygan Memorial Airport (SBM), Sheboygan, Wisconsin, when the accident occurred.
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.
Accident investigation:
 |
|
Sources:
NTSB: https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20041228X02038&key=1
Location
Images:
Photos: NTSB
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 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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