Accident Piper PA-31-350 N555MC,
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ASN Wikibase Occurrence # 294501
 
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Date:Tuesday 14 September 2004
Time:18:15 LT
Type:Silhouette image of generic PA31 model; specific model in this crash may look slightly different    
Piper PA-31-350
Owner/operator:Mcoco Inc.
Registration: N555MC
MSN: 31-7752154
Year of manufacture:1977
Total airframe hrs:6542 hours
Engine model:Lycoming TIO-540-J2BD
Fatalities:Fatalities: 0 / Occupants: 2
Aircraft damage: Substantial
Category:Accident
Location:Sweeny, Texas -   United States of America
Phase: Unknown
Nature:Private
Departure airport:PORT LAVACA, TX (T97)
Destination airport:Houston-William P. Hobby Airport, TX (HOU/KHOU)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
The 1,800-hour commercial pilot reported that while in cruise flight, the left engine stopped producing power and the left propeller fell forward approximately six inches. The pilot secured the engine and made a precautionary landing. The airplane sustained substantial damage during the forced landing to a field. A review of aircraft maintenance records revealed that the airplane experienced a gear-up landing in January 2002, which resulted in a propeller strike. The left engine was removed and inspected per the manufacturer's overhaul manual and returned to service. The engine had accrued approximately 440 hours since it was overhauled. Examination of the engine revealed that the entire three-bladed propeller assembly and the #1 cylinder had separated from the engine. The engine was disassembled and the crankshaft, along with an intact #3 connecting rod assembly and the fractured #2 connecting rod assembly were examined by a Safety Board Materials Engineer. The crankshaft was fractured in two places; one fracture was just forward of the #3 rod journal in the crank cheek, and the other fracture was in the aft crank cheek adjacent to the #2 main journal. The interior surface of the #1 and #2 main bearing halves exhibited significant rubbing and a portion of the bearing liner material was delaminated and was missing from the forward end of the bearing. On the oil slinger face, just forward of the #1 main journal, 360 degree rubbing damage was noted just outboard of the radius. In the rub region, metallic transfer was present with a color consistent with aluminum material. No evidence of radial cracks was observed in this area. An exact determination for the crankshaft failure could not be determined; however, evidence supported two possibilities that could have attributed to its demise. One possibility was that the crankshaft fracture initiated from rubbing damage between the crank cheek aft of the #2 main journal (thrust face) and the crankcase, with the other fatigue region being secondary. The exact cause for the rubbing was not clear, but one possibility was that the bearing liner delaminated and liberated a section causing a reduction in the clearance between the crankshaft and the crankcase as it was rubbing/exiting through the oil slinger. The other possibility was that the propeller strike caused the rubbing/cracking to occur, which was not detected during the subsequent overhaul/inspection.

Probable Cause: The fracture failure of the left engine crankshaft for undetermined reasons.

Accident investigation:
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Investigating agency: NTSB
Report number: FTW04LA238
Status: Investigation completed
Duration: 12 months
Download report: Final report

Sources:

NTSB FTW04LA238

Revision history:

Date/timeContributorUpdates
11-Oct-2022 18:53 ASN Update Bot Added

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