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ASN Wikibase Occurrence # 22714
Last updated: 13 December 2017
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Date:16-AUG-2008
Time:15:40
Type:Silhouette image of generic RALL model; specific model in this crash may look slightly different
Socata MS.894A Rallye Minerva
Owner/operator:Private
Registration: N31BF
C/n / msn: 11682
Fatalities:Fatalities: 0 / Occupants: 2
Airplane damage: Substantial
Category:Accident
Location:2 miles south of the Oswego County Airport, Fulton, New York -   United States of America
Phase: Manoeuvring (airshow, firefighting, ag.ops.)
Nature:Private
Departure airport:Fulton, NY (FZY)
Destination airport:Fulton, NY (FZY)
Investigating agency: NTSB
Narrative:
The pilot stated that he was level at 400 feet above ground level when he heard a "bang," the airplane began to vibrate, and the engine stopped. He lowered the nose for the airplane's best glide speed and initiated a forced landing to a nearby open field. While on final approach to the field the airplane collided with trees and then the ground. The crankshaft and connecting rod were forwarded to the Safety Board's Metallurgical Laboratory for further analysis. Examination of the crankshaft's ten bearing journals revealed surface finishes that were consistent with a turning operation but not with a grinding operation as specified in the overhaul manual. Examination of the engine assembly revealed that the crankshaft and the No. 3 engine cylinder connecting rod had failed. The examination revealed that the crankshaft failed in fatigue and initiated in machining marks in the rear radius of the No. 3 and 4 connecting rod bearing journals. An engine logbook entry indicated that the main and rod bearing journals had been "turned" and their diameter reduced by 0.010-inch in accordance with the Franklin overhaul manual. Journal diameters were measured and were consistent with 0.010-inch begin removed; however, the table in the overhaul manual specified a tolerance of 0.0010-inch and the dimensions indicated a tolerance of 0.0020-inch, which was contrary to the overhaul manual. The overhaul manual also recommends that the crankshafts be returned to the factory for grinding and re-nitriding. No logbook entries were located to verify that re-nitriding had been carried out.
Probable Cause: A loss of engine power due to fatigue failure of the crankshaft and the No. 3 engine cylinder connecting rod as a result of improper machining of the engine crankshaft during engine overhaul by maintenance personnel.

Sources:

NTSB: https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20080826X01318&key=1
FAA register: 2. FAA: http://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?omni=Home-N-Number&nNumberTxt=31BF


Revision history:

Date/timeContributorUpdates
07-Sep-2008 11:42 angels one five Added
20-Oct-2008 10:51 RobertMB Updated
26-May-2016 19:58 Dr.John Smith Updated [Time, Operator, Location, Nature, Source, Damage, Narrative]
21-Dec-2016 19:14 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
21-Dec-2016 19:16 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
21-Dec-2016 19:20 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
03-Dec-2017 11:55 ASN Update Bot Updated [Other fatalities, Departure airport, Destination airport, Source, Narrative]

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