Accident Beechcraft A36 N7214Y,
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ASN Wikibase Occurrence # 285987
 
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Date:Sunday 8 June 2008
Time:19:30 LT
Type:Silhouette image of generic BE36 model; specific model in this crash may look slightly different    
Beechcraft A36
Owner/operator:
Registration: N7214Y
MSN: E-2169
Year of manufacture:1984
Total airframe hrs:3214 hours
Engine model:Continental IO-550-B1F
Fatalities:Fatalities: 0 / Occupants: 3
Aircraft damage: Substantial
Category:Accident
Location:Grand Rapids, Minnesota -   United States of America
Phase: En route
Nature:Private
Departure airport:Falls International Airport, MN (INL/KINL)
Destination airport:Minneapolis-Flying Cloud Airport, MN (FCM/KFCM)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
The pilot stated that about 40 minutes into the flight he heard a loud noise followed by a rapid deceleration of the engine, and then a "distinct bang." The windshield was immediately covered with a film of oil, completely obstructing forward visibility. He established a descent at best glide airspeed and established a course for the nearest suitable airport. During the descent, the engine continued to run rough and smoke entered the cockpit. It became apparent to the pilot that he did not have enough altitude to reach the airport. He attempted to increase engine power in order to slow the descent; however, the engine seized shortly afterward. He set up for a forced landing to a clearing adjacent to a set of power lines. During the forced landing, the airplane impacted trees and a utility pole, which separated the left tip tank and left aileron from the airframe. The airplane slid approximately 50 feet and came to rest upright. A postaccident inspection revealed that the propeller assembly had separated from the engine propeller flange. The propeller flange appeared intact. The propeller assembly was not recovered. Two propeller bolt fragments and one propeller alignment pin fragment were recovered from the engine cowling. Examination of the fracture surfaces revealed features consistent with reverse bending fatigue cracking. In addition, the washer faces of both nuts were worn and polished consistent with relative movement against the crankshaft flange. Maintenance records indicated that the propeller spinner bulkhead was replaced approximately one year prior to the accident in order to comply with a manufacturer's service letter. At the time of the accident, the propeller assembly had accumulated 1,906 hours total time in service, with 235 hours since replacement of the spinner bulkhead. About 531 hours had accumulated since overhaul of the propeller assembly.

Probable Cause: A loss of engine thrust due to the propeller separating from the aircraft as a result of fatigue failure of the propeller attachment bolts caused by the insufficient torque of the bolts during installation.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: CHI08LA154
Status: Investigation completed
Duration: 9 months
Download report: Final report

Sources:

NTSB CHI08LA154

Location

Revision history:

Date/timeContributorUpdates
02-Oct-2022 18:02 ASN Update Bot Added

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