Accident Grumman G-164B Turbo Ag-Cat N62375,
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ASN Wikibase Occurrence # 344717
 
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Date:Sunday 20 June 2021
Time:06:00 LT
Type:Silhouette image of generic G64T model; specific model in this crash may look slightly different    
Grumman G-164B Turbo Ag-Cat
Owner/operator:Scott Flying Service
Registration: N62375
MSN: 806B
Year of manufacture:1988
Total airframe hrs:14472 hours
Engine model:Honeywell TPE331-1-151G
Fatalities:Fatalities: 0 / Occupants: 1
Aircraft damage: Substantial
Category:Accident
Location:Sedgwick, Arkansas -   United States of America
Phase: En route
Nature:Agricultural
Departure airport:Fontaine, AR (KPVT)
Destination airport:Sedgwick, AR
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
The pilot was conducting an agricultural flight when the airplane had a sudden total loss of engine power. The pilot stated that the sound of the engine went from normal to silent, with no indication of an engine issue before the loss of engine power. The airplane impacted a levee and nosed over in a flooded rice field during the forced landing. The airplane's empennage, aft fuselage, and engine mounts were substantially damaged during the forced landing.

A postaccident engine examination and disassembly revealed the torque sensor assembly front spur gear was disengaged from the splined shouldered shaft on which it was installed. Additionally, the self-locking nut that secured the front spur gear to the shaft had backed off which allowed the front spur gear to disengage from the shaft.

The examination and testing were unable to determine if the front spur gear self-locking nut was improperly torqued at installation or if it became loose during operation due a loss of retention. However, had the self-locking nut not been seated properly at installation, the disengagement of the front spur gear would likely have occurred well before the accident (2,541.5 hours since the overhauled torque sensor was installed on the engine). Additionally, no anomalies were found with the self-locking nut to suggest why it would have lost retention during operation.

The engine-driven fuel pump and fuel control unit (FCU) are driven through a series of gears in the accessory gearbox, including the front spur gear, and any failure in the gear train that drives the fuel pump and FCU would prevent the fuel pump from delivering fuel to the FCU to sustain engine operation, resulting in an uncommanded engine shutdown.

Probable Cause: The total loss of engine power due to the failure and disengagement of the torque sensor assembly front spur gear from its splined shouldered shaft due to a loose self-locking nut.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: CEN21LA287
Status: Investigation completed
Duration: 2 years 1 month
Download report: Final report

Sources:

NTSB CEN21LA287

Location

Revision history:

Date/timeContributorUpdates
19-Aug-2023 16:32 ASN Update Bot Added
19-Aug-2023 16:37 harro Updated

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