Serious incident Fairchild SA227-DC Metro 23 N850LS,
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ASN Wikibase Occurrence # 357256
 
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Date:Tuesday 11 June 1996
Time:18:35 LT
Type:Silhouette image of generic SW4 model; specific model in this crash may look slightly different    
Fairchild SA227-DC Metro 23
Owner/operator:Lone Star Airlines
Registration: N850LS
MSN: DC-850B
Year of manufacture:1993
Total airframe hrs:4451 hours
Engine model:Garrett TPE-331-12UHR
Fatalities:Fatalities: 0 / Occupants: 8
Aircraft damage: None
Category:Serious incident
Location:Enid, OK -   United States of America
Phase: En route
Nature:Unknown
Departure airport:(KWDG)
Destination airport:Dallas, TX (KDFW)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
The airplane experienced an uncommanded shut down of the right engine during initial climb to altitude. An emergency was declared, and an uneventful single engine landing was made at the departure airport. Subsequent to the incident, metallic chips were found on the chip detector. The bearings of the accessory gear housing assembly (P/N 3103601-6) was missing all of the balls. Fragments of these ball bearings were found in the bottom of the engine case. Examination of the bearing races revealed pitting and scoring. According to the operator's diagnostics, the disintegration of the bearings allowed the gear shaft to drop down and contact the gears of the accessory drive idler gear assembly. Subsequently, the fuel pump drive gear was not driven, causing the engine to be starved of fuel. Inspection of the idler gear assembly revealed sheared gear teeth. Examination of the gearbox oiling system, revealed no evidence of failure or thermal distress prior to the initial bearing failure. The engine manufacturer had recently issued Service Bulletins addressing the installation of heavier duty gear assemblies in applicable engine installations.

Probable Cause: failure of the accessory drive bearing, causing the accessory drive gear teeth to shear and disengage the fuel pump accessory drive shaft, resulting in a disabled fuel pump and subsequent fuel starvation.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: FTW96IA248
Status: Investigation completed
Duration: 10 months
Download report: Final report

Sources:

NTSB FTW96IA248

Revision history:

Date/timeContributorUpdates
13-Mar-2024 15:55 ASN Update Bot Added

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