Serious incident de Havilland Canada DHC-8-102 N922HA,
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ASN Wikibase Occurrence # 364906
 
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Date:Tuesday 16 July 1991
Time:20:25 LT
Type:Silhouette image of generic DH8A model; specific model in this crash may look slightly different    
de Havilland Canada DHC-8-102
Owner/operator:Henson Airlines
Registration: N922HA
MSN: 094
Total airframe hrs:9081 hours
Engine model:P&W 120A
Fatalities:Fatalities: 0 / Occupants: 5
Aircraft damage: Minor
Category:Serious incident
Location:Savannah, GA -   United States of America
Phase: En route
Nature:Unknown
Departure airport:Hilton Head Isl, SC (49J
Destination airport:Jacksonville, FL (JAX
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
AFTER FLT 4317 TOOK OFF, THE MAIN LNDG GEAR DID NOT RETRACT. THE FLT CREW ACCOMPLISHED THE EMERG CHECKLIST, EXTDD THE LNDG GEAR & MADE AN UNEVENTFUL LNDG. AN EXAM OF THE ACFT DISCLOSED THAT THE RGT LNDG GEAR RETRACTION FITTING HAD FAILED & A HYDRAULIC LINE WAS SEVERED. ALSO, THE QUANTITY LIMITING VALVE(S) WERE CORRODED & THE RESPECTIVE PISTON MOVEMENT WAS RESTRICTED. SUBSEQUENTLY, BOTH HYDRAULIC SYSTEMS WERE DRAIN OF FLUID. AN EXAM OF THE FITTING ATTACHMENT BOLTS REVEALED THE TOP BOLT LOST TORQUE & THE BOLT FAILED IN FATIGUE; THE BOTTOM BOLTS FAILED IN OVERLOAD. ADNLY, THE FITTING SPIGOT FAILED DUE TO HYDROGEN EMBRITTLEMENT; AN IMPROVED FITTING HAS BEEN PRODUCED TO CORRECT HYDROGEN EMBRITTLEMENT PROBLEMS. THE OPER CONDUCTED A FLEET CAMPAIGN & FND 13 LOOSE BOLTS IN OTHER 100 SERIES ACFT. SVRL AIRWORTHINESS DIRECTIVES WERE ISSUED TO CORRECT THE LOSS OF TORQUE ON ATTACHMENT BOLTS, WHICH INCLUDED CHECKING THE TORQUE AT THE 300 HR LNDG GEAR INSPN.

Probable Cause: THE INADEQUATE INSPECTION PROCEDURES WHICH ALLOWED THE LOSS OF TORQUE ON THE TOP RETRACTION FITTING ATTACHMENT BOLT WHICH SUBSEQUENTLY FAILED IN FATIGUE. FACTORS WERE THE LOSS OF HYDRAULIC FLUID THROUGH A SEVERED LINE, AND THE CORROSION OF A HYDRAULIC QUANTITY LIMITING VALVE.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: ATL91IA134
Status: Investigation completed
Duration: 1 year and 7 months
Download report: Final report

Sources:

NTSB ATL91IA134

Location

Revision history:

Date/timeContributorUpdates
19-Mar-2024 20:09 ASN Update Bot Added

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