Accident Rockwell 690B Turbo Commander N480K,
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ASN Wikibase Occurrence # 353163
 
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Date:Wednesday 16 June 1999
Time:22:00 LT
Type:Silhouette image of generic AC90 model; specific model in this crash may look slightly different    
Rockwell 690B Turbo Commander
Owner/operator:Nathan Thompson
Registration: N480K
MSN: 11543
Year of manufacture:1976
Total airframe hrs:4687 hours
Engine model:Garrett TPE331-5-252K
Fatalities:Fatalities: 0 / Occupants: 5
Aircraft damage: Substantial
Category:Accident
Location:Monterey, CA -   United States of America
Phase: Landing
Nature:Executive
Departure airport:Tri-county, CO (48V)
Destination airport:(KMRY)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
The pilot and copilot reported that they were on approach and as they passed the outer marker, they observed three green lights indicating the landing gear was extended. They observed hydraulic pressure of about 1,000 psi during the landing checks. The pilot said he landed the airplane with a slight tailwind, observed two beta lights, and he pulled the power levers into ground idle/reverse. Shortly thereafter, he felt the left landing gear collapse and he observed one red unsafe light and two green landing gear lights, with a corresponding gear warning horn. Postaccident examination of the left main gear revealed that a piece was fractured from the inboard gear-forging boss, which houses a clevis for the attachment of the hydraulic cylinder. The clevis remained attached to the hydraulic cylinder, which in the fully extended position is consistent with gear down. Metallurgical examination of the fracture faces revealed features typical of overstress separation. No pre-existing cracks or other defects were found on the fracture. A review of the Commander maintenance manual indicates that an adjustment must be made to the cylinder over travel following gear maintenance to obtain the proper drag brace preload. The left hand hydraulic cylinder, main landing gear aft wheel well door, and hydraulic components were replaced about 34 hours before the accident.

Probable Cause: The failure of maintenance personnel to properly adjust the drag brace preload during recent landing gear maintenance, which resulted in the overload failure and separation of the hydraulic cylinder attach boss.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: LAX99LA241
Status: Investigation completed
Duration: 2 years and 2 months
Download report: Final report

Sources:

NTSB LAX99LA241

Location

Revision history:

Date/timeContributorUpdates
09-Mar-2024 11:02 ASN Update Bot Added

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