Accident Boeing 747-422 N174UA,
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Date:Monday 27 August 1990
Type:Silhouette image of generic B744 model; specific model in this crash may look slightly different    
Boeing 747-422
Owner/operator:United Airlines
Registration: N174UA
MSN: 24381/762
Year of manufacture:1990
Total airframe hrs:2952 hours
Cycles:402 flights
Engine model:Pratt & Whitney PW4056
Fatalities:Fatalities: 0 / Occupants: 343
Aircraft damage: Minor, repaired
Location:Los Angeles International Airport, CA (LAX) -   United States of America
Phase: Landing
Nature:Passenger - Scheduled
Departure airport:Sydney-Kingsford Smith International Airport, NSW (SYD/YSSY)
Destination airport:Los Angeles International Airport, CA (LAX/KLAX)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
The crew noted that the nose and main body gear indicated up and locked after normal gear extension. The crew used the alternate gear extension procedure, which was unsuccessful. The aircraft landed on runway 25R with the nose and main body gear retracted when the flight reached the minimum fuel state. Examination of the aircraft revealed that the selector valve for the affected gear was in the up and locked position, and the bolt which connects the valve arm to the cockpit control cable system was missing. The bolt for the wing gear selector valve arm was found partially backed out; the nut and cotter pin were missing. The aircraft was delivered to United in January of 1990 and had 2,952 flight hours and 402 cycles. Detailed review of the maintenance records proved that United had not performed any maintenance on the landing gear system. A second alternate gear extension procedure involving de-energizing the hydraulic system for the affected gear is not published in the crew manuals, taught during initial training, nor available on any checklist.

PROBABLE CAUSE: "The failure of the manufacturer to ensure that the landing gear selector valves and their associated drum link assemblies were properly installed prior to delivery of the aircraft. A factor in the accident was the lack of information available to the crew concerning the secondary alternate gear extension procedure."

Accident investigation:
Investigating agency: NTSB
Report number: LAX90IA305
Status: Investigation completed
Duration: 2 years and 4 months
Download report: Final report


Aviation Week & Space Technology 3.9.90 (p.205)

History of this aircraft

Other occurrences involving this aircraft
19 February 2013 N174UA United Airlines 0 over Pacific Ocean non


Revision history:


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