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Last updated: 20 April 2021
Statuts:Enquête Officielle
Date:lundi 27 août 1990
Heure:10:25
Type/Sous-type:Silhouette image of generic B744 model; specific model in this crash may look slightly different
Boeing 747-422
Compagnie:United Airlines
Immatriculation: N174UA
Numéro de série: 24381/762
Année de Fabrication: 1990-01-05 (8 months)
Heures de vol:2952
Cycles:402
Moteurs: 4 Pratt & Whitney PW4056
Equipage:victimes: 0 / à bord: 20
Passagers:victimes: 0 / à bord: 323
Total:victimes: 0 / à bord: 343
Dégats de l'appareil: Mineurs
Conséquences: Repaired
Lieu de l'accident:Los Angeles International Airport, CA (LAX) (   Etats-Unis d'Amérique)
Phase de vol: A l'atterrissage (LDG)
Nature:Transport de Passagers Intern.
Aéroport de départ:Sydney-Kingsford Smith International Airport, NSW (SYD/YSSY), Australie
Aéroport de destination:Los Angeles International Airport, CA (LAX/KLAX), Etats-Unis d'Amérique
Détails:
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:

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:
cover
Investigating agency: NTSB
Status: Investigation completed
Duration: 2 years and 4 months
Accident number: LAX90IA305
Download report: Summary report

Sources:
» Aviation Week & Space Technology 3.9.90 (p.205)


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Plan
Ce plan montre l'aéroport de départ ainsi que la supposée destination du vol. La ligne fixe reliant les deux aéroports n'est pas le plan de vol exact.
La distance entre Sydney-Kingsford Smith International Airport, NSW et Los Angeles International Airport, CA est de 12026 km (7516 miles).

Les informations ci-dessus ne représentent pas l'opinion de la 'Flight Safety Foundation' ou de 'Aviation Safety Network' sur les causes de l'accident. Ces informations prélimimaires sont basées sur les faits tel qu'ils sont connus à ce jour.
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