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Accident
Last updated: 17 October 2017
Statuts:Enquête Officielle
Date:dimanche 3 mars 1991
Heure:09:44
Type/Sous-type:Silhouette image of generic B732 model; specific model in this crash may look slightly different
Boeing 737-291
Compagnie:United Airlines
Immatriculation: N999UA
Numéro de série: 22742/875
Année de Fabrication: 1982-05-11 (8 years 10 months)
Heures de vol:26050
Cycles:19734
Moteurs: 2 Pratt & Whitney JT8D-17
Equipage:victimes: 5 / à bord: 5
Passagers:victimes: 20 / à bord: 20
Total:victimes: 25 / à bord: 25
Dégats de l'appareil: Détruit
Conséquences: Written off (damaged beyond repair)
Lieu de l'accident:6,4 km (4 milles) S of Colorado Springs, CO (   Etats-Unis d'Amérique)
Phase de vol: En approche (APR)
Nature:Transport de Passagers Nat.
Aéroport de départ:Denver-Stapleton International Airport, CO (DEN/KDEN), Etats-Unis d'Amérique
Aéroport de destination:Colorado Springs-Peterson Field, CO (COS/KCOS), Etats-Unis d'Amérique
Numéro de vol:UA585
Détails:
United Airlines flight 585 left Peoria for Colorado Springs, with intermediate stops at Moline, IL and Denver, CO. The aircraft took off from Denver at 09:23 for the last segment of the flight, estimating Colorado Springs at 09:42. The aircraft was cleared for a visual approach to runway 35. The aircraft then suddenly rolled to the right and started to pitch nose down. The crew tried to initiate a go-around by selecting 15-deg. flaps and an increase in thrust. The altitude decreased rapidly, acceleration increased to over 4G until the aircraft struck the ground of Widefield Park almost vertically.
After a 21-month investigation, the NTSB issued a report on the crash in December 1992. In that report, the NTSB said it 'could not identify conclusive evidence to explain the loss of' the aircraft, but indicated that the two most likely explanations were a malfunction of the airplane’s directional control system or an encounter with an unusually severe atmospheric disturbance.

Investigation into a September 1994 crash of a USAir Boeing 737-300 and an loss of control incident on June 9, 1996 (Eastwind Airlines Boeing 737-200), cited a malfunction in the plane’s rudder system as the most likely cause of all three events.

Probable Cause:

PROBABLE CAUSE: "A loss of control of the airplane resulting from the movement of the rudder surface to its blowdown limit. The rudder surface most likely deflected in a direction opposite to that commanded by the pilots as a result of a jam of the main rudder power control unit servo valve secondary slide to the servo valve housing offset from its neutral position and overtravel of the primary slide."

Accident investigation:
cover
Investigating agency: NTSB
Status: Investigation completed
Duration: 10 years
Accident number: NTSB/AAR-01-01
Download report: Final report

Sources:
» Aviation Week & Space Technology 11.03.1991 (25-26)
» Flight International 14-21.12.1992 (34)
» NTSB Safety Recommendations A-92-57 and -58
» NTSB/AAR-92/06
» Scramble Vol.13, nr.04
» Scramble 165


Opérations de secours

NTSB issued 24 Safety Recommendations

Show all AD's and Safety Recommendations

Photos

photo of Boeing 737-291 N999UA
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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 Denver-Stapleton International Airport, CO et Colorado Springs-Peterson Field, CO est de 109 km (68 miles).
Accident location: Exact; as reported in the official accident report.

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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