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Last updated: 15 August 2020
Status:Definitief
Datum:zondag 3 maart 1991
Tijd:09:44
Type:Silhouette image of generic B732 model; specific model in this crash may look slightly different
Boeing 737-291
Luchtvaartmaatschappij:United Airlines
Registratie: N999UA
Constructienummer: 22742/875
Bouwjaar: 1982-05-11 (8 years 10 months)
Aantal vlieguren:26050
Aantal vluchten:19734
Motoren: 2 Pratt & Whitney JT8D-17
Bemanning:slachtoffers: 5 / inzittenden: 5
Passagiers:slachtoffers: 20 / inzittenden: 20
Totaal:slachtoffers: 25 / inzittenden: 25
Schade: Vernield
Gevolgen: Written off (damaged beyond repair)
Plaats:6,4 km (4 mijl) S of Colorado Springs, CO (   Verenigde Staten)
Fase: Nadering (APR)
Soort vlucht:Binnenlandse lijnvlucht
Vliegveld van vertrek:Denver-Stapleton International Airport, CO (DEN/KDEN), Verenigde Staten
Vliegveld van aankomst:Colorado Springs-Peterson Field, CO (COS/KCOS), Verenigde Staten
Vluchtnummer:UA585
Beschrijving:
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

Bronnen:
» Aviation Week & Space Technology 11.03.1991 (25-26)
» Flight International 14-21 December 1992 (34)
» NTSB Safety Recommendations A-92-57 and -58
» NTSB/AAR-92/06
» Scramble Vol.13, nr.04
» Scramble 165


Veiligheidsmaatregelen

NTSB issued 24 Safety Recommendations

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Foto's

photo of Boeing-737-291-N999UA
accident date: 03-03-1991
type: Boeing 737-291
registration: N999UA
 

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Kaart
Deze kaart geeft het vliegveld van vetrek weer en de geplande bestemming van de vlucht. De lijn tussen de vliegvelden geeft niet de exacte vliegroute weer.
De afstand tussen Denver-Stapleton International Airport, CO en Colorado Springs-Peterson Field, CO bedraagt 109 km (68 miles).
Accident location: Exact; as reported in the official accident report.

This information is not presented as the Flight Safety Foundation or the Aviation Safety Network’s opinion as to the cause of the accident. It is preliminary and is based on the facts as they are known at this time.
languages: languages

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