Accident
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| Status: | Final |
| Date: | 03 MAR 1991 |
| Time: | 09:44 |
| Type: | Boeing 737-291 |
| Operator: | United Airlines |
| Registration: | N999UA |
| C/n / msn: | 22742/875 |
| First flight: | 1982-05-11 (8 years 10 months) |
| Total airframe hrs: | 26050 |
| Cycles: | 19734 |
| Engines: | 2 Pratt & Whitney JT8D-17 |
| Crew: | Fatalities: 5 / Occupants: 5 |
| Passengers: | Fatalities: 20 / Occupants: 20 |
| Total: | Fatalities: 25 / Occupants: 25 |
| Airplane damage: | Destroyed |
| Airplane fate: | Written off (damaged beyond repair) |
| Location: | 6,4 km (4 mls) S of Colorado Springs, CO (United States of America)
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| Phase: | Approach (APR) |
| Nature: | Domestic Scheduled Passenger |
| Departure airport: | Denver-Stapleton International Airport, CO (DEN/KDEN), United States of America |
| Colorado Springs-Peterson Field, CO (COS/KCOS), United States of America | |
| Flightnumber: | 585 |
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. (MST). 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: "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. Events:
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
Official accident investigation report
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Photos
Video/animation
Map
This map shows the airport of departure and the intended destination of the flight. The line between the airports does not display the exact flight path.
Distance from Denver-Stapleton International Airport, CO (DEN/KDEN) to Colorado Springs-Peterson Field, CO (COS/KCOS) as the crow flies is 109 km (68 miles).
Distance from Denver-Stapleton International Airport, CO (DEN/KDEN) to Colorado Springs-Peterson Field, CO (COS/KCOS) as the crow flies is 109 km (68 miles).
