United Airlines Flight 585
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| Summary | |
|---|---|
| Date | March 3, 1991 |
| Type | Rudder Malfunction |
| Site | Colorado Springs, Colorado, USA |
| Passengers | 20 |
| Crew | 5 |
| Injuries | 0 |
| Fatalities | 25 |
| Survivors | 0 |
| Aircraft type | Boeing 737-291 |
| Operator | United Airlines |
| Tail number | N999UA [22742] (f/n 1299) |
| Flight origin | Greater Peoria Regional Airport |
| Last stopover | Stapleton International Airport |
| Destination | Colorado Springs Airport |
United Airlines Flight 585 was a scheduled domestic passenger airline flight from the now-decommissioned Stapleton International Airport in Denver to Colorado Springs Municipal Airport in Colorado Springs, Colorado.
On March 3, 1991, the Boeing 737-200, registered N999UA, carrying 20 passengers plus a flight crew of 5 (Captain Harold Green, First Officer Patricia Eidson and three flight attendants) crashed while on final approach to runway 35, at the Colorado Springs airport. There were no survivors.
Flight 585 suddenly rolled to the right and began to pitch downward, nose first. Attempts to initiate a go-around using a thrust increase and 15-degree flaps were unsuccessful. As the altitude decreased, acceleration increased to 4g. The 737 crashed into nearby Widefield Park, less than four miles from the runway threshold.
Patricia Eidson was the second female pilot to die in an accident involving a United States commercial airliner. The first female pilot fatality, was that of First Officer Zilda A. Spadaro-Wolan, in the Henson Airlines flight 1517 crash of September 23, 1985 near Grottoes, Virginia. [1]
Contents |
[edit] Investigations
The subsequent investigation by the NTSB lasted one year and 9 months.
Although the flight data recorder (FDR) outer protective case was damaged, the foil tape inside was intact and all the data was extractable. The FDR only recorded five parameters: heading; altitude; airspeed; normal acceleration (G loads); and microphone keying. The data proved insufficient to establish why the plane suddenly went into the fatal dive. The NTSB considered the possibilities of a malfunction of the rudder PCU servo (which might have caused the rudder to reverse) and the effect that powerful rotor winds coming off of the mountains might have had, but there simply wasn't enough evidence to prove either scenario.
Thus, the first NTSB report (issued on December 8, 1992) did not conclude with the usual "probable cause." Instead, it said "The National Transportation Safety Board, after an exhaustive investigation effort, could not identify conclusive evidence to explain the loss of United Airlines flight 585." [2]
[edit] Probable cause
After the crash of another B-737, USAir Flight 427, the NTSB reopened the UAL 585 case. It was finally determined that both crashes were the result of a sudden malfunction of the rudder power control unit (PCU). The pilots lost control of the airplane because "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."[3]
[edit] See also
[edit] Notes
[edit] External links
- AirDisaster.com Special Report: United Airlines Flight 585
- Accident description on the Aviation Safety Network
- Boeing 737 Rudder Design Defect
- Airliners.net Pre-crash photos
