United Airlines Flight 553
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| Summary | |
|---|---|
| Date | December 8, 1972 |
| Type | Aircraft stall |
| Site | Chicago, Illinois |
| Fatalities | 45 (2 on the ground) |
| Injuries | 16 |
| Aircraft | |
| Aircraft type | Boeing 737-222 |
| Operator | United Airlines |
| Tail number | N9031U |
| Passengers | 55 |
| Crew | 6 |
| Survivors | 18 |
United Airlines Flight 553, registration N9031U, City of Lincoln, was a Boeing 737-222 en route from Washington National Airport to Omaha, Nebraska via Chicago Midway International Airport on December 8, 1972. After the crew was told to go around and abort their first landing attempt on runway 31L, the aircraft struck trees and then roofs along West 71st Street before crashing into a home in the 3700 block of West 70th Place. A total of 45 people were killed in the accident, 43 of them on the plane.
The three-man flight crew was killed, but the three flight attendants survived. The pilots' union contract at the time compelled United Airlines to have three licensed pilots onboard, even though Boeing had designed the 737 to be flown by a crew of two, instead of three. The only person to survive in the forward part of the plane ahead of the wing was the First Class flight attendant. Her jumpseat collapsed, and she was severely injured in the crash. Fifteen passengers and the other two flight attendants in coach survived.
Among the passengers killed were Illinois Congressman George W. Collins and Watergate conspirator E. Howard Hunt's wife, Dorothy Hunt. Also killed was Michele Clark, a correspondent for CBS News. Clark was one of the first female African-American network correspondents.
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[edit] Investigation
The accident was, at the time, one of the most investigated airplane crashes in history. Mrs. Hunt's purse contained $10,585 in cash and she had purchased flight insurance for $250,000 prior to boarding the flight. Conspiracy theorists believed the plane was targeted by government agencies. The Federal Bureau of Investigation assisted the National Transportation Safety Board (NTSB) in its investigation when claims the flight was sabotaged surfaced. The office of the Cook County Medical Examiner convened a coroner's jury and launched a parallel investigation. Some have claimed the FBI withheld or destroyed evidence.[citation needed] Nixon administration figure Chuck Colson told TIME magazine that "I don't say this to my people. They'd think I'm nuts. I think the CIA killed Dorothy Hunt."[1][2] However, the same article speculated that Colson was accusing the CIA of the broad Watergate conspiracy in a desperate attempt to stave off President Richard Nixon's impeachment in the scandal, and that he may have "lost touch with reality" as he faced a prison sentence.[2]
The NTSB found that the the FDR (Flight Data Recorder) on board the aircraft, had become inoperative approximately 14 minutes before the crash. Fortunately, the ARTS-III (Automated Terminal Radar Services) system was in operation at the time of the accident, and that data was saved on tapes in the Midway Control Tower. Those tapes were analyzed extensively and compared to Boeing flight profile data, to develop the course, speed, rate of descent and altitudes of the plane, as it made its approach to Chicago Midway. The CVR (Cockpit Voice Recorder) was working normally and the tape in that "black box" was relatively undamaged. That enabled the NTSB to sequence it in time with the readings of ARTS-III. The NTSB then was able to determine the power output of the engines, at any given point in time, with CVR tape sound analysis. That correlation (CVR with ARTS-III) showed that the stick shaker (stall warning device attached to the pilots' control yoke) started 6 to 7 seconds after the plane leveled off at 1,000 ft MSL, and it continued until ground impact.
That ARTS-III system tracked the plane from a position of 55 miles east of its antennae site, to the point when the plane was stalling, at 380 ft. AGL.
The probable cause of the accident was the stalling of the airplane (speed got too low), because the captain failed to ensure that the flight remained within the required airspeed and altitude parameters, for that non-precision approach profile. No evidence was ever found of sabotage or foul play.
This was a classic "tunnel vision" accident, where the pilots got "behind the airplane," and while attempting to catch up, they failed to see the deteriorating flight conditions until it was too late. They were descending too fast, at too low of a speed, to be within the required "stabilized approach" SOP parameters. Ironically, that situation was created by the fact that the plane was too fast and too high, when they got close to the Outer Marker. At that point, SOP required them to initiate a missed approach procedure, but instead, they violated the cardinal rule----which required a stabilized approach from the OM inbound----and instead attempted to catch up while the plane was too close to the airport and the ground. When the captain finally did call for go-around thrust, they forgot to retract the in-flight wing spoilers (they had been using them for speed brakes, trying to slow the plane as rapidly as possible) and that increased the stall speed of the wings.
Thirty-three years later to the day, in 2005, Southwest Airlines Flight 1248 skidded off the same runway, now designated 31C, at Midway Airport and onto a residential street.
[edit] Trivia
- United still flies a flight under the 553 designation; currently this route is between Kansas City International Airport (MCI) and Denver International Airport (DEN).
[edit] References
- ^ The Yankee and Cowboy Way, by Carl Oglesby, Berkley Medallion Books, New York, 1977, p. 227, citing Time for July 8, 1974.
- ^ a b "Colson's Weird Scenario" July 8, 1974, TIME Magazine. Accessed January 26, 2007.
[edit] External links
- Chicago Public Library MRC Listing: Crash of United Airlines Flight 553
- NTSB report on United Air Lines Inc. Flight 553
