Investigation Summary
The accident occurred as the crew was attempting to compensate for a late descent and high airspeed while operating in instrument meteorological conditions (IMC). The area was overcast, with visibility for the runway reported only below 500 to 600 feet AGL, forcing the crew to rely heavily on instruments during the non-precision approach. To increase their rate of descent, the crew deployed the flight spoilers (speed brakes). However, they failed to retract them when leveling off at 1,000 feet MSL. This high-drag configuration, combined with the engines at low power, caused the airspeed to decay rapidly. When the air traffic controller ordered a go-around due to separation issues with a preceding aircraft, the stick shaker (stall warning) activated almost simultaneously. In the ensuing confusion, the crew retracted the flaps from 30 to 15 degrees while the spoilers were still extended and the airspeed was critically low. This further increased the stall speed, making the crash inevitable. The aircraft struck trees and houses approximately 1.5 miles southeast of the runway.
Final Conclusions
The NTSB determined the probable cause was the captain's failure to exercise positive flight management during a non-precision approach. This failure resulted in a critical deterioration of airspeed into a stall regime from which level flight could not be maintained. Contributing factors included the crew's distraction by a mechanical failure of the flight data recorder and a lack of cockpit discipline regarding altitude callouts and instrument monitoring.
Photographic Evidence (1)
Video Analysis
The Lever That Killed 45 People | United Airlines 553 — An analysis of the crash of United 553, focusing on the crew's mismanagement of the flight spoilers and the resulting stall during approach to Chicago Midway.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Crew Experience
Captain
Wendell Lewis Whitehouse, age 44.
First Officer
Walter O. Coble, age 43.
Second Officer
Barry J. Elder, age 31.
Systems & Failure Modes
Flight Spoilers
Used to increase drag and descent rate; their non-retraction during level-off was a primary factor in the speed decay.
Stick Shaker
The stall warning system that activated 6 to 7 seconds after the plane leveled off.
Flaps
Retracted prematurely from 30 to 15 degrees during the stall, which increased the stall speed.
Interesting Facts
- 01The crash was the first fatal accident involving a Boeing 737.
- 02The aircraft was named 'City of Lincoln'.
- 03The flight data recorder (FDR) was inoperative at the time of the crash due to a mechanical fault.
- 04Among the fatalities were Congressman George W. Collins and CBS News correspondent Michele Clark.
- 05Of the 45 total fatalities, 43 were occupants of the aircraft and 2 were residents on the ground.
- 06The two ground fatalities were Maggie Cuculich and her daughter Theresa Cuculich, whose home at 3722 West 70th Place was destroyed by the impact.
- 07Investigators used ARTS-III radar data from O'Hare to reconstruct the flight path since the onboard FDR failed.
Safety Actions & Advisories
Crew Coordination Emphasis
The NTSB reiterated concerns regarding cockpit discipline and crew coordination during non-precision approaches, leading to industry-wide focus on what would eventually become Crew Resource Management (CRM).
Known Controversies & Unanswered Questions
Watergate Conspiracy Theories
Reference ↗The presence of Dorothy Hunt, wife of Watergate conspirator E. Howard Hunt, carrying $10,000 in cash led to widespread speculation of sabotage. The NTSB and FBI investigated these claims and found no evidence of foul play.