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Accident description
Last updated: 26 June 2017
Date:Wednesday 31 March 1971
Type:Silhouette image of generic B720 model; specific model in this crash may look slightly different
Boeing 720-047B
Operator:Western Air Lines
Registration: N3166
C/n / msn: 19439/621
First flight: 1967-08-27 (3 years 7 months)
Total airframe hrs:11521
Engines: 4 Pratt & Whitney JT3D-3B
Crew:Fatalities: 5 / Occupants: 5
Passengers:Fatalities: 0 / Occupants: 0
Total:Fatalities: 5 / Occupants: 5
Airplane damage: Damaged beyond repair
Location:Ontario International Airport, CA (ONT) (   United States of America)
Phase: Approach (APR)
Departure airport:Los Angeles International Airport, CA (LAX/KLAX), United States of America
Destination airport:Ontario International Airport, CA (ONT/KONT), United States of America
Flightnumber: 366
Control was lost during a 3-engine missed ILS approach procedure and the aircraft crashed.
Failure of the aircraft rudder hydraulic actuator support fitting led to the loss of left rudder control. The loss of control situation was worsened by the degraded external visual clues (600 feet overcast; 1200 m visibility in fog haze and smoke).

Probable Cause:

PROBABLE CAUSE: "The failure of the aircraft rudder hydraulic actuator support fitting. The failure of the fitting resulted in the inapparent loss of left rudder control which, under the conditions of the flight, precluded the pilotsí ability to maintain directional control during a simulated engine-out missed-approach. The existing weather conditions degraded external visual cues, thereby hampering rapid assessment of aircraft performance by the flight check captain."

Accident investigation:
investigating agency: National Transport Safety Bureau (NTSB) - United States of America
status: Final
number: NTSB/AAR-72-18
released:7 June 1972
duration of investigation: 1 year and 2 months
download report: Western Air Lines, Inc., Boeing 720- 047B, N3166, Ontario International Airport, Ontario, California, March 31, 1971. (NTSB/AAR-72-18)

Low visibility

Loss of control



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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 Los Angeles International Airport, CA to Ontario International Airport, CA as the crow flies is 75 km (47 miles).

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Boeing 720

  • 154 built
  • 6th loss
  • 5th fatal accident
  • 3rd worst accident (at the time)
  • 4th worst accident (currently)
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