Event Details

Title:Pitch oscillation, Trans World Airlines, Inc., Boeing 707-331B, N8705T, Los Angeles, California, August 28, 1973
Micro summary:Uncommanded pitch oscillations affected this Boeing 707-331B on approach, seriously injuring several people.
Event Time:1973-08-28 at 2150 PDT
File Name:1973-08-28-US.pdf
Publishing Agency:National Transportation Safety Board (NTSB)
Publishing Country:USA
Report number:NTSB-AAR-74-8
Site of event:Descent; LAX, 22000' MSL
Departure:Honolulu International Airport, Honolulu, Hawaii, USA
Destination:Los Angeles International Airport, Los Angeles, California, USA
Airplane Type(s):Boeing 707-331B
Flight Phase:Approach
Operator(s):Trans World Airlines
Type of flight:Revenue
Serious Injuries:3
Other Injuries:0
Executive Summary:At 2150 on August 28, 1973, Trans World Airlines, Inc., Flight 742, a Boeing 707-331B (N8705T), experienced longitudinal oscillations (porpoised) while descending to the Los Angeles International Airport, Los Angeles, California. One hundred forty-one passengers and 11 crewmembers were aboard. As a result of the accident, one passenger was injured critically and died 2 days later; one flight attendant and two other passengers were injured seriously.

The flight was a scheduled passenger flight from Honolulu to Los Angeles. The flight was routine until the aircraft was about 35 miles west of Los Angeles. While it was descending through 22,000 feet pressure altitude at 350 knots indicated airspeed, the aircraft began to porpoise. Over 50 oscillations were experienced which produced peak acceleration forces of +2.4g to -0. 3g at the aircraft's center of gravity. The oscillations subsided as the indicated airspeed was reduced to about 300 knots. The flight continued to Los Angeles. without further difficulty.

The National Transportation Safety Board determines that the probable cause of this accident was a combination of design tolerances in the aircraft's longitudinal control system which, under certain conditions, produced a critical relationship between control forces and aircraft response. The atypical control force characteristics which were present in this particular aircraft's control system were conducive to overcontrol of the aircraft by the pilot. The pilot's normal reaction to an unexpected longitudinal disturbance led to a pitching oscillation which was temporarily sustained by his subsequent application of control column forces to regain stable flight.

The cause of the death and injuries was the impact of unrestrained persons with unyielding objects in the cabin environment.

As a result of the investigation, the Safety Board has submitted five recommendations to the Federal Aviation Administration.
Learning Keywords:Systems - Flight Control System
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