On July 10, 1993, a Mcdonnell Douglas DC-10-40 (registration N158US) was involved in an aviation accident near Detroit, MI. Investigators recorded the probable cause as: the failure of a navigation system (#1 INS) for reason or reasons undetermined. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During a climb through 20,000 feet, a failure in the number one inertial navigation system caused erroneous bank angle signals that moved the lower rudder hydraulic actuator.
What happened
While the aircraft was climbing through an altitude of 20,000 feet, a malfunction occurred within the number one inertial navigation system (INS). The gyroscope within this unit tumbled, causing its output to vary significantly. This tumbling produced a false bank angle signal that was subsequently transmitted to the yaw flight guidance computer.
The investigation
The failure mode of the INS allowed the erroneous bank angle information to reach the attitude monitoring and switching unit. In response to this incorrect data, the unit moved the lower rudder hydraulic actuator. This mechanical action caused the lower rudder to move unexpectedly during the climb phase.