IRU failures led to United 787 upset over Cote d’Ivoire – NTSB
March 19, 2025
A United Airlines Boeing 787-8 experienced an in-flight upset over Côte d’Ivoire after both its inertial reference units (IRUs) failed, causing altitude excursions that left one passenger seriously injured and 15 others with minor injuries.
The National Transportation Safety Board (NTSB) is now leading the investigation into the January 24 incident, which forced the crew to return to Lagos, Nigeria.
Flight UA613 had been cruising at 36,000 feet en route from Lagos’ Murtala Muhammed International Airport (LOS) to Washington Dulles International Airport (IAD) when the first IRU failure occurred, followed by the second approximately an hour later. IRUs are critical for providing accurate positioning and navigational data to the aircraft’s systems..
The subsequent cascading failures led to the autopilot disconnecting, leaving the flight crew to manage the upset manually.
According to preliminary data from the flight data recorder, the autopilot disconnected at 00:30:57 UTC, triggering master caution and warning alerts. Three seconds later, the autothrottle disengaged. Despite attempts to re-engage the autopilot, the aircraft continued to experience altitude deviations, reaching a peak of 36,203 feet and a low of 35,577 feet.
The disturbances lasted approximately 12 minutes while cabin service was underway, leading to injuries among passengers and crew. Emergency responders met the aircraft upon its return to Lagos, transporting the injured to a nearby clinic for treatment.
Following the incident, Côte d’Ivoire’s Bureau Enquêtes Accidents (BEA) delegated the investigation to the NTSB, given the aircraft’s US registration and manufacture.
Investigators have since transported the flight recorders, IRUs, and attitude heading reference units to the NTSB headquarters for further analysis. While the flight data recorder was successfully downloaded, the cockpit voice recorder’s two-hour capacity resulted in the loss of data from the event itself.
Specialists from the NTSB, along with representatives from the FAA, United Airlines, Boeing, Honeywell, and the Air Line Pilots Association, are collaborating on the ongoing investigation.
