DCA25LA093

On January 24, 2025, about 00:31 universal coordinated time (UTC), United Airlines (UAL) flight 613, a Boeing 787-8, experienced altitude excursions during cruise flight while transitioning over Cote d’Ivoire airspace at 36,000 feet. Of the 11 crew members and 243 passengers on board, one person sustained a serious injury and 15 people sustained minor injuries. The aircraft sustained minor damage. The flight was operating under the provisions of Title 14 Code of Federal Regulations Part 121 as a scheduled international passenger flight from Murtala Muhammed International Airport (LOS), Lagos, Nigeria, to Washington Dulles International Airport (IAD), Dulles, Virginia. About 1 hour and 5 minutes prior to the event, inflight data showed a left inertial reference unit (IRU) failure. About 55 minutes later, the data indicated a right IRU failure. According to flight data recorder data, at 00:30:57, the autopilot disconnected automatically, the flight crew took over manual control, and the master caution and master warning were recorded. Altitude excursions began at this time. Three seconds later, the autothrottle disconnected. At 00:31:14, a stick shaker activation was recorded. Twenty seconds later the autopilot was reengaged for one second, then disconnected automatically again. At 00:40:30, the airplane started a right turn back toward Lagos. At 00:44:39, the autopilot was reengaged and remained engaged until final approach into LOS. Altitude excursions from 36,000 mean sea level (msl) feet lasted for about 12 minutes, reaching a maximum altitude of 36,203 and a minimum altitude of 35,577 feet msl. At the time of these altitude excursions, meal service was being conducted in the cabin and injuries resulted. The flight crew elected to perform an air turn back and returned to LOS where the airplane landed uneventfully. Emergency responders met the airplane upon landing and transported injured persons to a nearby clinic. Pursuant to International Civil Aviation Organization (ICAO) Annex 13, the state of occurrence of the accident (Côte d'Ivoire) holds the responsibility to conduct the investigation and has the option to delegate the investigation to another ICAO member state as appropriate. Representing the state of registration, operator, design and manufacture of the aircraft, the NTSB requested and was granted delegation from the Bureau Enquêtes Accidents (BEA) Côte d'Ivoire to conduct the full accident investigation on Jan 27, 2025. The flight recorders, IRUs and attitude heading reference units (AHRUs) were removed from the aircraft in Lagos and flown to IAD on February 3, 2025. The NTSB took possession of these components at IAD and transported them to NTSB headquarters for readout and testing. The flight data recorder was successfully downloaded. The cockpit voice recorder with 2 hour recording capability was read out, and it was found that the accident event had been overwritten. The following NTSB specialists were assigned to investigatethe accident: Operations and Human Performance, Airplane Systems, Survival Factors, and Flight Data Recorder. The Federal Aviation Administration (FAA), United Airlines, Boeing, Honeywell, and Air Line Pilots Association (ALPA) are parties to the investigation. Per ICAO Annex 13, representing the state of occurrence, the BEA Côte d'Ivoire provided an accredited representative to the investigation. The NTSB’s investigation is ongoing.