What happened
During a nighttime climb over water, an aircraft was flying straight and level toward an intersection. The autopilot was not engaged, and the first officer was hand-flying the airplane. While climbing through 6,5 enough feet, the aircraft experienced a sudden roll to the right, reaching a maximum bank angle of 65.5 degrees.
The first officer responded by applying left aileron followed by left rudder input, which successfully returned the aircraft to level flight. Following the event, the crew declared an emergency and dumped 20,000 pounds of fuel before performing an uneventful landing at the departure airport. There were no injuries reported.
At the time of the incident, the captain noted there were no engine indication and crew alerting system warnings, nor were there any traffic collision avoidance system alerts. Weather conditions included a thin deck of clouds at 6,500 feet on a dark night with no moon. The first officer reported that there was no visible horizon, stars, or moon, describing the environment as total darkness.
The investigation
An examination of the aircraft's systems was conducted, which revealed no mechanical or computer-related discrepancies. Data retrieved from the digital flight data recorder (DFDR) showed that the right-hand rolls were initiated by control wheel input.