What happened
On September 1, 2011, a Boeing 767-300 was operating a scheduled international flight from Warsaw Chopin Airport (EPWA) to Chicago O'Hare International Airport (KORD). The aircraft was carrying 239 passengers and 11 crew members. During the takeoff roll, after the N1 thrust lever was advanced, the autothrottle failed to arm, forcing the crew to manually set the engine thrust.
As the aircraft climbed, the crew identified several significant malfunctions in the flight guidance systems. These included the loss of lateral navigation (LNAV) and vertical navigation (V/NAV) capabilities, as well as the failure of both the left and right autopilots (AP-L and AP-R). Additionally, the flight director bars (FD BAR) were missing from the left attitude director indicator (ADI), and the commanded airspeed bug was unavailable on the captain's airspeed indicator.
Initially, the crew navigated the departure procedure manually. Upon reaching approximately FL190, they managed to engage the right autopilot and VNAV system. To maintain operational monitoring, the captain transferred the instrument source selection and FMC to the right side. After verifying ETOPS conditions, the crew decided to continue the flight to the destination. During the Atlantic crossing, the crew also dealt with secondary issues, including the failure of a forward galley and a passenger cabin screen, as well as a standby horizon malfunction.
The investigation
The investigation, concluded by the PKBWL, reviewed the findings provided by the operator. The investigation focused on the sequence of automation failures and the subsequent manual handling of the aircraft. The technical analysis centered on the interaction between the Mode Control Panel (MCP), Flight Control Computers (FCC), and the Flight Management Computer (FMC).
Findings
- The primary cause of the incident was interface errors between the MCP/FCC-L, MCP/FCC-R, MCP/TMC, and FMC-L/MCP units.
- The autothrottle failed to arm during the takeoff roll.
- Multiple flight guidance functions, including LNAV, VNAV, and both autopilot channels, were unavailable.
- The crew experienced increased workload due to simultaneous failures in the cabin (galley and passenger screen) and the standby horizon.
- The aircraft landed safely at KORD without further incident.