What happened
On August 2, 2003, a Boeing 737-800 departed Corfu Airport (Korfu) for Düsseldorf, carrying 179 passengers and 6 crew members. Following takeoff from runway 17, the crew initiated the TIGRA 1C departure procedure. At approximately 600 feet, the crew engaged the L-NAV function and subsequently the autopilot.
Flight data recorder analysis revealed that the aircraft had already entered a left bank of approximately 34° due to manual aileron inputs prior to the autopilot being engaged. As the autopilot attempted to correct the flight path, the bank angle increased to 37°. To prevent further deviation, the pilot in command intervened manually, which caused the autopilot to switch into Control Wheel Steering (CWS) mode for approximately two seconds before disconnecting entirely. The aircraft was then flown manually for several seconds before the autopilot was re-engaged, eventually stabilizing the bank angle within operational limits.
The investigation
The BFU examined the flight data recorder and consulted with the aircraft manufacturer to determine if a technical malfunction had occurred. The investigation also reviewed the cockpit environment, including the weather conditions and the crew's workload during the departure phase.
Findings
- The investigation found no technical malfunction in the Auto-Flight System (AFS).
- The excessive bank angle was caused by the crew engaging the autopilot while the aircraft was already in a significant manual turn, combined with the aircraft's inherent inertia.
- The aircraft briefly exceeded the autopilot's operational limit of 35° bank angle.
- The co-pilot did not alert the commander when the bank angle exceeded the recommended 25° limit, likely because they were occupied with other cockpit tasks.
- High workload during the departure phase and turbulent weather conditions, including thunderstorms and rain, likely contributed to a lack of situational awareness and deficiencies in Crew Resource Management (CRM).
Safety action
The airline conducted an internal evaluation of the incident and implemented additional simulator training focusing on immediate turns after takeoff.