Uncontrolled Roll During Approach at Frankfurt/Main

Incident Overview and Aircraft Details On 5 November 2005, an Airbus A320-200 (A320) was conducting a positioning flight from Berlin-Schönefeld to Frankfurt/Main. The aircraft, manufactured in 2001 with serial number 1381, was operated by two pilots and had a mass of approximately 46 tonnes. During the approach to runway 25R, the A320 encountered a sudden uncontrolled roll at approximately 3,800 feet while intercepting the ILS glide path. A Boeing 747-400 was flying ahead of the A320. ## Flight Sequence and Recovery The uncontrolled roll occurred over a period of approximately three seconds, with the aircraft initially rolling 28 degrees to the right and then 8 degrees to the left. This roll was accompanied by an increase in angle of attack and a decrease in airspeed. The pilot disengaged the autopilot and automatic thrust control, and manually stabilized the aircraft. The incident ended approximately 400 feet above the glide path. With the runway in sight, the approach was continued and the aircraft landed without further issues. ## Investigation and Wake Turbulence Analysis The German Federal Bureau of Aircraft Accident Investigation (BFU) conducted the investigation, supported by the Institute of Flight Systems at the German Aerospace Center (DLR). The primary objective was to determine whether the A320 had entered the wake turbulence of the preceding B747. Analysis of flight data recorder (FDR) data, radar recordings, and meteorological data indicated that the B747 generated wake vortices at an altitude of 1,500 meters and a speed of 90 m/s (175 kt). The B747 was estimated to have an approach mass of 278 tonnes. Simulation of the wake turbulence behavior, accounting for vortex decay, wind drift, and induced descent, showed that the wake vortices descended toward the A320, which was flying on the ILS glide path below the B747. The estimated distance between the wake turbulence and the A320 at the time of the incident was approximately 72 meters vertically and 44 meters laterally. The circulation of the wake turbulence after 129 seconds of aging was estimated at 360 m²/s, which constitutes a strong wake turbulence for a medium-category aircraft. ## Conclusion Based on the flight path configuration, prevailing wind direction, and estimated approach distances, the investigation concluded that the following aircraft had come very close to or had encountered a strong wake turbulence. The report was closed summarily under § 18 FlUUG, presenting only the facts without a definitive probable cause determination.