What happened
On November 5, 2005, an Airbus A320-200 was performing a positioning flight from Berlin-Schönefeld to Frankfurt/Main. While on approach to runway 25R at approximately 05:40 local time, the aircraft encountered a sudden, uncommanded movement around its longitudinal axis. At an altitude of approximately 3,800 ft, as the aircraft was intercepting the Instrument Landing System (ILS) glideslope, it experienced a rapid roll of 28 degrees to the right followed by an 8-degree roll to the left within a three-second period. This motion was accompanied by an increase in the angle of attack and a loss of airspeed.
The crew responded by disconnecting the autopilot and autothrottle to manually stabilize the aircraft. The disturbance concluded approximately 400 ft above the glideslope. Because the runway remained visible, the crew continued the approach and landed the aircraft without further incident. At the time of the event, the aircraft was in a light configuration, with a mass of approximately 46 tonnes.
The investigation
The BFU investigation utilized flight crew statements, radar records, and flight data recorder (FDR) data. To determine if the aircraft had encountered the wake turbulence of a preceding Boeing 747-400, the BFU collaborated with the Institute of Flight System Technology at the German Aerospace Center (DLR).
Using the DLR "P2P Probabilistic Two–Phase WV transport & decay model," investigators simulated the behavior of the wake vortices. The analysis integrated radar positions of both aircraft, wind data, and the known flight parameters of the preceding heavy aircraft. The investigation specifically examined the vertical and lateral separation between the A320 and the vortex core, as well as the decay of the wake over time based on the 129-second interval since the vortex formation.