Wake vortex severity assessment – a core element of the safety case

Kurzfassung

In the framework of internal, national and European projects DLR has an extensive history in the field of wake vortex encounter analysis, severity assessment, wake vortex prediction and wake vortex advisory systems. A key question is: How close can an aircraft fly to a vortex of a given strength and respond with an acceptable aircraft reaction. This question has to be solved for any analysis of aircraft separation/ classes. It is the underlying question for any wake vortex related safety case with respect to operational implementation. Another main aspect for the safety case is the definition of the underlying wake vortex separation concept. DLR developed and demonstrated a wake vortex advisory system "WSVBS" in order to predict safe wake vortex separations. The expertise of the DLR Institute of Flight Systems comprises high fidelity aircraft simulations including wake vortex encounter simulation. Extensive work has been conducted in developing and validating the corresponding models. A unique method for wake vortex flow field identification based on in-situ measurements has been developed and successfully established with numerous flight tests including A380 measurements. Based on the same procedure Aerodynamic Interaction Models (AIMs) have been validated, which are vital for encounter simulation and analysis. A dynamic wake vortex hazard area prediction method SHAPe has been developed for the determination of required wake vortex separations factoring in weather and aircraft properties. The concept has been successfully validated based on piloted simulator and flight tests and is integrated in DLR's "WSVBS." The DLR Institutes of Atmospheric Physics and Flight Systems jointly with other DLR institutes developed the "WSVBS" in order to forecast and monitor the local weather and to predict and monitor wake transport and decay along the glide path. It is integrated into DLR's arrival manager AMAN. The system was successfully employed at Frankfurt International Airport for a field campaign. It ran stable for 66 days without any forecast breakdown and aircraft separations could have reduced in 75% of the time compared to ICAO standards. LIDAR measurements confirmed for about 1100 observed landings that the predictions were safe. The DLR system including concept and display was well accepted by controllers during real time simulations. From fast-time simulations the capacity gain for Frankfurt was estimated to be about 3% taking into account the real traffic mix and operational constraints in the period of one month. The topic of wake vortex separation prediction relates directly to the international efforts for a re-categorisation of the separation standards. Based on the valuable achievements in the above described fields high fidelity encounter simulation, flow field identification, validation of Aerodynamic Interaction Models (AIMs), hazard assessment, (simplified hazard areas/ prediction), and wake vortex prediction DLR is continuously doing research in the current DLR-internal 4-year project "Wetter & Fliegen" (Weather & Flying) embedded in various European activities including SESAR JU.