In-Flight Wake Encounter Prediction with the Wake Encounter Avoidance and Advisory System

Abstract

DLR is working on a Wake Encounter Advisory & Avoidance (WEAA) system to allow pilots to avoid potentially dangerous wake vortex encounters by a tactical evasion maneuver. Such maneuver is of small scale i.e. it tries to adhere to the planned flight track as closely as possible and is not intended to require ATC permission. The paper introduces system design and core functions of the WEAA system (meteorological data fusion, wake vortex prediction, trajectory prediction and conflict detection, hazard evaluation, avoidance trajectory generation, alerting and guidance) and briefly describes DLR's technical solutions. Initial results will be presented for the system implementation including first results from recent flight tests for on-board conflict detection employing DLR's Falcon 20E and A320 Advanced Technology Research Aircraft (ATRA). Nomenclature= coefficient of rolling moment induced by wake vortex C l max, δl = coefficient for maximum rolling moment obtainable by roll motivator deflection (roll control power) ∆H = vertical distance RCR = roll control ratio δ l = deflection of roll moment motivator (usually aileron and/or roll spoiler) σ = standard deviation a = horizontal extent of hazard area (relative to nearest vortex centre) b = vertical extent of hazard area (relative to nearest vortex centre) t * = normalised wake vortex age y * = normalised lateral wake vortex motion (distance travelled over initial wake vortex separation) ∆y = distance in spanwise direction I. MotivationHE encounter of sufficiently strong wake vortices of preceding or crossing aircraft can pose a substantial hazard to the follower as a consequence of • significant induced (linear and angular) accelerations leading to injuries of the aircraft's occupants or structural damages of the airframe, • induced forces and moments -often predominantly rolling moments -leading to a poorly controllable flight condition or even (temporary) loss of control, • hazardous flight path deviations resulting from the above effects, including altitude loss in the downdraft of the wake or as a consequence of the induced roll angle.Wake vortices are often encountered in departure and approach operations -even close to the threshold, which makes them particularly dangerous due to ground proximity -but encounters also regularly occur during cruise or in holding patterns. Separations as procedural means are applied under Instrument Flight Rules (IFR) to avoid

Probabilistic Multimodel Ensemble Wake-Vortex Prediction Employing Bayesian Model Averaging

“…Wake vortices [1], generated at the wings of aircraft as a response to lift, can induce a potentially hazardous rolling moment to any follower. As global air traffic is expected to double in the next 15 years [2] wake vortex forecasts may not only increase the safety in the terminal area but also in-flight [3]. Various fast-time wake vortex models have been developed [4,5,6,7,8,9,10,11] to achieve a safety gain and potential airport capacity benefits.…”

Development of a potential vortex-hazard index to predict cruise-level wake turbulence encounters

“…A potential safety issue of wake vortex encounters at cruise levels is anticipated [2,3] because of increasing air traffic, utilization of large transport aircraft like Airbus A380 and Boeing 747 by the airliners and the reduced vertical separation between two aircraft. A Wake Encounter Avoidance and Advisory system (WEAA) has been developed at German Aerospace Center and validated using data collected from flight tests [4,5]. At cruise altitude, though on-board systems and forecasting techniques are used to identify the presence of some of the weather hazards, currently there are no built-in systems to show the persistence of the trailing vortices behind the aircraft.…”

Multi-model ensemble wake vortex prediction

“…Both decay and transport are affected by atmospheric parameters, such as wind conditions, thermal stratification, shear layers, and turbulence. As global air traffic is estimated to double in the next 15 years [2] with regional growth rates over 4% (see Table 1.1) the risk to encounter wake vortices both in terminal area but also in-flight [3] is increased. As regulatory wake vortex separation distances are one of the bottlenecks of airport capacity, the air-traffic organizations decided to recategorize the separation standards.…”