Wake vortex encounter modelling, simulation, assessment, avoidance and alleviation
DLR Institute of Flight Systems > C. Schwarz et al. • Wake vortex encounter research > JUNE 2016 DLR.de • Chart 1
Carsten Schwarz Dennis Vechtel, Jana Schwithal, Dietrich Fischenberg, Tobias Bauer, Nicolas Fezans DLR Institute of Flight Systems
Wake vortex workshop 2016 DLR Braunschweig 08 JUNE 2016
Wake vortex encounter research Motivation and background • Wake encounter severity
• physical understanding important • severity assessment –
core element of procedure/ system design/ certification
DLR Institute of Flight Systems > C. Schwarz et al. • Wake vortex encounter research > JUNE 2016 DLR.de • Chart 2
• DLR Institute of Flight Systems • 16 years of wake encounter
research • numerous internal and EU-
projects and activities, industry contracts
• inter-disciplinary DLR framework • large research facilities:
aircraft and simulators
• DLR: Wake Vortex I & II Weather and Flying WoLv, L-bows
• EU: WakeNet-Europe
• contracts:
• cooperation/ standardisation: FAA/NIA, Eurocontrol, SAE, RTCA
1999 2001 2003 2005 2007 2009 2011 2013 2015
WakeNet2-Europe
DLR Flight Systems: wake vortex activities and cooperation
DLR Institute of Flight Systems > C. Schwarz et al. • Wake vortex encounter research > JUNE 2016 DLR.de • Chart 3
proposal
• Modelling and Simulation
• Severity assessment
• Wake turbulence separations
• Aircraft systems
Wake vortex encounter research Topics
DLR Institute of Flight Systems > C. Schwarz et al. • Wake vortex encounter research > JUNE 2016 DLR.de • Chart 4
Steve Morris
_______ measured -------- reconstructed motion induced
Modeling the wake vortex encounter Validated with flight tests Vortex model (flow field)
DLR Institute of Flight Systems > C. Schwarz et al. • Wake vortex encounter research > JUNE 2016 DLR.de • Chart 5
t [s]
alph
a [d
eg]
approach
cruise
Wake characterisation sheet
Airbus A320 Date: 30/3/2011 Cruise: FL 360 Wind: 268°/ 31 kt Weight: 62 t Duration: 8 min Heading: 251° Config.: CLEAN TAS: 440 kt
distance [nm]
tota
l circ
ulat
ion Γ
[m2 /s
]
lat.
posi
tion
[m]
Flig
ht L
evel
Circulation
Wake descent
distance [nm]
Lateral spacing
DLR Institute of Flight Systems > C. Schwarz et al. • Wake vortex encounter research > JUNE 2016 DLR.de • Chart 6
• Aerodynamic interaction/ aircraft reaction model: strip method
t [s] _______ simulation model output _______ flight test data
Modeling the wake vortex encounter Validated with flight tests
• Model improvement with CFD data
• Verification of local aerodynamic forces with pressure distribution
• Identify improvements for strip method
Wake vortex encounter pressure distribution – DLR project Digital-X/ DLR Institute of Aerodynamics and Flow Technology
Wake encounter severity assessment Simplified Hazard Area (SHA)
• „How close can an aircraft fly safely to a wake vortex?“
• concept: Simplified Hazard Area (SHA)
• conservative/ non-hazard approach, safe and undisturbed operations possible outside the hazard area, no go-arounds
• simple, robust severity criterion • roll control ratio: one parameter to cover complete A/C reaction • validated with pilot-in-the loop simulator & flight tests • dynamic hazard area size (vortex decay, weather) • A/C categories and individual/ pairwise
Roll control ratio RCR
DLR Institute of Flight Systems > C. Schwarz et al. • Wake vortex encounter research > JUNE 2016 DLR.de • Chart 7
• Using analytical models of straight vortices in aircraft simulation is simple for modelling but also a simplification compared to reality
• Therefore DLR also uses more sophisticated flow fields generated with LES for aircraft encounter simulation
• Encounter simulations during approach with pilots-in-the-loop in various full-flight-simulators and in-flight simulation with ATTAS
• Offline simulations for parameter variation during approach (OGE) and in ground vicinity (IGE)
• Investigation of the influence of vortex deformation (OGE + IGE), end effects and plate lines (IGE)
Wake encounter severity assessment Simulations with sophisticated vortex flow fields
DLR Institute of Flight Systems > C. Schwarz et al. • Wake vortex encounter research > JUNE 2016 DLR.de • Chart 8
Wake encounter severity criteria Selected results
no universal wake encounter severity criteria available!
additional activities: • CREDOS (EU FP 6) • WakeNet3-Europe (EU FP 7) • FAA risk matrix activity • RECAT/ SESAR
DLR Institute of Flight Systems > C. Schwarz et al. • Wake vortex encounter research > JUNE 2016 DLR.de • Chart 9
• RCR < 1 acceptable WVE [1972, Robinson, G. H., Larson, R. R.]
• RCR < 0.5 acceptable WVE [1988, Rossow V. J., Tinling, B. E.]
• RCR < 0.2-0.3 appropriate limit for acceptable WVE [1998, Stewart E. C.]
• RCR < 0.5 + 0.006⋅HRCRmax GA prediction [2002, Höhne,G., Reinke, A., Verbeek, M.]
• RCR < 0.2 operationally safe WVE [2006, Hahn, K.-U., Schwarz, C.]
• RCR < 0.2-0.3 operationally safe WVE including vortex deformation [2013, Vechtel, D.]
• Below RCRmax = 0.2 – 0.3 wake vortex impact • is acceptable • cannot be distinguished from other acceptable atmospheric disturbances
such as gusts, light turbulence or thermal • This outcome applies for
• intermediate and final approach • small encounter angles (typical for those flight phases) • roll-dominated and also less roll-dominated encounters
• and includes effects such as • vortex deformation due to the Crow instability • vortex ring formation
• Cruise flight phase to be investigated
Wake encounter severity assessment DLR’s general findings
DLR Institute of Flight Systems > C. Schwarz et al. • Wake vortex encounter research > JUNE 2016 DLR.de • Chart 10
Not every encounter with RCRmax > 0.2 is unacceptable, but below this value encounters can be considered non-hazardous
Simplified Hazard Area Prediction (SHAPe)
• all relevant wake vortex parameters parameterized based on MTOW with boundary fits
• determination of hazard area depending on vortex strength and RCR (worst case approach)
• dimension of safety area for any (generic) aircraft pairing
generator MTOW
follower MTOW
SHAPe
generator data
follower data
SHA calculation
A/C data base, e.g. b=f(MTOW)
SHA dimensions
RCR limit circulation
DLR Institute of Flight Systems > C. Schwarz et al. • Wake vortex encounter research > JUNE 2016 DLR.de • Chart 11
• Development of separation prediction tool WSVBS („Wirbelschleppenvorhersage und Beobachtungssystem“)
• Development of risk analysis/ assessment tool WakeScene • RECAT: Eurocontrol recategorisation activities
• contributions regarding severity assessment, involvement in Eurocontrol Wake Vortex Task Force
• RECAT-EU introduction started March 2016 in France
Wake turbulence separations
DLR Institute of Flight Systems > C. Schwarz et al. • Wake vortex encounter research > JUNE 2016 DLR.de • Chart 12
• Wake impact alleviation control system: reduce wake-induced aircraft reaction
• Safety increase • Reduce risk of injuries • Possibly far term enabler for reduced separation
minima with maintained safety capacity gain
• Information of forward-looking Doppler LiDAR sensor used to generate alleviating control commands
• Questions:
• What are the required LiDAR properties? • What is technologically feasible?
Wake Impact Alleviation
DLR Institute of Flight Systems > C. Schwarz • Wake vortex encounter research > JUNE 2016 DLR.de • Chart 13
Control Actions
Sensor Measurements
Signal Processing
?
• Remote LiDAR (Light Detection and Ranging) sensor measures line-of-sight components of wind velocities in front of aircraft
• Online Wake Identification (OWI) estimates parameters of wake vortex model on basis of LiDAR measurement
• Wake Impact Alleviation Control (WIAC) determines wake-induced disturbance moments resulting from detected wake vortex model and commands control surface deflections which compensate for this disturbance
Concept of Wake Identification Based Wake Impact Alleviation Control
DLR Institute of Flight Systems > C. Schwarz • Wake vortex encounter research > JUNE 2016 DLR.de • Chart 14
partly in cooperation with Airbus
• Success of wake identification and impact alleviation strongly depends on characteristics of lidar sensor
• analysis of sensor requirements ongoing in exchange with lidar experts • Alleviation of wake-induced bank angle of up to 95% and about 70% on average
possible
• Future studies: Anaysis and extention of OWIDIA system for deformed vortices
Wake Impact Alleviation Results and outlook
DLR.de • Chart 15 DLR Institute of Flight Systems > C. Schwarz • Wake vortex encounter research > JUNE 2016
w/o OWIDIAwith OWIDIA5° lateral encounter
A320 behind A340
• functionality as safety net / assistance system (increase of situational awareness)
• basic function: identification of a predicted, imminent or even current wake vortex encounter
• system extension: resolution of conflict by recommendation of tactical small-scale evasion manoeuvres
• conceivable to integrate wake encounter alleviation by F/CTL
Wake Encounter Avoidance & Advisory (WEAA)
DLR’s objectives: system proof-of-concept under operational conditions (in-depth investigation of selected components, comparative studies, benefit analysis)
Objectives: airborne information and warning system prevention of dangerous wake vortex encounters in all phases of flight
DLR Institute of Flight Systems > C. Schwarz et al. • Wake vortex encounter research > JUNE 2016 DLR.de • Chart 16
Exploitation of Existing DLR Knowledge for WEAA Components • Meteorological Data Fusion
(Airbus cooperation)
• Vortex Prediction Model: P2P (HOLZÄPFEL, DLR Atmospheric Physics)
• probabilistic two-phase model • effects of a/c configuration, wind,
wind shear, turbulence, stratification and ground proximity
• real-time capability • extensively validated on LIDAR
measurements and LES
• Hazard Assessment: SHAPe (HAHN, SCHWARZ, DLR Flight Systems)
• hazard rating by means of roll control ratio RCR
• simplified hazard areas (rectangular or elliptical)
• Conflict Detection (Airbus cooperation)
0.1 < RCR ≤ 0.2
0.2 < RCR ≤ 0.3
0.3 < RCR ≤ 0.5
0.5 < RCR ≤ 1.0
1.0 < RCR
DLR Institute of Flight Systems > C. Schwarz et al. • Wake vortex encounter research > JUNE 2016 DLR.de • Chart 17
WV Warning and Avoidance – HMI Navigation Display – Scientific Mode
own track prediction
conflict position
current vortex wake
generator track prediction generator position
(past) generator track (scientific mode only)
time and distance to conflict
Conflict Warning
proposed avoidance trajectory
distance and bearing to generator (for flight test safety only)
Conflict Resolution
NB these are engineering displays for development of the system functions and not necessarily final designs for the operational pilot HMI
DLR Institute of Flight Systems > C. Schwarz et al. • Wake vortex encounter research > JUNE 2016 DLR.de • Chart 18
WEAA Flight Test Campaign 2014 with ATRA and Falcon F-20E
encounter distance ~ 4 nm
Feasibility demonstration of WEAA conflict detection under operational conditions
3 trial flights in April 2014 from Braunschweig 70+ intentional wake encounters for validation of
operational wake vortex prediction and visualisation, conflict detection
experience brought to standardisation activities (RTCA - wake vortex tiger team, SAE G-10WV)
DLR Institute of Flight Systems > C. Schwarz et al. • Wake vortex encounter research > JUNE 2016 DLR.de • Chart 19
www.DLR.de • Slide 20
Sample Encounter Video
Synergies with corresponding activities (1/2) Formation flight/ wind turbine wakes Cruise formation flight trim results – fuel benefits
Wind turbine wake roll control ratio – glider aircraft
DLR.de • Chart 21 DLR Institute of Flight Systems > C. Schwarz et al. • Wake vortex encounter research > JUNE 2016
Δ Fuel Flow [%]
leader
sweet spot
drawn to scale
wind 10 m/s
drawn to scale
x [m]
z [m]
Synergies with corresponding activities (2/2) Aerial refueling / Load control based on remote gust sensing
DLR.de • Chart 22 DLR Institute of Flight Systems > C. Schwarz et al. • Wake vortex encounter research > JUNE 2016
Modelling activites within aerial refueling projects
Lidar-based gust sensing and feedforward load alleviation
DLR Institute of Aerodynamics and Flow Technology
Airbus
position
vertical wind
• Wake turbulence separations/ wake encounter severity assessment
• Aircraft systems
• Wake impact alleviation:
wake measurement and identification based wake impact alleviation control
• Cockpit wake information and warning
Future wake turbulence activities
DLR.de • Chart 23 DLR Institute of Flight Systems > C. Schwarz et al. • Wake vortex encounter research > JUNE 2016
Steve Morris