An Acoustic Tomography System for
Making High resolution Measurements of Aircraft
Wake Vortices(Andrew Martin)
System DescriptionFirst Results (Don Delisi has provided valuable assistance)Wind ProfilerFuture PlansQuestions Patents applied for,
pending and granted
Far Wake Workshop, Marseille 27-29May 2008
System DescriptionAcoustic Chirp Sounders - 1
• This is an active acoustic tomographic system• Use coded acoustic chirp waveforms and a
matched filter receiver to detect the transmitted chirp.– Matched filter used only to recover the transmitted
signal, not to detect the vortex!!– Makes no assumptions about the vortex signal
• Provides high resolution distance measurements.• Transmit-while-listen, 1 transmit and 32 receive
antennas for wake vortex, 3 transmit and 3 receive antennas for meteorology.
• Theory of system operation well developed.
System DescriptionAcoustic Chirp Sounders - 2
• Very high S/N for wake vortex and meteorological measurements, >10dB.
• High spatial and temporal resolution, sees vortices higher than ~10m above ground.
• High noise immunity, works in rain and fog.• Simple hardware, complex software.• Remotely manageable.• Fully automatic.• Theory of acoustic reflection for vortices is being
improved.
System Parameters• Measurements made every 2.7 seconds
– Uses 35 chirps (but not limited to), 0.5 sec transmit, 2.7sec receive includes transmit time.
• 32 receivers each sampled at 96,000.• Every measurement is independent.• Transmit left and right simultaneously,
minimal interference, but sometimes makes current analysis a bit more complex (dual frequency solves this).
• Provides measurements of both vortices every 2.7 sec.
0 20 40 60 80 100 120 140 160 180 200
10-1
100
101
Range gate number (1.5m/gate)
Log
scal
e V
olts
WV Signal Levels From One Receiver
Direct signal Vortex signal insingle range gate
Noise level
20 to 50dB S/N
Noise in rainup to +15db
Rain noise fromrain drops hitting
microphones.
Acoustic Tomography System Layout
Porttransmitter
31 receivers4.4m apart132m long
Approx 60m
Starboardtransmitter
Sonic Anemometer
Instrumentation hut
This is the first experimentalsystem to be deployed.
System optimizationwork now begins!!
Vortex Location Using Acoustic Tomography
port WVposition
for one chirpport transmit, port xmit receivers 1-31 star xmit
Amplitude
Picture is 220m x 80mport transmitted signal only for port vortex,starboard transmit shows starboard vortex.
10dB tomographyprocessing gain,
overall S/N30 to 60dB,
15 to 45dB in rain
What Has Been Measured Landing @ 1km
DH8A vortex position
0
10
20
30
40
50
60
70
-60 -40 -20 0 20 40 60
Lateral position from centre
Hei
ght (
m)
Wind 0.3m/s
port vortex starboard vortex
B777 Vortex Position
0
10
20
30
40
50
60
70
-80 -60 -40 -20 0 20 40 60 80
Lateral position from centre (m)
Hei
ght (
m)
port vortex starboard vortex
Wind 0.1m/s
Position looks good, strength is promising
Saab 340 B777
61m21m
up to
Lateral Position vs Time B738 ExamplesLateral Position vs Height
0
10
20
30
40
50
60
70
-90 -80 -70 -60 -50 -40 -30 -20 -10 0
Lateral position (m)
Hei
ght (
m)
Wind 1.9m/s
port vortex starboard voretx
Lateral Position vs Height
0
10
20
30
40
50
60
-90 -80 -70 -60 -50 -40 -30 -20 -10 0 10
Lateral position (m)
Hei
ght (
m)
Wind 1.6m/s
port vortex starboard voretx
Lateral Position vs Height
0
10
20
30
40
50
60
-80 -60 -40 -20 0 20 40 60 80
Lateral position (m)
Hei
ght (
m)
Wind 0.1m/s
port vortex starboard voretx
Lateral Position vs Height
0
10
20
30
40
50
60
-80 -60 -40 -20 0 20 40 60 80
Lateral position (m)
Hei
ght (
m)
Wind 1.4m/s
port vortex starboard voretx
Altitude vs Time, B738, 8 May 2008, Melbourne
y = -1.72x + 55.0R2 = 0.997
0
10
20
30
40
50
60
70
0 10 20 30 40 50 60Wake Age (seconds)
Alti
tude
(m)
8 May, 1725, Port 8 May, 1725, Starboard 8 May, 1735, Port 8 May, 1735, Starboard 8 May, 1756, Port 8 May, 1756, Starboard 8 May, 1808, Port 8 May, 1808, Starboard 8 May, 1817, Port 8 May, 1817, Starboard 8 May, 1830, Port 8 May, 1830, Starboard 8 May, 1834, Port 8 May, 1834, Starboard 8 May, 1844, Port 8 May, 1844, Starboard Median Altitude Median Altitude, t = 0-12 secLinear ( Median Altitude, t = 0-12 sec)
Altitude vs Time, B738, 11 May 2008, Melbourne
y = -1.72x + 59.0R2 = 0.999
0
10
20
30
40
50
60
70
0 10 20 30 40 50 60Wake Age (seconds)
Alti
tude
(m)
11 May, 1045, Port 11 May, 1045, Starboard 11 May, 1136, Port 11 May, 1136, Starboard 11 May, 1146, Port 11 May, 1146, Starboard 11 May, 1152, Port 11 May, 1152, Starboard 11 May, 1201, Port 11 May, 1201, Starboard 11 May, 1207, Port 11 May, 1207, Starboard 11 May, 1228, Port 11 May, 1228, Starboard 11 May, 1251, Port 11 May, 1251, Starboard 11 May, 1311, Port 11 May, 1311, Starboard 11 May, 1322, Port 11 May, 1322, Starboard 11 May, 1353, Port 11 May, 1353, Starboard 11 May, 1402, Port 11 May, 1402, Starboard 11 May, 1409, Port 11 May, 1409, Starboard 11 May, 1420, Port 11 May, 1420, Starboard 11 May, 1438, Port 11 May, 1438, Starboard 11 May, 1444, Port 11 May, 1444, Starboard 11 May, 1448, Port 11 May, 1448, Starboard 11 May, 1458, Port 11 May, 1458, Starboard 11 May, 1507, Port 11 May, 1507, Starboard 11 May, 1554, Port 11 May, 1554, StarboardSeries41 Series42
bo vs Time, B738, Melbourne
0
10
20
30
40
50
60
70
80
0 10 20 30 40 50
Wake Age (seconds)
bo (m
) B738-29Apr-1335 B738-29Apr-1345 B738-29Apr-1403 Elliptical bo B738-8May-1725 B738-8May-1808 B738-8May-1817 B738-8May-1830 B738-8May-1834 B738-8May-1844 B738-11May-1045 B738-11May-1136 B738-11May-1146 B738-11May-1152 B738-11May-1201 B738-11May-1207 B738-11May-1228 B738-11May-1251 B738-11May-1311 B738-11May-1322 B738-11May-1353 B738-11May-1402 B738-11May-1409 B738-11May-1420 B738-11May-1438 B738-11May-1444 B738-11May-1448 B738-11May-1458 B738-11May-1507 B738-11May-1554 Average
Elliptical bo
After 6 sec vortices diverge at average of approx 1m/sup to about 28 sec
average bo at 5.5 sec = 29.5m
WV Measurement Summary• Real measurements every 2.7 sec show…• Vortices fall at close to previously
measured values.• Advection of Vortices with the wind before
ground effect.• In zero cross wind vortices separate in
ground effect as expected.• Downwind vortex moves at about 0.7m/s
faster than wind.• Showing “in-ground” effects at ~50m for
B738.
Wake Vortex Specifications
Very high S/N ensures excellent noise immunity
Noise immunity
Simple components, low maintenancePhysical
Fully automatic (uses aircraft noise peak)Operation
All weather including rainEnvironment
180m longAntenna array
Simultaneous WV circulation looks possibleMeasurements
Simultaneously and independently detects each WV position
Measurements
>95% (up to B777, B747 probably also)Detection probability
33 x 0.7m X 1.5mAntennas
400 watts, adjustableOutput acoustic power
<3mRange error
1.5mResolution
Every 2.7 seconds, to at least 100secondsUpdate rate
10m to100m H x 200m W (to be extended)Range, Day & Night (current)
A High resolution Wind Profiler for assisting in WV system
development and deployment.
Calibration
Sonic anemometer @ 428m
Sonic anemometer @ 52m
DoD
LF
Com
mun
icat
ions
Tow
er (p
revi
ousl
y O
meg
a)
Current System Capability
Wind Profiler SpecificationsAcoustic chirpTechnology
Temperature being developedMeasurements
TKE, EDR is promisingMeasurements
Wind H & V + std dev + shearMeasurements
Simple components, low maintenance (MTBF >1 year)
Hardware
6 x 1.5m parabolicAntennas
40 wattsOutput acoustic power
<6m at 30km/hrRange error (speed dependent)
<6m at 30km/hrResolution (speed dependent)
Every 30 secondsUpdate rate
20m to 1000mRange
Future Plans, 1-3 years• Develop Melbourne Airport (YMML) as an international
centre–of-excellence for aviation meteorology.• Improve models and theory of acoustic reflection from
vortex.• Commence discussions about other trial locations.• Investigate requirements to increase range to cover
~300m high x 500m wide.• Deploy improved capability vortex detection system.• Deploy vertical profilers.• Further develop theory and models for WV behavior
using YMML high resolution vertical profiles and WV measurements (+ various other locations).
• Deploy full scale system at YMML.• Validation trials at YMML (+ other locations as well).
Real-time measurements to assist in solving a complex
scientific and engineering problem.
Questions?
