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7/31/2019 Thedford-ADS-B In_Out Tech Issues-Tuesday Track1
1/23
I n t e g r i t y - S e r v i c e - E x c e l l e n c e
War-winning CapabilitiesOn Time, On CostDelivering what we promised when we promised
I n t e g r i t y - S e r v i c e - E x c e l l e n c e
ADS-B IN/OUT Technical Issues
Aerospace Management Systems Division
Wm A. Thedford, Ph. D.
Jacobs Technology, Inc.
USAF ESC/HBAI
Lead Surveillance EngineerDistribution Statement A:Approved for public release: 66 ABW-2011-0731Distribution unlimited
7/31/2019 Thedford-ADS-B In_Out Tech Issues-Tuesday Track1
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Topics
ADS-B OUT The use of 1090ES and UAT in USAF aircraft
Transponders standards
Comparison of US, European, Canadian, andAustralian standards and requirements
Position requirements and military issues
ADS-B IN
Integration of UAT, 1090ES, and TCAS data USAF considerations
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ADS-B OUT1090ES and UAT
There are 3 ADS-B links VDL Mode 4 only in Northern Europe and
Southern Ring
Universal Access Transceiver only in the US
1090ES (Extended Squitter) is the internationalstandard
Version 0 and 1 accepted except in the US and Europe
Based on DO 260/DO 260A and DO 181C
Version 2 accepted as the required standard in the USand Europe in 2020
Based on DO 260B and DO 181E
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ADS-B OUT1090ES and UAT(Continued)
1090ES OUT is accepted in all countries
Version 2 to be include in the updated APX 119
Version 2 is accepted world wide at all altitudes
UAT is restricted by statute to below 18,000 ft
Used in the US and is being studied in China
There is no plan to integrate UAT into the APX 119 at
this time
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ADS-B OUT1090ES and UAT(Continued)
1090 ES UAT
Operating Frequency 1090 MHz 978 MHz
Spectrum issues Serious concern: Samefrequency as Mode S;ATCRBS/TCAS II;
Mode 4; Mode 5
No Concern;: Samefrequency of a few DMEsin some in the US)
Data Format Same as Mode S replies Unique
Position squitter rate 2 Hz 1 Hz
Operating constraints none For aircraft flying below18,000 feet
Operational areas US, Canada, centralAmerica, Europe, Asiaand the Pacific.
US only
USAF use All IFF equipped aircraft Some trainers
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ADS-B OUT TransponderStandards (Continued)
Aircraft Identification (Flight ID) DO 181C specifies that the ADS-B register 0816
contain exactly the Aircraft Identification (likeRCH123) as the Mode S register 2016. If register 2016times out, then so does 0816
DO 181E specifies that 0816 shall never time out
Mode 3/A code
Do 181C requires that the 3/A code always bebroadcast
DO 181E requires that the 3/A code is alwaysbroadcast if it is not 10008 (in which case it is notbroadcast)
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ADS-B OUT Comparison ofRequirements
Information FAA Europe Elsewhere Note
Length/Width of Aircraft Use in ground applications
Emitter Category Aircraft Type
ADS-B In Capable? X
TCAS II Installed X
Latitude and Longitude WGS 84
Accuracy and Integrity Version 0 and 1 are different for Version 2
Velocity
Geometric Altitude Aircraft Identification (Flight ID or Call Sign)
TCAS II RA (if operable)
Mode 3/A
Emergency
ATC Ident
24 Bit Address
Barometric Altitude
Heading or Ground track X Used on the Ground
Selected Altitude X XBaromentric Altitude Setting X X
GPS antenna Offset R X Used on the Ground
Geometric Vertical Accuracy R X
- requred, R-recommended, X-not required
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ADS-B: Position Requirements
Horizontal Position Source: GPS (PPS?) or tightly coupled INS
The source must have data integrity of 10-7 peroperating hour
Requires valid position accuracy and integrity data
Integrated so position latency supports:
Total latency < 2 seconds (US requirement)
Uncompensated latency < 0.6 seconds
Vertical Position
Accuracy and Integrity data
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ADS-B OUT GPS Receivers
TSO-129 TSO-196 TSO-146/146, MSO 145
Availability SA on 89.0%SA off 99.0%SBAS 99.9%
SBAS 99.9%
Source IntegrityLevel (SIL)
SIL = 2 when directly connected
Horizontal Figureof Merit (HFOM)
Confirmationneeded Provided Provided
Geometric AltitudeConfirmationneeded
Provided Provided
Horizontal velocityConfirmationneeded
Provided Provided
Vertical positionaccuracy
Not provided Not providedSome modes ofoperation only
LatencyConfirmationneeded
Use Standard Use Standard
Bold text indicates that the FAA required capability is provided.
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ADS-B Receiver Data
Data from GPS (via ARINC 429):ARINC Label Encoding Data Bounds
76 BNR 00B GNSS Altitude (Msl) Feet 131072 20 0.125 200 1200
110 BNR 00B GNSS Latitude Degrees
10820 0.0001722001200
111 BNR 00B GNSS Longitude Degrees
10820 0.0001722001200
112 BNR 00B GNSS Ground Speed Knots 4096 15 0.125 200 1200
136 BNR 00B Vertical Figure Of Merit Feet 32, 768 18 0.125 200 1200
165 BNR 00B Vertical Velocity Feet/Min 32768 15 1.0 200 1200
167 BNR
002 EPU Estimate Position
Uncertainty/ (ANP), Actual
Navigation Performance NM 0-128 16 0.00195
247 BNR 00B Horizontal Figure Of Merit NM 16 18 6.1 E-5 200 1200
370 BNR 00B GNSS Height Feet
131,072 20 0.125 2001200
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ADS-B OUT: Position Total Latency
Total Latency (of horizontal position) is to be less than or equal to 2 seconds. Itis the age of the position data that is being used.
It is the time from when the signal is received (left side of the diagram, positionsource time of measurement) to when the position data is transmitted.
TOMB1 TDTOMDTCTOMCTB1
TB1C TCD
MeasuringEquipment(GNSSengine, integrated
GPS/INS hybrid, etc.)
Data Transfer and Processing(e.g.,Data Concentrator, Federated GPS/INS,
FMS)
ADS-B TransmittingEquipment
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ADS-B OUT: Position Total Latency(Continued)
1. Use Time ofMeasurement (TOM)from GPS manufactureror standard.
2. Use standard todetermine latency in thereceiver and thedistribution of data fromthe receiver.
3. Use measure data for
delay in transfer of datafrom the receiver to thetransponder.
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ADS-B OUT: Position Total Latency(Continued)
4. Transponderinternal processesproduce about 0.2seconds latency.
5. Total latency is thetime from TOM totransmit.
6. Reduce totallatency by:
a. Direct connect
b. Position sourceupdate > 1Hz
c. Use source that isTSOed > C129
d. Use GPS timemark
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ADS-B OUT: Position Total Latency(Continued)
There are two paths: Route position data through the system
architecture
Analysis must show the worst case delay is less than 2
seconds Equipment in the data path must be tested to determine
the delay in each case
Direct connect the position source
Referred to as a compliant architecture
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ADS-B OUT: UncompensatedLatency
Uncompensated latency is the Timedifference between the actual time and thetime at which the aircraft was at the positionit broadcast
Last reported location from the PositionSource is extrapolated forward in time usingthe horizontal velocity
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ADS-B OUT: UncompensatedLatency (Continued)
Things to consider for compensation Use 50% of the known fixed delays
If the position source updates position every second, use0.5 seconds
Use 0.1 seconds in the calculation to compensate for
ADS-B position latency since register (0516) needs to beupdated every 0.2 seconds
If part of the data path (e.g. through the bus) doesnot have a fixed time, use the average delay time
Direct connect avoids these issues
Determine the time since the last position updatefrom the source and use that
Requires time delivered to the transponder and a T=1
ADS-B implementation
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ADS-B OUT: LatencyAnalysis Example
Note 1: ADS-B equipment compensated latency is bounded by theasynchronous nature of the position source delivery and ADS-B systemtransmission. Thus ADS-B equipment compensated latency is included inthe asynchronous delay row.
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ADS-B OUT Standards andCertification Guidelines
Version 0 or version 1 (Canada and Asia) RTCA DO 260 or 260A first 1090ES standards
RTCA DO 181C Transponder Standard ifintegrated in the transponder
European Aviation Safety Agency (EASA)AMC-20-24 for ADS-B OUT Certification Guidelines(or local variants of this document)
Version 2 (US and Europe, accepted by all)
RTCA DO 260B current 1090ES standard RTCA DO 181E New Transponder Standard
No EASA certification guidelines at this time
FAA AC 20-165 certification guidelines19
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ADS-B IN
ADS-B IN is the aircraft function that receivesADS-B broadcasts and provides the data foruse in the cockpit
The ADS-B broadcasts may come from: Another aircraft
Rebroadcast (called ADS-R) of data on a differentlink (e.g., UAT)
Broadcast in ADS-B format of secondarysurveillance data from the ground (called TrafficInformation Service Broadcast, TIS-B)
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ADS-B IN Integration of Data
To display position information on proximateaircraft it is necessary to take all of thesources of position information on an aircraftand integrate it into one position
The different sources may be
TCAS II (range, azimuth, and altitude relative toown position)
Received ADS-B OUT broadcast (Latitude,Longitude, Barometric / Geometric Altitude)
Received ADS-R or TIS-B broadcast (Latitude,Longitude, Altitude)
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ADS B IN I i f D
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ADS-B IN Integration of Data(Continued)
Problems to be handled ADS-B OUT broadcasts have known data latency (0.6
seconds uncompensated), accuracy, and integrity
TCAS II position data has low data latency
Range to the other aircraft is very accurate and the azimuthto the other aircraft is very poor (+- 9o)
ADS-R and TIS-B have uncertain data latency and do
not transmit data accuracy or integrity data
The ADS-B IN certification guidance is in FAAAC 20-172
For TCAS II equipped civil aircraft this is in the TCASII processor. The military architectures may vary
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ADS-B IN USAF Considerations
What are the benefits? Difficult to quantify
How should it be integrated into the aircraft?
TCAS II equipped aircraft
For transponder without ADS-B IN, install a softwareupgrade from the manufacturer
For transponder with ADS-B IN
Import the IN data to the TCAS II processor, and installhardware/software in the TCAS II processor
Host the application in a separate processor
Aircraft without TCAS II
Reformat data to display on installed displays
Install additional equipment to support the applications(e.g., Electronic Flight Bag, EFB)
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