Thedford-ADS-B In_Out Tech Issues-Tuesday Track1

7/31/2019 Thedford-ADS-B In_Out Tech Issues-Tuesday Track1

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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

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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


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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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7/23I 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 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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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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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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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 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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