Aerospace Management Systems Division Delivering what we promised when we promised

War-winning Capabilities…On Time, On Cost

Integrity - Service - Excellence

ADS-B IN/OUT Technical Issues

Distribution Statement A: Approved for public release: 66 ABW-2011-0731 Distribution unlimited

Wm A. Thedford, Ph. D. Jacobs Technology, Inc. USAF ESC/HBAI Lead Surveillance Engineer

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Topics Delivering what we promised when we promised

War-winning Capabilities…On Time, On Cost

• ADS-B OUT – The use of 1090ES and UAT in USAF aircraft – Transponders standards – Comparison of US, European, Canadian, and Australian 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 OUT –1090ES and UAT Delivering what we promised when we promised

War-winning Capabilities…On Time, On Cost

• 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 international standard • 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 US and Europe in 2020 – Based on DO 260B and DO 181E

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ADS-B OUT –1090ES and UAT (Continued) Delivering what we promised when we promised

War-winning Capabilities…On Time, On Cost

• 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 Integrity - Service - Excellence

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ADS-B OUT –1090ES and UAT (Continued) War-winning Capabilities…On Time, On Cost

Delivering what we promised when we promised

1090 ES

UAT

Operating Frequency

1090 MHz

978 MHz

Spectrum issues

Serious concern: Same frequency as Mode S; ATCRBS/TCAS II; Mode 4; Mode 5

No Concern;: Same frequency of a few DMEs in 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 below 18,000 feet

Operational areas

US, Canada, central America, Europe, Asia and the Pacific.

US only

USAF use

All IFF equipped aircraft

Some trainers

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ADS-B OUT – Transponder Standards Delivering what we promised when we promised

War-winning Capabilities…On Time, On Cost

• If ADS-B OUT function is integrated in the IFF transponder, RTCA DO 181E must be implemented (DO 181C in today’s transponders) • What happened to DO 181D? – Included new standards for European Elementary and Enhanced Surveillance (ELS and EHS) and some corrections and clarifications to DO 181C – Did not meet the needs of ADS-B version 2

• Why DO 181E? – Some modifications to correctly support ADS-B version 2 Integrity - Service - Excellence

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ADS-B OUT – Transponder Standards (Continued) Delivering what we promised when we promised

War-winning Capabilities…On Time, On Cost

• Aircraft Identification (Flight ID) – DO 181C specifies that the ADS-B register 0816 contain exactly the Aircraft Identification (like RCH123) as the Mode S register 2016. If register 2016 times 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 be broadcast – DO 181E requires that the 3/A code is always broadcast if it is not 10008 (in which case it is not broadcast) Integrity - Service - Excellence

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ADS-B OUT – Comparison of Requirements War-winning Capabilities…On Time, On Cost

Delivering what we promised when we promised Information

FAA

Length/Width of Aircraft Emitter Category ADS-B In Capable? TCAS II Installed Latitude and Longitude Accuracy and Integrity 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 Selected Altitude Baromentric Altitude Setting GPS antenna Offset Geometric Vertical Accuracy √ - requred, R-recommended, X-not required

√ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ X X R R

Europe Elsewhere Note √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √

√ √ X X √ √ √ √ √ √ √ √ √ √ √ X X X X X

Use in ground applications Aircraft Type

WGS 84 Version 0 and 1 are different for Version 2

Used on the Ground

Used on the Ground

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ADS-B: Position Requirements Delivering what we promised when we promised

War-winning Capabilities…On Time, On Cost

• Horizontal Position – Source: GPS (PPS?) or tightly coupled INS – The source must have data integrity of 10-7 per operating 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 Integrity - Service - Excellence

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ADS-B OUT – GPS Receivers War-winning Capabilities…On Time, On Cost

Delivering what we promised when we promised

Availability

TSO-129

TSO-196

SA on – 89.0%

SA off – 99.0% SBAS – 99.9%

Source Integrity Level (SIL)

TSO-146/146, MSO 145 SBAS 99.9%

SIL = 2 when directly connected

Horizontal Figure of Merit (HFOM)

Confirmation needed

Provided

Provided

Geometric Altitude

Confirmation needed

Provided

Provided

Horizontal velocity

Confirmation needed

Provided

Provided

Vertical position accuracy

Not provided

Not provided

Some modes of operation only

Latency

Confirmation needed

Use Standard

Use Standard

Bold text indicates that the FAA required capability is provided. Integrity - Service - Excellence

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ADS-B – Receiver Data Delivering what we promised when we promised

War-winning Capabilities…On Time, On Cost

Data from GPS (via ARINC 429): ARINC Label Encoding Data 76 BNR 00B GNSS Altitude (Msl) Feet 110

BNR

111 112 136 165

BNR BNR BNR BNR

167 247

BNR BNR

370

BNR

Bounds ±131072 20 0.125 200 1200 ±108° 20 0.000172° 200 00B GNSS Latitude Degrees 1200 ±108° 20 0.000172° 200 00B GNSS Longitude Degrees 1200 00B GNSS Ground Speed Knots 4096 15 0.125 200 1200 00B Vertical Figure Of Merit Feet 32, 768 18 0.125 200 1200 00B Vertical Velocity Feet/Min ±32768 15 1.0 200 1200 002 EPU Estimate Position Uncertainty/ (ANP), Actual Navigation Performance NM 0-128 16 0.00195 00B Horizontal Figure Of Merit NM 16 18 6.1 E-5 200 1200 ±131,072 20 0.125 200 00B GNSS Height Feet 1200

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ADS-B OUT: Position Total Latency War-winning Capabilities…On Time, On Cost

Delivering what we promised when we promised

ΔTB1→C

TOMB1

TB1

Measuring Equipment (GNSS engine, integrated GPS/INS hybrid, etc.)

ΔTC→D

TOMC

Data Transfer and Processing (e.g., Data Concentrator, Federated GPS/INS, FMS)

TC

TOMD TD

ADS-B Transmitting Equipment

Total Latency (of horizontal position) is to be less than or equal to 2 seconds. It is 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, position source time of measurement) to when the position data is transmitted. Integrity - Service - Excellence

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ADS-B OUT: Position Total Latency (Continued) Delivering what we promised when we promised

War-winning Capabilities…On Time, On Cost

1. Use Time of Measurement (TOM) from GPS manufacturer or standard. 2. Use standard to determine latency in the receiver and the distribution of data from the receiver. 3. Use measure data for delay in transfer of data from the receiver to the transponder.

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ADS-B OUT: Position Total Latency (Continued) Delivering what we promised when we promised

War-winning Capabilities…On Time, On Cost

4. Transponder internal processes produce about 0.2 seconds latency. 5. Total latency is the time from TOM to transmit. 6. Reduce total latency by: a. Direct connect b. Position source update > 1Hz c. Use source that is TSOed > C129 d. Use GPS time mark Integrity - Service - Excellence

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ADS-B OUT: Position Total Latency (Continued) Delivering what we promised when we promised

War-winning Capabilities…On Time, On Cost

• 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: Uncompensated Latency Delivering what we promised when we promised

War-winning Capabilities…On Time, On Cost

• Uncompensated latency is the Time difference between the actual time and the time at which the aircraft was at the position it broadcast • Last reported location from the Position Source is extrapolated forward in time using the horizontal velocity

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ADS-B OUT: Uncompensated Latency (Continued) Delivering what we promised when we promised

War-winning Capabilities…On Time, On Cost

• Things to consider for compensation – Use 50% of the known fixed delays • If the position source updates position every second, use 0.5 seconds • Use 0.1 seconds in the calculation to compensate for ADS-B position latency since register (0516) needs to be updated every 0.2 seconds

– If part of the data path (e.g. through the bus) does not have a fixed time, use the average delay time • Direct connect avoids these issues

– Determine the time since the last position update from the source and use that • Requires time delivered to the transponder and a “T=1” ADS-B implementation Integrity - Service - Excellence

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ADS-B OUT: Latency Analysis Example Delivering what we promised when we promised

War-winning Capabilities…On Time, On Cost

Note 1: ADS-B equipment compensated latency is bounded by the asynchronous nature of the position source delivery and ADS-B system transmission. Thus ADS-B equipment compensated latency is included in the asynchronous delay row. Integrity - Service - Excellence

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ADS-B OUT – Standards and Certification Guidelines Delivering what we promised when we promised

War-winning Capabilities…On Time, On Cost

• Version 0 or version 1 (Canada and Asia) – RTCA DO 260 or 260A – first 1090ES standards – RTCA DO 181C – Transponder Standard if integrated 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 guidelines Integrity - Service - Excellence

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ADS-B IN Delivering what we promised when we promised

War-winning Capabilities…On Time, On Cost

• ADS-B IN is the aircraft function that receives ADS-B broadcasts and provides the data for use in the cockpit • The ADS-B broadcasts may come from: – Another aircraft – Rebroadcast (called ADS-R) of data on a different link (e.g., UAT) – Broadcast in ADS-B format of secondary surveillance data from the ground (called Traffic Information Service Broadcast, TIS-B)

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ADS-B IN – Integration of Data Delivering what we promised when we promised

War-winning Capabilities…On Time, On Cost

• To display position information on proximate aircraft it is necessary to take all of the sources of position information on an aircraft and integrate it into one position • The different sources may be – TCAS II (range, azimuth, and altitude relative to own position) – Received ADS-B OUT broadcast (Latitude, Longitude, Barometric / Geometric Altitude) – Received ADS-R or TIS-B broadcast (Latitude, Longitude, Altitude) Integrity - Service - Excellence

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ADS-B IN – Integration of Data (Continued) Delivering what we promised when we promised

War-winning Capabilities…On Time, On Cost

• 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 azimuth to 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 FAA AC 20-172 – For TCAS II equipped civil aircraft this is in the TCAS II processor. The military architectures may vary Integrity - Service - Excellence

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ADS-B IN – USAF Considerations Delivering what we promised when we promised

War-winning Capabilities…On Time, On Cost

• 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 software upgrade from the manufacturer • For transponder with ADS-B IN – Import the IN data to the TCAS II processor, and install hardware/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) Integrity - Service - Excellence

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