asas tn third workshop, 19-21 april 2004, toulouse 1 asas implementation in avionics pierre gayraud...

1ASAS TN Third Workshop, 19-21 April 2004, Toulouse

ASAS Implementation in Avionics

Pierre GAYRAUD

Thales Avionics

in collaboration with ACSS


Content

• ASAS functions to implement• ADS-B-out• ADS-B-in • EUROCONTROL ASFA study• ASAS-ACAS relationship• Surveillance data processing• AEEC Equipment standards• Conclusion


ASAS functions to implement

ADS-B In Rx

ADS-B

Out

Tx

HMI

Aircraft data

Message Processing

Applications

ADS-B-Out

ADS-B-In


ASAS Package I functions to implement

ADS-B Out ADS-B In

Application category Aircraft data

ADS-BTx

ADS-BRx

Applications

HMI

Ground

surveillance

ADS-B-ACC, TMA, NRA, APT, ADD

Airborne

Situational Awareness ATSA-SURF ATSA-AIRB and Visual acquisitionATSA S&A ATSA-SVA

surveillance Airborne spacing

ASPA-S&M, ASPA-ITP,

ASPA-C&P


ADS-B out Transmitters

• Mode S 1090 ES link transmitters already on board– Mode S transponder (mandatory on all IFR aircraft in Europe as of

31/03/2005)

The transmission of Extended Squitters is part of the standard (provided Registers are loaded)

• UAT and VDL Mode 4 transmitters – Tx/Rx boxes


ADS-B OutData

• Data allowed to be broadcast are defined by the existing ICAO SARPS (at least for Mode S ES and VDL Mode 4)

– Aircraft identification, horizontal position and altitudes, velocity

• The definition of Intents is not stable• ADS-B raises new problems concerning the quality of the data

– Instead of predetermined data characteristics (e.g. radar data),qualifiers are associated to the transmitted data according to the aircraft avionics capabilities (accuracy, integrity…)

– The current SARPS requires transmission of an Horizontal Protection limit and uncertainty characteristics

– There are plans to update SARPS (NIC, SIL, NAC…) for air-air applications (backwards compatibility for air-ground)

– There are also works within RTCA about the transmission of additional quality data (continuity, latency) through a TQL (Transmit Quality level)

=> Standards not totally stable


ADS-B-In functions

Surveillance layer Applications layerData Link layer

ASAS domain

ACAS domain

Common ACAS/ASAS

Display

TA/RAACAS tracksTA/RA

ACAS tracks

CAS LogicACAS Surveillance

ADS-BTIS-B

SurveillanceData

Processing

(A-SDPD)

Own positionOther Systems (MCDU, FMS, …)

ASAS tracks

ASAS tracks,Selected target, Guidance data

Display Management

ASAS Applications

UA

T

VD

L M

4R

ecei

vers

Act

ive

repl

yA

ctiv

e In

terr

og

109

0 R

ecei

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(DF

17/D

F18

)


Airborne Surveillance Functional Architecture (ASFA Study)

• EUROCONTROL ADS program has sponsored two teams• Main outcomes

– ASAS/ACAS relationship

– Functional, performance and interface requirements for Surveillance Data Processing (or A-SDPD: Airborne Surveillance Data Processing and Distribution)

– A-SDPD architecture

• Follow-on: A-SDPD prototype test on the ADS-B Validation Testbed (AVT) at EEC


ADS-B-InASAS-ACAS relationship

• Common parts– ACAS and ASAS tracks have to be displayed consistently to the

crew

=> A synthesis of ACAS and ASAS display tracks is necessary before display (one symbol per aircraft)

– For Mode S ES, the 1090 receiver can be shared by ACAS and ASAS (ICAO SARPS have provision for)

• Interactions– ICAO has specified the ACAS « hybrid surveillance »

– A-SDPD may use ACAS tracks to consolidate ASAS tracks



• But some principles have to be followed:– Independence is required by ICAO

• no ASAS-ACAS common failure cause (it could induce an infringed separation while preventing ACAS to detect dangerous geometry)

=> Separated ACAS and ASAS surveillance processing– Compatibility is required

• the operations of one system shall not degrade the performance of the other(e.g.: no increase of the TA or RA rates during manoeuvres supported by ASAS)

– Interoperability is desirable• ACAS « hybrid surveillance » decreases the 1090 interrogation rate

(ICAO requirements prevent to jeopardize independence)• Comparison of ASAS data with ACAS tracks improves the integrity of

ASAS data without impacting the independence (comparison is used only when in agreement)



• Partitioning techniques (software and hardware) allow – The ASAS functions (A-SDPD, Applications, Display Management)

to be hosted in a TCAS Computer

– While fulfilling the independence conditions

• Advantages– Box count minimization (direct cost, weight, reliability, maintenance)

– No new antenna required for ASAS (as far as 1090 ES is used)

– Facilitates interactions between the two functions

• Some ASAS applications could require services from FMS

=> The TCAS Computer becomes the « Traffic Computer »


A-SDPD can receive 3 types of data – Directly through ADS-B links from the

ADS-B capable surrounding aircraft– Via one or several TIS-B links for aircraft

covered by each TIS-B+ ACAS tracks from ACAS surveillance

TIS-B

UAT

UAT

Via three potential links– Mode S extended Squitter– UAT– VDL Mode 4

VDL Mode 4

VDL Mode 4

1090 ES

1090 ES

1090 ES

1090 ES

Surveillance data processing

Dat

a li

nk

rece

iver

s

TIS-B

TIS-B

Surveillance Data Processing(A-SDPD)

Objective: to provide display and applications with « clean » data


• The ASFA study has analysed the functional aspect

• Due to the number of combinations « what-if » analysis have been performed

• Package I applications will not use the complete set of combinations (probably only 1090 ES, TIS-B ?)

• The main objectives is to provide the data integrity and continuity matching the applications needs

• Data sources (target position, altitude, velocity…)– The number of independent sources which can be used to increase the

integrity is limited• Horizontal position: ADS-B and ACAS (and in some cases TIS-B)• Vertical data: no redundancy, only the altitude transmit by the target

aircraft



• Data links– Data link redundancy mainly improve continuity

• Applications– Differing requirements according to the considered applications

– But not determined yet Top down analysis required (On-going within the Requirement

Focus Group)

Critical role of the 24-bit ICAO address, the only unique target aircraft identifier on which tracks correlation is based (subsequently the case of Mode A/C aircraft not adequately solved yet)



Track Management

Data Distribution

Data Management

1090 ES(ADS-B TIS-B)

UAT(ADS-B TIS-B)

VDL M4(ADS-B TIS-B)

+ ACAS

Applicationrequests


DisplayApplications


AEEC Equipment standards

AEEC (Airlines Electronic Engineering Committee) is defining the preferred airborne architectures

ASAS

ACAS

– SAI Committee: the best place for ADS-B-In is the TCAS Computer (turned it in a Traffic Computer)

Ex: ACSS TCAS3000

– ISS Committee is working on ARINC 768 (Integrated Surveillance System)

An architecture to simplify on-board surveillance installation:Benefiting from the partitioning techniques it is possible to add:

• Mode S Transponder, TAWS, WXR

+ Alarm and display prioritization because those functions display data on the ND and/or raise alarms

=> The Traffic Computer is the backbone of the ISS concept (Integrated Surveillance System)

TAWS

WXR

Mode S Transponder


Conclusion

• The avionics of modern Air Transport Aircraft can accommodate Package 1 ASAS applications without any addition of boxes or antennas

• ADS-B-Out and ADS-B-In to be hosted– ADS-B-Out: by the Mode S Transponder

– ADS-B-In: mainly by the TCAS computer (Traffic Computer)(2 when required by architecture considerations)

It is the first step of the Integrated Surveillance System

• Don’t forget the system integration with the surrounding equipment (impact on EIS/CDTI, Warning systems, FMS…)

• Definition of standards not stable

asas tn third workshop, 19-21 april 2004, toulouse 1 asas implementation in avionics pierre gayraud...

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