ASAS Implementation in Avionics

1
ASAS Implementation in Avionics

• Pierre GAYRAUD
• Thales Avionics
• in collaboration with ACSS

2
Content

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

3
ASAS functions to implement
Message Processing
Applications
Aircraft data
4
ASAS Package I functions to implement
ADS-B Out ADS-B Out ADS-B In ADS-B In ADS-B In
Application category Application category Aircraft data ADS-B Tx ADS-B Rx Applications HMI
Ground surveillance ADS-B-ACC, TMA, NRA, APT, ADD ? ?
Airborne Situational Awareness ATSA-SURF ATSA-AIRB and Visual acquisition ATSA SA ATSA-SVA ? ? ? ?
surveillance Airborne spacing ASPA-SM, ASPA-ITP, ASPA-CP ? ? ? ? ?
5
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

6
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)
• gt Standards not totally stable

7
ADS-B-In functions
8
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

9
ADS-B-InASAS-ACAS relationship

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

10
ADS-B-InASAS-ACAS relationship

• 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)
• gt 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)

11
ADS-B-InASAS-ACAS relationship

• 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
• gt The TCAS Computer becomes the  Traffic
  Computer 

12
Surveillance Data Processing (A-SDPD)
TIS-B
TIS-B
TIS-B

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

• 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

13
Surveillance Data Processing (A-SDPD)

• 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

14
Surveillance Data Processing (A-SDPD)

• 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)

15
Surveillance Data Processing (A-SDPD)
Application requests
Data Distribution
Display Applications
Track Management
1090 ES (ADS-B TIS-B) UAT (ADS-B TIS-B) VDL
M4 (ADS-B TIS-B) ACAS
Data Management
16
AEEC Equipment standards

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

• 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
• gt The Traffic Computer is the backbone of the
  ISS concept (Integrated Surveillance System)

17
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
• Dont forget the system integration with the
  surrounding equipment (impact on EIS/CDTI,
  Warning systems, FMS)
• Definition of standards not stable