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ASAS Thematic Network Second Workshop 6-8 October 2003. ADS-B Safety Analysis (ASA & GSA). Bob Darby EUROCONTROL ADS Programme. OUTLINE. Background Current work analysis processes comments on the methods, not the results Wider context & Conclusions Safety is only part of SPR / IA

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ads b safety analysis asa gsa

ASAS Thematic Network

Second Workshop 6-8 October 2003

ADS-B Safety Analysis (ASA & GSA)

Bob Darby


  • Background
  • Current work
    • analysis processes
    • comments on the methods, not the results
  • Wider context & Conclusions
    • Safety is only part of SPR / IA
    • Requirements Focus Group
    • Longer term
  • Points of Contact
safety work history
Safety Work History
  • 1999-2000: Stage 0
    • Initial Safety Study - brief look high level workshops
  • 2000-2001: Stage 1
    • Operational Hazard Analysis (OHA) based on “Case Studies”
  • Difficulty - not detailed enough definition of the applications
safety work history1
Safety Work History
  • 2002:
    • Package I proposed at Rome
    • CARE-ASAS / EUROCONTROL development of Package I
    • EUROCAE WG51 & RTCA SC-186
      • Common applications review & proposal
      • Common methodology proposal - ED78A / DO-264
      • Guidelines for Approval of the Provision and Use of Air Traffic Services supported by Data Communications
  • In parallel:
  • Stage 2A Safety Contract launched
    • At the time (Jan 2002) the aim was to
      • Use EUROCONTROL Safety Assessment Methods (SAM)
      • Use ED78A as a means of compliance with the SAM
    • Aim has changed as ESARR4 developed and use of ED78A has proceeded, to establish an effective methodology. Differences/complementarity handled as an outcome.
stage 2a safety contract
Stage 2A Safety Contract
  • Coordinated with CBA and Architecture work
  • Assessment of some ADS-enabled ASA and GSA applications defined in the Package I OSED - including ADS-B in a mixed surveillance environment
  • For each Package I application
    • OHA: building on the results of the ADS Programme Stage 1 OHA
    • ASOR: allocation to elements / domains within the architecture
    • from ASOR options: safety requirements for the ADS-B element based on the specific enabling infrastructure.
    • PSSA for one application, using a specific architecture
  • Issues:
    • Methodology and Software tools equally important as the results
logical flow


Case Studies





(Draft) OSEDs


& Tools

inc database









- architecture






Logical Flow
applications assessed
Applications assessed

Ground Surveillance Applications (GSA)

ATC surveillance in en-route airspace

ATC surveillance in terminal areas

ATC Surveillance in non-radar area

Airport Surface Surveillance

Surface Traffic Awareness application

Runway Incursion application

Airborne Surveillance Applications (ASA)

Enhanced traffic situational awareness on the airport surface

Surface Traffic Awareness application

Runway Incursion application

Enhanced successive visual approaches

Sequencing and merging applications

oha output example
OHA output (example)

From “Enhanced Successive Visual Approach”

  • OHA is summarised in a diagram.
  • Details in several tables:
  • OH summary table, that refers to
  • Candidate safety requirements lists
    • environmental
    • procedural
    • technical
  • Recommendations list
  • Causes list
  • Supported by detailed OH tables
oha comments on process
OHA - comments on process
  • Exhaustive & detailed ...
  • … time-consuming to develop and to review
  • Mature process, used (with slight variations) by many European projects, NUP, MFF, …
  • Needs tool support to ensure
    • consistency between diagrams and tables
    • traceability and accurate cross-referencing between all tables
    • database is being developed
  • Derived from application model in OSED
    • Changes to OSED may mean complete rework of OHA
asor process
ASOR process
  • Follows on from OHA
    • traceability essential
  • Objective: identify
    • responsible domains/elements (ATC, aircraft, crew,…)
    • system failure relationships
    • mitigation means strategy
  • Key processes:
    • Building the fault tree
      • stop when the safety requirement can be exclusively met in a domain
    • Allocation of safety requirements
      • several options
asor comments on process
ASOR - comments on process
  • Relatively new process - learning as we proceed
  • More complex for surveillance than for communications
  • No single correct answer - tradeoffs will occur
  • Trees give the understanding - tables give the detail
  • Tools for traceability and consistency essential
  • Specific to a particular implementation
  • Assess if the proposed architecture is safe for its intended purpose
    • ASOR has already mapped safety requirements to the domain
    • Now look at the architecture within the domain: i.e. main functional (and physical) components
  • EUROCONTROL study example: Toulouse airport
  • Package I applications:
    • Airport Surface Surveillance
    • Enhanced traffic situational awareness on the airport surface
      • Surface Traffic Awareness application
      • Runway Incursion application
  • Just starting this phase of the study
overall comments
Overall Comments
  • Learning about the processes as we use themgoing from the generic to the specific
  • Status
    • OHA: mature but effort intensive
    • ASOR: developing well
    • PSSA: just started but relatively straightforward
  • Overall: large effort
  • Tool support essential, especially when iterating and reworking
  • Complementary approach to identify critical areas would pay dividends
  • OSED is critical - clarity and accuracy of application modelling is vital
safety is only part of the process
Safety is only part of the process


Operational Service &

Environment Definition


Operational Safety




Operational Performance


Identify & allocate

performance requirements





Safety & Performance




preparation for rfg 3
Preparation for RFG/3
  • Joint EUROCONTROL, FAA, EUROCAE, RTCA “Requirements Focus Group”
    • 1st-4th December 2003, Washington DC
  • OSEDs: OSED Harmonisation Group
    • First complete PI OSED due out soon
  • Safety: EUROCONTROL, NUP, MFF, …
    • Convergence on the methods
    • More coordination and consensus needed - EC can help?
  • SPR & IA as a whole
    • ad-hoc SPR/IA group working since July
    • aiming at common approach for Europe and USA; extend world-wide?
longer term considerations
Longer term considerations
  • Operational expertise to validate the analysis conclusions
  • Complementary methods could be of value
    • for greater efficiency overall
    • for confirming results
  • Coordination with Safety Unit, SRC and EASA
points of contact
    • visit the ADS Programme website:
  • STNA & Sofréavia
    • who have carried out the detailed work and developed in a practical form the processes described today
  • RFG colleagues
    • discussions in preparation of material for RFG/3