CARE/ASAS Activity 3: ASM workshop Br

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CARE-ASAS Activity 3 ASMTime-Based Sequencing
OHA
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Objectives and tasks

• Objectives
• Qualitative operational hazards assessment of
  Time-Based Sequencing (TBS) procedures
• Identification of safety-influencing factors
• RD work, not definitive results
• Tasks
• High-level description of operational procedures
  and CNS/ASAS functions based on TBS-OSED
• Analysis of operational failure scenarios
• Consolidation of risk mitigation measures

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ASAS operations description
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Identified operational hazards

• During TBS procedure initialisation
• Missing, delayed or incorrect initialisation
  preventing procedure execution (OH 1 to OH 5)
• During TBS procedure execution
• Inappropriate, incorrect or misleading time-based
  sequencing by flight deck (OH 6 to OH 10)
• Interaction with air traffic control and other
  aircraft operations (OH 11 to OH 13)
• During TBS procedure ending
• Incorrect or abnormal end of the procedure (OH 14
  to OH 16)
• Multiple air/ground OHs during abnormal end of
  the procedure (OH 17,18)

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Main OSED mitigations (1/3)

• Time-based separation compatible with airborne
  separation minima (ASS/ENV 2)
• Appropriate training of air traffic controllers
  and flight crews (ASS/OPS 1)
• Appropriate flight crews tools and assistance
  (ASS/OPS 3)
• At TBS procedure initialisation
• Positive identification of target aircraft
  (ASS/OPS 5)
• Clear and unambiguous identification by air
  traffic controller and confirmation by flight
  crew
• Applicability conditions of specific
  Merge/Remain behind clearance (ASS/OPS 9, 13)
• Initial check by air traffic controller and
  validation by flight crew

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Main OSED mitigations (2/3)

• During TBS procedure execution
• Flight crews responsibilities
• Flight crew monitoring of separation from the
  selected target aircraft, using ASAS information
  (ASS/OPS 15 )
• ASAS alerting in case of a predicted loss of
  selected time-based separation, or airborne
  separation minima (ASS/SYS 8)
• Air traffic controllers responsibilities
• Provision of (ATC) separation between aircraft
  involved in TBS and other flights under control
  (ASS/OPS 17)
• Provision of compatible instructions (and
  clearances) to both aircraft involved in TBS
  (ASS/OPS 18)

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Main OSED mitigations (3/3)

• At transfer between sectors
• Aircraft executing a TBS procedure contacts the
  receiving controller and announces the specific
  clearance he is complying with (ASS/OPS 20)
• At TBS procedure ending
• Interruption either by flight crew or air traffic
  controller
• In case of system failure, or inappropriate
  target a/c configuration, compromising or
  forbidding procedure execution (ASS/OPS 24)
• In case of unexpected a/c behaviour during
  procedure, or inappropriate traffic situation,
  particularly in case of radar vectoring (ASS/OPS
  25)

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Additional OHA mitigations (1/3)

• At TBS procedure initiation, execution and
  ending
• Air traffic controller shall not initiate a TBS
  procedure when applicable separation minima is,
  or is about to be, lost (SR/OPS 3)
• Flight-crew shall not (deviate from his flight
  path to) follow the target aircraft without
  controller clearance/instruction (SR/OPS 5)
• In normal circumstances, time-based separation
  between aircraft at procedure ending shall be
  compatible with ATC separation minima (SR/OPS 11)
• In case of abnormal end of TBS procedure, air
  traffic controller shall re-establish, if
  necessary and as far as practical, ATC separation
  minima (SR/OPS 16)

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Additional OHA mitigations (2/3)

• Misleading target aircraft identification during
  TBS procedure
• () Only if airborne separation minima are lower
  than ATC separation minima

• Detected loss of airborne separation between a/c
  involved in TBS procedure by Short-Term Conflict
  Alert (SR/SYS 2)
• OR
• () Detected loss of (airborne) separation by
  flight crew of target aircraft (SR/OPS 8)
• OR
• () Detected loss of (airborne) separation with
  aircraft distinct from selected target a/c by
  flight crew (SR/OPS 9)

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Additional OHA mitigations (3/3)

• Loss of air-ground communications
• In case of loss of airborne voice communications
• Air traffic controller shall move away target
  aircraft, if necessary (SR/OPS 20)
• Flight-crew shall continue the last TBS clearance
  received, as far as practical (SR/OPS 21)
• In case of loss of ground communications
• Flight-crews executing TBS procedures shall
  comply with last clearances received, as far as
  practical (SR/OPS 22)
• May be safer than same OH in current environment

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Other safety influencing factors (1/2)

• Air ground system performances
• Minimum TIS-B ground system performances,
  particularly in an ADS-B partial equipage
  environment (SR/SYS 1)
• Minimum aircraft ADS-B, TIS-B and ASAS system
  performances (SR/SYS 3)
• Minimum aircraft navigation system performances
  (SR/SYS 6)
• To reduce likelihood of system-related OHs

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Other safety influencing factors (2/2)

• Air ground environmental factors
• Not initiating TBS procedure during specific
  phases of flight with high workload inside the
  cockpit (REC/OPS 2)
• Waiting for flight crews clearance
  acknowledgement prior to initiating a chain of
  aircraft (REC/OPS 8 )
• To reduce likelihood of TBS procedure
  interruption
• Not assigning similar SSR codes to flows of
  traffic flying in the same airspace (REC/OPS 3 )
• To reduce likelihood of target aircraft
  misidentification

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Main OHA results
OHs (18) with severity assignmentSafety
influencing factors including OPS (59), SYS
(28), ENV (4) with ASS (36), SR (30), REC (25)

• Related to both ATC and flight deck
  operations (including air-ground
  communications)
• Analysis of operational failure scenarios,
  with distinction between human and system
  errors