1. page 1 CARE/ASAS Activity 3: ASM workshop Brétigny, 19 December 2001 Time-Based Sequencing OHA CARE-ASAS Activity 3: ASM Time-Based Sequencing OHA

2. page 2 CARE/ASAS Activity 3: ASM workshop Brétigny, 19 December 2001 Time-Based Sequencing OHA Objectives and tasks  Objectives:  Qualitative operational hazards assessment of Time-Based Sequencing (TBS) procedures  Identification of “safety-influencing factors”  R&D 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

3. page 3 CARE/ASAS Activity 3: ASM workshop Brétigny, 19 December 2001 Time-Based Sequencing OHA ASAS operations description OperationsProcess (or communications) OP1Process by controller and/or ATC tools OP2Process by flight crew and/or airborne systems CO1Communications from ground-to-air CO2Communications from air-to-ground CO3Communications from ground-to-ground Phase(s) P1.1 P1.2 No OP1.2 OP2.3 Agent ATC Flight deck Process (or Communication) Check for procedure (e.g. “Merge behind”) conditions of applicability Crosscheck of target aircraft position Input Traffic information on CWP Target a/c position from ATC and information on ASAS display

4. page 4 CARE/ASAS Activity 3: ASM workshop Brétigny, 19 December 2001 Time-Based Sequencing OHA 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)

5. page 5 CARE/ASAS Activity 3: ASM workshop Brétigny, 19 December 2001 Time-Based Sequencing OHA 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

6. page 6 CARE/ASAS Activity 3: ASM workshop Brétigny, 19 December 2001 Time-Based Sequencing OHA Main OSED mitigations (2/3)  During TBS procedure execution:  Flight crew’s 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 controller’s 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)

7. page 7 CARE/ASAS Activity 3: ASM workshop Brétigny, 19 December 2001 Time-Based Sequencing OHA 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)

8. page 8 CARE/ASAS Activity 3: ASM workshop Brétigny, 19 December 2001 Time-Based Sequencing OHA 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)

9. page 9 CARE/ASAS Activity 3: ASM workshop Brétigny, 19 December 2001 Time-Based Sequencing OHA 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)

10. page 10 CARE/ASAS Activity 3: ASM workshop Brétigny, 19 December 2001 Time-Based Sequencing OHA 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

11. page 11 CARE/ASAS Activity 3: ASM workshop Brétigny, 19 December 2001 Time-Based Sequencing OHA 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

12. page 12 CARE/ASAS Activity 3: ASM workshop Brétigny, 19 December 2001 Time-Based Sequencing OHA 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 crew’s 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

13. page 13 CARE/ASAS Activity 3: ASM workshop Brétigny, 19 December 2001 Time-Based Sequencing OHA Main OHA results o Related to both ATC and flight deck operations (including air-ground communications) o Analysis of operational failure scenarios, with distinction between human and system errors OHs (18) with severity assignment & Safety influencing factors including OPS (59), SYS (28), ENV (4) with ASS (36), SR (30), REC (25)