Time Based Separation Transitional Step (TBS-TS) & Crosswind - - PowerPoint PPT Presentation

Time Based Separation – Transitional Step (TBS-TS) & Crosswind Operations (CROPS)

David, BOOTH Senior Expert - Airports david.booth@eurocontrol.int

The European Organisation for the Safety of Air Navigation

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High-level concept of operations

• Procedure change only, with limited system support
• Authorise a 0.5NM reduction of wake turbulence distance based

separation, between WT pairs (as per ICAO Doc 4444), on final approach

• Conditional application – only in specific headwind / crosswind

conditions

• Both CONOPS mature, only requiring final update after safety

assessment

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Required wind conditions

• TBS - Surface headwind component wind is equal to or stronger

than 10kt (still to be confirmed) plus a buffer

• CROPS - A 6kt crosswind (still to be confirmed) plus a buffer
• Wind forecast confirms favourable wind speed and directions for

winds aloft for the entire planning period

• No significant MET situations are forecasted
• Unfavourable MET conditions need to be defined, e.g.

thunderstorms, wind shear.

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Safety deliverables

• Safety plan developed
• Safety Assessment report supported by more than 5 years of

scientific work, including terabytes of LIDAR data, – almost complete

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Safety assessment of CROPS

• Operational objective:

– Take advantage of cross-wind effect on wake turbulence transport and decay

• Expected benefits:

– Increase runway throughput or absorb delays

• Scope of preliminary safety assessment:

– Specimen final approach segment and IFR arrivals – Safety assurance of acceptability of conditional reduction of WT separation minima – Heavy-Heavy & Heavy-Medium pairs

• Guidance to support safety assessment in local implementation

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Specimen final approach segment (as per ICAO Doc 8168)

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Safety criteria and strategy

• Relative safety criterion:

The risk (likelihood) per approach of a WT-induced loss of control accident when reduced WT distance-based separation minima are applied to a Medium or Heavy aircraft on final approach behind Heavy in minimum cross wind conditions as defined by CROPS shall not be greater than the risk per approach of WT- induced loss of control accident when ICAO provisions for WT separation minima as applied today in all wind conditions by European ANSPs

• Comparative (quantified) Wake Vortex Encounter (WVE) risk assessment principle:
• Evidence from (Leader) WV measurements, data processing and computation

Circulation Strength - (m^2/s) Frequency - f Circulation Strength - (m^2/s) Frequency - f

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WT hazardous scenarios and conditions on final approach

• Operational threat: WT-induced loss of control
• Potential WVE for follower aircraft all along the glide (normal landing)
• WVE more likely to occur in low wind conditions

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WVE risk quantification and comparison (in fault-free conditions)

Baseline selection:

• Current WT-induced loss of control accident risk in ECAC (considering ICAO provisions

applied fault-free) is acceptable in all weather (wind) conditions, incl. low wind WT-induced LoC risk characterisation:

• WT-induced LoC risk is characterized by the risk (likelihood) distribution of potential WVE

strength (representing the induced roll moment effect) for a given arrival pair at a given time separation, derived from equivalent distance, and in given weather conditions, (further called WVE risk)

• Severity metric for WVE risk: WV circulation

WVE risk distribution in worst reasonable conditions:

• Heavy leader aircraft configuration: all most frequent aircraft types of the category
• Use of reference final approach speed per category being representative and conservative
• 4D geometry: at minimum separation on final (ICAO minimum DBS-equivalent TBS)
• Weather: Low total wind (below 5 kts) for baseline case

Approach legitimacy:

• Previous cases with similar approach: A380 WT and WIDAO at Paris CDG

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CCDF (Complementary Cumulative Density Function) is defined for a certain , as the probability to observe a wake vortex with a circulation higher than * CCDF(*) = P(>*) Safety corridor: +/-100m

Acceptable WVE risk for Heavy landing behind Heavy at 4NM in low wind (baseline)

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Acceptable WVE risk for Medium landing behind Heavy at 5NM in low wind (baseline)

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CROPS must be specified to meet safety criteria

• Safety performance objectives (fault-free) for ANS/ATM system functions to meet safety

criteria / targets: 1. Determination of WT separation minima 2. Correct application of WT separation minima to arrival pairs (local)

SPO-02a WT separation conditionally reduced in crosswind shall be provided (created and maintained) such that Heavy arrival on final approach is correctly separated from preceding Heavy arrival SPO-02b WT separation conditionally reduced in crosswind shall be provided (created and maintained) such that Medium arrival on final approach is correctly separated from preceding Heavy arrival SPO-01a Conditional reduction in crosswind of WT DBS minima applicable to Heavy sequenced and descending behind Heavy on final approach shall be determined such that the frequency (per approach) of WVE (of a given severity) by this following Heavy on final approach will not be higher than when a Heavy is landing behind another Heavy at ICAO WT separation minimum in low wind conditions. SPO-01b Conditional reduction in crosswind of WT DBS minima applicable to Medium sequenced and descending behind Heavy on final approach shall be determined such that the frequency (per approach) of WVE (of a given severity) by this following Medium on final approach will not be higher than when a Medium is landing behind another Heavy at ICAO WT separation minimum in low wind conditions.

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WVE risk comparison for H behind H at 3.5NM WT DB minima with at least 5 and 6 kts surface crosswind or above 5 kt 6 kt

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WVE risk comparison for M behind H at 4.5NM WT DB minima with at least 5 and 6 kts surface crosswind or above 5 kt 6 kt

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Safety conditions for CROPS application

• For Heavy arrival to be separated at 3.5NM behind preceeding Heavy:
• For Medium arrival to be separated at 4.5NM behind preceeding Heavy:

SCO-11a A surface crosswind component speed of 6 kts or greater (CW1) shall prevail in order to allow application of WT separation at 3.5 NM for Heavy behind Heavy on final approach SCO-11b A surface total wind speed of 10 kts or greater shall prevail in order to allow application of WT separation at 3.5 NM for Heavy behind Heavy on final approach SCO-12 Wind forecast confirms favourable wind speed and direction during the planned period of application and on the whole final approach segment SCO-21a A surface crosswind component speed of 6 kts or greater (CW1) shall prevail in order to allow application of WT separation at 4.5 NM for Heavy behind Medium on final approach SCO-21b A surface total wind speed of 10 kts or greater shall prevail in order to allow application of WT separation at 4.5 NM for Heavy behind Medium on final approach SCO-22 Wind forecast confirms favourable wind speed and direction during the planned period of application and on the whole final approach segment

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WV data collection and analysis

• WV data collection campaign at EGLL over 2 years
• More than 100.000 wake vortex tracks
• Correlation with weather and aircraft data
• WV data processing and analysis
• Data cleaning by filtering
• Region of interest
• Sanity check

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Key assumptions, open issues, limitations

Assumptions for generalisations:

• Wind band of 1 knot
• Wind distribution is uniform with each wind band

Open issues:

• Buffer to be added to cross-wind safety conditions = function
• f local wind forecast
• Manual cleaning check of WV data – on-going

Limitations:

• Missed approach influence not verified at generic level

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Local ANS/ATM system characteristics to be considered

• Local safety assessment required on changes to ANS/ATM system
• Final approach profile and runway occupancy time
• Specific WT categories and separation minima
• Wind behaviour and forecast accuracy at aerodrome to meet

conditional wind criteria

• Proposed ANS/ATM system architecture (data quality, tools,

procedures, roles) supporting application of CROPS reduced WT separation minima on final approach

• Safety objectives to be set consistent with SMS
• Safety requirements for ANS/ATM system elements, to be designed

and implemented to allow CROPS application

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