ACAS II IMPLEMENTATION

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ACAS II IMPLEMENTATION
John LAW ACAS Programme Manager
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ACAS II OPERATION IN EUROPE
ACAS II plays central role in resolving airprox
with risk of collision Supports ATM 2000
Strategy safety level improvement objective
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ACAS II Implementation

• Phase 1 complete
• Phase 2 with effect from 1 January 2005, all
  civil fixed wing turbine-engined aircraft having
  a maximum certificated take-off mass exceeding
  5700kgs, or a maximum approved passenger seating
  configuration of more than 19, will be required
  to be equipped with ACAS II
• Military authorities - voluntary commitment to
  fit ACAS II to transport-type a/c by January 2005

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Content

• ACAS II - Implementation Issues
• ACAS Training
• ACAS Monitoring provisions

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Reason for Mandate

• Safety Improvement
• Airspace
• Individual aircraft

• APSG TF - Phase 2 provisions review

• Extensive Safety Studies
• ACASA Project WP1 Safety Benefit of ACAS II
  Phase 1 2
• In both CVSM RVSM, risk of collision sensitive
  to
• The proportion of ACAS equipped a/c
• The proportion of pilots following their RAs
  correctly

• APSG TF Recommended maintain current Phase 2
  provisions

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Implementation Issues

• Complex compliance tracking task - approx 35
  already equipped

• Number of operators delaying
• Expectation that Phase 2 requirements will be
  relaxed
• Reluctance to commit to installation.

• No known technical issue precluding fitment

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ACAS Training

• In both CVSM RVSM, the risk of collision is
  very sensitive to
• The proportion of ACAS equipped a/c
• The proportion of pilots following their RAs
  correctly

• Not following RAs debases ACAS II performance
• Training is of primary importance

Failure to respond is a danger to others as well
as own aircraft
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ACAS Training - ENSURING CORRECT RESPONSE

• Controllers have theoretical knowledge of ACAS
  but little or no practical experience of reacting
  to a TCAS RA

• Instruction is fundamental to ATC
  training/continuation training
• Safety cannot be dependent on instinctive
  response

• Ensure consistency of ACAS procedures with ICAO
  ACAS provisions. Correct response to TCAS from
  both pilot and controller is essential

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ACAS Training Courses and Packages

• ACAS Training for Operations in RVSM environment
  (Project ACTOR)
• Replay Interface for TCAS Alerts (RITA2)
• ACAS Training Courses
• ACAS II Safety Bulletins

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ACAS Training Courses

• Revised and updated ACAS training courses for
  controller instructors, both about ACAS and how
  to use RITA, will be available at IANS from
  December 2003.
• These ACAS training courses can be provided on
  site if required. Available now.
• RITA 2 Distribution

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Operational monitoring of ACAS

• Current situation - technical/operational
  monitoring
• European ACAS operational monitoring funded by
  ACAS Programme

• Funding terminates in 2004

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Need for Operational Monitoring

• Feedback on how the ACAS system performs
• Input to ACAS specifications/standards
• Detect operational problems
• Need to monitor flight crew response
• Examples for group training
• Distribute report to airlines and ANSP/ ATCCs
• RA safety indicator

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ACAS Monitoring - RA Safety Indicator

• Identify RA clusters - HotSpots - relationship
  with airspace environment design
• 1000ft level-off geometry RA is potential
  risk-bearing level bust scenario
• risk of collision exists if there was a level bust

• Altitude busts not uncommon
• TCAS II is effective in reducing risk of
  collision when associated with a level bust

But do not rely on TCAS II

• Potentially some airspace design level-off
  procedures not fail-safe

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ACAS Monitoring

• Anything that changes encounters between aircraft
  can/will affect ACAS performance.

• ACAS performance could affect operations in new
  airspace design /procedure

• ACAS Monitoring is necessary - if it is not known
  it cannot be corrected

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Recommendations

• European CAAs / ANSPs are urged to
• Take all necessary actions to ensure ACAS Phase 2
  implementation

• Ensure provision of appropriate and effective
  ACAS training - flight crew, but also controllers
  - improve and standardise
• ensure consistency of ACAS procedures with ICAO
  ACAS provisions

• Support the need for continued ACAS operational
  monitoring on a pan-European basis
• ACAS performance
• RA potential as an airspace safety indicator

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HotSpot- Paris TMAWesterly operations - FL50 -
FL150
HotSpot
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Safety Studies - Results

• ACAS reduces the risk of collision in European
  airspace to 0.299 - 30 of the risk in the
  absence of ACAS

• ACAS reduces the risk of collision for an
  aircraft 0.277 of the risk in the absence of ACAS
• ACASA Project WP1

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Safety Studies

• ACAS safety studies show ACAS reduces collision
  risk even though ACAS induces some collision risk
• They do not show ACAS is safe, e.g.
• risk that the TCAS computer catches fire is not
  considered
• The studies quantify risk ratio

• There is no target level of safety for ACAS

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Safety Studies

• Logic risk ratio
• tests whether the logic works
• assumptions have to be stated
• equipage, pilot response
• assumes other components (e.g. surveillance) work

• System risk ratio
• event tree or fault tree usually used
• considers all factors and processes
• makes best estimate for the real world
• needs many logic risk ratios as input

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Safety Studies

• Will ACAS reduce the level of collisions that
  would otherwise occur?
• Yes but it will not eliminate it

• Will ACAS cause collisions in encounters that it
  is attempting to resolve?
• Possible, but in smaller numbers than would
  occur in the absence of ACAS

• Will ACAS cause collisions with 3rd party
  aircraft?
• Not considered to be an issue

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Safety Studies

• ACAS safety studies do not set out to prove that
  the risk of collision is reduced below a
  particular level - other than ACAS makes flight
  safer by reducing the risk of collision.
• Nor that ACAS reduces the risk of collision in
  all circumstances, nor that ACAS works in every
  case.

• ACAS safety justification is based on the
  evidence that there will be fewer collisions if
  aircraft fit ACAS than there would be if ACAS
  were not fitted.

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ACAS Monitoring - RA Safety Indicator

• EMOTION 7 Project - Issue OP06
• severity assessment analysis
• - TCAS thresholds already minimised
• - autoflight systems altitude capture laws
• procedural rectification proposal

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ACAS Monitoring - RA Safety Indicator

• EMOTION 7 - OP06 rectification proposals
• - no short term technical TCAS II fix
• procedural airspace design solution
• - Separate simultaneous horizontal and vertical
  converging aircraft by 2000ft
• - Delay vertical convergence after horizontal
  convergence
• - Both these solutions decrease number of RAs and
  increase safety

• Capacity initial assessments show negligible
  constraints
• - Need for specific studies
• - May be inappropriate for some airspaces
• - Already applied successfully by one ATS
  provider
• EMOTION 7 report published

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AGASACAS Recommendations

• Safety performance of ACAS must be maximised

• Recommendations targeted to maximise ACAS
  performance
• reinforce/improve operational procedures -
  consistency of operation
• provide improved compatibility with ATM
  (including potential technical improvements)

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ACAS II / TCAS II

• ACAS II / TCAS II - uses SSR technology to
  detect and track nearby aircraft
• Independent from
• All external systems (e.g. ground radars,
  satellites)
• ATC
• Auto-flight
• NAV systems (e.g. GPS, INS)

• Provides warnings to pilot of potential collision
  threats
• Traffic Alerts (TAs) - indication of traffic that
  may become a threat
• Resolution Advisories (RAs) - if a risk of
  collision is calculated - vertical manoeuvre
  advice to avoid

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ACAS II Threat Detection

• TCAS alerts are based on diagnosed time to go
  to possible collision - concept of closest point
  of approach (CPA)
• Time thresholds at which an alert is issued vary
  with altitude.
• TAs - nominal warning time varies from 20s near
  the ground to 48s at high altitude
• RAs - nominal warning time varies from 15s near
  the ground to 35s at high altitude.

• When both aircraft are TCAS equipped, RAs are
  coordinated

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ACAS Provisions Procedures

• Annex 2 Rules of the Air, Chapter 3, paragraph
  3.2.2, Right-of-way.
• Annex 6 Operation of Aircraft, Part I
  International Commercial Air Transport
  Aeroplanes
• Annex 11 Air Traffic Services, Chapter 2,
  paragraph 2.25, Establishment of requirements for
  carriage and operation of pressure-altitude
  reporting transponders.
• Procedures for Air Navigation Services Air
  Traffic Management (PANS-ATM, Doc 4444), Chapter
  15, Procedures Related to Emergencies,
  Communication Failure, and Contingencies
• Annex 10 Aeronautical Telecommunications, Volume
  IV Surveillance Radar and Collision Avoidance
  Systems, Attachment A, paragraph 3.5.8.10.3,
  Contrary pilot response.
• State letter AN 7/1.3.72-97/77 dated 8 August
  1997, and AN 11/19-02/82 dated 30 August 2002 -
  Proposed ACAS performance -based training
  objectives.
• Procedures for Air Navigation Services Aircraft
  Operations, Volume I Flight Procedures (PANS-OPS,
  Doc 8168), Part VIII, Secondary Surveillance
  Radar (SSR) Transponder Operating Procedures,
  Chapter 3, Operation of ACAS equipment.

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ACAS Provisions Procedures

• PANS-OPS, Doc 8168 - Amendment 12 Nov 2003
• ACAS provisions reinforced - Follow the RA
• ACAS flight crew training guidelines included as
  an Attachment
• PANS-ATM, Doc 4444 - review of ACAS provisions in
  progress
• Proposal to include ACAS controller training
  guidelines as an Attachment
• ICAO ACAS Manual being developed

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ACAS Provisions Procedures Interception of
Civil Aircraft

• ICAO Convention on International Civil Aviation
  (Doc 7300)
• Article 3bis in case of interception, the
  lives of persons on board and the safety of
  aircraft must not be endangered

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ACAS Provisions Procedures Interception of
Civil Aircraft

• ICAO State Letter AN13/38.OPEN-01/114 dated 21
  November 2001
• Noted increase in number of interceptions of
  civil aircraft after 11 September 2001
• Reiterated advice to civil and military
  authorities
• 20 nm interceptor suppress transmission of
  pressure altitude
• - Mode C replies or in the AC field of Mode S
  replies
• Review procedures
• - Annex 2 Rules of the Air Appendix 12
• - Annex 11
• - Doc 9433 Manual Concerning Interception of
  Civil Aircraft
• - Doc 9554 Manual Concerning Safety Measures
  Relating to Military Activities Potentially
  Hazardous to Civil Aircraft Operations

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ACAS Training - Documentation

• ACAS Brochure ACASA/WP6.1/015 Version 2.0
  May 2000
• EUROCONTROL
• State letter AN 7/1.3.72-97/77, dated 8 August
  1997, Attachment E, Proposed ACAS
  performance-based training objectives
• ICAO
• Introduction to TCAS II Version 7 November 2000
• FAA
• TGL 6 - Guidance material on the approval of
  aircraft and operators for flight in airspace
  above flight level 290 where a 300 m (1000 ft)
  vertical separation minimum is applied-01/07/98
• JAA
• TGL 11 - Guidance for operators on training
  programmes for the use of Airborne Collision
  Avoidance Systems (ACAS) 01/06/98
• JAA
• ACAS II Operations in the European RVSM
  Environment -
• ACTOR/wp1/BROC/D Version 1.0 - 03-08-2001
  EUROCONTROL
• RITA1 RITA2 - pc-based ACAS training tool
• EUROCONTROL
• Note. This list is not exhaustive

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RITA2
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RITA2
Manoeuvre opposite to the RA (TMA) (09)

• TCAS-TCAS coordination is always efficient. It is
  hazardous to manoeuvre contrary to the RA.
• Pilots must follow all RAs, even with a contrary
  ATC instruction.
• Pilots must inform ATC as soon as possible of the
  RA.
• When controllers are not aware of an RA, and if
  they are providing the aircraft with instructions
  for avoiding action, horizontal instructions are
  more appropriate as they will not adversely
  affect any vertical manoeuvres required by
  TCAS II RAs.