Safety Functions in ATC Systems

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Safety Functions in ATC Systems
Airspace Infringement WorkshopBrussels, 24
January 2008

• Stan Drozdowski
• EUROCONTROL DAP/ATS, Safety Nets Expert

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094530
ONR852 070?040
7000 044
7000 023
HRN5067 030
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Are there any system defences?

• Ground ATC systems and aircraft are equipped with
  safety nets for added safety
• Safety-nets can
• Alert controllers about airspace infringements
• Alert controllers about separation violations
• Provide pilots with the collision avoidance
  advice
• Alert pilots and controllers about proximity to
  the terrain

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System defences
APW Area Proximity Warning
STCA Short Term Conflict Alert
ACAS (TCAS)1
1) ACAS Airborne Collision Avoidance System /
TCAS Traffic alert and Collision Avoidance
System
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APW (Area Proximity Warning)1

• Ground based safety net
• To alert controllers about penetrations or
  excursions from defined airspace volumes

1) Also known as DAIW (Danger Area Infringement
Warning)
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094535
ONR852 070?040
7000 023
HRN5067 030
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APW (Area Proximity Warning)

• Ground based safety net
• To alert controllers about penetrations or
  excursions from defined airspace volumes
• Present in many ATC systems (often with limited
  functionality)
• Passive alerting (no resolution given)
• Controller action may be required
• EUROCONTROL Specification under development

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STCA (Short Term Conflict Alert)

• Ground based safety net
• To alert controllers about potential or actual
  losses of separation

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094530
ONR852 070?040
7000 044
7000 023
HRN5067 026 ?
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STCA (Short Term Conflict Alert)

• Ground based safety net
• To alert controllers about potential or actual
  losses of separation
• Present in the majority of ATC systems
• Passive alerting (no resolution given)
• Controller action required
• EUROCONTROL Specification has been agreed

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TCAS (Traffic alert Collision Avoidance System)

• Airborne safety net
• Independent of ground based safety nets
• TCAS II will issue a collision Resolution
  Advisory (RA) to pilots when there is a risk of
  collision
• Following RAs is mandatory
• RAs are coordinated between equipped aircraft
• TCAS II is the only implementation of ACAS II
  (Airborne Collision Avoidance System) ICAO
  standard
• Equipage requirement
• Turbine engined, fixed wing
• MTOM over 5,700 kg or
• 19 passenger seats

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094530
ONR852 070?040
7000 023
HRN5067 024 ?
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Loss of transponder functionality

• Transponder source of information for ATC
  TCAS
• No transponder / transponder off / signal lost
• Aircraft invisible to ATC
• No TCAS functionality

HRN907 266?320
02
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Transponder
ATC Display
TCAS Traffic Display
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Summary

• Ground-based safety nets are designed to alert
  controllers about separation and airspace
  infringements
• ACAS II (TCAS II) provides collision avoidance
  advice to equipped aircraft
• Ground based safety nets alerting time frame may
  vary depending on local implementation
• Operational transponder is essential for both
  ground and airborne safety nets

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Recommendations

• Altitude reporting transponder must be carried
  and operated at all times
• Area Proximity Warning functionality must be
  implemented in ATC systems

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? www.eurocontrol.int/safety-nets ?
www.eurocontrol.int/acas ? safety-nets_at_eurocontr
ol.int