TRAFFIC COLLISION AVOIDANCE SYSTEM

ACAS

Airborne Collision Avoidance System

TCAS

Traffic Alert and Collision Avoidance System

PURPOSE OF TCAS (ACAS)

Provides alert information of conflicting traffic and warns of impending collision.

Mode A

Provides a 4-digit octal identification code for the aircraft, set in the cockpit but assigned by the air traffic controller. Mode A is often combined with Mode C to provide altitude information as well

Mode C

Provides the aircraft's pressure altitude and is usually combined with Mode A to provide a combination of a 4-digit octal code and altitude

Mode S

Provides multiple information formats to a selective interrogation. Each aircraft is assigned a fixed 24-bit address giving details such as callsign, alt, etc. Periodically broadcasts it, enabling it to be tracked, displayed and RA solutions to be presented on some systems.

ADS-B

Automatic Dependent Surveillance-Broadcast is a surveillance technology in which an aircraft determines its position via satellite navigation or other sensors and periodically broadcasts it, enabling it to be tracked, displayed and RA solutions to be presented on some systems.

TCAS COMPONENTS

Transponder - Locates target aircraft uses Mode "S" - (Target must have Mode "C" operating to be seen)

- Computer processor

- Display (electronic) - Displays targets on area map or moving map.

- Aural warning device.

- Two Directional antennae. - (That is QTY 2)

OPERATING PRINCIPLE

Your Transponder in Mode "S"

- Interrogates target aircraft transponder with mode "S" or "C"

- Detects bearing and range

- Computes rate of closure and relative direction of travel

ADVANTAGES

- Provides better situational awareness (More on this in FANS)

- May provide corrective advisories

- Minimal additional equipment

SYMBOLS No threat

hollow white or blue diamond

SYMBOLS Proximate traffic

solid white or blue diamond

SYMBOLS TA (all types)

solid yellow/amber circle - 40 sec

SYMBOLS RA

RA, vertical only (ACAS/TCAS type II & III)

solid red square - 15 to 25 sec

All with height data (providing threat A/C has mode C selected)

Type III

RA's vertical & horizontal - not yet fully developed.

TCAS 1

Power up, climb and put the VSI in the Green

G1000 TAS (Traffic Advisory System)

30 seconds notice

No Resolution Advisory

ESCAPE MANOEUVRES

- TCAS I - If VMC gain visual

- Take appropriate avoidance action - advise ATC

- TCAS II & III - follow resolution guidance - advise ATC (Target must have Mode S)

- Maintain separation from other targets

- Return to flight plan

- Whisper/shout - single advisory

- Once safe - "CLEAR OF CONFLICT" & no red square

LIMITATIONS

- Aircraft responding might conflict with a third party - as an aircraft avoids a collision, it may endanger itself with other aircraft

- False alarms - false, reflected signals or ground interference

- Conflict with other warning systems - noisy cockpit

- Distraction when proximity known - Focused on the conflicting aircraft and not other important aspects of flying the aircraft

- Target must have Mode C - the other aircraft must have a minimum of Mode C or you can't see it.

CALIBRATION

- Required regularly - In conjunction with 24 month transponder test and at fitment

- Power output test

- Address test (hex code)