18AIRBORNE COLLISION AVOIDANCE SYSTEM

8/7/2019 18AIRBORNE COLLISION AVOIDANCE SYSTEM

1/22

AIRBORNE COLLISIONAIRBORNE COLLISION

AVOIDANCE SYSTEMAVOIDANCE SYSTEM

ACASACAS


2/22

WHAT IS ACASWHAT IS ACAS

ACAS (Airborne Collision Avoidance System) is alsoknown as TCAS (Traffic Alert and Collision AvoidanceSystem).

It is a transponder based interrogation system capable ofdisplaying conflicting traffic and providing resolutionadvice.

Provides an extra level of protection against mid-aircollision.

ACAS is mandatory for all aircraft over 10 seatsoperating in US airspace.

Transport Canada requires large aircraft to be equippedwith ACAS.


3/22

HOW ITWORKSHOW ITWORKS

ACAS consists of aircraft mounted antennas,computer processor, flight deck display and controls,and Mode S transponder.

Altimeter and radar altimeter inputs are used todetermine relative altitude and inhibit RAs close tothe ground.

ACAS is capable of displaying targets for othertransponder equipped aircraft.

The ACAS set transmits an interrogation signalwhich other aircraft transponders reply to.

The ACAS computer determines rate of distancechange. TAs and RAs are based on this closure

rate.


4/22


5/22

20NM

300kt closure

PROTECTION THRESHOLDSPROTECTION THRESHOLDS

NOTE: protectionthresholds will vary

with closure rate and

altitude.


6/22

HOW ITWORKSHOW ITWORKS

Targets are displayed on the ACAS screen as differentsymbols which depict level of threat.

The visual cues will be accompanied by an auralwarning. EX: TA Traffic, Traffic or RA Climb, Climb

Relative altitude will be displayed in conjunction with atrend arrow.

Relative altitude is the targets altitude in relation to theaircraft. EX: -03 depicts a target 300 feet below and

climbing at 600fpm or more. If the target is climbing or descending at less than

600fpm the arrow will not appear.

ACAS is incapable of displaying aircraft withouttransponders.


7/22

ADVISORIESADVISORIES

Traffic Advisory (TA)- help the pilots in thevisual search for the intruder aircraft, andalert them to be ready for a potential

resolution advisory. Resolution Advisory (RA)- avoidance

manoeuvres recommended to the pilot;

when the intruder aircraft is Mode Sequipped both systems will co-ordinatetheir RAs through datalink.


8/22

TYPESTYPES

There are three main types of ACAS in different

stages of use or development:

ACAS l- will provide a warning (TA traffic advisory) of

proximate traffic without guidance to avoid potentialcollisions.

ACAS ll- will provide warning (TA traffic advisory) and

vertical plane guidance (RA resolution advisories) to

avoid potential collisions. ACAS lll- the next generation of ACAS still under

development will provide TAs and RAs which include

vertical plane and horizontal plane guidance.


9/22

ACAS lACAS l

A traffic advisory (TA) is given anytime a targetenters the TA range and altitude limits of the

ACAS. (The TA will be an aural Traffic, Traffic)

Traffic with Mode A transponders will bedepicted with position information only.

Traffic with Mode C transponders will bedepicted with position and relative altitudeinformation.

Traffic with Mode S transponders will bedepicted with position and relative altitudeinformation.


10/22

TYPICAL ACAS l DISPLAYTYPICAL ACAS l DISPLAY


11/22


12/22

ACAS llACAS ll

ACAS ll is capable of providing resolution advisories(RA) anytime an aircraft enters the RA range and altitudelimits of the ACAS.

The RA will be a combination of aural and visual cues.

Traffic with Mode A transponders do not allow the ACASto compute an RA.

Traffic with Mode C transponders allow the ACAS todetermine and display a RA.

Traffic with Mode S transponders allow the two aircraft tocommunicate via datalink and provide complimentaryRAs. EX: one aircraft climbs while the other descends.


13/22

TYPICAL ACAS ll DISPLAYTYPICAL ACAS ll DISPLAY


14/22

ACAS lllACAS lll

ACAS lll will have the added capability ofproviding lateral and vertical RAs.

No equipment currently exists due totechnical and operational difficulties.

Safe and accurate RAs in the vertical andhorizontal plane are difficult to program

especially when dealing with multipletargets.


15/22

ACAS SYMBOLOGYACAS SYMBOLOGY

Hollow blue or white diamond- non-

intruding traffic.

Solid blue or white diamond- intrudingtraffic.

Solid amber circle- intruder which triggers

a TA

Solid red square- threats which trigger a

RA


16/22

-03

An intruder target 300 feet below and

climbing at 600fpm or more.


17/22

Non-intruding

traffic

Intruding traffic

Traffic advisory

Resolution

advisory


18/22

RESOLUTION ADVISORYRESOLUTION ADVISORY

The RAs are displayed on an electronic IVSI.

Red arcs depict rate of climb/descent whichmust be avoided.

Green arcs depict required climb/descent ratesto resolve conflict.

The visual resolution will be accompanied by anaural message.

Descend, descend Maintain vertical speed, maintain

Clear of conflict


19/22


20/22


21/22

PILOT/CONTROLLERPILOT/CONTROLLER

ACTIONSACTIONS Pilots shall not manoeuvre their aircraft inresponse to TAs only.

In the event of an RA to alter flight path the

alteration should be the minimum required andATC must be notified as soon as possible.

Pilots who deviate from an ATC instruction or

clearance in response to an RA shall promptly

return to the terms of that instruction or

clearance when the conflict is resolved.


22/22

CAUTIONSCAUTIONS

ACAS is designed as a tool to improvesituational awareness and as a last resortmeasure to avoid mid-air collision when other

safety precautions fail. An intimate understanding of each specific

system is required in order to accuratelyinterpret the displayed information.

The visual information displayed to the pilot islimited and can be misleading, caution isadvised.

18AIRBORNE COLLISION AVOIDANCE SYSTEM

Documents

Transcript of 18AIRBORNE COLLISION AVOIDANCE SYSTEM