Lecture 10: Traffic alert
and Collision Avoidance
• At the end of this lecture, the student should
Previous be able to:
– Describe the theory of early warning system
What is TCAS
Home • TCAS stand for Traffic alert and Collision
• TCAS is a special system designed to reduce the
incidence of Mid-air Collisions (MAC) between
• According to ICAO, all aircraft with MTOW over
5700 kg or carry more than 30 passengers are
compulsory to equipped with TCAS.
Mid-Air Collision (MAC)
Previous Worst MAC in History
•Saudi Arabian Airlines VS
Kazakhstan Airlines , 1996
(349 people killed)
•Bashkirian Airlines collided
with DHL,2002 (71 People
A mid-air collision is an aviation accident in which two or
more aircraft come into contact during flight.
HOW TCAS WORKS
• TCAS operates similar as Secondary Surveillance
Previous Radar (SSR), but in air to air role.
HOW TCAS WORKS
Home • TCAS consists of antennas on aircraft body,
computer processor & TCAS display inside cockpit.
• TCAS antenna continually surveys the airspace
Next around an aircraft & transmit the signal.
Help • Other aircraft that also equipped with TCAS in the
surrounding area will reply the signal.
• TCAS continuously calculates tracked aircraft
position, therefore TCAS display constantly
updated and provide real time position
HOW TCAS WORKS
• Targets (other aircraft) are displayed on the
TCAS screen as different symbols which show
level of threat.
• Aircraft relative altitude also will be displayed.
– Relative altitude is the targets altitude in
relation to the aircraft. EX: -03↑ depicts a
target 300 feet below and climbing.
• TCAS can not display aircraft without TCAS
Traffic Advisory (TA) &
Resolution Advisory (RA)
Home Determination of the alerts: TA & RA AUDIO WARNING
Traffic Advisory (TA) Intruder be at 45 “Traffic, Traffic”
help the pilots in the visual search and 35 seconds
for the intruder aircraft, and alert
Next them to be ready for a potential from the collision
resolution advisory area.
Resolution Advisory (RA) Intruder be at 30 “Climb, Climb”
avoidance maneuvers and 20 seconds “Descent,
recommended to the pilot.
from the collision Descent”
• Range = 14 NM
• Maximum number of aircraft processed = 30
TYPICAL TCAS DISPLAY
In modern glass cockpit aircraft, the TCAS display may be integrated in the
• Highly accurate distance measurements, with a
Previous one-second refresh rate.
• All threats taken into account
• Detection of all transponding aircraft, including
those which are not displayed on the air traffic
• Independent system, which acts as a last resort
measure to avoid mid-air collision when other
safety precautions fail.
• TCAS reduced the risk of mid-air collision
• No detection of aircraft without or not
Previous operating transponders (e.g. VFRs, military
• No knowledge of the pilot’s intentions and of
the ATC separation minima
• Basic display: no identification, no past
positions, no speed vector
• Sometime generate unnecessary alerts.