Research Paper ion Traffic collision avoidance system in IEEE Format

1. Traffic Collision Avoidance System
(TCAS)
M. Shahar Zad
Electrical Engineering
Sharif College of Engineering & Technology
Lahore, Pakistan
muhammadshehrzad@yahoo.com
M. Rizwan
Electrical Engineering
Sharif College of Engineering & Technology
Lahore, Pakistan
mrizwanjani96@gmail.com
Ammar Ahmed
Electrical Engineering
Sharif College of Engineering & Technology
Lahore, Pakistan
m.ammarahmed69@gmail.com
M. Khizar
Electrical Engineering
Sharif College of Engineering & Technology
Lahore, Pakistan
m.khizarsaleem@gmail.com
Abstract—A traffic collision avoidance system both
pronounced as TCAS, and (te-kas) is an airliner collision
avoidance system designed specifically to reduce the
incidents of mid air collisions between airplanes. It checks
the airspace around an airplane for other airliners which are
equipped with an active transponder device, irrespective
of air traffic control commands it warns pilots about the
existence of other same instrument prepared airliner which
may result in a mid air collision (MAC).It uses cross
communication with other airliner which is equipped with the
same device. In the case of any intruder it sounds an alarm in
the cockpit which tells the pilot that there is another airliner
flying in the same airspace with a gap of less then 500 feets.
After that it makes sure to maintain a distance of at least 500 ft
among both of these two airliners. This is how this system
works.
I. INTRODUCTION
Before the invention of TCAS, radars were used to
navigate the positions of an airliners and in the case of any
intruder flying in the same airspace, it was the ATC’s
responsibility to make it sure that both of these airliners pass
by each other with enough distance so that they made not end
in a collision. But this idea was proven wrong very soon when
a number of collisions occurred in a calendar year. In 1956 a
deadly collision took place over Grand Canyon between a
United Airlines DC-7 and a TWA Flight. At that time it was
the deadliest accident, so research started to develop an anti-
collision system to avoid such kind of incidents in future. In
1960-70’s many collision avoidance systems were designed
but gave useless alarms when tested in heavy traffic regions.
In 1978 a PSA Flight 182 collided with a 4-seated small plane
near San Diego Airport, killing all 144 passengers on board.
After this incident Federal Aviation Authority (FAA)
developed a system which now called TCAS. This system
involves messaging between all airliners equipped with
a transponder which is enabled and installed properly. Each
TCAS equipped airliner monitors all other airliners in a
specific range about their positions (through the
1.03 GHz radio frequency) and all other airliners reply to the
monitoring cross communications via (1.09 GHz). This cross-
examination and response process can occur more than one
times per second. This system creates a multi dimensional
map of airliners in the airspace, keeping in view their height
(as reported by the monitoring airliner) and behavior (by the
respective directional aerial from the reaction). By
checking existing range and height difference to probable
expected values, it determines if a possible accident risk
exists.FAA had made it compulsory for all airliners with a
capacity of more than 18 passengers to have TCAS on board.
Since then all such airliners have TCAS. Further research
made it more efficient in present time.
A. Information Table
TABLE I. TABLE STYLES
Typ
e
Text Meaning Required action
TA
Traffic;
traffic.
Intruders near both flat
and upright.
Effort visual contact, and be
prepared to plan if an RA
occurs.
RA Climb; climb. Intruder will pass below
Begin going up at 1500–
2000 feet/min
RA
Descend.
Descend.
Intruder will pass above.
Begin moving down at 1500–
2000 feet/min

2. RA
Increase
climb.
Intruder will pass just
below
Mo up at 2500 – 3000 ft/min.
RA
Increase
descend.
Intruder will pass just
above.
Move down at 2500 –
3000 ft/min.
RA Reduce climb.
Intruder is probably well
below.
Move up at a slower rate.
RA
Reduce
descend.
Intruder is probably well
above.
Move down at a slower rate.
RA
Climb; climb
now.
Intruder that was passing
above, will now pass
below.
Move up immediately.
Exerimental Acknowledgments
TCAS consists of following mechanism:
1. TCAS computer unit.
2. Aerials.
3. Cockpit Presentation.
Jointly using three gears it performs airspace observation,
intruder tracking, its own airliner height tracking, hazard
detection, resolution advisory (RA) resolving and selection,
and making of advisories. The TCAS Processor uses pressure
height, radar altitude, and distinct airliner category inputs from
its own airliner to control the accident avoidance judgment
parameters that determine the defense level around the TCAS
airliner. The aerials used by TCAS II include a directional
aerial that is installed on the top of the airliner and either a
multi directional or an aerial installed on the base of the
airliner. Most installations use the elective sided aerial on the
base of the airliner. In addition to the two TCAS aerials, two
aerials are also required for the Mode S transponder. One
aerial is installed on the top of the airliner while the other is
installed on the base. The TCAS cross points with the pilots
providing them by two displays: the traffic display and the RA
display. These two displays can be implemented in a number
of ways, including displays that includes both displays into a
single physical unit. Despite of the implementation, the
information displayed is alike.
Figure 1: Working of TCAS.
Discussions
A new edition has been planned but has not been
implemented because the research is still in progress on it
named TCAS 7.1, it involves certain new features in it like
dispatching an alarm before 100 feets mark between two
airliners and making a decisions even right before the
accident, which means that it can change the direction of
airliner keeping in view the information being transmitted and
received by the transponders of both airliners. Researchers are
discussing upon the idea to give TCAS 7.1 more priority than
the commands of Air Traffic Control (ATC). Because it has
more reliability and especially it is able to make quick and fast
decisions in very less time. It’s speciality is that it can make a
reversal decision if RA is not obeyed by the other aircraft.
Suppose that if two aircrafts are flying at 2000 ft mark, the
TCAS 7.1 will sound an alarm in cockpits of both airliners. If
one follows the orders of TCAS and other ignores them, then
it will detect that an aircraft is not following the commands
and tell the other airliner to either climb or descend with
respect to the situation.
Figure 2: Working of TCAS 7.1

3. Conclusions
Following results were being observed out and were
implemented sternly after a long research on TCAS :
• Although the system rarely suffers from fake alarms,
pilots are now under severe instructions to look upon
all TCAS messages as valid alerts demanding an
instant, high precedence rejoin.
• Only Wind shear Detection and GPWS alerts and
warnings will have higher precedence than the TCAS.
• The TCAS RA always takes priority (this is mainly
because of the TCAS-RA naturally contains a more
current and inclusive picture of the state than air traffic
controllers, whose radar transponder updates usually
occur at a much slower rate than the TCAS cross-
communications).
• If one airliner follows a TCAS RA and the other
follows opposing ATC instructions, a collision can
occur, so both airliners must follow the instructions
of TCAS.
• This system thus improved the safety measures and
hence number of collisions decreased after it’s
implementation
References
[1] www.eurocontrol.int/articles/tcas-ii-version-7.1
[2] en.wikipedia.org/wiki/Traffic_collision_avoidance_system#Types_of_tr
affic_and_resolution_advisories ICAO Document 9863 - Chapter 6.
[3] www.ivao.aero/training/documentation/books/PP_ADC_ACAS_TCAS.
pdf
[4] www.nbaa.org/ops/cns/tcas/
[5] en.wikipedia.org/wiki/Traffic_collision_avoidance_system#Alerts