Title: EEE381B Aerospace Systems
1EEE381BAerospace Systems Avionics
- Identification Systems
- Ref Moir Seabridge, Chapter 7
- Dr Ron Smith
2Outline
- Introduction
- Transponders
- ATC
- TCAS
- IFF
- Network-centric warfare
- In-class exercises
31. Introduction
- Identification the classification and
identification of a target before engagement as
dictated by the rules of engagement.
41.1 Identification (transponder) systems
- Military aircraft employ a number of different
interrogators and transponders - Distance measurement equipment (DME)
- Tactical air navigation (TACAN)
- Air traffic control (ATC) mode S
- Traffic collision avoidance system (TCAS)
- Automatic dependent surveillance (ADS)
- Identification friend or foe (IFF)
DME and TACAN will be described in the
Navigation section of the course.
51.2 RF Spectrum1
- Identification equipment
- Air traffic control (ATC)
- Collision Avoidance (TCAS)
- Identification friend or foe (IFF)
62. Transponders
- A transponder is a receiver / transmitter device
designed to transmit a response signal when
legitimately interrogated. NATO definition - An automatic device that transmits a
predetermined message in response to a predefined
received signal. Wikipedia
72.1 Air traffic control (ATC)
- A ground-based primary surveillance radar (PSR)
detects the presence of an aircraft and indicates
its bearing and distance. - At the same time a secondary surveillance radar
(SSR), synchronized (on boresight) with the PSR,
interrogates the aircraft using a series of
pulses. - The aircraft transponder responds with a
different series of pulses containing situational
information, typically its aircraft identifier
and altitude. - The information from the PSR and SSR is then
integrated and presented on the ATC console.
82.1.1 Air traffic control (ATC)
92.1.2 Air traffic control (ATC)
- This system is also known as identification
friend or foe / secondary surveillance radar
(IFF/SSR) - The onboard aircraft equipment consists of
- an ATC transponder control unit for setting the
modes of operation and the control codes, - a dedicated ATC transponder, and
- antennas.
102.1.3 Air traffic control (ATC)
- Mode A (simple system)
- Aircraft identification (Call-sign)
- Mode C (more advanced)
- Mode A altitude
- Mode S (more recently)
- Mode C 24 bit address identifier (unambiguous)
- Provides limited air-air and air-ground
communications - Can also provides whereabouts of other aircraft
in its vicinity - Uses digital error-correcting codes for improved
reliability
112.2 Traffic Collision Avoidance System
TCAS
- A type of collision and avoidance system that
functions independently from the ground based ATC
suite. - Used to detect possible aircraft conflicts
- Requires that all possible conflict aircraft are
equipped with an SSR transponder. - Mandated above 10,000 ft and within 30 miles of
major airports.
122.2.1 TCAS architecture 1
132.2.2 TCAS operation
- Altitude and identification is obtained from
modes C or S of an airborne ATC transponder (only
bearing from mode A). - Distance is obtained by calculating the response
delay. - Directional antennas obtain the bearing of the
responding aircraft.
142.2.3 TCAS operation
- TCAS builds a three-dimensional map of the
aircraft within vicinity and extrapolates their
closing distance and altitudes to determine if
there are any possible collisions. - Vicinity is typically defined as 15-40 nm
forward, 5-15 nm aft and 10-20 nm on each side. - Remember that the system can only communicate
with aircraft equipped with serviceable
transponders.
152.2.4 TCAS types
- TCAS I
- Indicates distance and bearing
- Issues traffic advisories (TA)
- 'TRAFFIC, TRAFFIC
- TCAS II
- Negotiates and indicates deconfliction strategies
- Issues resolution advisories (RA)
- Climb Climb Climb,
- Descend Descend Descend,
- Maintain vertical speed , ...
162.3 Identification friend or foe (IFF)
- Used in two ways
- Provide 360 coverage to respond to
interrogations and receive interrogation returns
from friendly aircraft (very similar to the
airborne operation of ATC mode S when used in
combination with TCAS)
AN/APX-113(V) by BAE Systems
172.3.1 Identification friend or foe (IFF)
- Used to specifically identify targets seen by the
primary radar.
183. Network-centric operations 3
- Based upon the hypothesis that
- A robustly networked force improves information
sharing - Information sharing enhances the quality of
information and shared situational awareness - Shared situational awareness enables
collaboration and self-synchronization, and
enhances sustainability and speed of command and
- These, in turn, dramatically increase mission
effectiveness.
193.1 Network-centric operations
- Employs
- High speed, high bandwidth digital communications
- Sophisticated signal processing
- High speed internal (onboard) networks
- Integrates
- Command control structure (C2)
- Ultra high resolution sensors
- Sensor and weapons delivery platforms
203.2 Network-centric operations 1
213.3 NCO example 4
224. In-class exercises
234.1 Quick response exercise 1
- You are flying (VFR) in an aircraft equipped with
a modern, serviceable TCAS system. - You receive a traffic advisory (TA) that a
potential conflict exists directly in your flight
path range is closing and the bearing is
straight ahead. - You perform the necessary visual check, but you
do not see any other aircraft. - What is a likely explanation?
244.2 Quick response exercise 2
- What problem do you see with having the IFF
transponder oriented co-boresight with the
primary radar?
25References
- Moir Seabridge, Military Avionics Systems,
American Institute of Aeronautics Astronautics,
2006. Sections 2.6 2.7 - Wikipedia
- Military Communication Systems, LFTSP course
notes, ECE Dept, RMC, 2007 - Air Power Australia, http//www.ausairpower.net/TE
-NCW-JanFeb-05.html. - Georgia State University, hyperphsyics,
http//hyperphysics.phy-astr.gsu.edu/hbase/audio/b
cast.htmlc3 - Mark A. Hicks, "Clip art licensed from the Clip
Art Gallery on DiscoverySchool.com"