AirTrafficCntlRadarT1WhtBG

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Air Traffic Control Radar

Aircraft Design Class

AIAA Team 1

Presenters: Stephen Bruso, Lamar Berry

Group: Robert Adams, Ryan Arnaudin, William Black,Anne Brooks, Nicholas Carlson, Shelley Biagi

29 September 06


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Overview

Why we need Air Traffic Control (ATC)

History

Identify Friend or Foe (IFF)

Air Traffic Control Beacon System (ATCBS)

Transponders

Mode S

Traffic Collision Avoidance System (TCAS)

Radar


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History Timeline World War I Pilots begin taking radios into planes

1920's - Airlines use radio to transmit weather information topilots

1921 - Army deployed rotating beacons in a line betweenColumbus and Dayton, OH

1932 - Department of Commerce constructed 83 radiobeacons that transmitted directional beams

1935 - First air traffic control tower established at the NewarkInternational Airport in NJ

World War II - Americans developed IFF (Identify Friend orFoe), installing transponders above Allied aircraft

1958 - Federal Aviation Agency, charged with establishingand running an air traffic control system


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Notable Accidents

Grand Canyon, June 30, 1956

United Airlines DC-7 collided with a TWA Constellation128 passengers killed. The aircraft were flying inuncontrolled airspace, under visual flight rules

New York City, Dec. 16, 1960

United Airlines DC-8 and a TWA Super Constellationover New York City killed 128 people on board and 8

people on the ground. The United flight had experiencedpartial navigation equipment failure but failed to report itto the air traffic controllers.
http://mit.edu/6.933/www/Fall2000/mode-s/collisions.htmlhttp://mit.edu/6.933/www/Fall2000/mode-s/collisions.htmlhttp://mit.edu/6.933/www/Fall2000/mode-s/collisions.htmlhttp://mit.edu/6.933/www/Fall2000/mode-s/collisions.htmlhttp://mit.edu/6.933/www/Fall2000/mode-s/collisions.html


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New York City Dec 16,1960

From Massachusetts Institute of Technology webpage


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Notable Accidents

Hendersonville, NC, July 19, 1967 Piedmont Airlines B-727 collided with a private Cessna,

82 people killed. Accident was closely tied to lack ofsecondary surveillance radar and confusingtransmissions by the air traffic control

Cerritos, CA, August 31, 1986

Aeromexico DC-9 with 64 passengers collided with aprivate Cessna aircraft carrying a family of three. TheDC-9 crashed into a neighborhood and destroyed18

homes and killed 15 people on the ground. The accidentwas blamed on inadequate radar approach anddeparture equipment and procedures.
http://mit.edu/6.933/www/Fall2000/mode-s/collisions.htmlhttp://mit.edu/6.933/www/Fall2000/mode-s/collisions.htmlhttp://mit.edu/6.933/www/Fall2000/mode-s/collisions.htmlhttp://mit.edu/6.933/www/Fall2000/mode-s/collisions.htmlhttp://mit.edu/6.933/www/Fall2000/mode-s/collisions.html


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Cerritos, CA, August 31, 1986

http://mit.edu/6.933/www/Fall2000/mode-s/collisions.htmlhttp://mit.edu/6.933/www/Fall2000/mode-s/collisions.html


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IFF

A ground-based transmitter, the interrogator,broadcasts a radio signal to the aircraft

A transponder on the aircraft would receive and

reply to this signal

Interrogations used very specific types of signals(1030 and 1090 MHz)

If a plane did not respond correctly the systemdetermined that the target was an enemy aircraft


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ATCRBS

System shares the same frequency bands as IFF

A sensor on the ground sends out an interrogation signal

(1030 MHz) from a rotating antenna to aircraft flying in its

sector

Aircraft equipped with transponders receive these

interrogations and send back a reply (1090 MHz)

There are two primary types of interrogations

Mode A interrogations are used for plane identification

information

Mode C interrogations are used for altitude information


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Problems with ATCRBS

ATCRBS uses a rotating antenna to continuously sendout interrogations

An aircraft can be interrogated up to 20 times per sweep

Each time, the transponder sends back a separate reply

Causes interference and overload in the 1030/1090 MHzchannels

When interference occurs the ground station receives

garbled signals As traffic increases, the number of airplanes at a given

time within the antenna's interrogation beam willincrease


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Transponders

Mandated if aircraft flies above 10,000 ft or within 30 miles of amajor airport

Primary Surveillance Radar (PSR) transmits radar energy detectedby the aircraft by reflected radar energy

Aircraft return is displayed on the ATC console at a range and

bearing with aircraft position

The Secondary Surveillance Radar (SSR) transmits a series ofinterrogation pulses received by the aircraft transponder

Transponder replies with a different series of pulses that givesaircraft identifier and altitude

PSR and SSR are synchronized, both returns will be displayed onthe ATC console


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How everything works

From Civilian Avionics Systems, Fig 6.13


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Mode S

Discrete Address Beacon System (DABS) laterrenamed Mode S

S=Select: uses discrete addressing to

interrogate just one aircraft Is a Secondary Surveillance Radar (SSR)

beacon

Ground-air-ground data link system

Uses sophisticated monopulse techniques todetermine azimuth bearing of aircraft


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Mode S Interoperability

Several specific design decisions that were influenced byinteroperability:

Frequency - 1030/1090 MHz was made so Mode S andATCRBS could communicate on the same channel

Modulation - chosen partially to minimize the effects ofinterference due to shared frequency channels

Signal Formats - the Mode S signal itself had to bedesigned so that it was transparent to existingtransponders

Error Correction - ATCRBS limitations forced the Mode Ssignal to be short, so parity and addressing bits wereoverlaid to maximize data block size
http://mit.edu/6.933/www/Fall2000/mode-s/frequency.htmlhttp://mit.edu/6.933/www/Fall2000/mode-s/modulation.htmlhttp://mit.edu/6.933/www/Fall2000/mode-s/signal.htmlhttp://mit.edu/6.933/www/Fall2000/mode-s/ecc.htmlhttp://mit.edu/6.933/www/Fall2000/mode-s/ecc.htmlhttp://mit.edu/6.933/www/Fall2000/mode-s/signal.htmlhttp://mit.edu/6.933/www/Fall2000/mode-s/signal.htmlhttp://mit.edu/6.933/www/Fall2000/mode-s/modulation.htmlhttp://mit.edu/6.933/www/Fall2000/mode-s/modulation.htmlhttp://mit.edu/6.933/www/Fall2000/mode-s/frequency.htmlhttp://mit.edu/6.933/www/Fall2000/mode-s/frequency.html


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Mode S Frames

Transmission between transponder andstation use 56 or 112 bit format called frames

Three Main categories: 56 bit Survellience formats

112 bit communication format with 56 bit datafield

112 bit communication format with 80 bit datafield


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Planned Improvements

Two major Preplanned Product Improvementscurrently underway

Technology upgrades from 68020 to 68040processors, currently in keysite test at GrandJunction, CO

Traffic Information Service (TIS), a data link servicethat assist general aviation (GA) pilots in visualacquisition of surrounding air traffic by delivering

automatic traffic advisories to the pilot, currently inkeysite test at Dulles and Andrews AFB


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Mode S Antenna Site



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Traffic Collision Avoidance System

Tracks up to 30 aircraft, displays the 25 highest priority aircraft

All commercial aircraft must be equipped with TCAS by 1993

Uses three separate systems to plot positions of nearby aircraft

Directional antennae receives Mode S transponder signals toprovide a bearing to neighboring aircraft, accurate to a fewdegrees of bearing

Mode C used to plot the altitude of nearby aircraft

The timing of the Mode S interrogation/response protocol ismeasured to find the distance of an aircraft


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TCAS I

Gives the pilot relative position and velocity of all aircraftwithin a 10-20 mile range

Has a traffic advisory capacity which provides a warningwhen an aircraft in the vicinity gets too close

Does not provide instructions on how to maneuver inorder to avoid the aircraft

Warns aircraft of other aircraft within +-8700 ft ofaircrafts own altitude

Selected range 15-40 n miles forward

5-15 n miles aft

10-20 n miles each side


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TCAS II

Provides pilots with airspace surveillance, intrudertracking, threat detection, and avoidance maneuvergenerations

Determines whether each aircraft is climbing,

descending, or flying straight and level, and suggests anevasive maneuver

Evasive maneuvers are coordinated via air-to-airtransmissions so the proposed maneuvers will not

cancel each other out

TCAS II Change 7, software changes and updatedalgorithms that alter operating parameters


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Types of Radar

Altimeter

Doppler

Weather


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Altimeter

Radar transmissions to reflect off the surfaceimmediately below the aircraft

Provides absolute reading of altitude

Differs from barometric or air data altimeter,which commonly reference sea level altitude

Operates over a max range of 0 5000 ft

Display shown has a max reading of 2000 ft


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How an Altimeter Works

From Civilian Avionics Systems, Figs 5.27, 5.28


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Doppler

Transmits energy through 3 or 4 beams skewed to the

front and rear of the aircraft Radiated energy is reflected from the terrain

Forward facing beams return a higher frequency, with theincrease being proportional to the aircraft ground speed

Aft facing beams returns a lower frequency Beams also detect lateral frequency difference from cross

wind

Sensitivity is 30 Hz per knot of speed

Horizontal velocity error is on magnitude of 0.015 per centper degree of error in pitch angle

Common on helicopter, however GPS has phased it outof transport aircraft


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How Doppler Works



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Weather

Radiates energy in narrow beam reflected by clouds

Beam width of ~3 deg

Antenna maybe tilted in elevation around +-15 deg from

horizontal, some have automated tilt

Displays are typically in color

Transmitter operates at 9.345 GHz

3 Basic Modes Weather and map, with max range of 320 n miles

Turbulence (TURB) mode out to 40 n miles

Wind Shear detection out to 5 n miles


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Weather Radar



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Sources

http://www.tc.faa.gov/its/cmd/visitors/data/ACT-300/modes.pdf

http://mit.edu/6.933/www/Fall2000/mode-

s/index.html

http://www.faa.gov/ATpubs/ATC/INDEX.HTM

Book Civilian Avionics Systems, author Ian Moirand Allan Seabridge, AIAA education series,copyright 2003
http://www.tc.faa.gov/its/cmd/visitors/data/ACT-300/modes.pdfhttp://www.tc.faa.gov/its/cmd/visitors/data/ACT-300/modes.pdfhttp://mit.edu/6.933/www/Fall2000/mode-s/index.htmlhttp://mit.edu/6.933/www/Fall2000/mode-s/index.htmlhttp://www.faa.gov/ATpubs/ATC/INDEX.HTMhttp://www.faa.gov/ATpubs/ATC/INDEX.HTMhttp://www.faa.gov/ATpubs/ATC/INDEX.HTMhttp://mit.edu/6.933/www/Fall2000/mode-s/index.htmlhttp://mit.edu/6.933/www/Fall2000/mode-s/index.htmlhttp://mit.edu/6.933/www/Fall2000/mode-s/index.htmlhttp://mit.edu/6.933/www/Fall2000/mode-s/index.htmlhttp://www.tc.faa.gov/its/cmd/visitors/data/ACT-300/modes.pdfhttp://www.tc.faa.gov/its/cmd/visitors/data/ACT-300/modes.pdfhttp://www.tc.faa.gov/its/cmd/visitors/data/ACT-300/modes.pdf


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