ATM Communications Navigation and Surveillance

1
ATM Communications Navigation and Surveillance

• SYST 460 560
• Fall 2003
• G.L. Donohue

2
Evolution of CNS/ATM
ADS-B GPS
1935, an airline consortium opened the first
Airway Traffic Control Station
1922 ATC begins
1940s Impact of radar
1930 Control Tower
Airway Centers
1960s 70s
Page 11-15 Katon, Fried
3
Radio Frequencies
Name Abbreviation Frequency Frequency Wave length
Very low VLF 3 to 30 kHz 100 to 10km
Low LF 30 to 300 kHz 10 to 1km
Medium MF 300 to 3000 kHz 1km to 100 m
High HF 3 to 30 MHz 100 to 10m
Very high VHF 30 to 300 MHz 10 to 1cm
Ultrahigh UHF 300 to 3000 MHz 1m to 10cm
Super high SHF 3 to 30 GHz 10 to 1cm
Extremely high EHF 30 to 300 GHz 10 to 1mm
4
Line-of-Sight Waves

• VHF and UHF have about 70 nmi. Range at 6,000 ft.
  altitude

Line-of-sight range
5
Weather

• Instrument meteorological conditions (IMC) are
  weather conditions in which visibility is
  restricted, typically less than 3 miles
• Acft operating in IMC are supposed to fly under
  IFR

6
Visibility Categories (by ICAO) (1)

• Category I
• Decision height not lower than 200 ft visibility
  not less than 2600 ft, or Runway Visual Range
  (RVR) not less than 1800 ft with appropriate
  runway lighting.
• The pilot must have visual reference to the
  runway at the 200ft DH above the runway or abort
  the landing.
• Acft require ILS and marker-beacon receiver
  beyond other requirements for flights under IFR.
• Category I approaches are performed routinely by
  pilots with instrument ratings

7
Visibility Categories (by ICAO) (2)

• Category II
• DH not lower than 100 ft RVR not less than 1200
  ft (350m)
• The pilot must see the runway above the DH or
  abort the landing
• Additional equipment that acft must carry include
  dual ILS receivers, either a radar altimeter or
  an inner-marker receiver to measure the DH, an
  autopilot coupler or dual flight directors, two
  pilots, rain-removal equipment (wipers or
  chemicals), and missed-approach attitude
  guidance. An auto-throttle system also may be
  required

8
Visibility Categories (by ICAO) (3)

• Category III subdivided into
• IIIA. DH lower than 100 ft and RVR not less than
  700 ft (200m)-sometimes called see to land it
  requires a fail-passive autopilot or a head-up
  display
• IIIB. DH low than 50 ft RVR not less than 150
  ft (50m)-sometimes called see to taxi it
  requires a fail-operational autopilot an
  automatic rollout to taxing speed
• IIIC. Zero visibility. No DH or RVR limits. It
  has not been approved anywhere in the world

9
Decision Height

• Acfts are certified for decision heights, as are
  crews
• When a crew lands an acft at an airport, the
  highest of the three DHs applies.
• An abort at the DH is based on visibility
• Alert height is the altitude below which landing
  may continue in case of equipment failure
• Typical Alert height is 100 ft

10
Integrated Avionics Subsystems (1)

• Navigation
• Communication
• intercom among the crew members one or more
  external two-way voice data links
• Flight control
• Stability augmentation autopilot
• The former points the airframe controls its
  oscillations
• The latter provides such functions as
  attitude-hold, heading-hold, altitude hold
• Engine control
• The electronic control of engine thrust(throttle
  management)

11
Integrated Avionics Subsystems (2)

• Flight management
• Stores the coordinates of en-route waypoints and
  calculates the steering signals to fly toward
  them
• Subsystem monitoring control
• Displays faults in all subsystems and recommends
  actions to be taken
• Collision-avoidance
• Predicts impending collision with other acft or
  the ground recommends an avoidance maneuver

12
Integrated Avionics Subsystems (3)

• Weather detection
• Observes weather ahead of the acft so that the
  route of flight can be alerted to avoid
  thunderstorms areas of high wind shears
• Sensors are usually radar and laser
• Emergency locator transmitter(ELT)
• Is triggered automatically on high-g impact or
  manually
• Emit distinctive tones on 121.5, 243, and 406 MHz

13
The Vehicle
Avionics Placement on multi-purpose transport
14
Architecture (1)

• Displays
• Present information from avionics to the pilot
• Information consists of vertical and horizontal
  navigation data, flight-control data (e.g. speed
  and angle of attack), and communication data
  (radio frequencies)

15
Architecture (2)

• Flight controls
• The means of inputting information from the pilot
  to the avionics
• Traditionally consists of rudder pedals and a
  control-column or stick
• Switches are mounted on the control column,
  stick, throttle, and hand-controllers

16
Architecture (3)

• Computation
• The method of processing sensor data
• Two extreme organizations exist
• Centralized Data from all sensors are collected
  in a bank of central computer in which software
  from several subsystems are intermingled
• Decentralized Each traditional subsystem retains
  its integrity

17
Architecture (4)

• Data buses
• Copper or fiber-optics paths among sensors,
  computers, actuators, displays, and controls
• Safety partitioning
• Commercial acft sometimes divide the avionics to
• Highly redundant safety-critical flight-control
  system
• Dually redundant ,mission-critical
  flight-management system
• Non-redundant maintenance system
• Military acrft sometimes partition their avionics
  for reason other than safety

18
Architecture (5)

• Environment
• Avionics equipment are subject to
• acft-generated electricity-power transient, whose
  effects are reduced by filtering and batteries,
• externally generated disturbances from radio
  transmitters, lightening, and high-intensity
  radiated fields
• The effect of external disturbances are reduced
  by
• shielding metal wires and by using fiberoptic
  data buses
• add a Faraday shielding to meal skin of the acft

19
Architecture (6)

• Standards
• Navaid signals in space are standardized by ICAO
• Interfaces among airborne subsystems, within the
  acft, are standardized by Aeronautical Radio INC.
  (ARINC), Annapolis Maryland, a nonprofit
  organization owned by member airlines
• Other Standards are set by
• Radio Technical Commissions for Aeronautics,
  Washington DC
• European Organization for Civil Aviation
  Equipment (EUROCAE)
• etc.

20
Human Navigator

• Large acft often had (before 1970) a third crew
  member, flight engineer
• To operate engines and acft subsystems e.g. air
  conditioning and hydraulics)
• Use celestial fixes for positioning
• Production of cockpits with inertial, doppler,
  and radio equipments facilitated the
  automatically stations selection,
  position/waypoint steering calculations and
  eliminated the number of cockpit crew to two or
  one.

21
Communications is the Glue for ATM-CNS
22
Context for Communication Architecture
23
Air-Ground Comm Functional Architecture
AIRBORNE WEATHER OBSERVATION
VOICE
OPERATIONS, MAINTENANCE
MESSAGING
AIRCRAFT
NEGOTIATION
AIRCRAFT
ADS-B
POSITION/ INTENT
AUTOMET
FIS TIS APAXS

• TV, RADIO
• INTERNET

• WEATHER
• NAS
• STATUS

AOC COMM
CPC
ADS-B
Commercial Service Provider
CPDLC
OTHER AUTHORIZED USERS

• INTERNATIONAL
• MILITARY
• FBOS

DSSDL
NWIS
AIR TRAFFIC CONTROL
AIRLINES OPERATIONS CENTER
24
Benefits Driven Concept
Aircraft
Technical Concepts
Range of User Equipage
Tactical Control
2-way

• CPC
• CPDLC

Human- based
Strategic CDM

• CPC
• CPDLC
• AOCDL

DSS- based
Automated Negotiation

• DSSDL

• TIS
• ADS-B
• FIS
• AUTOMET

Broadcast
Info Base
Static Data

• FIS

AOCDL
Air Traffic Control
Aeronautical Operational Control
25
Functional Analysis

• 9 Technical Concepts
• Defined Message categories and message types for
  each Technical Concept
• Concept Description
• Concept Diagram

26
Architecture Alternatives Summary
27
Operational Concept - Tech Concept
28
Message Categories
29
Concept Description - Flight Information Service

• Aircraft continually receive dynamic Flight
  Information to enable common situational
  awareness
• Weather Information
• NAS Status
• NAS Traffic Flow Status
• Note We assume that static data will be loaded
  on aircraft via portable storage media prior to
  flight.

30
FIS Message Set
31
Flight Information Service - FIS
Wx Sensor(s)
NAS / SUA STATUS
AAIS
ATIS
CSP
FIS PROC
Comm I/F
VDL RCVR
MFDS
OASIS

• NOTAM

SAT COM RCVR
NWIS INTEGRATED NETWORK
WARP
SATCOM
UAT XCVR
Portable Storage Media
UAT
NEXRAD
NWS
Wx Vendor(s)
ADAS
Ground-Based Pilot PC
32
Traffic Information Services TIS
Aircraft
Air / Ground Comm
Ground Systems
ADS-B Processor
ADS-B XCVR
ADS-B GND RCVR
A C N E T W O R K
VDL-B
VDL-B XCVR
Secondary
Primary
AAIS
SATCOM RCVR

• MFDS
• CDTI

SATCOM
Comm I/F
Automation
ATC Facility
UAT
33
Controller / Pilot Data Link Communications CPDLC
ARTCC
Automation
Comm I/F
AAIS
MFDS
VDL-3 XCVR
TRACON
Automation
Comm I/F
TOWER
Automation
Comm I/F
FSS
Automation
Comm I/F
34
CPC Controller/Pilot Voice Communication
VHF Voice Radio
Pilot Voice
Voice Switch
FTI Comm Network
Comm Head
ATC Voice
Existing A/G Radio
VDL Radio
Voice Data
NEXCOM RADIO
35
Decision Support System Data Link DSSDL
ARTCC
Automation
Comm I/F
AAIS
A C N E T W O R K
VDL-3 XCVR
TRACON
Automation
Comm I/F
FMS
TOWER
Automation
Comm I/F
36
Aeronautical Operational Control Data Link AOCDL
AOC
Comm
Automation
I/F
AAIS
CSP VDL-2 Comm Network
MFDS
VDL-2
XCVR
FMS
37
AOCDL Message Set
38
Automatic Dependent Surveillance - Broadcast
ADS-B
Aircraft
Air / Ground Comm
Ground Systems
AAIS
GPS
GPS RCVR
MFDS
A C N E T W O R K
Secondary
Primary
ADS-B GND RCVR
FMS
ADS-B XCVR
ADS-B
Comm I/F
Automation
ATC Facility
39
Automated Meteorological Transmission - AUTOMET
Wx Sensor(s)
NASA
UAT XCVR
AOC
CSP
FMS
PROC
Comm I/F
VDL XCVR
NWS
FSL
SAT COM XCVR
SATCOM
40
Data Link Summary
41
Top Down Architecture -
Primary 2-way CPC / CPDLC / DSSDL
VDL-3
NEXCOM Site
FTI Network
Secondary 2-way AOC / AUTOMET
VDL-2
CSP Network
CSP Interface
SATCOM
CSP Network
FTI Network
FIS / TIS / APAXS
Data Transmit ADS-B
UAT VDL-4 Mode-S
ADS-B Site
FTI Network
Aircraft
Ground
Link
42
2007 Architecture - UAT Data
Ground
Link
Aircraft
VHF-AM
NEXCOM Site
FTI Network
CPC - Voice
Secondary 2-way CPDLC / DSSDL AOC / AUTOMET
VDL-2
CSP Network
CSP Interface
VDL-B
FIS - Regional
CSP Network
FTI Network
UAT
FIS / TIS
Data Transmit ADS-B
ADS-B Site
FTI Network
SATCOM
CSP Network
APAXS
43
Communication Architecture Schedule - FIS
00
10
11
12
13
14
15
01
02
03
04
05
06
07
09
08
Integrated Demo
Research
SATCOM Ant / Rcvr
Standards
FIS-B SATCOM
FIS-B
Avionics
UAT
Systems
FIS-B
SATCOM
FIS-B SATCOM
FIS-B
Certification
FIS Data Compression
Research
Link Simulation
Standards
Air-Ground Comm
Systems (data links)
VDL-B
UAT
V- SATCOM
Research
NAS Wide Info System
NWIS Data
Standards
Ground-Comm
AOC / CDM Network
Systems
WARP Wx Network
FTI
NWIS
System Operational time span
44
Communication Architecture Schedule - TIS
00
10
11
12
13
14
15
01
02
03
04
05
06
07
09
08
Integrated Demo
Research
SATCOM Ant / Rcvr
Standards
Avionics
UAT
Systems
VDL-B
SATCOM
Certification
TIS Data Compression
Research
Link Simulation
Standards
Systems (data links)
Air-Ground Comm
UAT
VDL-B
SATCOM
V- SATCOM
Research
NAS Wide Info System
NWIS Data
Standards
Ground-Comm
AOC / CDM Network
Systems
FTI
NWIS
System Operational time span
45
Communication Architecture Schedule - CPDLC
00
10
11
12
13
14
15
01
02
03
04
05
06
07
09
08
Research
Demo
Standards
Avionics
Systems
VDL-2 MMR
VDL-3 MMR
Certification
Research
Prioritization of HzWx on VDL-2
Standards
Systems (data links)
Air-Ground Comm
VDL-2
VDL-3
Research
NAS Wide Info System
Standards
Ground-Comm
DLAP
Systems
DLAP -R
FTI
NWIS
System Operational time span
46
Communication Architecture Schedule - AOCDL
System Operational time span
47
Communication Architecture Schedule - ADS-B
00
10
11
12
13
14
15
01
02
03
04
05
06
07
09
08
Research
Standards
Avionics
Systems
Mode-S / UAT / VDL-4
Certification
Research
Standards
Systems (data links)
Technology Link Decision
Air-Ground Comm
Mode-S
UAT
VDL-4
Research
NAS Wide Info System
NWIS Data
Standards
Ground-Comm
Systems
FTI
NWIS
System Operational time span
48
Communication Architecture Schedule -
Cross-cutting
00
10
11
12
13
14
15
01
02
03
04
05
06
07
09
08
Research
NAS Wide Info System
Cross-cutting
Standards
Systems (data links)
Mode-S
VHF-AM
UAT
VDL-B
Air-Ground Comm
VDL-2
C, Ku, S SATCOM
VDL-3
SATCOM
V- SATCOM
Systems
FTI
AOC / CDM Network
Ground-Comm
WARP Wx Network
NWIS
System Operational time span
49
Cross Cutting Technology Gaps
50
Navigation
51
Navigation Geometry of The Earth

• For navigational purposes, the earths surface
  can be represented by an ellipsoid of rotation
  around the Earths spin axis
• The size shape of the best-fitting ellipsoid is
  chosen to match the sea-level equal-potential
  surface.

52
Geometry of The Earth
Fig 2.2
Median section of the earth, showing the
reference ellipsoid gravity field
53
Coordinate Frames

• The position, velocity and attitude of the
  aircraft must be expressed in a coordinate frame
  WGS-84

Navigation coordinate frame
54
Navigation Phases
Picture courtesy of MITRE Corporation
55
Aircraft System Hierarchy
Time to go Range, bearing to displays,
FMS Steering signals to autopilot
56
Terminal Area Navigation

• Departure begins from maneuvering out the
  runway, ends when acft leaves the
  terminal-control area
• Approach acft enters the terminal area, ends
  when it intercepts the landing aid at an approach
  fix
• Standard Instrument Departure (SIDs) Standard
  Terminal Approach Route (STARs)
• Vertical navigation? Barometric sensors
• Heading vectors ? Assigned by traffic controller
  

57
En Route Navigation

• Leads from the origin to the destination and
  alternate destinations
• Airways are defined by navaids over the land and
  by lat/long over water fixes
• The width of airways and their lateral separation
  depends on the quality of the navigation system
• From 1990s use of GPS has allowed precise
  navigation
• In the US en-route navigation error must be less
  than 2.8 nm over land 12 nm over ocean

58
Approach Navigation

• Begins at acquisition of the landing aid until
  the airport is in sight or the acrft is on the
  runway, depending on the capabilities of the
  landing aid
• Decision height (DH) altitude above the runway
  at which the approach must be aborted if the
  runway is not in sight
• The better the landing aids, the lower the the DH
• DHs are published for each runway at each airport
• An acrft executing a non precision approach must
  abort if the runway is not visible at the minimum
  descent altitude (typically700 ft above the
  runway)

59
Landing Navigation

• Begins at the DH ends when the acrf exits the
  runway
• Navigation may be visual or navigational sets
  may be coupled to a autopilot
• A radio altimeter measures the height of the main
  landing gear above the runway for guiding the
  flare
• The rollout is guided by the landing aid (e.g.
  the ILS localizer)

60
Missed Approach

• Is initiated at the pilots option or at the
  traffic controllers request, typically because
  of poor visibility. And alignment with the runway
• The flight path and altitude profile are
  published
• Consists of a climb to a predetermined holding
  fix at which the acrf awaits further instructions
• Terminal area navaids are used

61
VHF Omnidirectional Range(VOR)

• Receiver characteristics
• The airborne equipment comprises a horizontally
  polarized receiving antenna a receiver. This
  receiver detects the 30 Hz amplitude modulation
  produced by the rotating pattern compares it
  with the 30 Hz frequency-modulated reference.
• Fig 4.16

62
Doppler VOR

• Doppler VOR applies the principles of wide
  antenna aperture to the reduction of site error
• The solution used in US by FAA involves a 44-ft
  diameter circle of 52 Alford loops, together with
  a single Alfrod loop in the center
• Reference phase?The central Alford loop radiates
  an omni-directional continuous wave that is
  amplitude modulated at 30 Hz
• The circle of 52 Alford loops is fed by a
  capacitive commutator so as to simulate the
  rotation of a single antenna at a radius of 22ft
• Rotation is at 30rps, a carrier frequency 9960
  Hz higher than that in the central antenna is fed
  to the commutator
• With 44-ft diameter a rotation speed of 30
  rps, the peripheral speed is on the order of 1400
  meters per second, or 480 wavelengths per second
  at VOR radio frequencies

63
Distance-Measuring Equipment (DME) (1)

• DME is a internationally standard pulse-ranging
  system for acft, operating in the 960 to 1215 MHz
  band. In the US in 1996, there were over 4600
  sets in use by scheduled airlines and about
  90,000 sets by GA

DME Operation
64
Distance-Measuring Equipment (DME) (2)

• The acft interrogator transmits pulses on one of
  126 frequencies, spaced 1 MHz apart, in the 1025
  to 1150 MHz band. Paired pulses are used in
  order to reduce interference from other pulse
  systems. The ground beacon(transponder) receives
  these pulses after a 50 ?sec fixed delay,
  retransmits them back to the acft. The airborne
  automatically compares the elapsed time between
  transmission and reception, subtracts out the
  fixed 50 sec delay, displays the result on a
  meter calibrated in nautical miles.

65
Hyperbolic Systems

• Named after the hyperbolic lines of position
  (LOP) that they produce rather than the circles
• Loran-C
• Omega
• Decca
• Chayka

Measure the time-difference between the signal
from two or more transmitting station
Measure the phase-difference between the signal
transmitted from pairs of stations
66
Long-Range Navigation(Loran)

• A hyperbolic radio-navigation system beginning
  before outbreak of WW II
• Uses ground waves at low frequencies, thereby
  securing an operating range of over 1000 mi,
  independent of line of sight
• Uses pulse technique to avoid sky-wave
  contamination
• A hyperbolic system?it is not subject to the site
  errors of point-source systems
• Uses a form of cycle (phase) measurements to
  improve precision
• All modern systems are of the Loran-C variety

67
Long-Range Navigation (Loran-C)

• Is a low-frequency radio-navigation aid operating
  in the radio spectrum of 90 to 110 kHz
• Consists of at least three transmitting stations
  in groups forming chains
• Using a Loran-C receiver, a user gets location
  information by measuring the very small
  difference in arrival times of the pulses for
  each Master -Secondary pair
• Each Master-Secondary pair measurement is a time
  difference. One time difference is a set of
  points that are, mathematically, a hyperbola.
  Therefore, position is the intersection of two
  hyperbolas. Knowing the exact location of the
  transmitters and the pulse spacing, it is
  possible to convert Loran time difference
  information into latitude and longitude

68
Loran-C (2)
Signal shape
Position determination
69
Loran-C (2)
70
NAVSTAR Global Positioning System

• GPS was conceived as a U.S. Department of Defense
  (DoD) multi-service program in 1973, bearing some
  resemblance to consisting of the best elements
  of two predecessor development programs
• The U.S. Navys TIMATION program
• The U.S. Air Forces program
• GPS is a passive, survivable, continuous,
  space-based system that provides any suitably
  equipped user with highly accurate
  three-dimensional position, velocity, and time
  information anywhere on or near the earth

71
Principles of GPS System Operation

• GPS is basically a ranging system, although
  precise Doppler measurements are also available
• To provide accurate ranging measurements, which
  are time-of-arrival measurements, very accurate
  timing is required in the satellite. (tlt3 nsec)
• GPS satellite contain redundant atomic frequency
  standards
• To provide continues 3D navigation solutions to
  dynamic users, a sufficient number of satellite
  are required to provide geometrically spaced
  simultaneous measurements.
• To provide those geometrically spaced
  simultaneous measurements on a worldwide
  continues basis, relatively high-altitude
  satellite orbits are required

72
GPS Satellite System Configuration

• Consists of three segments
• Space segment
• Control segment
• User segment

73
GPS System Configuration
74
General System Characteristics

• The GPS satellites are in approximately 12 hour
  orbits(11 hours, 57 minutes, and 57.27 seconds)
  at an altitude of approximately 11,000 nmi
• The total number of satellite in the
  constellation has changed over the years 24
• Each satellite transmits signals at two
  frequencies at L-Band to permit ionosphere
  refraction corrections by properly equipped users

75
General System Characteristics

• The GPS satellites are in approximately 12 hour
  orbits(11 hours, 57 minutes, and 57.27 seconds)
  at an altitude of approximately 11,000 nmi
• The total number of satellite in the
  constellation has changed over the years 24
• Each satellite transmits signals at two
  frequencies at L-Band to permit ionosphere
  refraction corrections by properly equipped users

76
The GPS segments
Segments Input Function Product
Space Satellite commands Navigation messages Provide atomic time scale Generate PRN RF signals Store forward navigation message PRN RF signals Navigation message Telemetry
Control PRN RF signals Telemetry Universal coordinated Time(UTC) Estimate time ephemeris Predict time ephemeris Manage space assets Navigation message Satellite commands
User PRN RF signals Navigation messages Solve navigation equations Position, velocity, time
77
GPS Space Segment

• The space segment is comprised of the satellite
  constellation made up of multiple satellites. The
  satellite provides the basic navigation frame of
  reference and transmit the radio signals from
  which the user can collect measurements required
  for his navigation solution
• Knowledge of the satellites position and time
  history (ephemeris and time) is also required for
  the users solutions.
• The satellite also transmit that information via
  data modulation of the signals

• CDMA _at_ 1.2 to 1.5 GHz
• LB and P C
• Very accurate atomic clocks lt nanosecond

78
GPS Control Segment

• Consists of three major elements
• Monitor stations that track the satellites
  transmitted signals collect measurements
  similar to those that the user collect for their
  navigation
• A master control station that uses these
  measurements to determine predict the
  satellites ephemeris time history and
  subsequently to upload parameters that the
  satellite modulate on the transmitted signals
• Ground station antennas that perform the upload
  control of the satellite

79
User Segment

• Is comprised of the receiving equipment and
  processors that perform the navigation solution
• These equipments come in a variety of forms and
  functions, depending upon the navigation
  application

80
Basics of Satellite Radio Navigation (1)

• Different types of user equipments solve a basic
  set of equations for their solutions, using the
  ranging and/or range rate (or change in range)
  measurements as input to a least-squares, or a
  Kalman filter algorithm.
• Fig 5.2

Ranging satellite radio-navigation solution
81
Basics of Satellite Radio Navigation (2)

• The measurements are not range range rate (or
  change in range), but quantities described as
  pseudorange pseudorange rate (or change in
  pseudorange). This is because they consisit of
  errors, dominated by timing errors, that are part
  of the solution. For example, if only ranging
  type measurements are made, the actual
  measurement is of the form
• is the measured peseudorange from
  satellite i
• is the geometric range to that satellite,
  is the clock error in satellite i, is
  the users clock error, c is the speed of light
  and is the sum of various correctable
  or uncorrectable measurements error

82
Basics of Satellite Radio Navigation (3)

• Neglecting for the moment the clock and other
  measurement errors, the range to satellite i is
  given as
• are the earth-centered, earth
  fixed (ECEF) position components of the satellite
  at the time of transmission and are
  the ECEF user position components at that time

83
Atmospheric Effects on Satellite Communication

• Ionosphere
• Shell of electrons and electrically charged atoms
  molecules that surrounds the earth
• Stretching from 50km to more than 1000km
• Result of ultraviolet radiation from sun
• Free electrons affect the propagation of radio
  waves
• At frequency below about 30 MHz acts like a
  mirror bending the radio wave to the earth
  thereby allowing long distance communication
• At higher frequencies (satellite radio
  navigation) radio waves pass through the
  ionosphere

84
System Accuracy

• GPS provides two positioning services, the
  Precise Positioning Service (PPS) the Standard
  Positioning Service (SPS)
• The PPS can be denied to unauthorized users, but
  SPS is available free of charge to any user
  worldwide
• Users that are crypto capable are authorized to
  use crypto keys to always have access to the PPS.
  These users are normally military users,
  including NATO and other friendly countries.
  These keys allow the authorized user to acquire
  track the encrypted precise (P) code on both
  frequencies to correct for international
  degradation of the signal
• WAAS lt 3 m horizontal
• lt 7.5 m vertical
• GPS ?15m

85
Automatic Landing Systems (1)

• Air carrier acft that are authorized for
  precision-approach below category II must have
  automatic landing (auto-land) system.
• Guidance control requirements by FAA
• For category II the coupled autopilot or crew
  hold the acft within the vertical error of or-
  12 ft at the 100ft height on a 3deg glide path
• For category III the demonstrated touchdown
  dispersions should be limited to 1500ft
  longtudinally -or 27ft laterally

86
Automatic Landing Systems (2)

• Flare Guidance
• During the final approach the glide-slope gain in
  the auto-land system is reduced in a programmed
  fashion. Supplementary sensors must supply the
  vertical guidance below 100ft
• Lateral Guidance
• Tracking of the localizer is aided by heading (or
  integral-of-roll), roll, or roll-rate signals
  supplied to the autopilot and by rate
  acceleration data from on-board inertial system

87
Instrument Landing System(ILS) (1)

• Is a collection of radio transmitting stations
  used to guide acft to a specific runway.
• In 1996 nearly 100 airports worldwide had at
  least one runway certified to Category III with
  ILS
• More than one ILS in high density airports
• About 1500 ILSs are in use at airports throughout
  the US

88
Instrument Landing System(ILS) (2)

• ILS typically includes
• The localizer antenna is centered on the runway
  beyond the stop end to provide lateral guidance
• The glide slope antenna, located beside the
  runway near the threshold to provide vertical
  guidance
• Marker beacons located at discrete positions
  along the approach path to alert pilots of their
  progress along the glide-path
• Radiation monitors that, in case of ILS failure
  alarm the control tower, may shut-down a Category
  I or II ILS, or switch a Category III ILS to
  backup transmitters

89
ILS Guidance Signals (1)

• The localizer, glide slope, and marker beacons
  radiate continues wave, horizontally polarized,
  radio frequency, energy
• The frequency bands of operation are
• Localizer, 40 channels from 108-112 MHz
• Glide slop, 40 channels from 329-335 MHz
• Marker beacons, all on a signal frequency of 75
  MHz

90
ILS Guidance Signals (2)

• The localizer establishes a radiation pattern in
  space that provides a deviation signal in the
  acft when it is displaced laterally from the
  vertical plane containing the runway centerline
• The deviation signal drives the left-right needle
  of the pilots cross-pointer display may be
  wired to the autopilot/flight-control system for
  coupled approaches
• The deviation signal is proportional to azimuth
  angle usually out to 5 deg or more either side of
  the center line

91
ILS Guidance Signals (3)
Sum difference radiation patterns for the
course (CRS) clearance (CLR) signals of a
directional localizer array
92
The Localizer (1)

• The typical localizer is an array usually located
  600 to 1000 ft beyond the stop end antenna of the
  runway
• The array axis is perpendicular to the runway
  center line

Log-periodic dipole antenna used in many
localizer arrays
93
The Localizer (2)
Category IIIB localizer
94
The Glide Slope (1)

• There are five different of glide-slope arrays in
  common use three are image systems two are not
• Image arrays depend on reflections from level
  ground in the direction of approaching acft to
  form the radiation pattern
• The three image systems are null-referenced
  system, with two antennas supported on a vertical
  mast 14 28 ft above the ground plane
• The sideband-reference system, with two antennas
  7 and 22ft above the ground plane
• The capture-effect system, with 3 antennas 14,
  28, and 42 ft above the ground plane

95
The Glide Slope(2)
Category IIIB capture-effect glideslope Tasker
transmissometer
96
The Glide Slope (3)
Glide-slope pattern near the runway. DDM counters
are symmetrical around the vertical, but signal
strength drops rapidly off course
97
The Glide Slope (4)

• The cable radiators of the end-fire array are
  installed on stands 40 in. high are site
  alongside the runway near desired touchdown point
• Fig 13.10
• Fig 13.11

Front slotted-cable radiator of an end-fire glide
slope
Standard end-fire glide-slope system layout
98
ILS Marker Beacons (1)

• Marker beacons provide pilot alerts along the
  approach path
• Each beacon radiates a fan-shaped vertical beam
  that is approximately or- 40deg wide along the
  glide path by -85deg wide perpendicular to the
  path
• The outer marker(OM) is placed under the approach
  course near the point of glide-path intercept
  it is modulated with two 400 Hz Morse-code dashed
  per second

99
ILS Accuracy Allocation
100
Standard lighting Pattern

• Airports at which Category II landings are
  permitted must be equipped with the standard
  lighting pattern

Category III runway configuration
101
The Mechanics of Landing (1)

• The approach
• Day night landings are permitted under visual
  flight rules (VFR) when the ceiling exceeds 1000
  ft the horizontal visibility exceeds 3 mi, as
  juged by the airport control tower
• In deteriorated weather, operations must be
  conducted ubder Instrument Flight Rules (IFR)
• An IFR approach is procedure is either
  non-precision (lateral guidance only) or
  precision (both lateral vertical guidance
  signals)
• Category I, II, and III operations are
  precision-approach procedures

102
The Mechanics of Landing (2)

• An afct landing under IFR must transition from
  cruising flight to the final approach along the
  extended runway center line by using the standard
  approach procedures published for each airport
• Approach altitudes are measured barometrically,
  and the transition flight path is defined by
  initial final approach fixes (IAF FAF) using
  VOR, VOR/DME
• Radar vectors may be given to the crew by
  approach control

103
The Mechanics of Landing (3)

• From approximately 1500 ft above runway, a
  precision approach is guided by radio beams
  generated by ILS. Large acft maintain a speed of
  100 to 150 knots during descent along the glide
  path beginning at the FAF (outer marker)
• The glide-path angle is set by obstacle-clearance
  and noise-abatement considerations with 3 deg as
  the international civil standard
• The sink rate is 6 to 16 ft/sec, depending on the
  acfts speed on headwinds

104
The Mechanics of Landing (4)

• The ICAO standard glide path will cross the
  runway threshold at a height between 50 60 ft.
  Thus, the projected glide path intercepts the
  runway surface about 1000 ft from the threshold.

Wheel path for instrument landing of a jet acft
105
Wide Area Augmentation System(WAAS)

• Developed by the FAA in parallel with European
  Geostationary Navigation Overlay Service (EGNOS)
  Japan MTSAT Satellite-Based Augmentation System
• A safety-critical system consisting of a
  signal-in-space a ground network to support
  en-route through precision approach air
  navigation
• The WAAS augments GPS with three services all
  phases of flight down to category I precision
  approach
• A ground integrity broadcast that will meet the
  Required Navigation Performance (RNP)
• Wide area differential GPS (WADGPS) corrections
  that will provide accuracy for GPS users so as to
  meet RNP accuracy requirements
• A ranging function that will provide additional
  availability reliability that will help satisfy
  the RNP availability requirements

106
WAAS Concept (1)
107
WAAS Concept (2)
Inmarsat-3 four ocean-region deployment showing
5deg elevation contours
108
WAAS Concept (3)

• Uses geostationary satellite to broadcast the
  integrity correction data to users for all of
  the GPS satellites visible to the WAAS network
• A slightly modified GPS avionics receiver can
  receive these broadcasts
• Since the codes will be synchronized to the WAAS
  network time, which is the reference time of the
  WADGPS corrections, the signals can also be used
  for ranging

109
WAAS Concept (4)

• A sufficient number of GEOs provides enough
  augmentation to satisfy RNP availability
  reliability requirements
• In the WAAS concept, a network of monitoring
  stations (wide area reference stations, WRSs)
  continuously track the GPS (GEO) satellite
  rely the tracking information to a central
  processing facility
• Geo ? 2 minimum 4 desired

110
WAAS Concept (5)

• The central processing facility (wide area master
  station, WMS)m in turn, determines the health
  WADGPS corrections for each signal in space
  relays this information, via the broadcast
  messages, to the ground earth station (GESs) for
  uplink to the GEOs
• The WMS also determines relays the GEO
  ephemeris clock state messages to the GEOs

111
Surveillance

• GPSWAASDL ADS-B

112
Automatic Dependent Surveillance - Broadcast
(ADS-B)

• A technology designed to address both airspace
  and ground-based movement needs.
• Collaborative decision making is possible through
  ADS-B surveillance information available to both
  ATC and aircrews.
• ADS-B combined with predictable, repeatable
  flight paths allow for increased airspace
  efficiencies in high density terminal areas or
  when weather conditions preclude visual
  operations.
• Additionally, ADS-B allow for enhanced ground
  movement management (aircraft and vehicles) and
  improved airside safety

113
ADS-B
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