These materials are to be used only for the purpose of individual, private study and may
not be reproduced in any form or medium, copied, stored in a retrieval system, lent, hired,
rented, transmitted, or adapted in whole or in part without the prior written consent of
Jeppesen.
Copyright in all materials bound within these covers or attached hereto, excluding that material
which is used with the permission of third parties and acknowledged as such, belongs exclusively
to Jeppesen.
Certain copyright material is reproduced with the permission of the International Civil Aviation
Organisation, the United Kingdom Civil Aviation Authority, and the Joint Aviation Authorities
(JAA).
This book has been written and published to assist students enrolled in an approved JAA Air
Transport Pilot Licence (ATPL) course in preparation for the JAA ATPL theoretical knowledge
examinations. Nothing in the content of this book is to be interpreted as constituting instruction or
advice relating to practical flying.
Whilst every effort has been made to ensure the accuracy of the information contained within this
book, neither Jeppesen nor Atlantic Flight Training gives any warranty as to its accuracy or
otherwise. Students preparing for the JAA ATPL theoretical knowledge examinations should not
regard this book as a substitute for the JAA ATPL theoretical knowledge training syllabus
published in the current edition of “JAR-FCL 1 Flight Crew Licensing (Aeroplanes)” (the Syllabus).
The Syllabus constitutes the sole authoritative definition of the subject matter to be studied in a
JAA ATPL theoretical knowledge training programme. No student should prepare for, or is
entitled to enter himself/herself for, the JAA ATPL theoretical knowledge examinations without
first being enrolled in a training school which has been granted approval by a JAA-authorised
national aviation authority to deliver JAA ATPL training.
Contact Details:
Sales and Service Department
Jeppesen GmbH
Frankfurter Strasse 233
63263 Neu-Isenburg
Germany
Tel: ++49 (0)6102 5070
E-mail: [email protected]
For further information on products and services from Jeppesen, visit our web site at:
www.jeppesen.com
JA310103-000 © Jeppesen Sanderson Inc., 2004 Printed in Germany
All Rights Reserved
ii ISBN 0-88487-353-6
PREFACE_______________________
As the world moves toward a single standard for international pilot licensing, many nations have
adopted the syllabi and regulations of the “Joint Aviation Requirements-Flight Crew Licensing"
(JAR-FCL), the licensing agency of the Joint Aviation Authorities (JAA).
Though training and licensing requirements of individual national aviation authorities are similar in
content and scope to the JAA curriculum, individuals who wish to train for JAA licences need
access to study materials which have been specifically designed to meet the requirements of the
JAA licensing system. The volumes in this series aim to cover the subject matter tested in the
JAA ATPL ground examinations as set forth in the ATPL training syllabus, contained in the JAA
publication, “JAR-FCL 1 (Aeroplanes)”.
The JAA regulations specify that all those who wish to obtain a JAA ATPL must study with a
flying training organisation (FTO) which has been granted approval by a JAA-authorised national
aviation authority to deliver JAA ATPL training. While the formal responsibility to prepare you for
both the skill tests and the ground examinations lies with the FTO, these Jeppesen manuals will
provide a comprehensive and necessary background for your formal training.
Jeppesen is acknowledged as the world's leading supplier of flight information services, and
provides a full range of print and electronic flight information services, including navigation data,
computerised flight planning, aviation software products, aviation weather services, maintenance
information, and pilot training systems and supplies. Jeppesen counts among its customer base
all US airlines and the majority of international airlines worldwide. It also serves the large general
and business aviation markets. These manuals enable you to draw on Jeppesen’s vast
experience as an acknowledged expert in the development and publication of pilot training
materials.
We at Jeppesen wish you success in your flying and training, and we are confident that your
study of these manuals will be of great value in preparing for the JAA ATPL ground examinations.
The next three pages contain a list and content description of all the volumes in the ATPL series.
iii
ATPL Series
Meteorology (JAR Ref 050)
• The Atmosphere • Air Masses and Fronts
• Wind • Pressure System
• Thermodynamics • Climatology
• Clouds and Fog • Flight Hazards
• Precipitation • Meteorological Information
General Navigation (JAR Ref 061)
• Basics of Navigation • Dead Reckoning Navigation
• Magnetism • In-Flight Navigation
• Compasses • Inertial Navigation Systems
• Charts
Radio Navigation (JAR Ref 062)
• Radio Aids • Basic Radar Principles
• Area Navigation Systems
• Self-contained and • Basic Radio Propagation Theory
External-Referenced
Navigation Systems
Airframes and Systems (JAR Ref 021 01)
• Fuselage • Hydraulics
• Windows • Pneumatic Systems
• Wings • Air Conditioning System
• Stabilising Surfaces • Pressurisation
• Landing Gear • De-Ice / Anti-Ice Systems
• Flight Controls • Fuel Systems
Powerplant (JAR Ref 021 03)
• Piston Engine • Engine Systems
• Turbine Engine • Auxiliary Power Unit (APU)
• Engine Construction
Electrics (JAR Ref 021 02)
• Direct Current • Generator / Alternator
• Alternating Current • Semiconductors
• Batteries • Circuits
• Magnetism
iv
Instrumentation (JAR Ref 022)
• Flight Instruments
• Automatic Flight Control Systems
• Warning and Recording Equipment
• Powerplant and System Monitoring Instruments
Principles of Flight (JAR Ref 080)
• Laws and Definitions • Boundary Layer
• Aerofoil Airflow • High Speed Flight
• Aeroplane Airflow • Stability
• Lift Coefficient • Flying Controls
• Total Drag • Adverse Weather Conditions
• Ground Effect • Propellers
• Stall • Operating Limitations
• CLMAX Augmentation • Flight Mechanics
• Lift Coefficient and Speed
Performance (JAR Ref 032)
• Single-Engine Aeroplanes – Not certified under JAR/FAR 25
(Performance Class B)
• Multi-Engine Aeroplanes – Not certified under JAR/FAR 25
(Performance Class B)
• Aeroplanes certified under JAR/FAR 25 (Performance Class A)
Mass and Balance (JAR Ref 031)
• Definition and Terminology
• Limits
• Loading
• Centre of Gravity
Flight Planning (JAR Ref 033)
• Flight Plan for Cross-Country • Meteorological Messages
Flights • Point of Equal Time
• Point of Safe Return
• ICAO ATC Flight Planning • Medium Range Jet Transport
• IFR (Airways) Flight Planning
• Jeppesen Airway Manual Planning
Air Law (JAR Ref 010)
• International Agreements • Air Traffic Services
and Organisations • Aerodromes
• Facilitation
• Annex 8 – Airworthiness of • Search and Rescue
Aircraft • Security
• Aircraft Accident Investigation
• Annex 7 – Aircraft Nationality • JAR-FCL
and Registration Marks • National Law
• Annex 1 – Licensing
• Rules of the Air
• Procedures for Air Navigation
v
Human Performance and
Limitations (JAR Ref 040)
• Human Factors
• Aviation Physiology and Health Maintenance
• Aviation Psychology
Operational Procedures (JAR Ref 070)
• Operator • Low Visibility Operations
• Air Operations Certificate • Special Operational Procedures
• Flight Operations
• Aerodrome Operating Minima and Hazards
• Transoceanic and Polar Flight
Communications (JAR Ref 090)
• Definitions • Distress and Urgency
• General Operation Procedures Procedures
• Relevant Weather Information • Aerodrome Control
• Communication Failure • Approach Control
• VHF Propagation • Area Control
• Allocation of Frequencies
vi
Table of Contents
CHAPTER 1
Basic Radio Theory
Wave Motion .................................................................................................................................................1-1
Introduction ...................................................................................................................................................1-1
Electro-Magnetic Waves ...............................................................................................................................1-2
Properties of Radio Waves ...........................................................................................................................1-2
Refraction, Diffraction, and Reflection...........................................................................................................1-2
Relationship between Frequency, Wavelength, and Velocity .......................................................................1-3
Phase Difference ..........................................................................................................................................1-5
Radio Spectrum ............................................................................................................................................1-6
Wave Propagation ........................................................................................................................................1-7
Surface Wave ...............................................................................................................................................1-8
Type of Surface.............................................................................................................................................1-8
Sky Wave......................................................................................................................................................1-9
Critical Angle.................................................................................................................................................1-9
Dead Space ................................................................................................................................................1-10
The Ionosphere...........................................................................................................................................1-10
Frequency and Skip Distance .....................................................................................................................1-11
Ionisation and Skip Distance.......................................................................................................................1-11
Space Wave................................................................................................................................................1-11
Duct Propagation ........................................................................................................................................1-12
Aerials ........................................................................................................................................................1-13
Aerial Characteristics ..................................................................................................................................1-13
Aerial Length...............................................................................................................................................1-14
Polar Diagrams ...........................................................................................................................................1-14
Omni-Directional Aerials .............................................................................................................................1-14
Simple Half-Wave Dipole ............................................................................................................................1-14
Marconi Quarter Wave Aerial......................................................................................................................1-14
Aerial Feeders.............................................................................................................................................1-15
Aerial Directivity ..........................................................................................................................................1-15
Modulation ..................................................................................................................................................1-17
Keying .........................................................................................................................................................1-17
Amplitude Modulation (AM).........................................................................................................................1-19
Frequency Modulation (FM) ........................................................................................................................1-20
Pulse Modulation (PM)................................................................................................................................1-20
Classification of Emissions..........................................................................................................................1-21
Basic Radar Theory ....................................................................................................................................1-21
Radar Frequencies .....................................................................................................................................1-22
Principles ....................................................................................................................................................1-22
Pulse Radars ..............................................................................................................................................1-22
Radar Direction Finding ..............................................................................................................................1-23
Lobe Comparison........................................................................................................................................1-24
Beam Direction Finding...............................................................................................................................1-24
Radar Terminology .....................................................................................................................................1-24
Choice of Frequency...................................................................................................................................1-26
Radio Navigation vii
Table of Contents
CHAPTER 2
VHF Direction Finding
Introduction .................................................................................................................................................. 2-1
Principles of Operation................................................................................................................................. 2-1
Frequency .................................................................................................................................................... 2-1
Emission Characteristics .............................................................................................................................. 2-1
Operation ..................................................................................................................................................... 2-2
Services ....................................................................................................................................................... 2-2
Siting ............................................................................................................................................................ 2-2
Receiving a Bearing ..................................................................................................................................... 2-2
Asking For a Bearing.................................................................................................................................... 2-3
Position Fix .................................................................................................................................................. 2-3
VDF Approach.............................................................................................................................................. 2-3
Decoding the Chart ...................................................................................................................................... 2-5
Part 1 – Administration................................................................................................................................. 2-5
Part 2 – The Plan View ................................................................................................................................ 2-6
Part 3 – The Elevation View......................................................................................................................... 2-7
Refusal of Service ........................................................................................................................................ 2-7
Automatic VDF ............................................................................................................................................. 2-7
Range and Errors......................................................................................................................................... 2-8
CHAPTER 3
Non-Directional Beacons and Automatic Direction Finding
Introduction .................................................................................................................................................. 3-1
Principles of Operation................................................................................................................................. 3-1
Frequency .................................................................................................................................................... 3-1
Emission Characteristics .............................................................................................................................. 3-1
Loop Theory ................................................................................................................................................. 3-2
Sensing ........................................................................................................................................................ 3-3
NDB Operation............................................................................................................................................. 3-3
ADF Operation ............................................................................................................................................. 3-4
Bearing Determination ................................................................................................................................. 3-5
Types ........................................................................................................................................................... 3-5
Control Panels and Indicators ...................................................................................................................... 3-6
Control Panel ............................................................................................................................................... 3-6
TEST Switch ................................................................................................................................................ 3-7
Bearing Indicators ........................................................................................................................................ 3-7
Relative Bearing Indicator (RBI)................................................................................................................... 3-7
Radio Magnetic Indicator (RMI).................................................................................................................... 3-9
Direct Wave Limitations ............................................................................................................................... 3-9
Sky Wave Limitations................................................................................................................................. 3-10
Night Effect ................................................................................................................................................ 3-10
Errors of the ADF ....................................................................................................................................... 3-11
Quadrantal Error ........................................................................................................................................ 3-11
Dip (Bank) Error ......................................................................................................................................... 3-11
Coastal Refraction...................................................................................................................................... 3-12
Multipath Signals........................................................................................................................................ 3-12
Noise.......................................................................................................................................................... 3-13
Synchronous Transmission ........................................................................................................................ 3-14
Promulgated Range ................................................................................................................................... 3-14
Absence of Failure Warning ....................................................................................................................... 3-14
Accuracy .................................................................................................................................................... 3-14
viii Radio Navigation
Table of Contents
CHAPTER 4
NDB Navigation
Introduction ...................................................................................................................................................4-1
ADF Bearing .................................................................................................................................................4-1
Line of Position (LOP) Using the RBI............................................................................................................4-1
Line of Position (LOP) Using the RMI ...........................................................................................................4-2
Homing .........................................................................................................................................................4-2
Intercepting a Course....................................................................................................................................4-3
Inbound to the Beacon..................................................................................................................................4-4
Outbound From the Beacon..........................................................................................................................4-5
Tracking ........................................................................................................................................................4-7
NDB Approach ..............................................................................................................................................4-9
Part 1 Administration...................................................................................................................................4-10
Part 2 the Plan View ...................................................................................................................................4-11
Part 3 the Elevation View............................................................................................................................4-12
Part 4 Limits and Other Information ............................................................................................................4-12
CHAPTER 5
VHF Omnidirectional Radio Range (VOR)
Introduction ...................................................................................................................................................5-1
Principle of Operation ...................................................................................................................................5-1
Frequency .....................................................................................................................................................5-1
Polarisation ...................................................................................................................................................5-1
Emission Characteristics...............................................................................................................................5-1
Conventional VOR ........................................................................................................................................5-2
Reference Signal ..........................................................................................................................................5-2
Variable Signal..............................................................................................................................................5-2
Aircraft Receiver ...........................................................................................................................................5-2
Bearing Measurement...................................................................................................................................5-2
Aircraft Equipment ........................................................................................................................................5-3
Aerial.............................................................................................................................................................5-3
Receiver........................................................................................................................................................5-3
Frequency Selector.......................................................................................................................................5-3
Indicators ......................................................................................................................................................5-4
Monitoring .....................................................................................................................................................5-4
Terrain ..........................................................................................................................................................5-4
Designated Operational Coverage (DOC) ....................................................................................................5-4
Cone of Confusion or Cone of Silence..........................................................................................................5-5
Accuracy .......................................................................................................................................................5-5
Airway Navigation .........................................................................................................................................5-6
Test VOR ......................................................................................................................................................5-6
Doppler VOR.................................................................................................................................................5-6
Radio Navigation ix
Table of Contents
CHAPTER 6
VOR Navigation
Introduction .................................................................................................................................................. 6-1
Radio Magnetic Indicator ............................................................................................................................. 6-1
Omni-Bearing Selector................................................................................................................................. 6-2
Using the OBS ............................................................................................................................................. 6-4
Horizontal Situation Indicator (HSI) .............................................................................................................. 6-6
VOR Navigation ........................................................................................................................................... 6-8
Establishing Position .................................................................................................................................... 6-8
Tracking a Radial Inbound From a Present Position .................................................................................... 6-8
Intercepting a Radial .................................................................................................................................... 6-8
VOR Approaches ......................................................................................................................................... 6-9
Part 1 – Administration............................................................................................................................... 6-11
Part 2 – Plan View...................................................................................................................................... 6-11
Part 3 – Elevation View .............................................................................................................................. 6-12
Part 4 – Notes ............................................................................................................................................ 6-12
CHAPTER 7
Distance Measuring Equipment (DME)
Introduction .................................................................................................................................................. 7-1
Principle of Operation................................................................................................................................... 7-1
Frequency .................................................................................................................................................... 7-1
Emission Characteristics .............................................................................................................................. 7-1
Aircraft Equipment........................................................................................................................................ 7-2
Transponder................................................................................................................................................. 7-2
Frequency Allocation.................................................................................................................................... 7-2
Jittered PRF ................................................................................................................................................. 7-3
Reflected Transmissions .............................................................................................................................. 7-4
Memory ........................................................................................................................................................ 7-4
Beacon Saturation........................................................................................................................................ 7-4
Co-Location of Beacons............................................................................................................................... 7-5
Slant Range ................................................................................................................................................. 7-6
DME Navigation ........................................................................................................................................... 7-6
DME Procedures.......................................................................................................................................... 7-7
Slant Range ................................................................................................................................................. 7-7
Flight Overhead the DME............................................................................................................................. 7-8
Failure Indications ........................................................................................................................................ 7-8
Accuracy ...................................................................................................................................................... 7-8
x Radio Navigation
Table of Contents
CHAPTER 8
Instrument Landing System (ILS)
Introduction ...................................................................................................................................................8-1
Principle of Operation ...................................................................................................................................8-1
Frequency .....................................................................................................................................................8-2
Emission Characteristics...............................................................................................................................8-2
Localiser........................................................................................................................................................8-2
Localiser Coverage .......................................................................................................................................8-4
Glidepath.......................................................................................................................................................8-5
Glidepath Coverage ......................................................................................................................................8-6
Airborne Equipment ......................................................................................................................................8-6
Frequency Pairing.........................................................................................................................................8-6
Localiser and Glidepath Receivers ...............................................................................................................8-7
ILS Indicator..................................................................................................................................................8-7
Horizontal Situation Indicator (HSI)...............................................................................................................8-8
ILS Accuracy.................................................................................................................................................8-9
False Beams ...............................................................................................................................................8-10
Localiser Back Beam ..................................................................................................................................8-10
ILS Performance Categories.......................................................................................................................8-13
ILS Operational Performance Categories ...................................................................................................8-13
Protection Range and Monitoring................................................................................................................8-14
Use of ILS ...................................................................................................................................................8-15
ILS Identification .........................................................................................................................................8-15
Flying the Localiser .....................................................................................................................................8-15
Flying the Glidepath ....................................................................................................................................8-15
ILS Without Glidepath .................................................................................................................................8-16
Distance Measuring Equipment ..................................................................................................................8-19
Rate of Descent (ROD) ...............................................................................................................................8-19
Height Passing on the Approach.................................................................................................................8-19
CHAPTER 9
Marker Beacons
Introduction ...................................................................................................................................................9-1
Principle of Operation ...................................................................................................................................9-1
Frequency .....................................................................................................................................................9-1
Emission Characteristics...............................................................................................................................9-1
Airborne Equipment ......................................................................................................................................9-1
Airway Marker ...............................................................................................................................................9-3
Ground Installation........................................................................................................................................9-3
CHAPTER 10
Microwave Landing System
Introduction .................................................................................................................................................10-1
Principle of Operation .................................................................................................................................10-1
Frequency ...................................................................................................................................................10-1
Polarisation .................................................................................................................................................10-1
Ground Installation......................................................................................................................................10-2
Azimuth Coverage ......................................................................................................................................10-2
Elevation Coverage.....................................................................................................................................10-3
DME/P ........................................................................................................................................................10-4
Back Azimuth ..............................................................................................................................................10-4
Signal Transmission Format .......................................................................................................................10-4
Time Reference Scanning Beam ................................................................................................................10-5
Angular Measurement in Azimuth and Elevation ........................................................................................10-5
Airborne Equipment ....................................................................................................................................10-6
Accuracy .....................................................................................................................................................10-6
Radio Navigation xi
Table of Contents
CHAPTER 11
Radar Principles and the Cathode Ray Tube
Pulse Techniques and Associated Terms .................................................................................................. 11-1
The Components of a Radar Unit............................................................................................................... 11-1
The Timebase ............................................................................................................................................ 11-2
The Display ................................................................................................................................................ 11-2
The Transmitter.......................................................................................................................................... 11-2
Choice of Frequency .................................................................................................................................. 11-2
The Aerial................................................................................................................................................... 11-4
Beamwidth ................................................................................................................................................. 11-4
The Receiver.............................................................................................................................................. 11-5
Timer – Cathode Ray Tube ........................................................................................................................ 11-6
Cathode ..................................................................................................................................................... 11-6
Grid ............................................................................................................................................................ 11-6
Focussing Assembly .................................................................................................................................. 11-6
Electronic Beam Deflection ........................................................................................................................ 11-7
Screen........................................................................................................................................................ 11-7
Time Base.................................................................................................................................................. 11-7
Saw Tooth Voltage..................................................................................................................................... 11-8
Radar Performance.................................................................................................................................... 11-8
Secondary Radar ....................................................................................................................................... 11-9
CHAPTER 12
Ground Radar
Introduction ................................................................................................................................................ 12-1
Long Range Surveillance Radar ................................................................................................................ 12-1
Terminal Surveillance Radar ...................................................................................................................... 12-2
Aerodrome Surveillance (Approach) Radar ............................................................................................... 12-2
Range, Accuracy, and Limitations of Surveillance Radar........................................................................... 12-3
Surveillance Radar Procedures.................................................................................................................. 12-3
Enroute ...................................................................................................................................................... 12-3
Approach.................................................................................................................................................... 12-3
Precision Approach Radar (PAR)............................................................................................................... 12-4
PAR Procedure .......................................................................................................................................... 12-5
Airfield Surface Movement Indicator (ASMI) .............................................................................................. 12-6
Weather Radar........................................................................................................................................... 12-7
CHAPTER 13
Secondary Surveillance Radar (SSR)
Introduction ................................................................................................................................................ 13-1
Principles of Operation............................................................................................................................... 13-1
Pulse Spacing ............................................................................................................................................ 13-2
Side Lobe Suppression .............................................................................................................................. 13-3
Operation ................................................................................................................................................... 13-5
SPI Code.................................................................................................................................................... 13-6
Use of Transponder ................................................................................................................................... 13-6
Presentation and Interpretation .................................................................................................................. 13-6
Limitations .................................................................................................................................................. 13-7
Fruiting ....................................................................................................................................................... 13-7
Garbling ..................................................................................................................................................... 13-7
Mode S....................................................................................................................................................... 13-8
Operation of Mode S .................................................................................................................................. 13-8
ATC Services ............................................................................................................................................. 13-9
xii Radio Navigation
Table of Contents
CHAPTER 14
Airborne Weather Radar (AWR)
Introduction .................................................................................................................................................14-1
Principle of Operation .................................................................................................................................14-1
Frequency ...................................................................................................................................................14-1
Frequency Range .......................................................................................................................................14-1
AWR Aerial .................................................................................................................................................14-2
Control Panel ..............................................................................................................................................14-2
Power Switch and Timebase Range Switch................................................................................................14-2
Function Switch...........................................................................................................................................14-4
Weather Function (WEA) ............................................................................................................................14-4
Contour Function (CON) .............................................................................................................................14-4
Mapping Function (MAP) ............................................................................................................................14-5
Manual Function (MAN) ..............................................................................................................................14-6
Contrast ......................................................................................................................................................14-6
Manual Gain................................................................................................................................................14-6
Tilt Control...................................................................................................................................................14-6
Colour Displays...........................................................................................................................................14-7
Cloud Height Determination ........................................................................................................................14-8
Shadow .......................................................................................................................................................14-9
Test .............................................................................................................................................................14-9
Hold ............................................................................................................................................................14-9
Target Alert .................................................................................................................................................14-9
Use of the Radar on the Ground .................................................................................................................14-9
CHAPTER 15
Doppler
Introduction .................................................................................................................................................15-1
Frequency ...................................................................................................................................................15-1
Doppler Effect .............................................................................................................................................15-1
Doppler Measurement of Groundspeed......................................................................................................15-3
Two Beam Janus Array...............................................................................................................................15-4
Further Janus Arrays ..................................................................................................................................15-5
Doppler Aerial .............................................................................................................................................15-6
Signal Characteristics .................................................................................................................................15-6
Output and Presentation .............................................................................................................................15-6
Accuracy and Limitations ............................................................................................................................15-8
Sea Bias......................................................................................................................................................15-8
Memory Mode .............................................................................................................................................15-8
Pitch and Roll Error.....................................................................................................................................15-8
Height Hole Error ........................................................................................................................................15-8
Sea Movement Error...................................................................................................................................15-9
Computational Errors ..................................................................................................................................15-9
Heading Error..............................................................................................................................................15-9
Summary of Errors......................................................................................................................................15-9
Advantages .................................................................................................................................................15-9
Disadvantages ..........................................................................................................................................15-10
Radio Navigation xiii
Table of Contents
CHAPTER 16
Hyperbolic Navigation
Introduction ................................................................................................................................................ 16-1
Hyperbolic Family....................................................................................................................................... 16-1
Lines of Position (LOP) .............................................................................................................................. 16-4
Errors of Hyperbolic Navigation.................................................................................................................. 16-4
Propagation Errors ..................................................................................................................................... 16-4
Height Error................................................................................................................................................ 16-5
Simple Hyperbolic Calculation ................................................................................................................... 16-5
CHAPTER 17
LORAN C
Introduction ................................................................................................................................................ 17-1
Principle of Operation................................................................................................................................. 17-1
Frequency .................................................................................................................................................. 17-2
Typical LORAN C Chain ............................................................................................................................ 17-2
LORAN C Transmission............................................................................................................................. 17-2
Operation ................................................................................................................................................... 17-2
Coverage, Limitations, and Accuracy......................................................................................................... 17-5
LORAN C Coverage................................................................................................................................... 17-5
Sky Waves ................................................................................................................................................. 17-5
Static Disturbances .................................................................................................................................... 17-5
Radio Propagation Speed .......................................................................................................................... 17-5
Geometry of Crossing Angles .................................................................................................................... 17-6
Use of LORAN C........................................................................................................................................ 17-6
LORAN C Navigation ................................................................................................................................. 17-7
Transmitter Fault Indication........................................................................................................................ 17-7
Range and Accuracy.................................................................................................................................. 17-8
Accuracy Limits .......................................................................................................................................... 17-8
CHAPTER 18
Global Navigation Satellite Systems (GNSS)
Introduction ................................................................................................................................................ 18-1
System Capability ...................................................................................................................................... 18-1
Frequency .................................................................................................................................................. 18-2
Basic Principle of Operation ....................................................................................................................... 18-2
The GPS System ....................................................................................................................................... 18-4
The Space Segment .................................................................................................................................. 18-4
GPS Timing................................................................................................................................................ 18-5
Frequency and Coding............................................................................................................................... 18-6
Navigation Message................................................................................................................................... 18-7
The Control Segment ................................................................................................................................. 18-8
The User Segment ..................................................................................................................................... 18-8
GPS Operating Principles .......................................................................................................................... 18-9
Pseudo Range ......................................................................................................................................... 18-10
Velocity Measurement.............................................................................................................................. 18-12
GPS Receiver .......................................................................................................................................... 18-13
System Limitations ................................................................................................................................... 18-14
Number of Users ...................................................................................................................................... 18-14
Coverage ................................................................................................................................................. 18-14
Reliability/Integrity .................................................................................................................................... 18-14
Receiver Autonomous Integrity Monitoring (RAIM) .................................................................................. 18-15
GPS Integrity Broadcast (GIB) ................................................................................................................. 18-15
Coverage Problems ................................................................................................................................. 18-15
Accuracy and Error Sources .................................................................................................................... 18-16
Accuracy for Civil Use .............................................................................................................................. 18-16
xiv Radio Navigation
Table of Contents
User Equivalent Range Errors ..................................................................................................................18-16
Dilution of Precision (DOP) .......................................................................................................................18-17
Error Predictions .......................................................................................................................................18-17
Differential GPS (DGPS)...........................................................................................................................18-17
DGPS Principle of Operation ....................................................................................................................18-18
Summary of GPS Error Sources ...............................................................................................................18-18
Pseudolite/DGPS ......................................................................................................................................18-19
Satellite Based Augmentation Systems (SBAS) .......................................................................................18-20
RAIM in the Wide Area Augmentation System..........................................................................................18-22
GLONASS.................................................................................................................................................18-22
Basic concepts of the GLONASS system .................................................................................................18-22
Integrated Navigation Systems .................................................................................................................18-23
GNSS Applications ...................................................................................................................................18-24
CHAPTER 19
Area Navigation Systems
Introduction .................................................................................................................................................19-1
Area Navigation Concepts ..........................................................................................................................19-2
Accuracy of RNAV Equipment ....................................................................................................................19-3
Basic RNAV ................................................................................................................................................19-3
Use of Basic RNAV.....................................................................................................................................19-5
RNAV Limitations........................................................................................................................................19-7
CHAPTER 20
Introduction to the Flight Management System (FMS)
Introduction .................................................................................................................................................20-1
The Role of FMS.........................................................................................................................................20-1
Use of FMS .................................................................................................................................................20-3
Output Information ......................................................................................................................................20-5
CHAPTER 21
An Overview of CNS/ATM
Introduction .................................................................................................................................................21-1
Communications .........................................................................................................................................21-1
Air Traffic Management and FANS 1 ..........................................................................................................21-1
Controller/Pilot Data Link Communication (CPDLC) ...................................................................................21-2
Aeronautical Telecommunications Network (ATN)......................................................................................21-3
Navigation ...................................................................................................................................................21-3
Eurocontrol BRNAV and PRNAV ................................................................................................................21-3
Required Navigation Performance (RNP) ...................................................................................................21-3
Terminal Area Initiatives .............................................................................................................................21-3
Surveillance ................................................................................................................................................21-4
Automatic Dependent Surveillance (ADS) ..................................................................................................21-4
Automatic Dependent Surveillance Broadcast (ADS-B)..............................................................................21-4
Mode S Data Link .......................................................................................................................................21-4
Radio Navigation xv
Table of Contents
CHAPTER 22
Electronic Display Systems
Glossary of Terms...................................................................................................................................... 22-1
Introduction ................................................................................................................................................ 22-1
General ...................................................................................................................................................... 22-2
General Certification Considerations.......................................................................................................... 22-2
Display Function Criticality ......................................................................................................................... 22-2
Loss of Display........................................................................................................................................... 22-2
Navigation Information ............................................................................................................................... 22-3
Propulsion System Parameter Displays ..................................................................................................... 22-3
Crew Alerting Display................................................................................................................................. 22-3
Flight Crew Procedures.............................................................................................................................. 22-3
Information Display .................................................................................................................................... 22-3
Information Display Colours ....................................................................................................................... 22-4
CHAPTER 23
Boeing 737 Electronic Flight Instrument System (EFIS)
Introduction ................................................................................................................................................ 23-1
System Architecture ................................................................................................................................... 23-1
EFIS Symbol Generator ............................................................................................................................. 23-2
EFIS Control Panel .................................................................................................................................... 23-3
EADI Controls ............................................................................................................................................ 23-4
EHSI Controls ............................................................................................................................................ 23-5
Electronic Attitude Direction Indicator ........................................................................................................ 23-6
EADI General ............................................................................................................................................. 23-6
Attitude Display .......................................................................................................................................... 23-7
Mode Annunciations................................................................................................................................... 23-7
Flight Director (F/D) Commands ................................................................................................................ 23-7
Glideslope (G/S) and Localiser ................................................................................................................. 23-7
(LOC) Deviation Displays ........................................................................................................................... 23-7
ILS Deviation Warning ............................................................................................................................... 23-8
Rising Runway Symbol .............................................................................................................................. 23-8
Attitude Comparator ................................................................................................................................... 23-8
Digital Radio Altitude and Decision Height................................................................................................. 23-8
Mach Display.............................................................................................................................................. 23-9
Groundspeed Display................................................................................................................................. 23-9
Pitch Limit Symbol...................................................................................................................................... 23-9
Speed Tape Scale...................................................................................................................................... 23-9
Digital Airspeed Readout ........................................................................................................................... 23-9
Airspeed Trend Arrow .............................................................................................................................. 23-10
Command Speed ..................................................................................................................................... 23-10
Max Operating Speed (VMO/MMO or Gear/Flap Placards) ..................................................................... 23-10
High Speed Buffet Margin ........................................................................................................................ 23-10
Next Flap Placard Speed ......................................................................................................................... 23-10
Flaps Up Manoeuvring Speed.................................................................................................................. 23-10
V1 (Decision Speed) ................................................................................................................................. 23-10
VR (Rotation Speed) ................................................................................................................................. 23-11
VREF (Reference Speed)........................................................................................................................... 23-11
Minimum Flap Retraction Speed .............................................................................................................. 23-11
Minimum Manoeuvring Speed.................................................................................................................. 23-11
Stick Shaker Speed.................................................................................................................................. 23-12
EADI Symbols .......................................................................................................................................... 23-12
Radio Altitude Dial.................................................................................................................................... 23-14
Speed Tapes............................................................................................................................................ 23-15
EFIS – EADI Fault Displays ..................................................................................................................... 23-20
EADI Failure Flags and Annunciations..................................................................................................... 23-20
EFIS Typical EHSI Centre Map, Map and Plan Displays ......................................................................... 23-21
EHSI Display Orientation ......................................................................................................................... 23-22
PLAN Mode.............................................................................................................................................. 23-22
xvi Radio Navigation
Table of Contents
Features of PLAN Mode ...........................................................................................................................23-23
MAP and CTR MAP Modes ......................................................................................................................23-23
Features of MAP Mode .............................................................................................................................23-24
Features of CENTRE MAP Mode .............................................................................................................23-25
NAV Mode Displays ..................................................................................................................................23-25
Features of EXPANDED NAVIGATION Mode ..........................................................................................23-25
Features of FULL NAVIGATION Mode .....................................................................................................23-26
VOR and ILS Displays ..............................................................................................................................23-26
Expanded VOR Mode ...............................................................................................................................23-27
Full Rose VOR Mode ................................................................................................................................23-28
Expanded ILS Mode .................................................................................................................................23-29
Full Rose ILS Mode ..................................................................................................................................23-30
EHSI Symbology.......................................................................................................................................23-30
EHSI System Failure Flags and Annunciation ..........................................................................................23-39
Range Disagreement Annunciations.........................................................................................................23-39
Weather Annunciations .............................................................................................................................23-40
Instrument Transfer Switching ..................................................................................................................23-42
Light Sensing and Brightness Controls .....................................................................................................23-43
CHAPTER 24
Boeing 737 Flight Management Computer (FMC)
General .......................................................................................................................................................24-1
Operation Overview ....................................................................................................................................24-3
CDU Function .............................................................................................................................................24-4
CDU Page Display General ........................................................................................................................24-4
Function and Mode Keys ............................................................................................................................24-5
Line Select Keys .........................................................................................................................................24-5
Keyboard.....................................................................................................................................................24-6
CDU Page Display ......................................................................................................................................24-7
Page Status ................................................................................................................................................24-8
Function and Mode Keys ............................................................................................................................24-8
Lights ........................................................................................................................................................24-11
System Components.................................................................................................................................24-11
Databases.................................................................................................................................................24-12
Operation ..................................................................................................................................................24-13
Lateral Navigation .....................................................................................................................................24-14
Vertical Navigation ....................................................................................................................................24-14
Required Time of Arrival (RTA) Navigation ...............................................................................................24-15
Radio Tuning.............................................................................................................................................24-15
Electrical Power ........................................................................................................................................24-17
Terminology ..............................................................................................................................................24-17
Executing ..................................................................................................................................................24-17
Inactive .....................................................................................................................................................24-17
Active ........................................................................................................................................................24-17
Page Status ..............................................................................................................................................24-18
Modification ...............................................................................................................................................24-18
Initialisation ...............................................................................................................................................24-18
Line Select ................................................................................................................................................24-18
Enter .........................................................................................................................................................24-18
Access ......................................................................................................................................................24-18
Propagate .................................................................................................................................................24-18
Page Concepts .........................................................................................................................................24-19
General .....................................................................................................................................................24-19
Page Sequence Logic ...............................................................................................................................24-19
CDU Messages.........................................................................................................................................24-21
Waypoint ...................................................................................................................................................24-22
Waypoint Identifiers ..................................................................................................................................24-22
Created Waypoints ...................................................................................................................................24-22
Conditional Waypoints ..............................................................................................................................24-23
Radio Navigation xvii
Table of Contents
CHAPTER 25
Boeing 737 Navigation Equipment and Flight Management
Inertial Reference System .......................................................................................................................... 25-1
IRS Mode Selector ..................................................................................................................................... 25-1
Align Light (White)...................................................................................................................................... 25-2
Fault Light (Amber) .................................................................................................................................... 25-2
On DC Light (Amber) ................................................................................................................................. 25-3
DC Fail Light (Amber) ................................................................................................................................ 25-3
Inertial Reference System .......................................................................................................................... 25-3
General ...................................................................................................................................................... 25-3
Alignment ................................................................................................................................................... 25-4
Alignment on the Ground ........................................................................................................................... 25-4
Fast Realignment on the Ground ............................................................................................................... 25-4
Loss of Alignment....................................................................................................................................... 25-4
IRS Display Unit ......................................................................................................................................... 25-5
Display Selector ......................................................................................................................................... 25-5
Brightness Control...................................................................................................................................... 25-6
Data Displays ............................................................................................................................................. 25-6
Enter Key ................................................................................................................................................... 25-6
Keyboard.................................................................................................................................................... 25-6
Instrument Transfer Switch/Instrument Transfer Switch Light.................................................................... 25-7
DME System .............................................................................................................................................. 25-7
Radio Distance Magnetic Indicator............................................................................................................. 25-8
VOR/ILS Navigation ................................................................................................................................... 25-9
Marker Beacon Switch ............................................................................................................................. 25-10
ADF Navigation ........................................................................................................................................ 25-10
SSR Transponder Selections ................................................................................................................... 25-11
Weather Radar......................................................................................................................................... 25-13
Radio Altimeters....................................................................................................................................... 25-15
xviii Radio Navigation
WAVE MOTION
INTRODUCTION
A wave is a progressive disturbance in a medium, formed by alternating pressures and tensions,
without any permanent displacement of the medium itself in the direction in which these stresses
are propagated.
This condition is readily observed on the surface of a pond. Throwing a stone into the water
produces a series of waves which radiate out until they reach the bank. A plastic duck in the pond
rises and falls as the wave pass underneath, demonstrating that there is no movement in the
direction of wave travel. While the wave moves toward the bank, the water does not.
The wave possesses the following characteristics:
¾ The form of the wave moves outward although the water itself does not.
¾ The wave possesses energy obtained from the stone. With the passage of the wave,
energy is lost due to friction. The wave becomes smaller as it moves away from the
source.
¾ The wave travels at a constant speed.
¾ The wave is sinusoidal; it travels as a sine wave.
Radio Navigation 1-1
Chapter 1 Basic Radio Theory
The radio wave is an alternating waveform and, as such, the following terms are used:
Cycle — a complete sequence of positive and negative values (AB).
Period — the duration of one cycle (T). In the figure above it is T = 1/100 seconds.
Velocity — the speed and direction of movement through a given medium.
Frequency — the number of complete waves passing a fixed point in one second,
denoted by the symbol f and usually expressed as Hertz (Hz).
Wavelength — the distance between similar points on successive waves, or the distance
occupied by one complete cycle when traveling in free space (AB), and denoted by the
symbol λ (Lambda).
Amplitude — the maximum height of the wave. This can be positive or negative. The
positive amplitude is represented by b.
ELECTRO-MAGNETIC WAVES
The atmosphere carries light, heat, and radio waves. These waves differ only in their wavelength
and the effects they have on different materials. Because of their electrical and magnetic nature,
they are termed electro-magnetic. All of these waves travel at the same velocity, denoted by the
letter c. For the Radio Navigation syllabus, this velocity is:
300 000 000 m/sec or 162 000 nm/sec
For simplicity, the speed of light in m/sec can expressed as 300 X 106 m/sec
PROPERTIES OF RADIO WAVES
Radio waves leaving a transmitter have the following properties:
¾ They consist of oscillating electric and magnetic fields that are at right angles to each
other and at right angles to the direction of propagation.
¾ They require no supporting medium.
¾ They can be reflected, refracted, and diffracted as discussed below.
¾ They are subject to interference and Doppler effect.
¾ They can pass through an opaque object such as a building, although they do suffer
attenuation in doing so.
Attenuation of an RF signal is the reduction in signal strength due to absorption, scattering, or
dispersion and diffraction.
REFRACTION, DIFFRACTION, AND REFLECTION
All radio waves are subject to refraction, diffraction, and reflection, and even combinations of
these phenomena.
Refraction occurs when the speed of the radio wave is affected differently on either side of the
centreline of the ray. This causes a difference in the propagation speed either side of the
centreline that bends the wave. The most common cause of refraction is when the wave travels
obliquely through mediums that have differing effects on the speed of propagation.
1-2 Radio Navigation
Basic Radio Theory Chapter 1
Diffraction occurs principally when a radio wave travels close to the Earth’s surface. The wave
travelling over the Earth’s surface induces a micro-voltage into the Earth, during which the wave
tends to attach itself to the Earth. As this induction takes place, the signal is attenuated and
slowed, causing the wave to bend and follow the Earth’s curvature.
Some surfaces exhibit reflective properties to radio energy, accepting the incoming signal and
then re-radiating it. Where a reflected signal is at a small angle to the direct line between
transmitter and receiver, the energy lost is minimal and can combine with the direct signal at a
different phase, causing significant interference at the receiver.
RELATIONSHIP BETWEEN FREQUENCY, WAVELENGTH, AND VELOCITY
The frequency of a sinusoidal wave is the number of cycles occurring in one second. The JAR
exam requires conversion of frequency to wavelength and vice versa. Frequency uses the symbol
f and the unit is the Hertz. Wavelength is λ and the unit used is metres.
c=f λ
Because of the large figures used in frequency, the following prefixes are used:
Prefix Magnitude
Kilo 103
Mega 106
Giga 109
Example 1000 Hertz = 1 Kilohertz = 1 kHz
1 000 000 Hz = 1 MHz
1 000 000 000 Hz = 1 GHz
Likewise, radio wavelength units can be small, so the following prefixes are used:
Prefix Magnitude
Milli 10-3
Micro or µ 10-6
10-9
Nano
Example: Convert 2 MHz to a wavelength
λ = c = 300 x 106 = 150 metres
f 2 x 106
Example: Convert 60 metres to a frequency
Radio Navigation
f = c = 300 x 106 = 5 MHz
λ 60
1-3
Chapter 1 Basic Radio Theory
Remember: The higher the frequency, the shorter the wavelength and vice versa.
Examples: Convert the following wavelengths into the corresponding frequencies
(The answers are given below):
1. 1500 m
2. 20 cm
3. 3500 m
Convert the following frequencies into the corresponding wavelength:
1. 300 kHz
2. 75 MHz
3. 600 MHz
4. 8800 MHz
5. How many wavelengths, to the nearest whole number, of frequency 200 MHz are
equivalent to 35 ft?
Answers:
Wavelength to Frequency
1. 200 kHz
2. 1500 MHz
3. 85.7 kHz
Frequency to Wavelength
1. 1000 m
2. 4 m
3. 50 cm
4. 3.41 cm
1-4 Radio Navigation
Basic Radio Theory Chapter 1
5. Number of wavelengths in 35 ft for a frequency of 200 MHz
λ = c = 300 x 106 = 1.50 metres
f 200 x 106
1 m is equivalent to 3.28 ft
1.5 m = 4.92 ft
The number of wavelengths in 35 ft = 35
4.92
which is approximately 7.
PHASE DIFFERENCE
In the diagram below the two waves are said to be in phase. The waves pass the same point of
their cycle at the same time.
In the diagram below the waves are said to 90° out of phase:
¾ Wave B leads wave A by 90°, or
¾ Wave A lags wave B by 90°
AB
Radio Navigation 1-5
Chapter 1 Basic Radio Theory
Where two waves have a phase difference of 180°, then they are said to be in anti-phase.
RADIO SPECTRUM
The diagram below shows the electromagnetic spectrum. Frequency determines the different
effects brought about by electro-magnetic waves. The lower limit is determined by the size and
efficiency of the aerials required and the upper limit by the attenuation and absorption of the radio
waves by the atmosphere.
Wavelength
L
Radio Infra Red I Ultra X-Rays Gamma Cosmic
Waves 300 GHz G Violet Rays Rays
H
3 KHz
T
The part of the frequency spectrum of interest to the pilot is further sub-divided below.
VLF LF MF HF VHF UHF SHF EHF
3 30 300 3 30 300 3 30 300
kHz MHz GHz
Radio Spectrum
1-6 Radio Navigation
Basic Radio Theory Chapter 1
WAVE PROPAGATION
There are three principle paths that radio waves may follow between the transmitter and the
receiver:
Surface Waves follow the contours of the Earth’s surface.
Sky Waves are refracted by the ionosphere and returned to Earth.
Space Waves are line of sight.
A combination of a surface and a space wave is called a ground wave.
The radio energy reaching a receiver may be made up of components of any one or more of
these mechanisms but depending on the part of the radio spectrum concerned, one of the three
predominates. In general:
¾ Low frequencies are propagated by surface wave.
¾ Middle range frequencies are propagated by sky wave.
¾ Upper range frequencies are propagated by space wave.
Ionosphere
Surface
Wave
Sky Space
Wave Wave
Radio Navigation 1-7
Chapter 1 Basic Radio Theory
SURFACE WAVE
The surface wave follows the curvature of the Earth, a process known as diffraction. The Earth’s
attenuation of the radio energy helps the process. The wave is slowed as it touches the Earth’s
surface. As a result, the wave front nearest the surface lags behind the wave farther from the
surface.
Wave front falls toward the Earth as it
progresses
The wave front tilts and diffractive bending occurs. The stability of this type of propagation makes
the low frequency surface wave suited to systems requiring consistency of signal over long
distances. The propagation does require large aerials and the cost of transmission can be
considerable.
TYPE OF SURFACE
High conductivity favours the passage of a radio signal. Therefore, passage over the sea is better
than over rock or desert.
Transmitter Power
Surface absorption and free space loss reduce the signal strength of a radio wave. If
there is no restriction in the available transmitter power, then global ranges can be
achieved by VLF radio waves.
Different types of surfaces will affect the transmission of a ground wave differently, but
all power to range ratios follow a square law rule. The basic rule of thumb formula to
calculate required transmitter power from a given range is: 3√P (in watts) for
transmission over water and 2√P (in watts) for transmission over land. In both cases
note that to double the range, the power must increase by a factor of 4.
1-8 Radio Navigation
Basic Radio Theory Chapter 1
Noise and Interference
Noise affects the lower frequencies, consequently affecting the signal/noise ratio. This
can limit the usable range.
For maximum ground wave range:
¾ Use low frequency for maximum diffraction and least attenuation.
¾ Use vertical polarisation (see polarisation).
SKY WAVE
The sky wave ascends into the upper atmosphere and encounters a region containing electrically
charged particles (the ionosphere) where it is refracted sufficiently to return to Earth.
β Is the Critical Angle. Note that it is measured from the vertical down.
β
Ground Wave
Dead Space
Skip Distance
When the wave enters the ionosphere it changes direction due to a change in velocity. If the
wave penetrates halfway through the layer before being bent parallel to the layer it will bend back
in the opposite direction to emerge from the top of the layer as an escape ray. This is likely if:
¾ The ionisation is insufficiently intense
¾ The frequency is too high
¾ The angle of entry is too acute
CRITICAL ANGLE
For a particular frequency and degree of ionisation, it is possible to define a critical angle below
which total refraction does not take place. Defining the critical angle also establishes the
minimum range or the skip distance. Any ray travelling away from the aerial at greater than the
critical angle will be freely refracted down to about 5° above the horizon.
Radio Navigation 1-9
Chapter 1 Basic Radio Theory
DEAD SPACE
Because of the high frequencies used in sky wave transmission, the ground wave travel is not as
far as the returning sky wave. The distance between the limit of the ground wave and the first
returning sky wave is the dead space.
THE IONOSPHERE
The ionosphere consists of a series of conducting layers between heights of 50 and 400 km. It
exists because of the transmission of ultra-violet radiation from the sun. Because of this
dependence upon radiation from the sun, the heights and densities of the layers vary according to
the time of day and season of the year.
There is also a connection between the 11-year sunspot cycle. Short-term effects occur in a
random fashion resulting in the ionised layers being in a state of constant turbulence. Three main
layers have been identified, designated as D, E, and F. The F layer splits into two separate layers
during the day, the time of highest ionisation. The D layer is a region of low ionisation that only
persists during the day. The E layer is more marked and remains weakly ionised by night with
little change in height. The F layer is the most strongly ionised and has the greatest diurnal
change in height.
400 km F2
200 km F1
100 km E
D
Day Night
1-10 Radio Navigation
Basic Radio Theory Chapter 1
FREQUENCY AND SKIP DISTANCE
At a fixed level of ionisation, an increase in frequency will cause the ray, previously the critical
ray, to become an escape ray. This causes an increase in skip distance.
IONISATION AND SKIP DISTANCE
At a fixed frequency, if ionisation decreases, the effect is the same as above. The critical ray
becomes an escape ray. This causes an increase in skip distance.
SPACE WAVE
Transmissions at VHF and above cannot propagate by either surface or sky wave. Attenuation is
so severe that the surface wave is virtually non-existent. These frequencies are too high to be
refracted by the ionised layers aloft. As a result, transmission is by straight line, or the direct
wave. In addition to the direct wave, a reflected wave can also exist. The two components make
up the space wave.
Because of the different emission paths, the direct and reflected wave is sometimes in phase and
sometimes out of phase. This produces lobes and nulls particularly when the receiver is close to
the station.
The range of a space wave appears to be line of sight. In practice it is termed quasi-optical:
¾ The lower atmosphere causes some refraction of the wave, which bends it beyond
the optical horizon.
¾ A further small increase is gained from diffraction when the wave becomes tangential
to the Earth’s surface
Radio Navigation 1-11
Chapter 1 Basic Radio Theory
This range can be approximated by the following formula:
Where: R R = 1.25(√HT + √HR)
HT
HR Range in nautical miles
Height of the transmitter in feet
Example: Height of the receiver in feet
An aircraft flying at 10 000 ft receives a transmission from a station at
400 ft. What is the maximum distance communications can occur
between the two stations?
R = 1.25(√10 000 + √400)
R = 1.25(100 + 20)
R = 150 nm
DUCT PROPAGATION
Under certain abnormal climatic conditions, transmissions on a frequency greater than 50 MHz
can be received at ranges in excess of the quasi-optical expected.
AIR TEMPERATURE SUBSIDING
DEW POINT TEMPERATURE AIR
-40° +7°
VERY DRY AND RELATIVELY WARM
-3°
INVERSION BASE
LOW CLOUDS TRAPPED BELOW INVERSION COOL AND MOIST
25 JANUARY 1989 - 0001 GMT. ST. HUBERT, BELGIUM
PRESSURE TEMPERATURE DEW POINT MODIFIED REFRACTIVE INDEX
900mb +7.1 -40.0 250.8
920mb +7.5 -28.0 257.3
945mb -3.5 -3.9 295.8
The conditions that cause this abnormal propagation are a temperature inversion and a rapid
decrease in humidity with height (steep humidity lapse rate). This forms a duct between the Earth
and a few hundred feet above the surface.
Radio waves have a wavelength that is small compared with the duct height. This allows the duct
to refract the wave back to Earth. The Earth’s surface then reflects the wave back to the duct
ceiling. A series of these refraction/reflection hops occur and thus the wave can be received well
in excess of the quasi-optical range. The same conditions can occur when there is an inversion
aloft.
1-12 Radio Navigation
Basic Radio Theory Chapter 1
TRANSMITTER ELEVATED DUCT LAYER OF HIGH
TRANSMITTER SURFACE DUCT DIELECTRIC
CONSTANT
EARTH
LAYER OF HIGH
HUMIDITY
LAPSE RATE AND
TEMPERATURE
INVERSION
These conditions are normally associated with large high-pressure systems, a condition that is a
regular feature in the tropics.
AERIALS
A transmitter/receiver is only as good as the aerial. An aerial is a device used for the efficient
transmission and reception of electromagnetic energy. Generally, aerials that radiate are looked
at; however, the properties of a transmitting aerial apply equally to the receiving aerial.
AERIAL CHARACTERISTICS
When an aerial radiates an electro-magnetic wave it transmits two radio frequency fields:
The E Field is the electric or electrostatic field.
The H Field is the magnetic field.
These fields transmit at right angles to each other.
Note: The H field is always at right angles to the aerial and the E field is always parallel to the
plane of the aerial.
By convention, the wave is said to be vertically polarised if the E Field is perpendicular to the
Earth and horizontally polarised if parallel to it.
A vertical aerial produces a vertically polarised wave, and conversely, a horizontal aerial
produces a horizontally polarised wave.
Radio Navigation 1-13
Chapter 1 Basic Radio Theory
A standard dipole receiver aerial must be aligned in the same polarity as the signal to be received
for maximum transfer of energy. For instance, a transmitted signal from a horizontal aerial needs
to be received by an aerial that is itself horizontal for optimum reception.
AERIAL LENGTH
The aerial is manufactured to a specific length dependent on the frequency to be used.
POLAR DIAGRAMS
The effective radiation or reception of an aerial is shown by a polar diagram. These can be
oriented to show the pattern as horizontal (looking down on the aerial from above) or vertical
(looking at the aerial from the side).
OMNI-DIRECTIONAL AERIALS
SIMPLE HALF-WAVE DIPOLE
In its simplest form, a dipole consists of a metal rod or a wire cut to a specified length. The aerial
is cut to a half wave-length.
Example For a frequency of 30 MHz
λ = 10 m
The aerial for this wavelength is λ /2 or 5 m.
This is called the Electrical Length.
In an ideal world, the Electrical Length would be the length of aerial required for a given
frequency. The speed of electro-magnetic radiation through a vacuum is constant. When an
aerial feeder is used, the speed of the radiation is slower. This slower speed is approximately 5%
less than the in-vacuo speed and we must consider this by factoring the Electrical Length to 95%
of its value. This is the Physical Length of the aerial for a given frequency.
Example For a frequency of 100 MHz
λ=3m
Electrical Length of the aerial = λ /2 = 150 cm
Physical Length = 95% of λ /2 = 142.5 cm
MARCONI QUARTER WAVE AERIAL
Most practical aerials are cut to one quarter of the wavelength (λ /4). By using the reflective
properties of electro-magnetic waves, the aerial compensates for the missing half of the dipole.
1-14 Radio Navigation
Basic Radio Theory Chapter 1
The Marconi aerial is particularly suitable for fitting into aircraft structures. To ensure that the
aerial can be used over a range of frequencies, an aerial loading unit (ALU) is fitted. This unit
electronically matches the aerial to the frequency selected.
AERIAL FEEDERS
There must be a connection between the transmitter/receiver and the aerial; this is a feeder. The
type of feeder depends upon the frequency to be used. The most common feeder in use in
aircraft communications is the co-axial cable (better known as the TV aerial wire). Higher
frequencies require a more sophisticated feeder, for example, radar requires a wave guide.
AERIAL DIRECTIVITY
The dipole radiates power evenly in all directions or omnidirectionally. The plan and side views
show the radiating pattern.
AERIAL
AERIAL
Plan View Side View
Note: The radiating polar diagram is from the centre of the aerial not the tip.
To modify the omni-directional properties and give the aerial directivity requires adding parasitic
elements. The most common directional aerial in everyday use is the TV antenna, or the Yagi.
The directional properties are derived by adding parasitic elements in front and behind the dipole.
Radio Navigation 1-15
Chapter 1 Basic Radio Theory
To change the omni-directional properties, a parasitic reflector 5% larger than the dipole is placed
at a distance of λ /4 from the dipole. The normally circular polar diagram now changes into an
elongated heart shape with the reflector reflecting the power back toward the aerial. Note that the
dipole is the only part of the aerial that has any power.
To enhance the directional properties, parasitic directors are added on the opposite side to the
parasitic reflector. These elements are 5% shorter than the dipole.
The resulting polar diagram is narrow in beam width and gives excellent directional properties.
One disadvantage is the production of unwanted side lobes. The side lobes are approximately
50% of the power of the main beam and can give spurious indications if not dealt with. Methods
of suppression or removal of the side lobes are discussed in individual chapters on equipment.
1-16 Radio Navigation
Basic Radio Theory Chapter 1
Side Lobes
Different polar diagrams can be achieved for different aerial combinations. An example of this is
the figure of eight produced by two dipoles.
The significance of changing the polar diagram becomes apparent upon discussing each piece of
equipment in detail.
MODULATION
Modulation is the superimposing of intelligence, such as speech or Morse identification, onto a
carrier wave. Varying a parameter of the carrier, such as its amplitude or frequency does this.
When electro-magnetic energy is radiated as a sinusoidal wave, it transmits no intelligence. The
frequency is beyond the scope of human hearing and the wave itself would be meaningless.
KEYING
Interrupting the wave, a process known as keying, makes it possible to transmit Morse code.
Transmitter DOT OFF DASH OFF DOT
ON ON ON
OFF
The signal may be identifiable as Morse code, but it is still outside the audible range. Converting
the carrier frequency into a signal within the audio range helps with audible reception.
Radio Navigation 1-17
Chapter 1 Basic Radio Theory
Mixing the received frequency with another known radio frequency produces a signal in the audio
range. The mixing of two radio frequencies, known as heterodyning rather than modulation, is the
mixing of a radio frequency and an audio frequency.
Example: Received frequency 500 kHz
Known frequency 501 kHz
Produces four frequencies:
500 kHz} outside the audible range
501 kHz}
1001 kHz} an audible frequency
1 kHz}
Selecting the BFO function (Beat Frequency Oscillator) enables heterodyning. The incoming
signal is received and mixed with the BFO frequency and the resulting audio frequency is fed to
the intercom system. As a result, an audio tone is only heard when the two frequencies are
present.
500 kHz 500 kHz
501 kHz
Detector 1001 kHz
1 kHz
On
Off
Beat
Frequency
Oscillator
(BFO)
501 kHz
Note: The only piece of equipment that uses a BFO in the aircraft is the ADF. Normally,
electromagnetic radiation is modulated by one of the three methods listed below:
1-18 Radio Navigation
Basic Radio Theory Chapter 1
AMPLITUDE MODULATION (AM)
AM is where the modulating frequency alters the amplitude of the wave.
Amp Time Modulating
Audio Note Waveform
Unmodified Carrier
Transmitter Wave
Output
Amplitude Amplitude
Moditied Modulated
Output Carrier Wave
Where a carrier is amplitude-modulated by a single tone, the resultant waveform consists of three
components:
¾ The carrier wave fc
¾ The upper sideband (fc + fs)
¾ The lower sideband (fc - fs), where fs is the modulating signal
The AM signal consists of:
1 500 kHz the carrier
2. 501 kHz the upper sideband
3. 499 kHz the lower sideband
Both sidebands carry intelligence. The spread of the side frequencies is known as the bandwidth.
For an amplitude modulated signal the bandwidth is 2 fs.
Both sidebands carry the same information. If one of the bands is suppressed (e.g. the upper
sideband) then the only frequencies that need transmitting are 500 kHz and 499 kHz. This type of
transmission has two main advantages:
¾ It requires less power to transmit one sideband and the carrier.
¾ The signal occupies less of the radio spectrum, meaning that the frequency band can
be used more efficiently.
HF transmissions make use of the single sideband transmission.
Radio Navigation 1-19
Chapter 1 Basic Radio Theory
FREQUENCY MODULATION (FM)
FM is where the modulating frequency alters the frequency of the wave.
The frequency of the carrier varies by an amount proportional to the instantaneous amplitude of
the modulating signal. The rate of change of the carrier frequency is proportional to the frequency
of the modulating signal with the amplitude of the modulated carrier remaining constant
throughout.
FM signals are relatively noise free. Unfortunately, this type of broadcast uses a much wider
bandwidth than AM, so FM has limited application in commercial aviation. FM is used in:
¾ VOR
¾ Radio Altimeters
¾ Doppler
PULSE MODULATION (PM)
PM is where the carrier is transmitted in short pulses. These pulses can be coded to carry
information. Two types of PM need consideration:
Pulse Amplitude Modulation (PAM)
In a manner similar to AM, it is possible for an audio waveform to modify the amplitude of
a fixed train of pulses.
Pulse Code Modulation (PCM)
PCM is a system where each pulse amplitude is assigned a binary number.
1-20 Radio Navigation
Basic Radio Theory Chapter 1
CLASSIFICATION OF EMISSIONS
Radio regulatory agencies have designed a coding system that fully describes the form that a
radio transmission may take. The table below details the coding system.
First Character Second Character Third Character
Type of Modulation Nature of the Modulating Type of Information Being
N – Unmodulated carrier Signal Transmitted
0 – No modulation
A – Amplitude N – No information
1 – Interrupted carrier transmitted
J – Single sideband (no
carrier) 2 – Keyed or digital audio A – Telegraphy – for aural
modulation reception
F – Frequency
3 – Telephony (voice or E – Telephony – including
P – Unmodulated pulses music) sound broadcasting
8 – Two or more channels of W – Combination of the
analogue information above
9 – Composite systems X – Cases not otherwise
comprising of 1 & 2 covered
above with 3 or 8
X – Cases not otherwise
covered
The emission characteristics pilots need to know for civil aviation use are:
ADF N0N A1A
N0N A2A
HF J3E
VHF A3E
VDF A3E
ILS A8W
VOR A9W
DME P0N
BASIC RADAR THEORY
INTRODUCTION
Radar is derived from the expression radio detection and ranging. It may be defined as any
system employing radio to detect the presence of objects and to determine their position and
movement.
Radio Navigation 1-21
Chapter 1 Basic Radio Theory
RADAR FREQUENCIES
Radar occupies the frequency bands from VHF upward. Higher frequencies are used because:
¾ They are free from external noise.
¾ Narrow beams operate more efficiently with a short wavelength.
¾ Primary radar uses pulses, and higher frequencies can utilise shorter pulses.
¾ The efficiency of reflection depends upon the size of the target in relation to
wavelength. High frequencies are reflected more efficiently.
PRINCIPLES
A transmitter sends out, via the aerial, a brief pulse of radio energy. Every 6.2 microseconds (µs)
this pulse travels 1 nautical mile. If this pulse strikes a target, a small proportion of the radio
energy reflects back to the aerial. The aerial picks up this reflected energy and passes it to the
receiver. By measuring the time of travel, the range can be calculated.
Tx pulses
Echo pulses
Transmitter Receiver
PULSE RADARS
Pulse radars are employed as:
¾ Primary radars - ATC surveillance radars, airborne weather radars
¾ Secondary radars - DME and SSR
¾ Doppler
The radar transmits energy in very short bursts of high energy. Timing the pulse yields a direct
measurement of the range and requires a sensitive receiver. The transmission, travel, and
reception of the pulse must occur before the next pulse is transmitted. This ensures having an
unambiguous target.
Primary Radar
Primary radar relies on the weak reflections from a passive target. The effectiveness of
the radar depends upon the transmitter power and the receiver sensitivity.
1-22 Radio Navigation
Basic Radio Theory Chapter 1
Because primary radar transmits a pulse and receives an echo, range is affected by
propagation outbound and inbound, both of which are subject to the range/power
formula discussed earlier under Type of Surface/Transmitter power. Therefore, to double
the range of a primary radar the transmitter power must be increased by a factor of 16.
Secondary Radar
Secondary radar relies on the target co-operating with the transmitter. The target
transmits a reply signal to an interrogatory signal such as in SSR and DME. The
interrogation and reply are usually on different frequencies.
Secondary radar has both advantages and disadvantages over primary radar:
Advantages
¾ Primary radars require much more power to achieve the same range.
¾ Target size and aspect are irrelevant because the target transmits the response.
¾ Responses on the secondary radar are much more reliable.
¾ Information can be encoded to give the transmitter and receiver information.
¾ Clutter on the radar screen can be eliminated.
Disadvantages
¾ The radar requires the co-operation of the target.
¾ Bearing resolution can be inferior.
¾ Side lobes can be a problem at short range.
¾ Beacon saturation can be a problem.
RADAR DIRECTION FINDING
There are two principle means of radar direction finding:
¾ Lobe Comparison
¾ Beam Direction Finding
Radio Navigation 1-23
Chapter 1 Basic Radio Theory
LOBE COMPARISON
Mainly used by secondary radars two aerials are used to define direction. The aerials are rotated
until an equal strength signal is received.
BEAM DIRECTION FINDING
By using a parabolic aerial, a near parallel beam can be achieved. Because the direction of the
aerial is known and the pulse is transmitted and received before the next pulse is transmitted, the
azimuth of the target can be calculated.
The beamwidth of a parabolic aerial can be calculated by the formula:
Beamwidth = 70λ/d
Where: λ = wavelength of the radar
d = diameter of the parabolic aerial
Remember with this calculation that λ and d must be in the same units.
RADAR TERMINOLOGY
Certain terms used in radar need to be understood.
Pulse Recurrence Frequency (PRF)
The radar transmits pulses at this rate. The unit of measurement is pulses per second
(pps). The fact that each pulse must be able to reach the most distant target and return
before transmission of the next pulse determines the maximum PRF. Otherwise there is
a possibility of ambiguous range measurement.
1-24 Radio Navigation
Basic Radio Theory Chapter 1
Pulse Recurrence Interval (PRI)
PRI is the time interval between pulses with the unit of measurement normally being
microseconds. The PRI determines the maximum range of the radar. The relationship
between PRI and PRF is simple.
PRI = 1 ÷ PRF
Example: For a radar with a PRF of 250 pps, find the maximum range:
PRI = 1/PRF = 1/250 = 0.004 seconds
0.004 seconds = 4000 µs
4000 µs = 4000 X 10-6 seconds
(To convert seconds into microseconds multiply by 1 000 000)
Distance = speed X time
The total time of travel out and back for the pulse is 4000 µs
The time of travel one way, to calculate the range =
2000 µs or 2000 X 10-6 seconds
Distance = (2000 X 10-6) seconds X (300 X 106) m/second
Distance = 600 000 metres = 600 kilometres
This is the maximum unambiguous range of the radar.
Pulse Width (PW)
PW is the duration of the pulse. This determines the minimum range of a radar. The
pulse must travel half its distance before it hits a target and returns to the radar.
Otherwise, the radar will still be transmitting the same pulse when the reflected signal
returns.
Example: What is the minimum range of a radar with a PW of 2 µs?
The minimum range must be half the time of travel, or 1 µs.
Distance = speed X time = (1 X 10-6) seconds X (300 X 106) metres
per second
Distance = 300 metres
Radio Navigation 1-25
Chapter 1 Basic Radio Theory
CHOICE OF FREQUENCY
To produce a narrow beam, a high frequency must be used. The advantages of using a narrow
beam are obvious:
¾ Bearing accuracy is greater.
¾ There is an increase in effective power.
¾ The radar is able to resolve closely spaced targets.
¾ High frequencies also generate a more square pulse shape.
¾ Wavelength must be shorter than the target size.
All of the above must be taken into consideration.
1-26 Radio Navigation
Basic Radio Theory Chapter 1
The basic radar has seven elements:
Master Timer
This is the trigger unit and has two functions:
¾ It generates the basic PRF.
¾ It synchronises the firing of the transmitter.
Modulator
The output from the modulator switches the transmitter on and off controlling the pulse
length of the transmitter output.
Transmitter
This delivers the pulse to the aerial.
Receiver
This is a sensitive superhet that can amplify the very weak returning echoes. These are
then processed for display.
T/R switch
The same aerial is used for both transmission and reception. The receiver must be
protected from the high power transmitter. This is accomplished by electronically isolating
the waveguides for both. A duplexer performs this isolation. In real terms, it is the brains
of the radar.
Indicator
Radar information is usually displayed on a Cathode Ray Tube.
Aerial
This is a parabolic dish on older aerials. Now a flat bed array electronically simulates a
parabolic dish.
Radio Navigation 1-27
Chapter 1 Basic Radio Theory
1-28 Radio Navigation
INTRODUCTION
Certain aerodromes have VHF Direction Finding (VDF) equipment. VDF provides an ATC
Controller with the means of determining the direction of the VHF signal from an aircraft. The only
onboard equipment required to obtain this service is a standard aircraft VHF radio. This is one of
the main advantages of the VDF service.
PRINCIPLES OF OPERATION
The basic VDF uses a phased array system based on the Doppler Principle. The modern VDF
aerial is shown below.
Frequency 2-1
VHF – 118 to 137 MHz
Emission Characteristics
A3E
Radio Navigation
Chapter 2 VHF Direction Finding
OPERATION
If the communications transmitter on an aircraft is tuned to the VDF frequency and the transmitter
activated, the aerials at the VDF unit detect the incoming transmission and each aerial element
feeds a signal to the VDF receiver.
¾ The aerial elements are all at slightly different distances from the source of the signal.
¾ Each detects a slightly different phase of the signal from the aircraft at the same
moment in time.
¾ The value of these detected phase differences directly relate to the direction of the
incoming signal.
¾ The phase differences are used to drive the bearing indicator.
On some VDF units a simple digital read-out gives the bearing. The ground VDF station can give
true or magnetic bearings.
SERVICES
It is common to use the Q codes to represent the bearings from a VDF station. The codes
originate from the days of telegraphy where it was convenient to transmit short codes instead of
full text messages. The Q codes are not abbreviations.
Listed below are the codes that are relevant to direction finding:
QTE: True track from the station
QDR: Magnetic bearing from the station
QUJ: True track to the station
QDM: Magnetic bearing to the station
QGH: DF controlled approach
QDL: DF steer
In practice, only QDM and QDR are normally used.
The accuracy of the bearing is measured in degrees. Accuracy is classified in accordance with
the ICAO defined classifications:
¾ Class A accurate within ± 2°
¾ Class B accurate within ± 5°
¾ Class C accurate within ± 10°
¾ Class D accuracy less than Class C
SITING
Due to topography, some VDF stations are approved for use only within certain sectors. Specific
information for an aerodrome is given in the AIP. Generally, the class of bearing is no worse than
class B (many states will not permit Class C & D bearings to be provided). Do not use ground
VDF stations as enroute navigation aids, as they do not provide the aircraft with continuous
tracking information. However, in case of emergency, or where other essential navigation aids
fail, their service is available. When flying VFR under marginal weather conditions, a VDF station
is a useful navigation tool for any pilot.
RECEIVING A BEARING
To request a bearing or a heading to steer, the pilot should call the aeronautical station on the
listed frequency. The pilot should then specify the type of service desired by using the appropriate
Q code.
2-2 Radio Navigation
VHF Direction Finding Chapter 2
Automatic VDF stations only require a short transmission, while older manual stations may
require a short preparatory period before being able to provide the service.
After requesting the bearing or heading to steer, the VDF station advises the aircraft station the
following way:
¾ The appropriate Q code
¾ The bearing or heading to steer
¾ The class of bearing and time of observation (if necessary)
The pilot will read back the bearing or heading to steer immediately upon receiving the message.
ASKING FOR A BEARING
Assume that the pilot of an aircraft G-BOBA needs to confirm its position.
Aircraft Cranfield Tower, G-BOBA, request QDM
Tower G-BOBA, QDM 180°, Class B
Aircraft QDM 180°, G-BOBA
Initially the pilot asks for the magnetic bearing from the aircraft to the airport (QDM). To home to
Cranfield, the pilot should fly a magnetic heading of 180°. Remember that the bearing applies to a
still air condition. If there is any wind, the initial QDM must be corrected for drift. Note that a QDM
only provides a line of position, not a fix position.
POSITION FIX
When a position fix is necessary, the request must be made to a station with the capability for
triangulation, such as the Distress and Diversion Cell on the international emergency frequency of
121.5. A bearing derived from one station is a line of position (LOP), while two LOPs are
necessary to get a position fix.
VDF APPROACH
The pilot may request a QGH procedure provided one is listed for the airfield. This is a procedure
in which the controller provides the pilot with a series of QDMs so that the pilot can follow a laid
down approach path. This approach path involves a number of steps described in the appropriate
approach chart, and are summarised as follows:
¾ Guiding the pilot into a position over the airfield
¾ Establishing the pilot on an outbound leg (about 20° off the reciprocal of the desired
final approach path).
¾ This path is flown at a safe level above the airfield and the surrounding obstructions.
¾ The pilot times the outbound leg (allowing for wind effect and using the distances
given in the approach plate) and, using the QDM information supplied, establishes
the drift being experienced.
¾ At the end of the appropriate time, the pilot carries out a rate one turn to intercept the
inbound final approach path.
¾ On intercepting the final approach, the course is maintained by using the drift
established outbound (with the sign changed) as an inbound wind correction angle.
This can be adjusted as the controller provides new QDM information.
¾ At the prescribed time, the let-down commences.
On the next page is an example VDF chart for Cranfield. 2-3
Radio Navigation
Chapter 2 VHF Direction Finding
2-4 Radio Navigation
The words you are searching are inside this book. To get more targeted content, please make full-text search by clicking here.
Jeppesen-Radio-Navigation
Discover the best professional documents and content resources in AnyFlip Document Base.
Search