09_goh keng joo
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Analysis on Avionics System Architecture and Navigation
Goh Keng Joo
School of Science and Technology
A thesis submitted to SIM University
in partial fulfillment of the requirements for the Degree of
Bachelor of Engineering.
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ACKNOWLEGEMENT
I would like to express my heartfelt gratitude to Mr. Chaganti and Toh Ser Khoon for his in-
valuable guidance and understanding over the entire course of my final year project.
They have always been patient and willing to spend time helping the students in their
understanding of the project.
I am also most grateful to all my friends who have been very supportive, and generous in
offering their help and advice.
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Abstract
Avionics and navigation products are not under the consumer product categories. Only who
are working in this field will have more chances to familiar with it. Thus, we are seldom heard
about our friend or relative talk about it.
In order to let more people understand about what are avionics products and how it function,
and how important to our life. My ultimately objective is to analysis avionics architecture and
navigation; then compile and summary all the related information, so that people will easily
understand.
In this project, I was able to complete MD-11 avionics architectures and navigation system as
below:
Architecture:
Auto Flight System (AFC)
AFS Actuator
Communication System
Entertainment System
Display System
Recording System
MD-11 Navigation System
MD-11 maintenance System
Generalized architecture for aircraft System Controller (ASC)
CNS/ATM
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Navigation System:
VHF Omnidirectional Range
Distance Measurement Equipment
Automatic Direction Finder
Instrument Landing System (LOC, GS and MB)
Global Positioning System
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ACKNOWLEDGEMENT i
ABSTRACT ii-iii
LIST OF FIGURES vii-viii
CHAPTER 1
INTRODUCTION1.1. Background Of Objective 1
1.2. Objective 1
1.3. Proposed approach and method to be employed 2
1.4. Project Plan 3
1.5. Planned Schedule 3
CHAPTER 2
INVESTIGATION OF PROJECT BACKGROUND
2.1. Introduction 4
2.2. Flight Controls (ATA 22-00 and 27-00) 5
2.3. Communication (ATA 23-00) 8
2.4. Entertainment System (23-00) 10
2.5. Display system (ATA 31-00) 11
2.6. Recording System (ATA 31-00) 13
2.7. Navigation System 14
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2.8. Maintenance System (ATA 45-00) 17
2.9. Aircraft Systems 19
2.10. CNS/ATM Architecture 20
CHAPTER 3
Navigation System
3.1. VHF Omnidirectional Range 22
3.1.1. Basic VOR principle 25
3.2. Distance Measuring Equipment (DME) 29
3.2.1. Basic DME principles 31
3.2.2. Distance calculation example 32
3.3. Automatic direction Finder (ADF) 33
3.3.1. ADF Receiver 35
3.3.2. Antenna 35
3.3.3. Control Box (Digital Readout Type) 37
3.3.4. Bearing Indicator 38
3.3.5. Automatic direction Finder (ADF) 41
3.4 Instrument Landing System (ILS) 44
3.4.1. Localizer (LOC) 45
3.4.1.1. Basic Localizer System Principles 45
3.4.2 Glideslope 47
3.4.2.1. Basic Glideslope Principles 47
3.4.3. Marker Beacons 50
3.4.3.1. Basic Marker Beacon Principles 51
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3.5. Global Positioning System (GPS) 53
3.5.1. Airplane Measures Time to Compute Distance to Satellite 54
3.5.2. Finding Position 55
3.5.3. GPS Receiver 56
CHAPTER 4
4.1. Conclusion 57
4.2. Recommendation and Future Work 58
REFERENCE 59
APPENDIX A
Acronyms 60-68
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List of Figures
Figure: 1 Avionics System 5
Figure: 2 Auto Flight System (AFS) Architecture 7
Figure: 3 AFS Actuator Architecture 7
Figure: 4 Communication System Architecture 9
Figure: 5 Antenna Layout 10
Figure: 6 Display System Architecture 12
Figure: 7 Recording System Architecture 13
Figure: 8 MD-11 Navigation System Architecture 15
Figure: 9 MD-11 Maintenance System Architecture 19
Figure: 10 Generalized Architecture for Aircraft System Controllers 19
Figure: 11 CNS/ATM Architecture 21
VOR Figure: 1 VHF Omnidirectional Range 22
VOR Figure: 2 The VOR and Cardinal radicals 25
VOR Figure: 3 CVOR ground station 27
VOR Figure: 4 Polar Diagram 27
DME Figure: 1 Distance Measuring Equipment 29ADF Figure: 1 Automatic Direction Finder 33
ADF Figure: 2 ADF external block diagram 34
ADF Figure: 3 Combined field of loop and sense antenna 36
ADF Figure: 4 ADF Control head 37
ADF Figure: 5 ADF Indicator 38
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viii
ADF Figure: 6 Reminders for some angle & directions 39
ADF Figure: 7 Relative Bearing Indicator (RBI) &
Relative Magnetic Indicator (RMI) 40
ADF Figure: 8 Radio Magnetic Indicator (RMI) 40
ADF Figure: 9 E-M Wave 41
ADF Figure: 10 Induced voltage Vs Relative Bearing angle 42
LOC Figure:1 Normal limit of localizer coverage 45
LOC Figure: 2 Localizer 46
GS Figure: 1 Radiation Pattern 47
GS Figure: 2 Glideslope 49
MB Figure: 1 Marker Beacon 50
GPS Figure: 1 Satellite Array 53
GPS Figure: 2 Time Difference between transmitter and receiver 54
GPS Figure: 3 Finding Position 55
GPS Figure: 4 GPS Receiver 56
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Chapter 1
Introduction
1.1 Project background
The objective of this project is to study analysis on avionics system architecture and
navigation. The outcome of this project may use as pedagogic material in aerospace
engineering. Hence, how to let this subject more interesting and easy understanding for
students or person who are interested are the tasks for me to achieve.
1.2 Objective:
In general, we all knew that since the airplane was created by human. It was shorter our
traveling time, booming the economic, closer human relationship and etc... These all
because of only navigation through the empty space would allow us having extreme speed
on our transport vehicle. In order to keep improving speed of aircraft again, we need to
educate more and more people to understand about the aircraft technologies and knowledge,
we hope that may be one day we finally having a vehicle is able to achieve light speed.
Now a day, people who understand about automobile technologies definitely is significantly
higher than aircraft, why? That is because automobile is more close to our life and easily to
get the information about the structure and control system on it.
Usually, when we talked about aircraft technologies, basically there are related to avionics
system and navigation; they are belonging to the complicated and sophisticated skills. This
may one of the reasons to stop us to proceed and challenge to study and do some
enhancement on aircraft design. Further more we have to consider about human life.
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1.4 Project Plan
Summary of project plan
1. Study and analysis The Avionics Handbook book by Cary R.Spitzer.
2. Select an avionics system for further analysis and studying.
3. Report writing by using Microsoft Office. Report includes charts, objective,
introduction, scope, methods, result and discussion and conclusion.
4. Oral presentation preparation.
1.5 Planned Schedule
2008 2009
No. Activities/Tasks
Start
Date
End
Date Aug Sep Oct Nov Dec Jan Feb Mar Apr May
1 Planning 28-Aug 13-Sep
2 Literature Search 3-Aug 31-Jan
3Study Guides/ ProjectMaterial 3-Aug 14-Sep
4 Meeting with Tutor 11-Aug 7-Jun
5
Write Initial Report
-TMA1 18-Aug 15-Sep
6
Gather all required
information from internet,
library, books and etc.
3-Aug 31-Jan
7
Selection of project
methods: Avionicssystem
18-Aug 15-Sep
8
Writing skeleton of
Final Report1-Dec 28-Feb
9
Writing, formatting and
finalizing contents of
Final Report
23-Mar 24-Apr
10
Make-Up Oral
Presentation22-May 28-May
11 Oral Presentation 30-May
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Chapter 2
INVESTIGATION OF PROJECT BACKGROUND
2.1 Introduction
There are many designs of airplane already in the market. Each design adopts different
avionics system. MD-11 model was chosen for investigating in this initial report, actually
it is a derivative of the DC-10 airplane, and is designed to be operated by a two-pilot crew.
The avionics system was represented the state of the art at the time of its introduction into
service in December 1990, almost twenty year the system was implemented or used. The
MD-11 flight deck, Figure 1 shown six identical 8-in. color CRT displays, which are used to
display flight instrument and aircraft systems information. A navigation system based on
triple Inertial Reference Systems (IRS) and dual Flight Management Systems (FMS) is
provided to automate lateral and vertical navigation. An Automatic Flight System (AFS)
based on dual Flight Control Computers (FCC) is also installed to provide full flight regime
autopilot and autothrottles, including fail-operational Category IIIb autoland capability.
Even though the hydraulic, electrical, environmental, and fuel systems also performed by
Aircraft System Controllers.
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Figure: 1
In commercial aviation, the various systems on an airplane are identified under chapter
numbers that are defined by the Air Transport Association (ATA). The architectures of each
of the systems (communication, navigation, displays, etc.) are discussed below under their
respective ATA chapters. Simplified schematic diagrams are provided where appropriate.
Note, ARINC 429 data buses have been simplified for illustration. Some of the data flows are
shown as a single bi-directional arrow only.
2.2 Flight Controls (ATA 22-00 and 27-00)
A dual-dual (four-channel) Auto Flight System (AFS) is installed on the MD-11 to provide
autopilot/autothrottle capabilities. The functions of the AFS include:
Flight Director (FD)
Automatic Throttle System (ATS)
Automatic Pilot (AP)
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Autoland (to Cat IIIb minima)
Yaw damper
Automatic stabilizer trim control
Stall warning
Wind shear protection (detection and guidance)
Elevator load feel
Flap limiter
Automatic ground spoilers
Altitude alerting
Longitudinal Stability Augmentation System (LSAS)
The AFS architecture shown in Figure 2 is built around the dual-dual Flight Control
Computers (FCC) and the Glareshield Control Panel (GCP). The AFS Control Panel is used
by the crew to reconfigure the system in the event of a failure. The dual-dual FCC architecture
is designed around the fail-operational Cat IIIb autoland requirement.
Each FCC has two independent computational lanes. Each of these lanes consists of a power
supply, two dissimilar microprocessors with dissimilar software and servo-electronics to
drive the actuators that move the aircrafts control surfaces. In fact this architecture is used for
the functions that require high integrity (e.g., autoland and LSAS). The system is designed to
allow the airplane to be dispatched with only one FCC operational, but not be able to perform
a Cat IIIb autoland.
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Figure: 2
Figure: 3
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Sometime we need to provide appropriate levels of redundancy in the interfaces to the
actuators for the flight control surfaces. We have to be considered:
Dispatch with one Flight Control Computer (FCC) or one lane inoperative.
Protection against both random and generic hardware and software failures/errors.
Minimize the probability of a multi-axis hardover.
Figure 3 shows how the elevator, aileron and rudder actuators interface to the various
channels of the FCC. The control surfaces are also interconnected mechanically, so driving
only one elevator, for example, will actually result in all elevator panels moving. Sufficient
control authority is retained in the event of loss of a single channel or even of a complete FCC.
2.3 Communications System (ATA 23-00)
The Communication System installed on the MD-11 is a highly integrated system. It includes
voice communication with the ground via VHF, HF, and SATCOM, as well as data link
communications using an optional Aircraft Communications Addressing and Reporting
System (ACARS) over the VHF radio, SATCOM, or HF data link (HFDL). The HF and VHF
radios are controlled by the Communication Radio Panels located in the pedestal on the flight
deck. Selective calling capability is provided by a SELCAL unit. The architecture is shown in
Figure 4. The basic features of this architecture, in terms of the communication facilities
provided, are dictated by Federal Aviation Regulations (FAR) Part 25, which mandate dual
independent communication facilities be provided throughout the flight.
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Figure: 4
The Audio Management Units (AMU) are provide flight and service interphone capabilities,
as well as supporting the aural alerts on the flight deck generated by the Central Aural
Warning System (CAWS), Traffic Alert and Collision Avoidance System (TCAS), and
Ground Proximity Warning System (GPWS). The Cockpit Voice Recorder (CVR) records all
transmissions by the pilots. Audio Control Panels are provided for all crew to control volume,
etc. Similarly, jack panels are provided for each crew members headset. SATCOM system
has provisions to allow this to be installed.
With all these communication systems, and the navigation systems described below, there is a
need for a very large number of antennas on the airplane, and the total installation has to be
designed to preclude interference between the different systems. The antenna layout on the
MD-11 is shown in Figure.5.
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Figure: 6
The architecture of the EIS is shown in Figure 6. Any Display Electronics Unit (DEU) can
support all six DUs, thus allowing the flight to continue in the event of loss of one or more
DUs, the system will automatically reconfigure to provide the appropriate displays according
to a fixed priority scheme. The lowest priority is accorded to the First Officers Navigation
Display (ND), and the highest priority to the Captains Primary Flight Display (PFD).
A standby display of air data (airspeed and altitude) and a standby attitude indicator are
provided on the main instrument panel. These are completely independent of the EIS, thus
providing an additional level of backup. These standby displays are mandated by Federal
Aviation Regulations (FAR).
On the MD-11 the Engine and Alert Display is part of the EIS. The DEUs thus contain all the
alerting logic for the airplane and drive the Master Caution and Warning indicators. They also
provide outputs to the Central Aural Warning System (CAWS) to generate voice alerts.
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Figure: 8
Ability to create flight plans, including airways, Standard Instrument Departures (SIDs), and
Standard Terminal Arrival Routings (STARs) by keyboard entry or data link.
Multi-sensor navigation using inertial reference data, together with inputs from GPS, DME,
VOR, and ILS.
Performance predictions for the complete flight plan, including altitude, speed, time of
arrival, and fuel state.
Guidance to the flight plan in three dimensions and controlling arrival time.
Take-off and approach speed generation.
Providing the VOR beam guidance mode.
On a long-range airplane, such as the MD-11, being able to dispatch the airplane when it is
several thousand miles from the airlines maintenance facility and one navigation system has
failed is very important to securing the bottom line for the operator. Such airplanes therefore
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usually have triple navigation systems. This capability to dispatch with a single failure is
provided on the MD-11 by having triple IRS (thus allowing for a failure in this system) and
having a standby navigation function provided in the Multipurpose Control/Display Units
(MCDU), thus allowing for an FMS failure.
The Inertial Reference System provides a good independent position solution for short-term
operation, or even for long-term operation within its capability of a drift of up to 2 nmi/h.
However to provide the accuracy necessary for the area navigation required in todays
airspace system or for terminal area operations, radio updating is necessary. This is provided
on the MD-11 by having dual VHF Omni-Range Receivers (VOR) and dual Distance
Measuring Equipment (DME) transceivers. Automatic Direction Finding (ADF) for flying
non precision approaches and Instrument Landing System (ILS) for precision approach and
landing are also provided. At the time that the MD-11 was designed, Microwave Landing
System (MLS) has provisions to be installed. Global Navigation Satellite Systems for
en-route operation and even in the future as a precision approach sensor are now the expected
future means of navigation, and the option to install this on the MD-11 is now available.
The antennas are not shown on the diagram, but one point that calls for a comment is that
because of the geometry of the MD-11, the glideslope antennas for the ILS, which are
installed in the radome, have to be replicated on the nose landing gear and the ILS must use
the gear-mounted antennas on final approach. This is to meet the FAA requirement to have
the antenna less than 19 ft above the wheels when crossing the runway threshold. The same
rule, obviously, applies to the equivalent MLS antennas.
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A dual air data system is also installed to provide airspeed, altitude, etc. for display to the crew
and as inputs for the other systems (AFS, FMS, etc.) that need such data. Selection of baro
reference is provided on the Glareshield Control Panel (GCP) which is part of the AFS (ATA
22-00) and is described there. There is an option to add a third air data system, in which case it
is configured as a hot spare with a separate switching unit.
Additionally, dual weather radar systems (with a single flat plate antenna) are provided,
together with radio altimeters, ATC transponders, and Traffic Alert and Collision Avoidance
System (TCAS). The weather radar is now available with the capability to detect wind shear
ahead of the airplane. TCAS is a requirement for U.S. operators and foreign operators flying
in U.S. airspace. All of this equipment is connected to the Centralized Fault Display System
(CFDS) to provide fault reporting on each of the units, although for clarity only the FMCU is
shown connected to the CFDIU in Figure 8.
2.8 Maintenance Systems (ATA 45-00)
The maintenance system on the MD-11 consists of two main elements, the Centralized Fault
Display System (CFDS) that is standard on the airplane, and the On-board Maintenance
Terminal (OMT) which is available as a customer option.
The CFDS consists of a Centralized Fault Display Interface Unit (CFDIU) and any of the
three MCDUs, with the capability to interface to all the major avionics subsystems on the
aircraft, using ARINC 604 protocols, as shown in Figure 9. The functions provided by the
CFDS are
A summary of Line Replaceable Units (LRUs) that have reported faults on the last flight.
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Figure: 9
2.9 Aircraft Systems
The general architecture for Aircraft System Controllers is shown in Figure 10.
Figure: 10
Automatic System Controllers (ASC) are provided for the primary systems as follows:
Environmental System Controller (ESC).
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Hydraulic System Controller (HSC).
Electrical Power Control Unit (EPCU).
Fuel System Controller (FSC) and Ancillary Fuel System Controller (AFSC).
Pneumatic System Controller, Air Conditioning Controllers, and Cabin Pressure Controllers
are also provided to control their respective subsystems.
2.10 CNS/ATM Architecture
One of the major changes affecting aircraft manufacturers and operators today is the need to
operate in the new Communication, Navigation, Surveillance/Air Traffic Management
(CNS/ATM) environment.
This began with the ICAO Committee on Future Air Navigation Systems (FANS). This
introduces a number of new CNS features in the airplane avionics systems:
Controller/Pilot Data Link Communications (CPDLC) to communicate with ATC.
Global Navigation Satellite System (GNSS) navigation.
Required Navigation Performance (RNP) certification.
Required Time of Arrival (RTA) navigation to control arrival times at waypoints.
Automatic Dependent Surveillance (ADS) to provide surveillance data to ATC and the
airline.
In the MD-11 CNS/ATM architecture, the FMC provides the computing resources for the new
functions, with the ACARS MU (or CMU) used as a communications link to the ground via
the SATCOM, VHF, and HF Data Link (HFDL) to the airline dispatch and ATC centers on
the ground. The architecture is shown in Figure 11.
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Figure: 11
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Chapter 3
Navigation System
3.1 VHF Omnidirectional Range (VOR)
VOR Figure: 1
One of the most common radio navigation aids for aviation is the VOR Very High
Frequency Omni-directional Range. The VOR ground station is oriented to magnetic north
and transmits azimuth information to the aircraft, providing 360 courses TO or FROM the
VOR station.
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VOR TRANSMITTER BLOCK DIAGRAM
VOR RECEIVER BLOCK DIAGRAM
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3.1.1 Basic VOR principles
VOR Figure: 2
The principle of operation is bearing measurement by phase comparison. This means that
the transmitter on the ground produces and transmits a signal, or actually two separate
signals, which make it possible for the receiver to determine its position in relation to the
ground station by comparing the phases of these two signals. In theory, the VOR produces a
number of tracks all originating at the transmitter. These tracks are called radials and are
numbered from 1 to 360, expressed in degrees, or . The 360 radial is the track leaving the
VOR station towards the Magnetic North, and if you continue with the cardinal points,
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radial 090 points to the East, the 180 radial to the South and the 270 radial to the West,
all in relation to the magnetic North. See VOR Figure: 2.
Before we look in detail at how the system works the following example illustrates the
principle and should make it easier to understand.
Think of a lighthouse at sea and imagine the white light rotating at a speed of one revolution
per minute (60 seconds). Every time this white narrow beam passes through Magnetic North,
a green omnidirectional light flashes. Omnidirectional means that it can be seen from any
position around the lighthouse. If we are situated somewhere in the vicinity of the light
sources and are able to see them, we can measure the time interval from the green light flash
until we see the white light. The elapsed time is directly proportional to our position line in
relation to the lighthouse.
The speed of 1 RPM corresponds to 6 per second, so if 30 seconds elapse between the time
we see the green flash and the white rotating light, we are on the 180 radial, or directly
south of the station (30 sec x 6/sec = 180). This calculation can be done from any position
and the elapsed time is directly proportional to our angular position (radial). We could name
these light signals, calling the green one the Reference (REF) signal and the white beam the
Variable (VAR) signal.
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VOR Figure: 3
VOR Figure: 4
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The ground equipment is set up on a fixed, surveyed site and consists of a transmitter
driving a combined aerial system; one part producing the Reference (REF) signal, the other
producing the Variable (VAR) signal. The REF signal is an omnidirectional continuous
wave transmission on the carrier frequency of that particular VOR station. It carries a 9960
Hz subcarrier that is frequency modulated at 30 Hz. Since this is an omnidirectional
transmission, the polar diagram of the REF signal is a circle.
In the receiver, it is the 30Hz component of this signal that is used as a reference for
measuring the phase difference. The variable signal (VAR) is transmitted from an aerial that
is effectively a loop. This loop produces a figure of 8 polar diagram, which is
electronically rotated at 30 revolutions per second. When the two signals (VAR & REF) are
mixed together, the resulting polar diagram will be a cardioid. We call it a limacon. It
rotates at 30 revolutions per second, indicated with an arrow on VOR Figure: 3 .
The rotation of the limacon creates an effective amplitude modulation of 30 Hz. The VOR
receiver splits these two signals into the two original components. The two signals are
processed through different channels and the phase of the 30 Hz modulations of the fixed
REF signal and the VAR signal are compared in a phase comparator. The phase difference
between these two signals is directly proportional to angular position with reference to the
VOR station.
As explained, magnetic North is the normal reference for the radials, so when 0 phase
difference is detected, the receiver is on the 360 radial from the station. VOR Figure: 4
shows the phase difference and variable signal at the cardinal points.
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3.2 Distance Measuring Equipment (DME)
DME Figure: 1
Distance Measuring Equipment, DME, is a ground-based radio navigation aid that allows
several aircraft to simultaneously measure their distance from a ground reference (DME
transponder). The distance is determined by measuring the propagation delay of a radio
frequency (RF) pulse that is emitted by the aircraft transmitter and returned at a different
frequency by the ground station.
The DME can provide distance to a runway when the DME is collocated with an instrument
landing system (ILS) station. En route distance information is provided when a DME is
collocated with a very-high-frequency omnidirectional radio range (VOR).
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The DME frequency is paired to the VOR frequency. A DME interrogator automatically
tunes the corresponding frequency when the associated VOR is selected. Since the VOR
tells us the radial and the DME gives the distance, we can determine our position from
just one VOR/DME pair.
DME distance is the actual distance from the aircraft to the station, not the distance along
the ground. For example, an aircraft 5280 feet directly above a DME station. The aircraft is
a mile away, just a mile straight up.
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3.2.1 Basic DME principles
DME equipped aircraft transmit encoded interrogating RF pulse pairs on the beacon's
receiving channel. The beacon replies with encoded pulse pairs on the airborne equipments
receiving channel, which is 63 MHz apart from the beacons channel.
The interval between the interrogation emission and the reply reception provides the aircraft
with the real distance information from the ground station; this information displays on the
cockpit indicator.
The ground transponder can answer 100 to 200 interrogators at a time; i.e., 2700 to 4800
pulse pairs per second (PPPS). It generates random pulse pairs (squitter) to maintain a
minimum pulse repetition frequency (PRF) of about 800 whenever the number of decoded
interrogations is lower than this range. Older DME ground equipment are typically limited
to 100 interrogators at a time (2700 PPPS), newer equipment can handle over 200.
The aircrafts receiver receives and decodes the transponders reply. Then it measures the
lapse between the interrogation and reply and converts this measurement into electrical
output signals. The beacon introduces a fixed delay, called the reply delay, between the
reception of each encoded interrogating pulse pair and the transmission of the corresponding
reply.
The transponder periodically transmits special identification pulse groups that are
interwoven with the reply and squitter pulses; the aircraft decodes these special pulses as
Morse tones keyed with the beacon code identification.
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The aircrafts receiver uses a stroboscopic technique to recognize the replies to its own
interrogations among the many other pulses transmitted by the beacon.
The DME theory of operation is summarized below.
3.2.2 Distance calculation example
A radio pulse takes around 12.36 microseconds to travel one nautical mile (1.9
km) to and from, this is also referred to as a radar-mile. The time difference
between interrogation and reply minus the 50 microsecond ground transponder
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delay is measured by the interrogator's timing circuitry and translated into
a distance measurement in nautical miles which is then displayed in the cockpit.
3.3 Automatic Direction Finder (ADF)
ADF Figure: 1
Onboard the aircraft, the Automatic Direction Finder, or ADF, detects the non-directional
beacons (NDB) signal. The NDB is a ground-based radio transmitter that transmits radio
energy in all directions.
The ADF determines the direction to the NDB station relative to the aircraft. This can be
displayed on a relative bearing indicator. The relative bearing indicator looks like a compass
card with a needle superimposed, except that the card is fixed with the 0 degree position
corresponding to the centerline of the aircraft. To track toward an NDB the aircraft is flown
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so that the needle points to the 0 position, the aircraft will then fly directly to the NDB.
ADF external block diagram
ADF Figure: 2
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3.3.1 ADF Receiver : pilot can tune the station desired and to select the mode of operation.
The signal is received, amplified, and converted to audible voice or Morse code
transmission and powers the bearing indicator. See below ADF Diagram: 1 .
ADF Diagram: 1
3.3.2 Antenna : The aircraft consist of two antennas. The two antennas are called LOOP
antenna and SENSE antenna. The ADF receives signals on both loop and sense antennas.
The loop antenna in common use today is a small flat antenna without moving parts. Within
the antenna are several coils spaced at various angles. The loop antenna sense the direction
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of the station by the strength of the signal on each coil but cannot determine whether the
bearing is TO or FROM the station. The sense antenna provides this latter information.
ADF Figure: 3
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ADF Figure: 6
Magnetic Bearing = Magnetic Heading + Relative Bearing
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ADF Figure: 7
ADF Figure: 8
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3.3.5 BASIC ADF PRINCIPLES
In order to fully understand the operation of an automatic direction finder (ADF) system, it
is advantageous to first examine the radio wave which induces the signals in an ADF
antenna system.
A radio wave consists of two electromagnetic field components; an electric field (E) and a
magnetic field (H). These fields are perpendicular in space and their amplitudes vary
sinusoidally with time. A simplified illustration of a plane electromagnetic wave is shown in
ADF Figure: 9. E-M WAVE.
ADF Figure: 4
Stations which broadcast in the ADF band (190 kHz - 1799 kHz) transmit vertically
polarized radio waves, meaning that the E field is vertical in space, while the H field is
horizontal. It is the magnetic field of the radio wave which induces voltages in the loop
windings of the ADF antenna.
The loop antenna consists of two mutually perpendicular windings on a square ferrite core.
The high magnetic permeability of the ferrite core serves to concentrate the magnetic field
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through the loops and increase the induced signal. The voltages that are induced in the loop
windings lag the H field by 90 due to their inductive nature. The axis of one winding is
aligned with the longitudinal axis of the aircraft, and the voltage in it is proportional to the
sine of the angle between the nose of the aircraft and the station, an angle known as the
relative bearing. The other winding axis is parallel to the lateral axis of the aircraft, and a
voltage proportional to the cosine of the relative bearing is induced in it. ADF Figure: 10
INDUCED VOLTAGES VS RELATIVE BEARING ANGLE illustrates the relationship of
the two induced voltages as the relative bearing changes through 360.
ADF Figure: 10
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modulating signals. The pattern to the left of the runway (in normal approach) is 90Hz
amplitude modulated while the pattern to the right is 150Hz amplitude modulated.
The ratio of 90Hz to 150Hz audio, after demodulation, is dependent only upon the position
of the aircraft within the patterns. The patterns are adjusted so they are of equal strength on
a vertical plane extending out from the runway centerline. When the aircraft is on this plane,
the 90Hz and 150Hz voltages will be equal.
LOC Figure: 2
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3.4.2 Glideslope
GS Figure: 1
Glideslope is the vertical path the descent path to the runway. The Glideslope Indicator
tells us if our vertical path is on target for touchdown at the correct spot on the runway, or if
we are too high or too low. If we are too high, well land long, and there may not be enough
runway to stop safely. If were too low, were in danger of touching down before the
runway.
3.4.2.1 BASIC GLIDESLOPE PRINCIPLES
The glide slope provides the pilot with vertical guidance. This signal gives the pilot
information on the horizontal needle of the CDI to allow the aircraft to descend at the proper
angle to the runway touchdown point. The glide slope radiates on a carrier frequency
between 329 and 335 MHz and is also modulated with 90 Hz and 150 Hz tones. The glide
slope frequencies are paired with the localizer, meaning the pilot has to tune only one
receiver control.
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The radiation patterns of a typical glide slope system are similar to those of the Localizer - if
you remember to rotate the pattern so that it is vertical instead of horizontal . The null in the
sideband-only (SBO) signal produces essentially a straight glide path angle for the aircraft.
The patterns are arranged so that 90 Hz modulation predominates above the glide path and
the 150 Hz modulation predominates below.
The glide path angle is normally referenced at 3 degrees. If the aircraft is on this
three-degree glide path, equal amounts of the 90 Hz and 150 Hz are received and the CDI
will be centered. If the aircraft is above the glide path, the 90 Hz modulation exceeds that of
the 150 Hz and produces a deflection on the CDI downwards. If the aircraft is below the
established glide path, the 150 Hz modulation predominates and produces a similar but
opposite deflection. This deflection corresponds to the direction the pilot must fly to
intercept the glide path and is proportional to the angular displacement from the glide path
angle. As with the localizer, the full scale deflection is 150 microamperes. Typically, the
glide slope sensitivity is set so that the full-scale indications occur at approximately 2.3 and
3.7 degrees elevation. See GS Figure: 2.
There are 40 glideslope frequencies in use today with a channel separation of 150KHz and
each of these is paired with a localizer frequency as shown in TABLE 1 SHARED LOC/GS
FREQUENCIES.
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Table 1 (Shared LOC/GS frequencies)
GS Figure: 2
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3.4.3 Marker Beacons
MB Figure: 1
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The three marker beacons tell the pilot how is the distance of aircraft is from the runway
threshold. They will give audio signals to the pilot to indicate the aircraft is approaching the
runway. The Outer Marker is about 4.0 NM from the runway threshold. It provides height,
distance and equipment checks to aircraft on final approach. The Middle Marker is about 0.6
NM from the runway. It indicates that visual contact with the runway is forthcoming. The
Inner Marker lets us know that we are close to arrive at the runway threshold.
3.4.3.1 BASIC MARKER BEACON PRINCIPLES
Marker Beacon receivers are used to provide accurate fixes by informing the pilot of his
passage over beacon stations located on airways and ILS approach courses. Three types of
beacons are used. They are the outer marker, middle marker, and inner marker. The three
markers are used in conjunction with radio instrument landing systems. The markers are all
transmitted at a frequency of 75MHz using three different frequencies of AM modulation.
The outer marker is normally positioned on the front localizer course near the point where
the glideslope approach path intersects the minimum inbound altitude after the procedure
turn. Distance from the airport will vary from 4 to 7 miles. Radio frequency from the outer
marker is projected vertically in an elliptical cone shaped pattern. The outer marker signal is
modulated at 400Hz: and is keyed to emit dashes at a rate of two per second. When passing
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the outer marker, the blue light flashes "on/off" at a two per second rate and the pilot hears a
series of low tone dashes.
The middle marker is normally located on the front localizer course about 3200 feet from
the approach end of the ILS runway. The radiated pattern is similar in shape and power to
the outer marker. The middle marker signal is modulated with 1300Hz and the modulation
is keyed to identify by alternate dots and dashes. When the equipped aircraft passes the
middle marker the pilot hears a medium pitched tone in a series of dots and dashes and the
amber light flashes synchronously with the tones.
The inner marker is located close to the end of the runway. Radio frequency from the inner
marker is projected in a vertical cone shaped pattern. The inner marker signal is modulated
at 3000Hz and is keyed to emit dots at a rate of six per second. When passing the inner
marker, the white light flashes "on/off" at a six per second rate and the pilot hears a series of
high tone dots. The inner marker is used to indicate a point approximately 1500 feet from
the runway and if on a proper glide path the altitude above the runway should be
approximately 100 feet.
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3.5 Global positioning system (GPS )
GPS Figure: 1
The most modern and accurate navigation system is a constellation of 24 satellites (21 active
and 3 spare) orbiting the earth - the Global Positioning System. The satellites circle the
Earth twice a day at an altitude of 11,000 miles. Over most of the earth, at least five or more
satellites are always available for navigation at any time.
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GPS Figure: 2
3.5.1 Airplane Measures Time to Compute Distance to Satellite
1) The signal from the satellite is transmitted as a pulse code. Each satellite sends a unique
identification, as represented by red, green and blue pulses.
2) The receiver in the airplane already knows the code patterns sent by every satellite. It
searches until it locates a satellite signal that matches a stored pattern. The satellite message
also tells the receiver the time the signal was transmitted. By comparing this time with the
time of arrival at the receiver, a time difference is calculated. This is multiplied by the speed
of light and the answer is distance.
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GPS Figure: 3
3.5.2 Finding Position
When only one signal is received, the airplane may be located anywhere on the surface of a
sphere (or bubble), with the satellite (SV1) at its center. After receiving a second satellite
(SV2) the spheres intersect and narrow the position is further refined. It takes a fourth
satellite to obtain latitude, longitude and altitude, which is a 3-dimensional fix.
Receiving a fourth satellite is required for correcting the clock in the GPS receiver. That
enables a low-cost clock to keep sufficiently accurate time for the distance-solving problem.
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3.5.3 GPS Receiver
GPS Figure: 4
By using the information encoded in the satellite radio signals, GPS receivers able to
calculate their current position - latitude, longitude, and elevation - and the precise time.
This information will use by many systems onboard the aircraft, including the FMS the
Flight Management System.
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Chapter 4
4.1 Conclusion
In this final year project, the requirement is doing analysis on avionics architecture and
navigation system; and I had been studied the MD-11 avionics architectures. By studying
those architectures, my knowledge really gained a lot. Although that is only one of the flight
I able to completely go through, that is more than enough for me to do research through the
year. On the other hand, Im also learned how to plan and proceed a project without over the
due date.
Actually, that is because the limitation of time and budget, what I can provide for this
project is just basic principle theory for each type of navigation product that I was explained
at the accordingly chapter.
Anywhere, Im proud to say that studying my project; it is good enough for beginners in
aerospace engineering.
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Appendix A
Acronyms
AC advisory circular
ACARS aircraft communications addressing and reporting system
ACAS airborne collision avoidance system
AD airworthiness directive
ADF automatic direction finder
ADS automatic dependent surveillance
ADS-B automatic dependent surveillance-broadcast
AER approach end of runway
AFCS automatic flight control system
A/FD airport/facility directory
AFM airplane flight manual or aircraft flight manual
AFSS Automated Flight Service Station
AGL above ground level
AIM aeronautical information manual
AIP aeronautical information publication
AIS airmens information system
ALAR approach and landing accident reduction
AMASS airport movement area safety system [delete term]
ANP actual navigation performance
ANR advanced navigation route
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ATC-TFM air traffic control traffic flow management
ATCT airport traffic control tower
ATD along-track distance
ATIS automatic terminal information service
ATM air traffic management
ATS air traffic service
ATT attitude retention system
AVN Office of Aviation System Standards
AWOS automated weather observing system
AWSS automated weather sensor system
Baro-VNAV barometric vertical navigation
BRITE bright radar indicator tower equipment
B-RNAV European Basic RNAV
CAA Civil Aeronautics Administration
CAASD Center for Advanced Aviation Systems Development
CARF central altitude reservation function
CAT category
CDI course deviation indicator
CDM collaborative decision making
CDTI cockpit display of traffic information
CDU control display unit C-2
CENRAP Center Radar ARTS Processing
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CFIT controlled flight into terrain
CFR Code of Federal Regulations
CGD combined graphic display
CIP Capital Investment Plan
CNF computer navigation fix
CNS communication, navigation, and surveillance
COP changeover point
COTS commercial off the shelf
CPDLC controller pilot data link communications
CRC cyclic redundancy check
CRCT collaborative routing coordination tool
CRM crewmember resource management
CRT cathode-ray tube
CTAF common traffic advisory frequency
CTD controlled time of departure
CVFP charted visual flight procedure
DA density altitude, decision altitude
D-ATIS digital automatic terminal information service
DACS digital aeronautical chart supplement
DBRITE digital bright radar indicator tower equipment
DER departure end of the runway
DH decision height
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DME distance measuring equipment
DOD Department of Defense
DOT Department of Transportation
DPs departure procedures
DSR display system replacement
DRVSM domestic reduced vertical separation minimums
DUATS direct user access terminal system
DVA diverse vector area
EDCT expect departure clearance time
EFB electronic flight bag
EFC expect further clearance
EFIS electronic flight information system
EGPWS enhanced ground proximity warning systems
EICAS Engine indicating and crew alerting system
EMS emergency medical service
EPE estimated position error
ER-OPS extended range operations
ETA estimated time of arrival
EWINS enhanced weather information system
FAA Federal Aviation Administration
FAF final approach fix
FAP final approach point
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FATO Final Approach and Takeoff Area
FB fly-by
FBWP fly-by waypoint
FD winds and temperatures aloft forecast
FD flight director
FDC NOTAM Flight Data Center Notice to Airmen
FDP flight data processing
FIR flight information region
FIS flight information system
FIS-B flight information service broadcast
FISDL flight information services data link
FL flight level
FMC flight management computer
FMS flight management system
FO fly-over
FOM flight operations manual
FOWP fly-over waypoint
FPM feet per minute
FSDO Flight Standards District Office
FSS Flight Service Station
FTE flight technical error
GA general aviation
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GAMA General Aviation Manufacturers Association
GBT ground-based transmitter
GCA ground controlled approach
GCO ground communication outlet
GDP ground delay programs
GDPE ground delay program enhancements
GLS Global Navigation Satellite System Landing System
GNE gross navigation error
GNSS Global Navigation Satellite System
GPS Global Positioning System
GPWS ground proximity warning system
G/S glide slope
GS groundspeed
GWS graphical weather service
HAA height above airport
HAR High Altitude Redesign
HAT height above touchdown
HDD head-down display
HEMS helicopter emergency medical service
HF high frequency
HFDL high frequency data link
HGS head-up guidance system
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HITS highway in the sky
HOCSR host/oceanic computer C-3 system replacement
HSI horizontal situation indicator
HSAC Helicopter Safety Advisory Council
HUD head-up display
IAF initial approach fix
IAP instrument approach procedure
IAS indicated air speed
ICA initial climb area
ICAO International Civil Aviation Organization
IF intermediate fix
IFR instrument flight rules
ILS instrument landing system
IMC instrument meteorological conditions
INS inertial navigation system
IOC initial operational capability
IPV instrument procedure with vertical guidance (this term has been renamed APV)
IRU Inertial Reference Unit
KIAS knots indicated airspeed
LAAS Local Area Augmentation System
LAHSO land and hold short operations
LDA localizer type directional aid, landing distance available
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MIA minimum IFR altitude
MIT miles-in-trail [delete term]
MLS microwave landing system
MNPS minimum navigation performance specifications
MOA military operations area
MOCA minimum obstruction clearance altitude
MOPS minimum operational performance standards
MORA minimum off route altitude
MRA minimum reception altitude
MSA minimum safe altitude
MSAW minimum safe altitude warning
MSL mean sea level
MTA minimum turning altitude
MVA minimum vectoring altitude
NA not authorized
NACO National Aeronautical Charting Office
NAR National Airspace Redesign
NAS National Airspace System
NASA National Aeronautics and Space Administration
NASSI National Airspace System status information
NAT North Atlantic
NATCA National Air Traffic Controllers Association
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NTAP Notice to Airmen Publication
NTSB National Transportation Safety Board
NTZ no transgression zone C-4
NWS National Weather Service
OCS obstacle clearance surface
ODP obstacle departure procedure
OEP Operational Evolution Plan
OpsSpecs operations specifications
OROCA off-route obstruction clearance altitude
PA precision approach
PAR precision approach radar
PARC performance-based operations aviation rulemaking committee
PCG positive course guidance
PDC pre-departure clearance
PDR preferential departure route
PF pilot flying
PFD primary flight display
pFAST passive final approach spacing tool
PIC pilot in command
PinS Point-in-Space
PIREP pilot weather report
PM pilot monitoring
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POH pilots operating handbook
POI principle operations inspector
PRM precision runway monitor
P-RNAV European Precision RNAV
PT procedure turn
PTP point-to-point
QFE transition height
QNE transition level
QNH transition altitude
RA resolution advisory, radio altitude
RAIM receiver autonomous integrity monitoring
RCO remote communications outlet
STAR standard terminal arrival
STARS standard terminal automation replacement system
STC supplemental type certificate
STMP special traffic management program
SUA special use airspace
SUA/ISE special use airspace/in-flight service enhancement
SVFR special visual flight rules
SWAP severe weather avoidance plan
TA traffic advisory
TAA terminal arrival area
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RJ regional jet
RNAV area navigation
RNP required navigation performance
ROC required obstacle clearance
RSP runway safety program
RVR runway visual range
RVSM reduced vertical separation minimums
RVV runway visibility value
RWY runway
SAAAR Special Aircraft and Aircrew Authorization Required
SAAR special aircraft and aircrew requirements
SAMS special use airspace management system
SAS stability augmentation system
SATNAV satellite navigation
SDF simplified directional facility
SER start end of runway
SIAP standard instrument approach procedure
SID standard instrument departure
SIGMET significant meteorological information
SM statute mile
SMA surface movement advisor
SMGCS surface movement guidance and control system
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VLJ very light jet
VMC visual meteorological conditions
VMINI minimum speedIFR.
VNAV vertical navigation
VNEI never exceed speed-IFR.
VOR very high frequency omnidirectional range
VORTAC very high frequency omnidirectional range/tactical air navigation
VPA vertical path angle
VREF reference landing speed
VSO stalling speed or the minimum steady flight speed in the landing configuration
WAAS Wide Area Augmentation System
WAC World Aeronautical Chart
WP waypoint