09_goh keng joo

8/8/2019 09_GOH KENG JOO

1/85

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.

2009


2/85

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.

i


3/85

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

ii


4/85

Navigation System:

VHF Omnidirectional Range

Distance Measurement Equipment

Automatic Direction Finder

Instrument Landing System (LOC, GS and MB)

Global Positioning System

iii


5/85

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

iv


6/85

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

v


7/85

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

vi


8/85

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

vii


9/85

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


10/85

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.

1


11/85


12/85

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

3


13/85

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.

4


14/85

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)

5


15/85

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.

6


16/85

Figure: 2

Figure: 3

7


17/85

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.

8


18/85

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.

9


19/85


20/85


21/85

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.

12


22/85


23/85


24/85

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

15


25/85

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.

16


26/85

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.

17


27/85


28/85

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).

19


29/85

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.

20


30/85

Figure: 11

21


31/85

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.

22


32/85


33/85

VOR TRANSMITTER BLOCK DIAGRAM

VOR RECEIVER BLOCK DIAGRAM

24


34/85

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,

25


35/85

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.

26


36/85

VOR Figure: 3

VOR Figure: 4

27


37/85

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.

28


38/85

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).

29


39/85

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.

30


40/85

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.

31


41/85

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

32


42/85

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

33


43/85

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

34


44/85

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

35


45/85

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

36


46/85


47/85


48/85

ADF Figure: 6

Magnetic Bearing = Magnetic Heading + Relative Bearing

39


49/85

ADF Figure: 7

ADF Figure: 8

40


50/85

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

41


51/85

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

42


52/85

43


53/85


54/85


55/85

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

46


56/85

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.

47


57/85

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.

48


58/85

Table 1 (Shared LOC/GS frequencies)

GS Figure: 2

49


59/85

3.4.3 Marker Beacons

MB Figure: 1

50


60/85

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

51


61/85

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.

52


62/85

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.

53


63/85

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.

54


64/85

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.

55


65/85

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.

56


66/85

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.

57


67/85


68/85


69/85

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

60


70/85


71/85

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

62


72/85

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

63


73/85

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

64


74/85

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

65


75/85

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

66


76/85

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

67


77/85


78/85

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

69


79/85


80/85

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

71


81/85

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

72


82/85


83/85

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

74


84/85


85/85

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

09_goh keng joo

Documents