Avionics Systems and Software part 1. Avionics Systems and Software * AVIONICS : An Embedded System * Avionics-Functionality * Major Components of Avionics

Avionics Systems and Software

part 1

Avionics Systems and Software

* AVIONICS : An Embedded System

* Avionics-Functionality

* Major Components of Avionics Systems

* Avionics Architecture

* Avionics Mission Functions

AVIONICS : An Embedded System

Avionics is an embedded part of a larger System-

-Flight System- comprising

* Aircraft

* Pilot/s

* Atmosphere

* Environment

** Air Traffic and Guidance Control

** External Sensors, Satellites,etc

** Enemy targets

AVIONICS : An Embedded System

Relationships with various parts

* Aircraft : Avionics is a part of the aircraft

* Pilot/s : Interact with Avionics Systems

* Atmosphere : Avionics measures atmospheric

parameters

* Environment : Transmits and receives data and

voice, releases weapons,etc

Role Of Avionics Systems

In a modern aircraft, Avionics enables a pilot to :

* Fly the aircraft (vehicle control or flight control system)

* Perform the operational role of the aircraft

** Transportation of passengers safely from one

place to another ( Commercial aircraft)

** perform various mission functions

*** Navigation

*** Release of missiles/bombs

Avionics- an embedded system

* Receives inputs

* Computes

* Generates outputs

Avionics- an embedded system

Receives inputs from :

* Rest of the aircraft : aircraft fuel, electrical,hydraulic

weapons status, etc

* Pilot/s : controls and switches

* Atmosphere : air data

* Environment : through data links, voice from ATC,etc

Avionics-an embedded system

* Computes required parameters for navigation and fire

control :

** Navigation algorithms:Guidance to steer point,

desired track ,etc

** Fire Control algorithms: weapon aiming,missile

launch,etc


* Outputs computed results to :

** Displays:

*** Basic flight , steering and navigation

parameters

*** Weapon aiming, missile launch symbologies

*** Sensor outputs

*** Failures and warnings


* Outputs computed results to :( continued)

** Audio System: Avionics status and warnings

** Weapons

* Outputs control weapon launch and firing

* Outputs control/coordinate/manage sensors

optimally

Avionics-Functionality

As an embedded system, Avionics must perform the following major functions :

* Basic Flight and Steering

* Navigation guidance including inertial , radio and

satellite navigation

** Inertial navigation Systems (INS)

** Radio Navigation Aids (TACAN, VOR)

** Satellite Navigation (GPS)

** Hybrid INS + GPS

Avionics-Functionality(continued)

* Communications : voice and data

** HF, VHF, UHF

* Identification : Friend or Foe

** IFF

* Landing Aids : ILS (Instrument Landing System)

* Passenger Entertainment

* Autopilot


* System Crew dialogue

** Cockpit Controls and inputs management

** Multifunction Displays

** Symbology Generation

** Display management

** Warnings management

* Failure management and reconfiguration


* Integrated Maintenance

** In Flight

** On Ground Supplementary

* Electronics warfare: ECM, ECCM

* Sensors :

** Electromagnetic Radars : Fire Control,

Weather, Terrain following /avoidance

** FLIR:Forward Looking Infrared Radar


* Sensors ( continued):

** LDP : Laser Designation Pods

** Air Data

** Radio Altimeter

** Collision avoidance ( TCAS)

* Operational Data Insertion and Retrieval

* Flight Control System (for Fly by Wire Aircraft)


* Flight Control System (for Fly by Wire Aircraft)

* Fire Control algorithms : Air to Air, Air to Ground,

Air to Sea

* Weapon Release Systems : Missiles, Smart and dumb

bombs, Guns

** Weapon selection and prepartion

** Launch/fire sequencing

Major Components of Avionics Systems

* Cockpit Area

** Pilot’s stick or Control column and switches

on it

** Throttle and switches on it

** Switches of all kinds on side console and Instrument panel,etc

** Up Front control Panel( on fighters only)

and small LCD display

Flight Instruments: Multi Function Displays

Major Components of Avionics Systems(continued)

* Cockpit Area

** Flight Management or Navigation

control panel and small LCD display

** Many Conventional Flight Instruments:

*** Pressure Altimeter

*** Rate of Climb Indicator(ROCI)

or Vertical Speed Indicator(VSI)

*** Artificial Horizon( gyroscopic)

MULTIFUNCTION PROCESSOR UNIT (MPU):The multifunction processor unit provides sensor input processing and switching and the necessary deflection and video signals for the multifunction display. The MPU can provide the deflection and video signals to the PFD and ND displays in the event of failures to either or both display processor units.


* Cockpit Area

**Conventional Flight Instruments(continued):

*** Pressure Altimeter

*** Rate of Climb Indicator(ROCI)

or Vertical Speed Indicator(VSI)

*** Artificial Horizon( gyroscopic)

*** Air Speed Indicator (ASI)

*** Angle of Attack Indicator


* Cockpit Area

**Conventional Flight Instruments(continued):

*** Various temperature gauges

*** Various Engine/s gauges

*** Central Warning Panel

*** Magnetic Compass

*** Gyro Compass


* Cockpit Area

** Electronic Display Systems

*** Heads Up Display ( HUD)--Fighters only

Symbology is displayed to the pilot on a transparent glass screen in front of him.

The pilot uses this symbology (focussed at infinity) as well as outside scenario to fly the aircraft

Typical field of view of a HUD is

about 20 degrees by 20 degrees

Flight Instruments: Head Up Display

F16 HUD


HUD Image


F22 HUD front


Example: Solid State Attitude sensing system that provides 3 axis angular rate information to the computer. This data generates an attitude display in the form of a Vertical Situation Indicator,VSI that eventually displays all flight perameters, like shown on the right.


Aircraft Symbology superimposed on horizon


*** Heads Up Display ( HUD)--Fighters only

# Type of Symbology displayed( monochrome)

## Basic flight and steering

## Navigation guidance

## ILS during Approach for landing

## Weapon release cues

## Warnings and safety cues



*** Color Multifunction Displays( MFD’s)

# Numbers vary from 2 to 8 in different aircraft

# Size varies from 5 x 5 to 8 x 8 ( inches)

# Technology :CRT or Active Matrix LCD

# Scanning : Raster, Cursive or both

# Smart or dumb MFD

# Display is organised in terms of pages

# Page selection by pilot through controls

on MFDs or event driven

Flight Instruments: Multi Function Displays

Multifunction Display Units

Flight Instruments: Multi Function DisplaysSome other Displays shown on MFDs:

3 D Terrrain Map Flight Chart

Engine Monitoring parameters

Engine rpm display

Flight Instruments: Multi Function DisplaysSome of the Displays shown on MFDs:

MULTI-FUNCTION DISPLAY MX20

GPS moving map for precision navigation.

Flight Instruments: Miscellaneous InstrumentsAs mentioned earlier, only precipitation (or objects more dense than water such as earth or solid structures) will be displayed on the indicator. The best radar reflectors are raindrops and wet hail. The larger the raindrop, the better it reflects. Because large drops in a concentrated area are characteristic of a thunderstorm, the radar displays the storm as a strong echo. Generally, ice, dry snow and dry hail have low reflective levels and often will not be displayed by the radar.

Color radars show intensity of echoes by using colors, usually red or magenta as the most severe (see Weather Radar Display figure, below right). Monochrome radars use the brightness of the display to indicate intensity.

Extreme weather can usually be identified by characteristic patterns: (1) fingers and protrusions; (2) hooks; (3) scalloped edges; and (4) U-shaped cloud edges.



# Some of the pages are :

For Basic flight and Steering and

Navigation guidance

## Attitude Director Indicator (ADI or SI)

## Horizontal Situation Indicator (HSI )

These are also referred to as Electronics

Flight Instrument System(EFIS)

Flight Instruments: Flight Director Systems

F. ELECTRONIC FLIGHT INSTRUMENT SYSTEM (EFIS)EFIS refers to a system where conventional electro-mechanical flight instruments have been replaced by cathode ray tubes (CRT). These CRTs electronically display flight information in much the same presentation as electro-mechanical instruments bur they also have the flexibility for selecting additional information to be added to the display and for altering the presentation.

The two most commonly used EFIS instruments are the electronic horizontal situation indicator (EHSI) and the electronic attitude director indicator (EADI) (see EFIS Primary Flight Display figure, right, and EFIS Navigation Display figure, next slide).


F. ELECTRONIC FLIGHT INSTRUMENT SYSTEM (EFIS)These can also be called an ND (Navigation Display) or a PFD (Primary Flight Display). The system may also include a multifunctional display (MFD) on a larger CRT which can provide expanded displays of HSI, radar, and navigation data from flight instruments and can include other data such as checklists, emergency procedures, etc. Data from various sources can be integrated into various combinations of displays depending on the equipment installed.



# Some of the pages are for(continued) :

## Engine parameters

## Hydraulic System status

## Electrical System status

## Flight Control System status

## Flight Plans

## Ground Maps



# Some of the pages are for(continued) :

## Radar displays(many pages)

## Optical and other sensor displays

## Weapon System status

## Maintenance

## Warnings and ‘what to do ‘ Instructions


* Navigation Systems

** Inertial Navigation System(INS)

Self contained Navigation. Does not require any

external reference once INS is ‘ aligned ‘ on the

ground with current Latitude , Longitude

as inputs.

# Platform based or # Strapdown

# Dry Tuned Gyros or Ring Laser Gyros(RLG)


An INS consists of:

# Accelerometers triad:determines acceleration

along triad axis

# Gyroscopes which determine/maintain the

direction of these accelerations along desired

coordinates/axes


An INS consists of:(continued)

# Computer: Integrates acceleration to obtain

velocity and distance traveled(current position)

* Reference Axis/Frame : local vertical

# True North, East, Vertical



In a Platform INS( gyros and accelerometers

are kept on a Stabilised Platform )

* Alignment consists of:

# Bringing the ‘ Stabilised Platform’ horizontal

to the Earth’s surface

# Bringing ‘ X ‘ accelerometer to point towards True North



Alignment is done by the INS computer

After Alignment, INS computer continuously

maintains this Stabilised Platform configuration

even as the aircraft

moves over the surface of the Earth



**In a Strapdown INS

# Accelerometers are mounted directed on the

aircraft body and the accelerometer axes are

fixed with respect to the aircraft axes.

# Gyros(RLG) continuously determine the

aircraft attitude( pitch, Yaw , Roll) with respect to

the local vertical



**In a Strapdown INS ,the computer takes as input :

# Accelerations in body coordinates( aircraft

longitudinal, lateral, and vertical axex)

# Aircraft attitudes( pitch , Yaw , Roll )

with respect to local vertical from RLG

# and computes accelerations and then velocities

and current position in terms of local vertical axes



**In a Strapdown INS , alignment consists of

determining the aircraft axes with respect to the local

vertical



# Major outputs of an INS

## Current Position( Lat, Long , Baro-inertial Alt)

Baro-Inertial Alt : combination of Barometric

and Inertial altitude

## Aircraft Body rates or velocities

## Aircraft Body accelerations

## Aircraft Pitch, Heading and Roll



# Major outputs of an INS

## Aircraft current Velocities( Ve, Vn, Vd)

## Ground Speed

## Aircraft Track( or Ground Track)

## Aircraft Heading



# Typical Position Accuacy ;

0.5 - 1.0 Nautical mile / hour

# INS suffers from gyro drift and position and

velocity accuracy degrades with time

# Hybrid INS + GPS


** Attitude and Heading Reference System(AHRS)

# provides Attitude and Heading Reference to be displayed to the pilot

# Consists of set of Gyroscopes and a Compass


* Radio Navigation Aids

** Tactical Air Navigation ( TACAN)

# secondary radar ( 960-1215 MHZ)

# Provides Range and bearing to a TACAN station

** VHF OMNI Range ( VOR)

# provides bearing to a VOR station

# 108 -136 MHZ


* Identification Friend or Foe ( IFF)

# Secondary Radar ( L Band)

# 3 main modes

# Transmit identification code when interrogated

by a ground station(radar)

Also transmits aircraft air data to ground station


* Instrument Landing System ( ILS)

# Aid to approach and Landing

# Consists of

## Localiser( 108-110 MHZ) which provides

info on deviation from runway center line

## Glide Slope unit ( 335-339 MHZ) which

provides info on deviation from desired angle

of descent( generally between 2 - 4 degrees)


* Instrument Landing System ( ILS)

# Aid to approach and Landing

# Consists of

## Marker Beacons( Inner, Middle, Outer ) 75 MHZ

These beacons help the pilot check his position in

in approach path as he flies over the beacons


* Communication Systems

# HF for long Range

# VHF / UHF line of sight ( main and stby)

** need for several channel : eg.

## Air Traffic Control

## Interception/Recovery

## Various Air Route Surveillance Radars

## Emergency

## GCA


* Autopilot

** Relieves Pilot of tedium , particularly during long

flights.

# Main modes

## Heading hold ## Heading Select / Acquire

## Altitude hold ## Altitude Select / Acquire

## Attitude hold


* Radars

# Fire Control, Terrain Following, etc

# Weather

* Laser Rangers/Laser Designators

* Forward Looking Infrared Radar( FLIR)

* Electronic Warfare Systems

* Air Data Computer : Pressure Altitude, Airspeed

Mach No.


* Cabin Intercommunication Systems

* Entertainment Systems: Audio Channels, video Channels,

personal TV’s

* Radio Altimeter

* Collision Avoidance System (TCAS)

* Flight Control System Computers


* Mission Computer

# Integrates all Sensors, Navigation aids, Cockpit

Displays and Controls ,Air Data Computer, Symbol

Generators or Display Processors ,Weapons,

Flight Controls systems, Autopilot, Electronic

Warfare systems, Engine monitoring unit ,etc

In short,

Integrates all electronic systems in the aircraft


* In most Commercial aircraft,

there is a Flight Management Computer instead of a Mission Computer as the integrating computer.

As Flight Management is the main mission function in a commercial aircraft

Avionics Architecture

Evolution

* Independent ( Analog )Avionics ( 1940-1950’s)

* Federated Avionics ( 1960-1970’s)

* Integrated Avionics ( 1980-1990’s)


* Independent ( Analog )Avionics ( 1940-1950’s)

Each functional area has separate, dedicated sensors,

processors and displays and the interconnect media is

point to point wiring

AVIONICS ARCHITECTURE

* INDEPENDENT AVIONICS (1940’S - 1950’S)

RADARDISPLAY

CONTROLS

TACANCONTROLS

DISPLAY

VOR/DMECONTROLS

DISPLAY

A D CCONTROLS

DISPLAY


* Federated Avionics ( 1960-1970’s)

* Typical of most military and commercial

avionics flying today

* Resource sharing occurs at the last link in the information chain, via controls and displays.

* Use of time shared multiplexed data buses

1553 B, Stanag 3910

* Standard data processors used to perform

variety of low bandwidth functions like:


* Federated Avionics ( 1960-1970’s)(continued)

navigation, weapon delivery,stores management

and flight control

* All high speed data processing and signal processing

done inside ‘ black boxes ‘ or LRU’s

* LRU ( Line Replaceable Unit)

* Such architectures simplified physical integration

and retrofit problems



# Generally, the distributed processing concept consists of :

## Sensor oriented functions are performed by

various sensor computers

INS, Radar, LDP, Communication units, NAV aids,etc

## Mission oriented functions are performed by

a central Mission Computer or a Flight

Management Computer



## Cockpit man machine equipment functions are

performed by Display Processors/Symbol

Generation units and various Control panels and Display surfaces


* FEDERATED AVIONICS (1960’S - 1970’S)

INS RACONTROLPANELS

RADAR

SGC V/ UHF SMSMISSION

COMPUTER

MIL STD1553 B

HUD MFD’S


* Integrated Avionics ( 1980-1990’s)

** Also called ‘Integrated Digital Avionics or

PAVE PILLAR Architecture

** Boeing 777

** Higher level of Integration

** Use of a small family of line replaceable modules

(LRM’s) to do all types of Signal and Data

Processing


* Integrated Avionics ( 1980-1990’s)(continued)

** Reduces maintenance effort, allows System

reconfiguration in real time , cost reduction through

common replicated modules



# Generally, the distributed processing concept consists of :

## Common Integrated Processing modules performing

various signal and data processing tasks.Real time

reconfiguration is a great benefit. There are no

individual units identifiable as a Radar, INS, ADC

LDP, etc.

## Individual RF and Sensing assemblies ( eg. RLG)

will be there



## Control Panels and Display Surfaces will be shared

as in Federated Avionics


* INTEGRATED AVIONICS (1980’s - 1990’s)

RADARRF

INS RLG

RARF

LDP OPTICAL

BANK OFCOMMON

INTEGRATEDPROCESSORS(DSP & DATA)

DISPLAYS

CONTROLS

Avionics Mission Functions

* Navigation Functions

* Air to Air Missiles/Gun functions

* Air to Ground/Sea Missiles/Gun/Bombs functions

The last two set of functions are for military aircraft only



# Basic Flight and Steering

# Navigation Guidance

## Direct Track Guidance

## Speed Guidance

## Desired Track Guidance

## Route Navigation or Automatic switch over

Navigation

## Approach for landing




This function helps the pilot to :

## Taxi

## Take off

## Perform Basic flying and Steering of the

Aircraft




## The pilot uses symbology on the HUD as well as symbology on the MFD’s

## In addition the pilotalso uses conventional Instruments like Artificial Horizon,

ASI, ROCI, Altimeter,AOA indicator

Compass,etc


# Basic Flight and Steering(continued)

## Some parameters displayed on the HUD

* Heading,Track,Drift

* Airspeed, Angle of Attack,Mach No.

* Horizon bar and pitch/roll bars

* Velocity vector

* Pressure Altitude & Baro-Inertial Altitude

* Ground speed


# Basic Flight and Steering(continued)

## Some parameters displayed on the MFD

* Most parameters displayed on the HUD

* Attitude Direction Indicator( ADI or EFIS)



Definitions

All Guidance is to a ‘ Waypoint ‘ or an ‘Offset Point ‘

A waypoint is defined by

* Latitude , Longitude , Altitude ( above msl)

An Offset Point is defined with respect to a waypoint

* Delta Latitude, Delta Longitude,

Delta Altitude


Definitions(continued)

Flight Plan

* An ordered or sequential list of Waypoints

or Offset Points is a flight plan.

Order No. Waypoint/ Offset point No.

1 5

2 6* ( offset to wp 6)

3 18

4 3




Guidance to go to a Waypoint directly from

the aircraft current position

Cues are displayed to the pilot on the HUD

and MFD. The parameters displayed are ;

* Range and bearing to Waypoint




* Deviation required from aircraft current

Track to reach the Waypoint

* Horizontal Situation Indicator(HSI) on

MFD(EFIS). An HSI indicates:

** Heading , Track, Range and bearing to

WP, Altitude,Airspeed, ground speed,

Mach No.



## Desired Track Guidance

Guidance to approach a WP along a Desired

Track. This could be to avoid missile and

ground defences. It could also be used to approach a busy airport along a certain path

Information displayed on HUD/MFD is similar to that

displayed in the case of Direct Track



## Speed Guidance

This function gives a Pilot cues to reach a WP at a

specific absolute time or a relative time with respect to the time at the previous WP

Speed Guidance cues( reduce speed, increase speed,

maintain speed, time to go ) are displayed to the pilot on the

HUD and MFD(HSI page)



## Route Navigation or Automatic Switch Over

Navigation

This function displays guidance cues to take an aircraft sequentially from one WP to another WP according to the Flight Plan. Flight plans are entered into the Avionics System at start up. Both speed guidance and direct track guidance can be superposed with this function.



## Route Navigation or Automatic Switch Over

Navigation

Route Navigation parameters( Current WP, Next WP,

Flight Plan No.) are displayed on the HUD/MFD(HSI)

A separate Flight Plan map page on the MFD displays all the WP’s in the selected Flight Plan along with the aircraft current position

ROUTE NAVIGATION

* FLIGHT PLAN MAP

TN

W18

W31 W22

W16



## Approach

In addition to Basic flight and steering symbology , Approach cues to the airport and landing cues( runway heading, length, synthetic runway symbology, glide slope , ILS localiser and glide slope ‘what to do ‘ parameters) are displayed on the HUD/MFD’s


1. PRIMARY FLIGHT DISPLAY (PFD): The typical PFD is a multicolor CRT or LCD display unit that presents a display of aircraft attitude and flight control system steering commands including VOR, localizer, TACAN, or RNAV deviation; and glideslope or preselected altitude deviation. Flight control system mode annunciation, auto-pilot engage annunciation, attitude source annunciation, marker beacon annunciation, radar altitude, decision height set and annunciation, fast-slow deviation or angle-altitude alert, and excessive ILS deviation (when Category II configured) can also be displayed (see EFIS Primary Flight Display figure, right).


2. NAVIGATION DISPLAY (ND): The typical ND is a multicolor CRT or LCD display unit that presents a plan view of the aircraft horizontal navigation situation. Information displayed includes compass heading, selected heading, selected VOR, localizer, or RNAV course and deviation (including annunciation or deviation type), navigation source annunciation, digital selected course/desired track readout, excessive ILS deviation (when Category II configured), to/from information, back course localizer annunciation, distance to station/waypoint, glideslope MGP, or VNAV deviation ground speed, time-to-go, elapsed time or wind, courseinformation and source annunciation from a second navigation source, weather radar target alert, waypoint alert when RNAV is the navigation source, and a bearing pointer that can be driven by VOR, RNAV or ADF sources as selected on the display select panel. The ND can also be operated in an approach format or an en route format with or without weather radar information included in the display (see EFIS Navigation Display figure, above right).


For outbound tracking, the pilot selects the desired track in the selector window and ensures that the TO-FROM indicator points toward the tail of the track arrow. The pilot then turns the aircraft in the shortest direction to an interception track that places the head of the track arrow in the upper half of the HSI with a suitable interception angle (normally 45°).

Immediately after passing the station, the pilot intercepts the outbound track by turning the aircraft to parallel the track. The pilot sets the outbound track in the selector window. When the track bar and bearing pointer stabilize, the pilot notes the degrees off track and turns towards the track by this amount, allowing for wind drift. The intercept angle should not exceed 45°.


The HSI provides a basic horizontal view of the aircraft's navigation picture. In the F-15E, it can provide navigation data to selected ground navigation facilities (TACAN or Instrument Landing System (ILS)) or to onboard navigation systems like the Inertial Navigation System (INS).

Instrument flying without an HSI requires a fair amount of mental gymnastics; for this reason, the HSI is becoming more prevalent in general aviation since it provides an excellent picture for precise navigation.

C. HORIZONTAL SITUATION INDICATOR

The electronic HSI in the F-15E provides a wealth of information. In the example above, the HSI provides the crew with the bearing and range to the selected TACAN (a ground based navigation instrument that transmits a signal 360 degrees from the station) is 305 degrees and 16.0 miles (the time required to fly to the TACAN is 2 minutes and 20 seconds); the bearing and distance to the point the INS is steering to is 105 degrees and 12 miles (the time required to fly to the INS steering point is 1 minute and 48 seconds).


The horizontal situation indicator (HSI) was developed to assist pilots to interpret and use aircraft navigational aids. There are various types of HSIs, but each performs the same function. The HSI (see figure, right) displays information obtained from combinations of the heading indicator, radio magnetic indicator (RMI), track indicator and range indicator. It may also display VOR, DME, ILS or ADF information.

The aircraft heading is displayed on a rotating compass card under the heading lubber line. The card is calibrated in 5° increments.

The hearing pointer provides magnetic bearing information from the aircraft to the selected ground station (VOR or ADF). The fixed aircraft symbol and floating track bar display the aircraft's position relative to the selected track (VOR or ILS localizer). When a VOR station is selected, the inner dot on the track bar azimuth scale indicates approximately 5° and the outer dot approximately 10° (the aircraft's operating manual should give details).

Documents

Avionics Systems and Software part 1. Avionics Systems and Software * AVIONICS : An Embedded System * Avionics-Functionality * Major Components of Avionics