aircraft electric & electronics

Aircraft Electrical & Electronic Systems

© 2010 Infosys Technologies Limited© 2010 Infosys Technologies Limited

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Agenda:

Aircraft systems –1. Avionic Systems

• Navigation System,

• Flight deck and cockpit systems

• Communication System2. Flight Control System, 3. Aircraft Electrical System

© 2010 Infosys Technologies Limited

3. Aircraft Electrical System

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• Avionics is actually a combination of Aviation & Electronics. • Represents the field of technology that encompasses the electronic equipment

and systems that are used on aircraft and aircraft components.• Avionics equipment is usually thought of as different from electrical or

electromechanical aircraft equipment but the lines between electrical systems and avionics systems are not always distinct, especially in the more modern aircraft.

• Supports the goal of helping flight crews get safely from point to point.

What is Avionics?


• Supports the goal of helping flight crews get safely from point to point.• Avionics helps pilots with their responsibilities in the cockpit to

• Aviate (Tracking and Controlling Aircraft Pitch, roll and yaw)

• Navigate (track position, way point estimates, deviation from desired course, avoiding collision with obstacles, in all weather conditions)

• Communicate (communicate flight progress with others who need to know –other crew members, ATC, other aircraft, Flight Service Stations and airlines).

• Function of Avionics Systems is to receive, compute and display • Navigation data,

• sense flight parameters,

• correlate information,

• consolidate and present information to crew,

• support crew by automating functions like flight control and flight management,

What are the functions of Avionics?


management,

• enhance safety,

• improve flight performance,

• permit communication with external elements.

• Help crews manage their workload, onboard systems and the flight situation

The Goal of avionics is to help the aircraft get from one location to another location in

almost any weather condition.

Terminologies used in Avionics

• ADF Automatic Direction Finder• NDB – Non directional Beacon• VOR - VHF omnidirectional range• DME – Distance Measuring Equipment• TACAN TACtical Air Navigation• VORTAC A special VOR which

combines VOR T TCAN• RNAV Area Navigation• RMI Radio Magnetic Indicator• HSI Horizontal Situation Indicator

20 Popular Avionics Abbreviations

Best way to learn Avionic Systems is using 5 Ws + H


• HSI Horizontal Situation Indicator• LORAN C Long Range Navigation• INS / IRS – Inertial Navigation System /

Reference• DNS: Doppler Navigation System • GPS: Global positioning System• ALS: Approach Lighting System• VASIS: Visual Slope Indicator System• ILS: Instrument Landing System• MB: Marker beacon• MLS: Microwave landing System• DGPS: Differential GPS

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1. What: is the purpose of this system2. Who is permitted use this system?

(Military – Civil Etc)3. Where: is the system situated?

Ground , Aircraft or space?4. Why is this system Good or Bad?5. When: was the system certified for

use in avionics & Future?6. How: does this system function?

Aircraft Navigation Systems

• Finding the way from one place to another is called NAVIGATION.

• Moving of an aircraft from one point to another is the most important part for any kind of mission. Plotting on the paper or on the map a course towards a specific area of the earth , in the past, used to be a task assigned to a specialized member of the aircraft's crew such a navigator. Such a task was quite complicated and not always accurate. Since it depended on the


complicated and not always accurate. Since it depended on the observation , using simple maps and geometrical instruments for calculations.

• Today, aerial navigation has become an art which nears to perfection. Both external Navaids (Navigational Aids) and on-board systems help navigate any aircraft over thousand of miles with such accuracy that could only be imagined a few decades ago.

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Methods of Navigation

The following are the main methods of air navigation. There are:1. Pilotage , 2. Dead Reckoning , 3. Radio. 4. Cele stial Navigation 5. Satellite Navigation

1. Pilotage or Piloting: ( Based on Visual Landmark s) is the most common method of air navigation. This method, the pilot keeps on course by following a series of landmarks on the ground. Usually before take-off, pilot will making pre-flight planning , the pilot will


before take-off, pilot will making pre-flight planning , the pilot will draws a line on the aeronautical map to indicate the desired course. Pilot will note various landmarks , such as highways , railroad tracks, rivers , bridges . As the pilot flies over each of landmark , pilot will checks it off on the chart or map. If the plane does not pass directly over the landmark , the pilot will know that he has to correct the course.

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Dead Reckoning

• 2. Dead Reckoning is the primary navigation method used in the early days of flying. It is the method on which Lindberg relied on his first trans-Atlantic flight. A pilot used this method when flying over large bodies of water, forest, deserts. It demands more skill and experience than pilotage does. It is based on time, distance, and direction only.

• The pilot must know the distance from one point to the next, the


• The pilot must know the distance from one point to the next, the magnetic heading to be flown. Pilot works on the pre-flight plan chart , pilot plan a route in advance. Pilot calculate the time to know exactly to reach the destination while flying at constant speed. In the air, the pilot uses compass to keep the plane heading in the right direction. Dead reckoning is not always a successful method of navigation because of changing wind direction. It is the fundamental of VFR flight..

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DR – Ground Speed estimation

© 2010 Infosys Technologies Limited 9

Radio Navigation, Celestial Navigation, Satellite Navigation

• 3. Radio Navigation is used by almost all pilots. Pilots can find out from an aeronautical chart what radio station they should tune to in a particular area. They can then tune their radio navigation equipment to a signal from this station. A needle on the navigation equipment tells the pilot where they are flying to or from station, on course or not

• 4. Celestial Navigation : Based on Navigational reference to


• 4. Celestial Navigation : Based on Navigational reference to heavenly bodies, Sun, Moon, planets, stars, satellites etc

• 5. Satellite Navigation: Navigation through use of data broadcast by a Satellite (SAT) based transmitter

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Navigating Across Oceans

• Pilots have special methods for navigating across oceans. Three commonly used methods are:1. Inertial Guidance : This system has computer and other special devices that tell pilots where are the plane located.2.LORAN: Long Range Navigation The plane has equipment for receiving special radio signals sent out continuous from transmitter stations. The signals will indicate the plane location


transmitter stations. The signals will indicate the plane location3.GPS Global Positioning System: is the only system today able to show your exact position on the earth any time, anywhere, and any weather. The system receiver on the aircraft will receives the signals from satellites around the globe.

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Presenting information to Crew - Display system Purp ose & Functions

Provides situational awareness to the pilot by displaying flight critical information for successful completion of the mission.

• Type of Information displayed• Primary flight performance - Airspeed, Attitude, Altitude, Heading, Vertical

Speed, Radio Direction & Distance, etc.• Navigation – Flight plan, approach, VOR, moving map, Situation

awareness, …• Engines – Torque, Np, Ng, ITT (Turbine inlet temperatures) , Oil


• Engines – Torque, Np, Ng, ITT (Turbine inlet temperatures) , Oil Pressure, Oil Temperature, Fuel Pressure, Fuel Flow, Fuel Qty (different tanks)

• Aircraft Utility System

• Pressurization/ air conditioning

• Hydraulic Power

• Auxiliary Power unit

A Typical Flight Deck – A380 Flight deck


Boeing 777 Flight Deck


DISPLAY FORMATS – WHY PFD , ND ?

Ideas of Orthographic Projection

Top View

Front View

Profile View


Front View in PFD Top View in ND Profile View in VSD as part of ND

DESIGN for 3 Dimensional Situational Awareness

Flight deck


EFIS

• An Electronic Flight Instrument System (EFIS) is a flight deck instrument display system in which the display technology used is electronic rather than electromechanical. EFIS normally consists of a primary flight display (PFD), multi-function display (MFD) and Engine Indicating and Crew Alerting System (EICAS) display. Although cathode ray tube (CRT) displays were used at first, liquid crystal displays (LCD) are now more


were used at first, liquid crystal displays (LCD) are now more common.

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Olden Days –Electromechanical Displays – Glass Tube display

Basic Flight instruments


PFD/ND Format

PFD - Basic “T” ND - VOR


MACHAirspeed

Tape

Attitude Indicator

Horz. Situation Ind.

AltitudeTape

Vert.SpeedTape

EFIS Format

Basic “T” NAV Display


Mach/Airspeed Ind.Radio Dist. Mag. Ind.

Attitude IndicatorHorz. Situation Ind.

AltimeterVertical Speed Ind.

Pitot instruments


Vertical Speed Indicator


Navigation Systems -Methods

Pilotage

Dead Reckoning

Celestial Navigation

Terrestrial or

Radio Navigation

Inertial Navigation System (INS)

Satellite

Navigation


ADF

VOR

DME

TACAN

LORAN

OMEGAHyperbolic Navigation

ILS

MLS

Precision Landing Aids

GPS

GLONAS

Self contained

ADF & VORs

ADF Provides Aircraft bearing with respect to a Ground station called NDB


VORs: Provides Aircraft radial W.R.T a ground station

DME

Distance measuring Equipment provides distance between Aircraft and DME ground station. Ideally we want a ground distance between Aircraft and DME station, but DME normally provides the slant distance


RMI Indicator Showing VOR, HDG and ADF


Question

Question : Why do you require 3 Navigational Aids DME, ADF and VORs? Can we do with one?


Over/Under Engine Format

Center Upper Display Unit Center Lower Display Unit


Primary Engine Display Secondary Engine Display

Navigation Aids

Air navigation needs 1. Earth model for reference

2. A co-ordinate system to identify position/fixes and to compute distances

3. Navigational aids for reducing the workload of Navigator/pilot

Basic Navigation aids

Aeronautical Charts: specialized maps that show more than geographical features -1. Navigation aids and airways which are highways in the air


1. Navigation aids and airways which are highways in the air

2. location of airports, Land marks like mountains, rivers, lakes etc.

3. National borders

Magnetic compass

Aeronautical Map / Chart

Understanding

Aeronautical Maps-

Video


Ex: Symbols – Navigational Aids

VOR, short for VHF omnidirectional radio range


Airspace Structure


Airspace


Class C & Class D


Class E & G


CNSA Systems

•NavigationHelps in en route navigation

•CommunicationInfrastructure providing connectivity between Air-Ground and Ground-Ground systems


•SurveillanceHelps gathering weather reports, collision detection etc.

•ATMManaging Air TrafficIntegrated CNS Architecture to improve ATM

Aircraft Communication Systems


Aircraft Communication Systems

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• Air Traffic Management (ATM)– Air Traffic Control (ATC)– Air Traffic Services (ATS)– Communication, Navigation, & Surveillance (CNS)

• Airline Operational Communications (AOC)– Flight Operations– Maintenance

Airport Operations

Aviation Communication Applications :Voice and Data


– Airport Operations

• Airline Administrative Communications (AAC)• Airline Passenger Communications (APC) Management (ATM)

Aviation Communication Equipment

• Voice Communication from Aircraft to Ground Station (ATC) and other aircraft using

• Digital Audio Control Panel

• VHF Radio

• HF Radio

• SATCOM…. For Passenger Telephony services


• Data Communication from Aircraft to Ground Station (GSPs) and in turn to ATC & Airlines (Terminal services) using

• ACARS/CMU (Aircraft Communications Addressing and Reporting Sy stem )

• VHF Radio

• HF Radio

• SATCOM

Fundamentals Of Modulation

• To Transmit Information Over Long Distances High Frequency Carriers Are Required

• Higher the Frequency, Smaller the Wavelength & Smaller the Antenna Dimensions

• For Example, Wavelength at 100MHz is 3 Meters• To Send Information (Voice &/or Data) we have to alter some

Characteristic of the Carrier Waveform as a Function of Information. This is called Modulation.


This is called Modulation.• Modulation can be Analog (Voice or Digital)• Carrier Frequencies are Allocated Internationally & Nationally for

Various Services Ex: Cellular Comm., TV, FM Radio, Air/Ground Communications

• Air/Ground Comm. Frequency Band is 118 MHz to 137 MHz.

Analog Communications Overview

• Modulating signal m(t)• Carrier = A Sin (ωct+φ)• Modulation schemes

• Amplitude Modulation

• Frequency Modulation

• Phase Modulation


Surveillance Systems


Surveillance Systems

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Surveillance Systems in Civil Aircraft

For all weather operation, Surveillance Systems needed in CivilAircraft are for:-

• Enhanced Ground Proximity Warning System (EGPWS) – Mostof the accidents happen under poor visibility and pilot isunaware of the terrain and flies into it.

• Traffic Collision Avoidance System (TCAS)TCAS provides advisories


• Traffic (indicating the presence of other aircraft) and

• Resolution (indicating the maneuver, climb or descend)• Weather Hazards (Weather Radar/EO Sensor) to indicate the

direction and location of Hazards such as Thunderstorms,Turbulence, Windshear, so that the pilot can steer the aircraftaway.

7 modes of EGPWS

Mode 1 : Excessive Descent Rate

Mode 2: Excessive Closure to Terrain

Mode 3: Altitude Loss after Takeoff

Mode 4: Unsafe Terrain Clearance

EGPWS- Basic Functions


Mode 5: Excessive Glideslope Deviation

Mode 6: Advisory Callout/Bank Angle

Mode 7: Wind shear Alerting

EGPWS: Video

Air Traffic Management


Air Traffic Management

1. Air traffic is monitored/managed through highly structured systems

2. Pilots are governed byFlight traffic Rules

3. Controllers instructs pilots during every stage of the flight

4. Ensures safety, avoids collisions, chaos


collisions, chaos

Flight Profile

Preflight :•Pilot fills flight plan•Gets weather info•Performs checks•Taxis Aircraft fromterminal gate to designated runway


designated runway

Flight Profile

Take Off :•Pilot receives permission fromLocal Control

(Tower) to take off•Powers Up aircraft•Begins take off roll


Flight Profile

Departure :•Departure Control takes over (TRACON)•Pilot is issued with altitude and route clearance


Flight Profile

Enroute :•Pilot receives instructions on what altitude maintain what frequencies to switch etc.


Flight Profile

Descent :•Pilot contacts Descent control. •Receives instruction to descent and change heading towards destination airport


Flight Profile

Approach :•Pilot receives Approach clearance.•Files flight procedure to get designated runway •Control changes from TRACON to Local Tower for landing clearance


Flight Profile

Landing :•Pilot receives clearance for landing on the designated runway• On touching the ground the control is transferred to ground controller• Ground controller directs the pilot across taxiways to reach the terminal gate


Flight Service Station (FSS)

FSS provides following services to private pilots •Preflight briefings

• Weather information departure airport, route and destination airport

•Three types of briefings•Standard

•Complete initial info


•Complete initial info•Abbreviated

•Updates to standards•Outlook

•Forecast information •Emergency Assistance

• Aircraft loses its way• Emergency Landing

Local Control ( Tower )

Control towers provide safe, orderly flow of air traffic at airport and its vicinity.

There are four major classifications of control tow ers1. Flight Data controller ( Pre flight )

• Relays Weather info and NOTAM ( Notice to Air Men)

• Operates Flight Data processing equipment

2. Clearance Delivery controller ( Pre flight )


2. Clearance Delivery controller ( Pre flight )• Responsible for obtaining and relaying departure clearances to pilots

3. Ground Controller ( Preflight Taxiing )• Is responsible for the ground movement of aircraft taxiing or vehicles

operating on taxiways or inactive runways

4. Local controller ( Take off and Approach )• Provides safety sequencing of Arrivals and departures

• Maintains separation between Arrivals and departures

TRACON- ( Terminal Radar Approach Control)

• TRACON controllers directaircraft during descent anddeparture

• One TRACON can handle multiple Air ports

• Aim is to maintain separationbetween the flights

•Equipped with Radars,


Bay Area Class B airspace

•Equipped with Radars,monitor Radar screens and maintain Voice/Data communication with Pilot

• Hands off control to next TRACON at the edge of Air Space

Center ( ARTCC)

• Center or Air Route Traffic Control Center directs

Aircraft during en route•Three controller positions

•Radar controller•Controller in-charge •Ensures separation between Aircrafts

•Lateral – 5 miles•Vertical – 1000ft ( below 29000 ft


•Vertical – 1000ft ( below 29000 ft2000ft ( Above 29000 ft)

•Associate controller•Receives Flight Plan 5 - 20 min

before Aircraft arrives the sector airspace

•Radar Handoff•Assists Radar controller during heavy traffic

Working Together

• During pre flight• Flight plan is filed• Weather info is obtained• Departure clearance is obtained• Receives instructions from the

ground controller to reach the designated take off run way

• Pilot receives “Cleared for Departure” from the local tower for the take off


the take off

• After take off pilot is instructed to change the fr equency to contact Departure controller in TRACON. Aircraft is routed away from airport through assigned heading with climb clearance for n ew altitude•Now aircraft is handed over to Center controller f or en route direction. Center controller monitors and gives instructions t o pilot throughout his airspace from sector to sector

Working Together

• Once the aircraft is around 150 miles from destination Airport it starts descent phase.

• It moves from cruising altitude to a lower altitude

• Around 50 miles from airport it is handed over to TRACON controller where the aircraft enters Approach phase

• Approach controller blends different streams of aircraft into a single line for landing in run ways


streams of aircraft into a single line for landing in run ways

• Flight is then handed over to Local Tower controlle r who give clearance for landing in the designated runway.•After landing the control is given to the ground co ntroller who directs the pilot across taxi ways to the terminal gate

London Heathrow

Take off

1 2

3 4

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Flight Control Systems



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1. Basic Object Motions.

2. Aircraft Motions & Control Surfaces.

4. Classification of Flight Control Surfaces.

3. Other flight control Surfaces.



5. Flight Control System.

1. Translation

2. Rotation

Basic Object Motions


We live in a world that isdefined by three spatialdimensions and one timedimension. Objects movewithin this domain in twoways. An object translates, orchanges location, from one

Basic Object Motion - Translation


point to another.

•And an object rotates, or changes its attitude. In general, the motion of any object involves both translation and rotation. The translations are in direct response to external forces. The rotations are in direct response to external torques or moments (twisting forces)

Basic Object Motion – Translation and Rotation


•There are many types of vehicles used to transport people and objects fromplace to place on Earth. How are these vehicles guided to a destination?For Car :- Turning the steering wheel changes a car's direction.

Control of Vehicles


For Boat :- The rudder is used to control the direction of a boat.

Control of Vehicles


For Bicycle :- A bicycle is controlled by turning the handle bars and shiftingthe rider's weight.

Control of Vehicles


The Wright 1902 Glider- Flight control


Control surfaces and aircraft six degrees of freedo m


Vertical Stabilizer

Rudder

Horizontal Stabilizer

Elevator


Aileron Airbrake / Spoilers

Airplane Parts - Control Surfaces


Flight Control System

1. Conventional Control System

2. Fly-By-Wire Control System

3. AutoPilot


•The flight control system is the system which controls the plane. This systemconsists of mechanical and electronic parts, and the pilot .• It has to improve safety by means of a high degree of fault tolerance , and alsoby relieving the tasks of the pilot:

•· Reduce the pilot’s workload by providing an intuitive user interface and byperforming some functions automatically.•· Prevent the crew from inadvertently exceeding the aircraft’s controllabilitylimits.•· Act to maintain the aircraft within its normal range of operation.•· Prevent the pilot from inadvertently entering a stall condition.

Flight Control System and its top level needs


Mission: The flight control system has to be highly unlikely to fail (effectively faulttolerant) so the plane can have safe flights.

Use profile: The system has to operate during each flight (from takeoff tolanding).

Lifecycle: Same as lifecycle of the plane, which is somewhere around 20-30years.

•To achieve flight control we require the capability to control theforces and moments acting on the vehicle ; if we can controlthese, then we have control of accelerations and hence velocities,translations and rotations.•Direct mechanical linkages were used between the pilot’s cockpitcontrols (pitch/roll stick and rudder pedals) and the control surfacesthat maneuver aircraft, which are : tail plane, ailerons and rudder.Advantages

Flight Control System


Advantages•This arrangement is inherently of high integrity, in terms ofprobability of loss of aircraft control, and provides us with a veryvisible baseline for explaining FCS developments.Issues

Pilot(s) work load is moreNon-optimized handling qualitiesMaintenance costs are high.

Mechanical Flight Controls


On aircraft of the A300 and A310 type, the pilot commands aretransmitted to the servo-controls by an arrangement of mechanicalcomponents (rods, cables, pulleys, etc.). In addition, specific computersand actuators driving the mechanical linkages restore the pilot feels onthe controls and transmit the autopilot commands

Electrical Flight Controls - FBW

The term fly -by-wire has been adopted to describe the use of electrical rather


The term fly -by-wire has been adopted to describe the use of electrical ratherthan mechanical signaling of the pilot’s commands to the flying controlactuators. One can imagine a basic form of fly-by-wire in which an airplaneretained conventional pilot’s control columns and wheels, hydraulic actuators(but electrically controlled), and artificial feel as experienced in the 1970s withthe Concorde program. The fly-by-wire system would simply provide electricalsignals to the control actuators that were directly proportional to the angulardisplacement of the pilot’s controls, without any form of enhancement.

Hydraulic System For Flight Control On Boeing 727 Aircraft


Control surfaces & Cockpit controls connectivity


Flight Controls

StabilizerPosition DisplayPitch Trim

Scale

Pitch TrimPointer

Pitch Trim DigitalReadout

Left ElevatorPosition Right Elevator

Position

Rudder Position

Left Flight Spoiler

Left Ground SpoilerPosition

Right GroundSpoiler Position

Right Flight SpoilerPosition


Left AileronPosition

Right AileronPosition

Left Flight SpoilerPosition

Position

Left Flap Position Right Flap Position

Left Flap DetentDigital Readout

Right Flap DetentDigital Readout

Left Tire Graphic Right Tire Graphic

Left WOW StatusAnnunciation

Right WOW StatusAnnunciation

Nose Tire Graphic

Nose WOW StatusAnnunciationCombined WOW Status

Annunciation

Static Stability of Aircrafts

If the airplane is disturbed, for example, by atmospheric turbulence, and noses up slightly (angle of attack increases), the airplane is no longer in equilibrium. If the new forces and moments, caused by the angle-of-attack increase, produce a tendency to nose up still further, the airplane is statically unstable and its motion will diverge from equilibrium. If the


motion will diverge from equilibrium. If the initial tendency of the airplane is to hold the disturbed position, the airplane has neutral static stability. On the other hand, if restoring forces and moments are generated by the airplane that tend initially to bring it back to its equilibrium straight and level condition, it is statically stable

Dynamic Stability of Aircrafts

If it is assumed that the airplane is statically stable, it may undergo three forms of motion with time. (1) It may nose down, overshoot, nose-up, overshoot to a smaller degree, and eventually return to its former equilibrium condition of straight and level flight. This type of decaying oscillatory motion


indicates that the airplane is dynamically stable. (2) It may continue to nose up and down thereafter at a constant amplitude. The airplane is said to have neutral dynamic stability. Or, in the worst case, (3) it may nose up and down with increasing magnitude and be dynamically unstable.

• Conventional aircraft control systems rely on mechanical and hydraulic links between the aircraft’s controls and the flight surfaces on the wings and tail. The controls and flight surfaces are directly connected. Mechanical links are also used for the engine control.

• In fly-by-wire systems, the cockpit controls generate electronic signals that are interpreted by a computer system and are then converted into outputs that drive the hydraulic system connected to the flight surfaces. Engine control is also mediated by the FCS computers.

Digital Fly-By-Wire flight control systemIn Summary…


• Pilot workload reduction

• The fly-by-wire system provides a more usable interface and takes over some computations that previously would have to be carried out by the pilots.

• Airframe safety

• By mediating the control commands, the system can ensure that the pilot cannot put the aircraft into a state that stresses the airframe or stalls the aircraft.

Advantages of ‘fly-by-wire’Advantages of Fly By Wire


aircraft.

• Weight reduction

• By reducing the mechanical linkages, a significant amount of weight (and hence fuel) is saved.

Aircraft control surface servo model


Aircraft control surface servo model


Hydraulic actuator

Autopilot

• Basic Function of autopilot is to control the flight of the aircraftand maintain it on a predetermined path in space without anyaction being required by the pilot, once the pilot has selected theappropriate control mode of the autopilot.

• The autopilot can thus relieve the pilot from the fatigue andtedium of having to maintain continuous control of aircraft’s flightpath on a long duration flight.


tedium of having to maintain continuous control of aircraft’s flightpath on a long duration flight.

• A well designed autopilot, properly integrated with FCS canachieve a faster response and maintain a more precise flight paththan the pilot. .

Autopilot Loop

Commanded

Flight PathAutopilot

Flight Control Loop Flight Path

Kinematics

Sensors

Flight Path Deviation

+

-


Autopilot –guidance function in outer loop- generates commands for FCSin inner loop

These are generally attitude commands which operate the aircraft’scontrol surfaces through a closed loop control system so that the aircraftrotates about the pitch and roll axes until the measured pitch and bankangles are equal to the commanded values. The changes in the aircraftattitude then cause the flight path to change through flight pathkinematics.

Autopilot Loop

• To correct a vertical deviation from the desired flight path, pitch attitude iscontrolled to increase or decrease the angular inclination of the flight pathto the horizontal. The resulting vertical velocity component thus causesthe aircraft to climb or dive so as to correct the vertical displacement fromthe desired flight path.

• To correct a lateral displacement from the desired flight path requires theaircraft to bank in order to turn and produce a controlled change in


aircraft to bank in order to turn and produce a controlled change inheading so as to correct the error.

• The pitch attitude control loop and the heading control loop, with its innerloop commanding the aircraft bank angle, are fundamental inner loops invarious autopilot modes.

• The outer autopilot loop is thus an essentially a slower, longer periodcontrol loop compared with the inner flight control loops which are faster,shorter period loops.

Autopilot modes

• Height Control• Heading Control• ILS/MLS Coupled autopilot


Autopilot


Aircraft Electrical System



Aircraft Electrical Systems

• The function of the aircraft electrical system is to generate, regulate and distribute electrical power throughout the aircraft

• New-generation aircraft rely heavily on electrical power because of the wide use of electronic flight instrument systems


Electrical Power Uses

• Aircraft electrical power is used to operate:• Aircraft Flight Instruments

• Essential Systems

• Passenger Services


Aircraft Electric Power

Aircraft ElectricPower

Aircraft ElectricPower

PowerGeneration

PowerGeneration Power

Distribution

PowerDistribution


PrimaryPower

Distribution

PrimaryPower

DistributionDC

Generation

DCGeneration External

Power

ExternalPowerAC

Generation

ACGeneration

SecondaryPower

Distribution

SecondaryPower

Distribution

StandbyPower

Distribution

StandbyPower

Distribution

Power Used

• Aircraft electrical components operate on many different voltages both AC and DC

• However, most of the systems use:• 115 VAC @ 400 Hz

• 28 VDC• 26 VAC is also used in some aircraft for lighting


Electrical Power Uses (cont.)

• Essential power is power that the aircraft needs to be able to continue safe operation

• Passenger services power is the power that used for:• Cabin lighting

• Operation of entertainment systems

• Preparation of food


Power Sources

•There are sever different power sources on large aircraft to be able to handle excessive loads, for redundancy, and for emergency situations.

•These power sources include:• Engine driven AC generators

• Auxiliary Power Units


• Auxiliary Power Units

• External power

• Ram Air Turbines

Engine Driven AC Generators

• Each of the engines on an aircraft drives an AC generator• The power produced by these generators is used in normal

flight to supply the entire aircraft with power


APU Power

• Most often the APUs power is used while the aircraft is on the ground during maintenance or for engine starting

• However, most aircraft can use the APU while in flight as a backup power source


External Power

• External power may only be used with the aircraft on the ground

• This system utilizes a Ground Power Unit (GPU) to provide AC power through an external plug on the nose of the aircraft

• GPUs may be either portable or stationary units


Main Generator APU Starter Converter

APU Generator

Primary PowerDistribution Panels

StandbyPowerDistributionPanel

Static Inverter

Secondary Power Distribution Panels

Electric Equipment Placement in Aircraft


Component Installations on a Generic Airplane

APU Battery

Secondary PowerDistribution Panels

APU Generator

Main Generator

GeneratorControl Units

Transformer Rectifier Units

Ram Air Turbine

Battery

Type Description Sources Reason to Use115Vac,400Hz

• Converter (AC-AC)• Ram Air Turbine• Inverter (DC-AC)

• Lower distributionlosses

• Many loads use this115Vac,VariableFrequency

• AC Generator• Ram Air Turbine

• Saves cost ofconversion fromgeneration source

28Vdc Battery Reliable supply

350-800Hz

400Hz

tv

t

v

Type of aircraft voltages


All systems use multiple power sources for redundancy!!

28Vdc • Battery• Converter (AC-DC

or DC-DC)

• Reliable supply• Safer voltage level

270Vdc • DC Generator• Ram Air Turbine• Converter (AC-DC)

• Lower distributionlosses

t

v

v

t

• AC Generators

• DC Generators

• RAT

• Variable Speed Constant Frequency

• DC-DC• AC-DC

• Power Distribution Units

• Embedded Bus• Smart

• Bus PowerControl (BPCU)

• Generator Control Unit (GCU)

• Motors• Motor Controls• Actuation

+ +Generation Conversion Distribution Utilization+ Control

Stages of electric power


• RAT• Turbo

Generators• EPU• Battery

• AC-DC• DC-AC• Starter

Generator Converter

• Smart Contactors

• Remote Contactors

• Circuit Breakers• Solid State

Power Controls (SSPC)

(GCU)• Electrical Load

Control (ELCU)

Ram Air Turbine

• Some aircraft are equipped with Ram Air Turbines, or “RATs”• These may be used, in the case of a generator or APU failure,

as an emergency power source• When necessary, the RAT may be deployed to be used as an

AC power source


Aircraft Batteries

• The aircraft’s nickel cadmium battery is final source of backup power

• The battery provides 28 VDC• It is also possible to change the 28 VDC into 115 VAC 400Hz

with the use of a static inverter• When using the battery, power usage is limited by the short life

of the battery


Electrical Power System Components

• AC Generator• Constant Speed Drive• Integrated Drive Generator• Transformer Rectifier Unit• Generator Control Unit


Constant Speed Drive

• The purpose of the Constant Speed Drive (CSD) is to take rotational power from the engine and, no matter the engine speed, turn the generator at a constant speed

• This is necessary because the generator output must be 400Hz

• CSD Operation


• The engine turns the CSD which uses a differential assembly and hydraulic pumps to turn the generator

Integrated Drive Generator

• Another method of regulating the generator speed is with the use of an Integrated Drive Generator (IDG)

• An IDG is simply a CSD and generator combined into one unit• There are two ways to mount the IDG:

• Co-axially• Side-by-side


Transformer Rectifier Unit

• Transformer Rectifier Units (TRUs) are utilized to 115 VAC, 400Hz into 28 VDC

• A transformer is used to reduce the voltage from 115 volts to 28 volts

• At this point the 28 volts is still AC current• To change the current from AC to DC, a rectifier is used• Each aircraft AC bus feeds a TRU which feeds a DC bus


• Each aircraft AC bus feeds a TRU which feeds a DC bus

Other Generator Controls and Monitoring Devices

•A Generator Control Unit (GCU), or voltage regulator, is used to control generator output

•Generator circuit protection monitors electrical system parameters• Voltage

• Frequency


• Frequency

• Overcurrent

• Undercurrent

• Differential Fault

Other Generator Controls and Monitoring Devices

• Load controls sense real system load to provide a signal to the CSD for frequency control

• Current transformers are used for current load sensing and differential fault protection

• The electrical system control panel may be found either on the pilot’s overhead panel or on the flight engineer’s panel


Function of System Components

• The basic functions of the electrical system’s components are to:• Generate Power

• Control Electrical Power

• Protect the Electrical System

• Distribute Electrical Power Throughout the Aircraft


Aircraft Lighting system


Wing tip lights indicates direction of flight

References

1. http://www.navfltsm.addr.com/basic-nav-general.htm2. http://www.luizmonteiro.com/Index.aspx3. http://www.thaitechnics.com/nav/nav_intro.html4. http://en.wikipedia.org/wiki/Electronic_Flight_Instrument_System


Thank you



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