Aviation Maintenance Technician HandbookAirframe

Volume 2

U.S. Department of TransportationFEDERAL AVIATION ADMINISTRATION

Flight Standards Service

2012

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Volume 1Preface.....................................................................v

Acknowledgments ................................................vii

Table of Contents ................................................xiii

Chapter 1Aircraft Structures ...............................................1-1

Chapter 2Aerodynamics, Aircraft Assembly, and Rigging .................................................................2-1

Chapter 3Aircraft Fabric Covering .....................................3-1

Chapter 4Aircraft Metal Structural Repair .........................4-1

Chapter 5Aircraft Welding ...................................................5-1

Chapter 6Aircraft Wood ......................................................6-1

Chapter 7Advanced Composite Materials .........................7-1

Chapter 8Aircraft Painting and Finishing ..........................8-1

Chapter 9Aircraft Electrical System ...................................9-1

Glossary ..............................................................G-1

Index ......................................................................I-1

Volume 2Chapter 10

Aircraft Instrument ...........................................10-1

Chapter 11Communication and Navigation .......................11-1

Chapter 12Hydraulic and Pneumatic .................................12-1

Chapter 13Aircraft Landing ................................................13-1

Chapter 14Aircraft Fuel System..........................................14-1

Chapter 15Ice and Rain Protection.....................................15-1

Chapter 16Cabin Environmental ........................................16-1

Chapter 17Fire Protection Systems ...................................17-1

Glossary ..............................................................G-1

Index ......................................................................I-1

Volume Contents

iv

vThe Aviation Maintenance Technician HandbookAirframe (FAA-H-8083-31) is one of a series of three handbooks for persons preparing for certification as an airframe or powerplant mechanic. It is intended that this handbook provide the basic information on principles, fundamentals, and technical procedures in the subject matter areas relating to the airframe rating. It is designed to aid students enrolled in a formal course of instruction, as well as the individual who is studying on his or her own. Since the knowledge requirements for the airframe and powerplant ratings closely parallel each other in some subject areas, the chapters which discuss fire protection systems and electrical systems contain some material which is also duplicated in the Aviation Maintenance Technician HandbookPowerplant (FAA-H-8083-32).

This volume contains information on airframe construction features, assembly and rigging, fabric covering, structural repairs, and aircraft welding. The handbook also contains an explanation of the units that make up the various airframe systems. Because there are so many different types of aircraft in use today, it is reasonable to expect that differences exist in airframe components and systems. To avoid undue repetition, the practice of using representative systems and units is carried out throughout the handbook. Subject matter treatment is from a generalized point of view and should be supplemented by reference to manufacturer's manuals or other textbooks if more detail is desired. This handbook is not intended to replace, substitute for, or supersede official regulations or the manufacturers instructions. Occasionally the word must or similar language is used where the desired action is deemed critical. The use of such language is not intended to add to, interpret, or relieve a duty imposed by Title 14 of the Code of Federal Regulations (14 CFR).

This handbook is available for download, in PDF format, from www.faa.gov.

The subject of Human Factors is contained in the Aviation Maintenance Technician HandbookGeneral (FAA-H-8083-30).

This handbook is published by the United States Department of Transportation, Federal Aviation Administration, Airman Testing Standards Branch, AFS-630, P.O. Box 25082, Oklahoma City, OK 73125.

Comments regarding this publication should be sent, in email form, to the following address:

AFS630comments@faa.gov

Preface

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vii

The Aviation Maintenance Technician HandbookAirframe (FAA-H-8083-31) was produced by the Federal Aviation Administration (FAA) with the assistance of Safety Research Corporation of America (SRCA). The FAA wishes to acknowledge the following contributors:

Mr. Chris Brady (www.b737.org.uk) for images used throughout this handbook

Captain Karl Eirksson for image used in Chapter 1

Cessna Aircraft Company for image used in Chapter 1

Mr. Andy Dawson (www.mossie.org) for images used throughout Chapter 1

Mr. Bill Shemley for image used in Chapter 1

Mr. Bruce R. Swanson for image used in Chapter 1

Mr. Burkhard Domke (www.b-domke.de) for images used throughout Chapter 1 and 2

Mr. Chris Wonnacott (www.fromtheflightdeck.com) for image used in Chapter 1

Mr. Christian Tremblay (www.zodiac640.com) for image used in Chapter 1

Mr. John Bailey (www.knots2u.com) for image used in Chapter 1

Mr. Rich Guerra (www.rguerra.com) for image used in Chapter 1

Mr. Ronald Lane for image used in Chapter 1

Mr. Tom Allensworth (www.avsim.com) for image used in Chapter 1

Navion Pilots Associations Tech Note 001 (www.navionpilots.org) for image used in Chapter 1

U.S. Coast Guard for image used in Chapter 1

Mr. Tony Bingelis and the Experimental Aircraft Association (EAA) for images used throughout Chapter 2

Mr. Benoit Viellefon (www.johnjohn.co.uk/compare-tigermothflights/html/tigermoth_bio_aozh.html) for image used in Chapter 3

Mr. Paul Harding of Safari SeaplanesBahamas (www.safariseaplanes.com) for image used in Chapter 3

Polyfiber/Consolidated Aircraft Coatings for images used throughout Chapter 3

Stewart Systems for images used throughout Chapter 3

Superflite for images used throughout Chapter 3

Cherry Aerospace (www.cherryaerospace.com) for images used in Chapters 4 and 7

Raytheon Aircraft (Structural Inspection and Repair Manual) for information used in Chapter 4

Mr. Scott Allen, Kalamazoo Industries, Inc. (www.kalamazooind.com) for image used in Chapter 4

Miller Electric Mfg. Co. (www.millerwelds.com) for images used in Chapter 5

Mr. Aaron Novak, contributing engineer, for charts used in Chapter 5

Mr. Bob Hall (www.pro-fusiononline.com) for image used in Chapter 5

Acknowledgments

viii

Mr. Kent White of TM Technologies, Inc. for image used in Chapter 5

Safety Supplies Canada (www.safetysuppliescanada.com) for image used in Chapter 5

Smith Equipment (www.smithequipment.com) for images used in Chapter 5

Alcoa (www.alcoa.com) for images used in Chapter 7

Mr. Chuck Scott (www.itwif.com) for images used throughout Chapter 8

Mr. John Lagerlof, Paasche Airbrush Co. (paascheairbrush.com) for image used in Chapter 8

Mr. Philip Love of Turbine Products, LLC (www.turbineproducts.com) for image used in Chapter 8

Consolidated Aircraft Coatings for image used in Chapter 8

Tianjin Yonglida Material Testing Machine Co., Ltd for image used in Chapter 8

Mr. Jim Irwin of Aircraft Spruce & Specialty Co. (www.aircraftspruce.com) for images used in Chapters 9, 10, 11, 13, 14, 15

Mr. Kevan Hashemi for image used in Chapter 9

Mr. Michael Leasure, Aviation Multimedia Library (www2.tech.purdue.edu/at/courses/aeml) for images used in Chapters 9, 13, 14

Cobra Systems Inc. (www.cobrasys.com) for image used in Chapter 10

www.free-online-private-pilot-ground-school.com for image used in Chapters 10, 16

DAC International (www.dacint.com) for image used in Chapter 10

Dawson Aircraft, Inc. (www.aircraftpartsandsalvage.com) for images used throughout Chapter 10

Mr. Kent Clingaman for image used in Chapter 10

TGH Aviation-FAA Instrument Repair Station (www.tghaviation.com) for image used in Chapter 10

The Vintage Aviator, Ltd. (www.thevintageaviator.co.nz) for image used in Chapter 10

ACK Technologies, Inc. (www.ackavionics.com) for image used in Chapter 11

ADS-B Technologies, LLC. (www.ads-b.com) for images used in Chapter 11

Aviation Glossary (www.aviationglossary.com) for image used in Chapter 11

AT&T Archives and History Center for image used in Chapter 11

Electronics International, Inc. (www.buy-ei.com) for image used in Chapter 11

Excelitas Technologies (www.excelitas.com) for image used in Chapter 11

Freestate Electronics, Inc. (www.fse-inc.com) for image used in Chapter 11

AirTrafficAtlanta.com for image used in Chapter 11

Western Historic Radio Museum, Virginia City, Nevada (www.radioblvd.com) for image used in Chapter 11

Avidyne Corporation (www.avidyne.com) for image used in Chapter 11

Kintronic Laboratories (www.kintronic.com) for image used in Chapter 11

Mr. Dan Wolfe (www.flyboysalvage.com) for image used in Chapter 11

Mr. Ken Shuck (www.cessna150.net) for image used in Chapter 11

Mr. Paul Tocknell (www.askacfi.com) for image used in Chapter 11

Mr. Stephen McGreevy (www.auroralchorus.com) for image used in Chapter 11

Mr. Todd Bennett (www.bennettavionics.com) for image used in Chapter 11

National Oceanic and Atmospheric Administration, U.S. Department of Commerce for image used in Chapter 11

RAMI (www.rami.com) for image used in Chapter 11

Rockwell Collins (www.rockwellcollins.com) for image used in Chapter 11

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Sarasota Avionics International (www.sarasotaavionics.com) for images used in Chapter 11

Southeast Aerospace, Inc. (www.seaerospace.com) for image used in Chapter 11

Sportys Pilot Shop (www.sportys.com) for image used in Chapter 11

Watts Antenna Company (www.wattsantenna.com) for image used in Chapter 11

Wings and Wheels (www.wingsandwheels.com) for image used in Chapter 11

Aeropin, Inc. (www.aeropin.com) for image used in Chapter 13

Airplane Mart Publishing (www.AirplaneMart.com) for image used in Chapter 13

Alberth Aviation (www.alberthaviation.com) for image used in Chapter 13

AVweb (www.avweb.com) for image used in Chapter 13

Belle Aire Aviation, Inc. (www.belleaireaviation.com) for image used in Chapter 13

Cold War Air Museum (www.coldwarairmuseum.org) for image used in Chapter 13

Comanche Gear (www.comanchegear.com) for image used in Chapter 13

CSOBeech (www.csobeech.com) for image used in Chapter 13

Desser Tire & Rubber Co., Inc. (www.desser.com) for image used in Chapter 13

DG Flugzeugbau GmbH (www.dg-flugzeugbau.de) for image used in Chapter 13

Expedition Exchange, Inc. (www.expeditionexchange.com) for image used in Chapter 13

Fiddlers Green (www.fiddlersgreen.net) for image used in Chapter 13

Hitchcock Aviation (hitchcockaviation.com) for image used in Chapter 13

KUNZ GmbH aircraft equipment (www.kunz-aircraft.com) for images used in Chapter 13

Little Flyers (www.littleflyers.com) for images used in Chapter 13

Maple Leaf Aviation Ltd. (www.aircraftspeedmods.ca) for image used in Chapter 13

Mr. Budd Davisson (Airbum.com) for image used in Chapter 13

Mr. C. Jeff Dyrek (www.yellowairplane.com) for images used in Chapter 13

Mr. Jason Schappert (www.m0a.com) for image used in Chapter 13

Mr. John Baker (www.hangar9aeroworks.com) for image used in Chapter 13

Mr. Mike Schantz (www.trailer411.com) for image used in Chapter 13

Mr. Robert Hughes (www.escapadebuild.co.uk) for image used in Chapter 13

Mr. Ron Blachut for image used in Chapter 13

Owls Head Transportation Museum (www.owlshead.org) for image used in Chapter 13

PPI Aerospace (www.ppiaerospace.com) for image used in Chapter 13

Protective Packaging Corp. (www.protectivepackaging.net, 1-800-945-2247) for image used in Chapter 13

Ravenware Industries, LLC (www.ravenware.com) for image used in Chapter 13

Renold (www.renold.com) for image used in Chapter 13

Rotor F/X, LLC (www.rotorfx.com) for image used in Chapter 13

SkyGeek (www.skygeek.com) for image used in Chapter 13

Taigh Ramey (www.twinbeech.com) for image used in Chapter 13

Texas Air Salvage (www.texasairsalvage.com) for image used in Chapter 13

The Bogert Group (www.bogert-av.com) for image used in Chapter 13

W. B. Graham, Welded Tube Pros, LLC (www.thefabricator.com) for image used in Chapter 13

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Zinko Hydraulic Jack (www.zinkojack.com) for image used in Chapter 13

Aviation Institute of Maintenance (www.aimschool.com) for image used in Chapter 14

Aviation Laboratories (www.avlab.com) for image used in Chapter 14

AVSIM (www.avsim.com) for image used in Chapter 14

Eggenfellner (www.eggenfellneraircraft.com) for image used in Chapter 14

FlightSim.Com, Inc. (www.flightsim.com) for image used in Chapter 14

Fluid Components International, LLC (www.fluidcomponents.com) for image used in Chapter 14

Fuel Quality Services, Inc. (www.fqsinc.com) for image used in Chapter 14

Hammonds Fuel Additives, Inc. (www.biobor.com) for image used in Chapter 14

Jeppesen (www.jeppesen.com) for image used in Chapter 14

MGL Avionics (www.mglavionics.com) for image used in Chapter 14

Mid-Atlantic Air Museum (www.maam.org) for image used in Chapter 14

MISCO Refractometer (www.misco.com) for image used in Chapter 14

Mr. Gary Brossett via the Aircraft Engine Historical Society (www.enginehistory.org) for image used in Chapter 14

Mr. Jeff McCombs (www.heyeng.com) for image used in Chapter 14

NASA for image used in Chapter 14

On-Track Aviation Limited (www.ontrackaviation.com) for image used in Chapter 14

Stewart Systems for image used in Chapter 14

Prist Aerospace Products (www.pristaerospace.com) for image used in Chapter 14

The Sundowners, Inc. (www.sdpleecounty.org) for image used in Chapter 14

Velcon Filters, LLC (www.velcon.com) for image used in Chapter 14

Aerox Aviation Oxygen Systems, Inc. (www.aerox.com) for image used in Chapter 16

Biggles Software (www.biggles-software.com) for image used in Chapter 16

C&D Associates, Inc. (www.aircraftheater.com) for image used in Chapter 16

Cobham (Carleton Technologies Inc.) (www.cobham.com) for image used in Chapter 16

Cool Africa (www.coolafrica.co.za) for image used in Chapter 16

Cumulus Soaring, Inc. (www.cumulus-soaring.com) for image used in Chapter 16

Essex Cryogenics of Missouri, Inc. (www.essexind.com) for image used in Chapter 16

Flightline AC, Inc. (www.flightlineac.com) for image used in Chapter 16

IDQ Holdings (www.idqusa.com) for image used in Chapter 16

Manchester Tank & Equipment (www.mantank.com) for image used in Chapter 16

Mountain High E&S Co. (www.mhoxygen.com) for images used throughout Chapter 16

Mr. Bill Sherwood (www.billzilla.org) for image used in Chapter 16

Mr. Boris Comazzi (www.flightgear.ch) for image used in Chapter 16

Mr. Chris Rudge (www.warbirdsite.com) for image used in Chapter 16

Mr. Richard Pfiffner (www.craggyaero.com) for image used in Chapter 16

Mr. Stephen Sweet (www.stephensweet.com) for image used in Chapter 16

Precise Flight Inc. (www.preciseflight.com) for image used in Chapter 16

SPX Service Solutions (www.spx.com) for image used in Chapter 16

xi

SuperFlash Compressed Gas Equipment (www.oxyfuelsafety.com)

Mr. Tim Mara (www.wingsandwheels.com) for images used in Chapter 16

Mr. Bill Abbott for image used in Chapter 17

Additional appreciation is extended to Dr. Ronald Sterkenburg, Purdue University; Mr. Bryan Rahm, Dr. Thomas K. Eismain, Purdue University; Mr. George McNeill, Mr. Thomas Forenz, Mr. Peng Wang, and the National Oceanic and Atmospheric Administration (NOAA) for their technical support and input.

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Volume Contents ...................................................iii

Preface.....................................................................v

Acknowledgments ................................................vii

Table of Contents ................................................xiii

Chapter 10Aircraft Instrument Systems ............................10-1Introduction ..................................................................10-1Classifying Instruments ...............................................10-3

Flight Instruments ....................................................10-3Engine Instruments ...................................................10-3Navigation Instruments ............................................10-4

Pressure Measuring Instruments ..................................10-5Types of Pressure .....................................................10-7Pressure Instruments.................................................10-8

Engine Oil Pressure ..............................................10-8

Manifold Pressure .................................................10-9

Engine Pressure Ratio (EPR) ................................10-9

Fuel Pressure .......................................................10-10

Hydraulic Pressure ..............................................10-10

Vacuum Pressure ................................................10-11

Pressure Switches ...............................................10-11

Pitot-Static Systems ...............................................10-12Pitot Tubes and Static Vents ...............................10-12

Air Data Computers (ADC) and Digital Air

Data Computers (DADC) ...................................10-14

Pitot-Static Pressure-Sensing Flight Instruments ...10-16Altimeters and Altitude .......................................10-16

Vertical Speed Indicator .....................................10-22

Airspeed Indicators .............................................10-24

Remote Sensing and Indication .................................10-26Synchro-Type Remote-Indicating Instruments .....10-26

DC Selsyn Systems .............................................10-26

AC Synchro Systems ..........................................10-28

Remote Indicating Fuel and Oil Pressure

Gauges ................................................................10-28

Mechanical Movement Indicators ..............................10-29Tachometers ...........................................................10-29

Mechanical Tachometers ....................................10-29

Electric Tachometers ..........................................10-30

Synchroscope..........................................................10-32Accelerometers .......................................................10-32Stall Warning and Angle of Attack (AOA)Indicators ................................................................10-34

Temperature Measuring Instruments .........................10-35Non-Electric Temperature Indicators .....................10-36Electrical Temperature Measuring Indication ........10-36

Electrical Resistance Thermometer ....................10-36

Ratiometer Electrical Resistance

Thermometers .....................................................10-38

Thermocouple Temperature Indicators ..................10-38Turbine Gas Temperature Indicating Systems ...10-39

Total Air Temperature Measurement .....................10-42Direction Indicating Instruments ...............................10-43

Magnetic Compass .................................................10-43Vertical Magnetic Compass ...................................10-45Remote Indicating Compass ...................................10-45Remote Indicating Slaved Gyro Compass (Flux Gate Compass) .......................................................10-45Solid State Magnetometers .....................................10-46

Sources of Power for Gyroscopic Instruments ..........10-46Vacuum Systems ....................................................10-48

Venturi Tube Systems .........................................10-48

Engine-Driven Vacuum Pump ............................10-48

Typical Pump-Driven System .............................10-49

Twin-Engine Aircraft Vacuum System

Operation ............................................................10-50

Pressure-Driven Gyroscopic Instrument Systems ..10-51Electrically-Driven Gyroscopic Instrument Systems ...................................................................10-51

Principles of Gyroscopic Instruments ........................10-52Mechanical Gyros...................................................10-52Solid State Gyros and Related Systems .................10-54

Ring Laser Gyros (RLG) ....................................10-54

Table of Contents

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Microelectromechanical Based Attitude and Directional Systems ............................................10-55

Other Attitude and Directional Systems .............10-55

Common Gyroscopic Instruments .............................10-56Vacuum-Driven Attitude Gyros .............................10-56Electric Attitude Indicators ....................................10-57Gyroscopic Direction Indicator or Directional Gyro (DG) ..............................................................10-58Turn Coordinators ..................................................10-58Turn-and-Slip Indicator .........................................10-58

Autopilot Systems ......................................................10-60Basis for Autopilot Operation ................................10-60

Autopilot Components ...............................................10-61Sensing Elements ...................................................10-61Computer and Amplifier .........................................10-61Output Elements .....................................................10-61Command Elements ...............................................10-63Feedback or Follow-up Element ............................10-63Autopilot Functions ................................................10-64Yaw Dampening .....................................................10-65

Automatic Flight Control System (AFCS) ................10-65Flight Director Systems .............................................10-65Electronic Instruments ...............................................10-67

Electronic Attitude Director Indicator (EADI) ......10-67Electronic Horizontal Situation Indicators (EHSI) ...................................................10-68

Electronic Flight Information Systems ......................10-68Electronic Flight Instrument System (EFIS) ..........10-70Electronic Centralized Aircraft Monitor (ECAM) ..................................................................10-71Engine Indicating and Crew Alerting System (EICAS) .....................................................10-72

Flight Management System (FMS) ............................10-73Warnings and Cautions ..............................................10-74

Annunciator Systems ..............................................10-74Aural Warning Systems..........................................10-75

Clocks ........................................................................10-76Instrument Housings and Handling ...........................10-77Instrument Installations and Markings .......................10-78

Instrument Panels ...................................................10-78Instrument Mounting ..............................................10-80Instrument Power Requirements ............................10-81Instrument Range Markings ...................................10-81

Maintenance of Instruments and Instrument Systems ......................................................................10-81

Altimeter Tests .......................................................10-82Pitot-Static System Maintenance and Tests ...........10-83Tachometer Maintenance .......................................10-84Magnetic Compass Maintenance and Compensation .........................................................10-84Vacuum System Maintenance ................................10-85

Autopilot System Maintenance ..............................10-85LCD Display Screens .............................................10-86

Chapter 11Communication and Navigation .......................11-1Introduction ..................................................................11-1

Avionics in Aviation Maintenance ...........................11-2History of Avionics ..................................................11-2Fundamentals of Electronics ....................................11-3

Analog Versus Digital Electronics .......................11-3

Analog Electronics ................................................11-4

Digital Electronics .............................................11-26

Radio Communication ...............................................11-30Radio Waves...........................................................11-31

Types of Radio Waves ........................................11-32

Loading Information onto a Radio Wave ...............11-32Amplitude Modulation (AM) .............................11-34

Frequency Modulation (FM) ..............................11-35

Single Side Band (SSB) .....................................11-36

Radio Transmitters and Receivers ..........................11-37Transmitters ........................................................11-37

Receivers .............................................................11-37

Transceivers ........................................................11-38

Antennas .................................................................11-38Length .................................................................11-38

Polarization, Directivity, and Field Pattern ........11-39

Types ...................................................................11-40

Transmission Lines .............................................11-41

Radio Navigation .......................................................11-41VOR Navigation System ........................................11-42Automatic Direction Finder (ADF) ........................11-46Radio Magnetic Indicator (RMI) ............................11-48Instrument Landing Systems (ILS) ........................11-49

Localizer .............................................................11-49

Glideslope ..........................................................11-49

Compass Locators ...............................................11-51

Marker Beacons ..................................................11-52

Distance Measuring Equipment (DME) .................11-52Area Navigation (RNAV) ......................................11-54Radar Beacon Transponder ....................................11-54

Transponder Tests and Inspections .....................11-58

Altitude Encoders ...............................................11-58

Collision Avoidance Systems .................................11-58Traffic Collision Avoidance Systems (TCAS) ..11-59

ADS-B ................................................................11-60

Radio Altimeter ......................................................11-62Weather Radar ........................................................11-64Emergency Locator Transmitter (ELT) ..................11-66

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Long Range Aid to Navigation System (LORAN) ...............................................................11-69Global Positioning System (GPS) ..........................11-69

Wide Area Augmentation System (WAAS) .......11-71

Inertial Navigation System (INS)/Inertial Reference System (IRS) ..............................................................11-71Installation of Communication and Navigation Equipment ..................................................................11-72

Approval of New Avionics Equipment Installations ............................................................11-72Considerations ........................................................11-72Cooling and Moisture ............................................11-73Vibration Isolation ..................................................11-73

Reducing Radio Interference .....................................11-74Shielding ................................................................11-74Isolation ..................................................................11-74Bonding .................................................................11-74Static Discharge Wicks ..........................................11-75

Installation of Aircraft Antenna Systems ...................11-75Transmission Lines ................................................11-76Maintenance Procedure ..........................................11-76

Chapter 12Hydraulic and Pneumatic Power Systems ......12-1Aircraft Hydraulic Systems ..........................................12-1Hydraulic Fluid ............................................................12-2

Viscosity ...................................................................12-2Chemical Stability ....................................................12-2Flash Point ................................................................12-3Fire Point ..................................................................12-3

Types of Hydraulic Fluids ...........................................12-3Mineral-Based Fluids ...............................................12-3Polyalphaolefin-Based Fluids ...................................12-3Phosphate Ester-Based Fluid (Skydrol) .................12-3Intermixing of Fluids ................................................12-3Compatibility with Aircraft Materials ......................12-3Hydraulic Fluid Contamination ................................12-4

Contamination Check ..........................................12-4

Contamination Control .........................................12-5

Hydraulic System Flushing ......................................12-5Health and Handling .................................................12-5

Basic Hydraulic Systems ............................................12-6Open Center Hydraulic Systems ..............................12-6Closed-Center Hydraulic Systems............................12-7

Hydraulic Power Systems ............................................12-7Evolution of Hydraulic Systems...............................12-7Hydraulic Power Pack System .................................12-7Hydraulic System Components ................................12-8

Reservoirs .............................................................12-8

Filters ......................................................................12-12Micron-Type Filters ............................................12-14

Maintenance of Filters ........................................12-14

Filter Bypass Valve ............................................12-14

Filter Differential Pressure Indicators ...............12-14

Pumps .....................................................................12-15Hand Pumps ..........................................................12-15Power-Driven Pumps .............................................12-16

Classification of Pumps ......................................12-16

Constant-Displacement Pumps ...........................12-17

Gear-Type Power Pump .....................................12-17

Gerotor Pump ......................................................12-17

Piston Pump ........................................................12-18

Vane Pump ..........................................................12-19

Variable-Displacement Pump ............................12-20

Valves ....................................................................12-23Flow Control Valves ...........................................12-23

Pressure Control Valves .....................................12-27

Shuttle Valves .....................................................12-29

Accumulators..........................................................12-30Types of Accumulators .......................................12-30

Heat Exchangers .....................................................12-32Actuators ................................................................12-32

Linear Actuators .................................................12-32

Rotary Actuators .................................................12-33

Hydraulic Motor ................................................12-34

Ram Air Turbine (RAT) ........................................12-35Power Transfer Unit (PTU) ....................................12-35Hydraulic Motor-Driven Generator (HMDG) ........12-35Seals .......................................................................12-35

V-Ring Packings .................................................12-35

U-Ring ...............................................................12-35

O-Rings ...............................................................12-35

Backup Rings ......................................................12-37

Gaskets ................................................................12-37

Seal Materials .....................................................12-37

O-Ring Installation ............................................12-38

Wipers ................................................................12-38

Large Aircraft Hydraulic Systems .............................12-38Boeing 737 Next Generation Hydraulic System ....12-38

Reservoirs ...........................................................12-38

Pumps .................................................................12-38

Filter Units ..........................................................12-40

Power Transfer Unit (PTU) ................................12-40

Landing Gear Transfer Unit ................................12-41

Standby Hydraulic System .................................12-42

Indications ...........................................................12-42

Boeing 777 Hydraulic System ................................12-42Left and Right System Description .....................12-43

Center Hydraulic System ....................................12-45

xvi

Aircraft Pneumatic Systems .......................................12-47High-Pressure Systems ...........................................12-48

Pneumatic System Components .........................12-48

Emergency Backup Systems ...............................12-51

Medium-Pressure Systems .....................................12-52Low-Pressure Systems ..........................................12-52Pneumatic Power System Maintenance .................12-52

Chapter 13Aircraft Landing Gear Systems ........................13-1Landing Gear Types .....................................................13-1

Landing Gear Arrangement ......................................13-2Tail Wheel-Type Landing Gear ...........................13-3

Tandem Landing Gear ..........................................13-3

Tricycle-Type Landing Gear ................................13-3

Fixed and Retractable Landing Gear ........................13-5Shock Absorbing and Non-Shock Absorbing Landing Gear ...........................................................13-5

Leaf-Type Spring Gear .........................................13-6

Rigid ....................................................................13-6

Bungee Cord .........................................................13-7

Shock Struts .........................................................13-7

Shock Strut Operation ............................................13-11Servicing Shock Struts ...........................................13-12Bleeding Shock Struts ............................................13-13

Landing Gear Alignment, Support, and Retraction ...13-14Alignment ...............................................................13-14Support ...................................................................13-15Small Aircraft Retraction Systems .........................13-16Large Aircraft Retraction Systems ........................13-20Emergency Extension Systems ..............................13-22Landing Gear Safety Devices .................................13-22

Safety Switch ......................................................13-22

Ground Locks .....................................................13-23

Landing Gear Position Indicators .......................13-24

Nose Wheel Centering ........................................13-24

Landing Gear System Maintenance ...........................13-25Landing Gear Rigging and Adjustment..................13-26

Gear Door Clearances .........................................13-28

Drag and Side Brace Adjustment ......................13-28

Landing Gear Retraction Test ............................13-29

Nose Wheel Steering Systems ...................................13-30Small Aircraft ........................................................13-30Large Aircraft .........................................................13-30Shimmy Dampers ...................................................13-32

Steering Damper .................................................13-33

Piston-Type .........................................................13-33

Vane-Type ..........................................................13-33

Non-Hydraulic Shimmy Damper ........................13-34

Aircraft Wheels ..........................................................13-34Wheel Construction ................................................13-34

Inboard Wheel Half ............................................13-35

Outboard Wheel Half ..........................................13-35

Wheel Inspection ....................................................13-35On Aircraft Inspection ........................................13-35

Proper Installation ...............................................13-35

Off Aircraft Wheel Inspection ...........................13-37

Aircraft Brakes ...........................................................13-42Types and Construction of Aircraft Brakes ...........13-43

Single Disc Brakes ..............................................13-43

Dual-Disc Brakes ................................................13-45

Multiple-Disc Brakes ..........................................13-46

Segmented Rotor-Disc Brakes ...........................13-47

Carbon Brakes ....................................................13-50

Expander Tube Brakes ........................................13-50

Brake Actuating Systems .......................................13-52Independent Master Cylinders ...........................13-52

Boosted Brakes ...................................................13-55

Power Brakes .....................................................13-56

Emergency Brake Systems ....................................13-59Parking Brake .....................................................13-61

Brake Deboosters ................................................13-61

Anti-Skid ................................................................13-61System Operation ................................................13-61

Wheel Speed Sensors ..........................................13-62

Control Units ......................................................13-63

Anti-Skid Control Valves ...................................13-64

Touchdown and Lock Wheel Protection ............13-66

Auto Brakes ........................................................13-66

Anti-Skid System Tests ......................................13-66

Anti-Skid System Maintenance ..........................13-68

Brake Inspection and Service .................................13-68On Aircraft Servicing .........................................13-68

Lining Wear ........................................................13-68

Air in the Brake System ......................................13-69

Bleeding Master Cylinder Brake Systems ..........13-69

Bleeding Power Brake Systems ..........................13-71

Off Aircraft Brake Servicing and Maintenance ..13-72

Replacement of Brake Linings ...........................13-73

Brake Malfunctions and Damage ..........................13-74Overheating ........................................................13-74

Dragging ............................................................13-75

Chattering or Squealing .....................................13-76

Aircraft Tires and Tubes ............................................13-76Tire Classification...................................................13-76

Types ...................................................................13-76

Ply Rating ...........................................................13-77

xvii

Tube-Type or Tubeless .......................................13-77

Bias Ply or Radial ...............................................13-78

Tire Construction ....................................................13-78Bead ...................................................................13-78

Carcass Plies .......................................................13-79

Tread ...................................................................13-79

Sidewall ..............................................................13-80

Tire Inspection on the Aircraft ...............................13-80Inflation ...............................................................13-80

Tread Condition ..................................................13-82

Sidewall Condition .............................................13-86

Tire Removal ..........................................................13-86Tire Inspection Off of the Aircraft .........................13-88Tire Repair and Retreading ....................................13-88Tire Storage ...........................................................13-89Aircraft Tubes.........................................................13-89

Tube Construction and Selection ........................13-89

Tube Storage and Inspection ..............................13-90

Tire Inspection ...................................................13-90

Tire Mounting ........................................................13-90Tubeless Tires .....................................................13-90

Tube-Type Tires .................................................13-91

Tire Balancing .......................................................13-93Operation and Handling Tips .....................................13-93

Taxiing ..................................................................13-94Braking and Pivoting ..............................................13-94Landing Field and Hangar Floor Condition ..........13-94Takeoffs and Landings ...........................................13-94Hydroplaning ..........................................................13-94

Chapter 14Aircraft Fuel System..........................................14-1Basic Fuel System Requirements .................................14-1

Fuel System Independence .......................................14-2Fuel System Lightning Protection ............................14-2Fuel Flow ..................................................................14-3Flow Between Interconnected Tanks .......................14-3Unusable Fuel Supply ..............................................14-3Fuel System Hot Weather Operation........................14-3

Fuel Tanks ....................................................................14-3Fuel Tank Tests ........................................................14-3Fuel Tank Installation ...............................................14-4Fuel Tank Expansion Space .....................................14-4Fuel Tank Sump .......................................................14-4Fuel Tank Filler Connection.....................................14-4Fuel Tank Vents and Carburetor Vapor Vents .........14-4Fuel Tank Outlet .......................................................14-5Pressure Fueling Systems .........................................14-5Fuel Pumps ..............................................................14-5Fuel System Lines and Fittings ...............................14-5Fuel System Components .........................................14-5

Fuel Valves and Controls .........................................14-5Fuel Strainer or Filter ...............................................14-6Fuel System Drains ..................................................14-6Fuel Jettisoning System ............................................14-6

Types of Aviation Fuel ................................................14-7Reciprocating Engine FuelAVGAS .....................14-7

Volatility ...............................................................14-7

Vapor Lock ...........................................................14-7

Carburetor Icing ....................................................14-7

Aromatic Fuels ......................................................14-8

Detonation .............................................................14-8

Surface Ignition and Preignition ...........................14-9

Octane and Performance Number Rating .............14-9

Fuel Identification ...............................................14-10

Purity ...................................................................14-10

Turbine Engine Fuels .............................................14-11Turbine Fuel Volatility .......................................14-12

Turbine Engine Fuel Types ................................14-13

Turbine Engine Fuel Issues ................................14-13

Aircraft Fuel Systems ................................................14-13Small Single-Engine Aircraft Fuel Systems ...........14-13

Gravity Feed Systems .........................................14-13

Pump Feed Systems ............................................14-14

High-Wing Aircraft With Fuel Injection

System .................................................................14-14

Small Multiengine (Reciprocating) Aircraft Fuel Systems ..........................................................14-15

Low-Wing Twin .................................................14-15

High-Wing Twin .................................................14-16

Large Reciprocating-Engine Aircraft Fuel Systems ...................................................................14-16Jet Transport Aircraft Fuel Systems .......................14-17Helicopter Fuel Systems .........................................14-22

Fuel System Components ..........................................14-22Fuel Tanks ..............................................................14-22

Rigid Removable Fuel Tanks .............................14-23

Bladder Fuel Tanks .............................................14-25

Integral Fuel Tanks .............................................14-25

Fuel Lines and Fittings ...........................................14-26Fuel Valves ............................................................14-26

Hand-Operated Valves ........................................14-28

Cone Valves ........................................................14-28

Poppet Valves .....................................................14-29

Manually-Operated Gate Valves ........................14-29

Motor-Operated Valves ......................................14-30

Solenoid-Operated Valves ..................................14-31

Fuel Pumps .............................................................14-31Hand-Operated Fuel Pumps ................................14-31

Ejector Pumps .....................................................14-32

xviii

Pulsating Electric Pumps ....................................14-34

Vane-Type Fuel Pumps ......................................14-35

Fuel Filters ..............................................................14-36Fuel Heaters and Ice Prevention .............................14-39Fuel System Indicators ...........................................14-40

Fuel Quantity Indicating Systems .......................14-40

Fuel Flowmeters .................................................14-44

Fuel Temperature Gauges ...................................14-46

Fuel Pressure Gauges ..........................................14-47

Pressure Warning Signal .....................................14-48

Valve-In-Transit Indicator Lights ......................14-48

Fuel System Repair ...................................................14-49Troubleshooting the Fuel System ...........................14-49

Location of Leaks and Defects ...........................14-49

Fuel Leak Classification .....................................14-50

Replacement of Gaskets, Seals, and Packings ....14-50

Fuel Tank Repair ....................................................14-50Welded Tanks .....................................................14-51

Riveted Tanks .....................................................14-51

Soldered Tanks ...................................................14-51

Bladder Tanks .....................................................14-51

Integral Tanks .....................................................14-52

Fire Safety ...........................................................14-52

Fuel System Servicing ...............................................14-54Checking for Fuel System Contaminants ...............14-54

Water ...................................................................14-54

Solid Particle Contaminants ...............................14-55

Surfactants ..........................................................14-55

Microorganisms ..................................................14-55

Foreign Fuel Contamination ...............................14-56

Detection of Contaminants .................................14-56

Fuel Contamination Control ...............................14-58

Fueling and Defueling Procedures .............................14-59Fueling ....................................................................14-59Defueling ................................................................14-61Fire Hazards When Fueling or Defueling ..............14-61

Chapter 15Ice and Rain Protection.....................................15-1Ice Control Systems .....................................................15-1

Icing Effects .............................................................15-2Ice Detector System .....................................................15-3

Ice Prevention ...........................................................15-3Wing and Horizontal and Vertical Stabilizer Anti-Icing Systems .......................................................15-4

Thermal Pneumatic Anti-icing .................................15-4Wing Anti-Ice (WAI) System ...............................15-4

Leading Edge Slat Anti-Ice System ......................15-6

Thermal Electric Anti-Icing ...................................15-10Chemical Anti-Icing ...............................................15-10

Wing and Stabilizer Deicing Systems ........................15-12Sources of Operating Air ........................................15-12

Turbine Engine Bleed Air ...................................15-12

Pneumatic Deice Boot System for GA Aircraft .....15-12GA System Operation .........................................15-13

Deice System for Turboprop Aircraft ....................15-14Deicing System Components .................................15-14

Wet-Type Engine-Driven Air Pump ...................15-14

Dry-Type Engine-Driven Air Pump ...................15-16

Oil Separator .......................................................15-17

Control Valve ......................................................15-17

Deflate Valve ......................................................15-18

Distributor Valve ................................................15-18

Timer/Control Unit .............................................15-18

Regulators and Relief Valves .............................15-18

Manifold Assembly ............................................15-19

Inlet Filter ...........................................................15-19

Construction and Installation of Deice Boots.........15-19Inspection, Maintenance, and Troubleshooting of Rubber Deicer Boot Systems .............................15-19

Operational Checks .............................................15-19

Adjustments ........................................................15-21

Troubleshooting ..................................................15-21

Inspection ............................................................15-21

Deice Boot Maintenance ........................................15-21Electric Deice Boots ...............................................15-22

Propeller Deice System ..............................................15-23Electrothermal Propeller Device System ..............15-23Chemical Propeller Deice .......................................15-23

Ground Deicing of Aircraft ........................................15-23Frost Removal ........................................................15-25

Deicing and Anti-icing of Transport Type

Aircraft ................................................................15-25

Ice and Snow Removal ...........................................15-27Rain Control Systems ................................................15-27

Windshield Wiper Systems ...................................15-27Chemical Rain Repellant ........................................15-27

Windshield Surface Seal Coating .......................15-28

Pneumatic Rain Removal Systems .........................15-28Windshield Frost, Fog, and Ice Control Systems ......15-28

Electric....................................................................15-28Pneumatic ...............................................................15-30Chemical .................................................................15-31

Portable Water Tank Ice Prevention ..........................15-32

Chapter 16Cabin Environmental Control Systems ...........16-1Physiology of Flight .....................................................16-1

Composition of the Atmosphere...............................16-1Human Respiration and Circulation .........................16-2

xix

Oxygen and Hypoxia ............................................16-2

Carbon Monoxide Poisoning ................................16-3

Aircraft Oxygen Systems .............................................16-3Forms of Oxygen and Characteristics ......................16-4

Gaseous Oxygen ...................................................16-4

Liquid Oxygen ......................................................16-4

Chemical or Solid Oxygen ...................................16-5

Onboard Oxygen Generating Systems

(OBOGS) ..............................................................16-5

Oxygen Systems and Components ...........................16-6Gaseous Oxygen Systems .....................................16-6

Chemical Oxygen Systems .................................16-16

LOX Systems ......................................................16-16

Oxygen System Servicing ......................................16-16Servicing Gaseous Oxygen .................................16-16

Filling LOX Systems ..........................................16-19

Inspection of Masks and Hoses ..........................16-19

Replacing Tubing, Valves, and Fittings .............16-20

Prevention of Oxygen Fires or Explosions.............16-20Oxygen System Inspection and Maintenance .....16-20

Aircraft Pressurization Systems .................................16-21Pressure of the Atmosphere ....................................16-21Temperature and Altitude .......................................16-22Pressurization Terms ..............................................16-23Pressurization Issues...............................................16-23Sources of Pressurized Air .....................................16-24

Reciprocating Engine Aircraft ...........................16-25

Turbine Engine Aircraft .....................................16-26

Control of Cabin Pressure .....................................16-27Pressurization Modes ..........................................16-27

Cabin Pressure Controller ...................................16-28

Cabin Air Pressure Regulator and Outflow

Valve ...................................................................16-30

Cabin Air Pressure Safety Valve Operation .......16-31

Pressurization Gauges .........................................16-32

Pressurization Operation ....................................16-32

Air Distribution ...................................................16-34

Cabin Pressurization Troubleshooting ................16-34

Air Conditioning Systems ..........................................16-34Air Cycle Air Conditioning ....................................16-35

System Operation ................................................16-36

Pneumatic System Supply ..................................16-36

Component Operation .........................................16-36

Water Separator ..................................................16-39

Cabin Temperature Control System ...................16-39

Vapor Cycle Air Conditioning ...............................16-40Theory of Refrigeration ......................................16-41

Vapor Cycle Air Conditioning System

Components ........................................................16-46

Vapor Cycle Air Conditioning Servicing

Equipment ...........................................................16-51

System Servicing ................................................16-55

Technician Certification ......................................16-58

Aircraft Heaters ..........................................................16-58Bleed Air Systems ..................................................16-58Electric Heating Systems........................................16-58Exhaust Shroud Heaters .........................................16-58Combustion Heaters ...............................................16-60

Combustion Air System ......................................16-60

Ventilating Air System ......................................16-60

Fuel System ........................................................16-61

Ignition System ...................................................16-61

Controls ...............................................................16-61

Safety Features ...................................................16-62

Maintenance and Inspection ...............................16-62

Chapter 17Fire Protection Systems ...................................17-1Introduction ..................................................................17-1

Classes of Fires .........................................................17-2Requirements for Overheat and Fire Protection Systems .....................................................................17-2

Fire Detection/Overheat Systems ................................17-2Thermal Switch System............................................17-2Thermocouple System ..............................................17-3Continuous-Loop Systems .......................................17-4

Fenwal System ......................................................17-4

Kidde System ........................................................17-4

Pressure Type Sensor Responder Systems ...............17-6Pneumatic Continuous-Loop Systems ..................17-6

Fire Zones .................................................................17-8Smoke, Flame, and Carbon Monoxide Detection Systems ........................................................................17-8

Smoke Detectors.......................................................17-8Light Refraction Type ...........................................17-8

Ionization Type .....................................................17-8

Flame Detectors ........................................................17-9Carbon Monoxide Detectors ....................................17-9

Extinguishing Agents and Portable Fire Extinguishers ..............................................................17-10

Halogenated Hydrocarbons ....................................17-10Inert Cold Gases .....................................................17-10Dry Powders ...........................................................17-10Water ......................................................................17-11Cockpit and Cabin Interiors ...................................17-11

Extinguisher Types .............................................17-11

Installed Fire Extinguishing Systems .........................17-11CO2 Fire Extinguishing Systems ............................17-11

xx

Halogenated Hydrocarbons Fire Extinguishing Systems ...................................................................17-11Containers ..............................................................17-12Discharge Valves ....................................................17-13Pressure Indication .................................................17-13Two-Way Check Valve ..........................................17-13Discharge Indicators ...............................................17-13

Thermal Discharge Indicator (Red Disk) ...........17-13

Yellow Disk Discharge Indicator .......................17-14

Fire Switch .............................................................17-14Cargo Fire Detection ..................................................17-14

Cargo Compartment Classification ........................17-15Class A ................................................................17-15

Class B ................................................................17-15

Class C ................................................................17-15

Class E ................................................................17-15

Cargo and Baggage Compartment Fire Detection and Extinguisher System .......................17-15

Smoke Detector System ......................................17-16

Cargo Compartment Extinguishing System .......17-16

Lavatory Smoke Detectors .........................................17-17Lavatory Smoke Detector System .........................17-17Lavatory Fire Extinguisher System ........................17-18

Fire Detection System Maintenance ..........................17-18Fire Detection System Troubleshooting ....................17-19Fire Extinguisher System Maintenance .....................17-20

Container Pressure Check ......................................17-20Discharge Cartridges ..............................................17-20Agent Containers ....................................................17-20

Fire Prevention ...........................................................17-21

Glossary ..............................................................G-1

Index ......................................................................I-1

10-1

IntroductionSince the beginning of manned flight, it has been recognized that supplying the pilot with information about the aircraft and its operation could be useful and lead to safer flight. The Wright Brothers had very few instruments on their Wright Flyer, but they did have an engine tachometer, an anemometer (wind meter), and a stop watch. They were obviously concerned about the aircrafts engine and the progress of their flight. From that simple beginning, a wide variety of instruments have been developed to inform flight crews of different parameters. Instrument systems now exist to provide information on the condition of the aircraft, engine, components, the aircrafts attitude in the sky, weather, cabin environment, navigation, and communication. Figure 10-1 shows various instrument panels from the Wright Flyer to a modern jet airliner.

Aircraft Instrument Systems

Chapter 10

10-2

Figure 10-2. A conventional instrument panel of the C-5A Galaxy

(top) and the glass cockpit of the C-5B Galaxy (bottom).

Figure 10-1. From top to bottom: instruments of the Wright Flyer,

instruments on a World War I era aircraft, a late 1950s/early 1960s

Boeing 707 airliner cockpit, and an Airbus A380 glass cockpit.

The ability to capture and convey all of the information a pilot may want, in an accurate, easily understood manner, has been a challenge throughout the history of aviation. As the range of desired information has grown, so too have the size and complexity of modern aircraft, thus expanding even further the need to inform the flight crew without sensory overload or overcluttering the cockpit. As a result, the old flat panel in the front of the cockpit with various individual instruments attached to it has evolved into a sophisticated computer-controlled digital interface with flat-panel display screens and prioritized messaging. A visual comparison between a conventional cockpit and a glass cockpit is shown in Figure 10-2.

There are usually two parts to any instrument or instrument system. One part senses the situation and the other part displays it. In analog instruments, both of these functions often take place in a single unit or instrument (case). These are called direct-sensing instruments. Remote-sensing requires the information to be sensed, or captured, and then sent to a separate display unit in the cockpit. Both analog and digital instruments make use of this method. [Figure 10-3]

10-3

Figure 10-3. There are two parts to any instrument systemthe

sensing mechanism and the display mechanism.

Sensor + Indication Sensor Indication

Direct-sensing instrument system

Remote-sensing instrument system

Figure 10-4. The basic T arrangement of analog flight instruments.

At the bottom of the T is a heading indicator that functions as

a compass but is driven by a gyroscope and not subject to the

oscillations common to magnetic direction indicators.

30.029.929.8

333330000.0222229999.92229292999.2 8222929.29.88

The relaying of important bits of information can be done in various ways. Electricity is often used by way of wires that carry sensor information into the cockpit. Sometimes pneumatic lines are used. In complex, modern aircraft, this can lead to an enormous amount of tubing and wiring terminating behind the instrument display panel. More efficient information transfer has been accomplished via the use of digital data buses. Essentially, these are wires that share message carrying for many instruments by digitally encoding the signal for each. This reduces the number of wires and weight required to transfer remotely sensed information for the pilots use. Flat-panel computer display screens that can be controlled to show only the information desired are also lighter in weight than the numerous individual gauges it would take to display the same information simultaneously. An added bonus is the increased reliability inherent in these solid-state systems.

It is the job of the aircraft technician to understand and maintain all aircraft, including these various instrument systems. Accordingly, in this chapter, discussions begin with analog instruments and refer to modern digital instrumentation when appropriate.

Classifying InstrumentsThere are three basic kinds of instruments classified by the job they perform: flight instruments, engine instruments, and navigation instruments. There are also miscellaneous gauges and indicators that provide information that do not fall into these classifications, especially on large complex aircraft. Flight control position, cabin environmental systems, electrical power, and auxiliary power units (APUs), for example, are all monitored and controlled from the cockpit via the use of instruments systems. All may be regarded as position/condition instruments since they usually report the position of a certain moveable component on the aircraft, or the condition of various aircraft components or systems not included in the first three groups.

Flight InstrumentsThe instruments used in controlling the aircrafts flight attitude are known as the flight instruments. There are basic flight instruments, such as the altimeter that displays aircraft altitude; the airspeed indicator; and the magnetic direction

indicator, a form of compass. Additionally, an artificial horizon, turn coordinator, and vertical speed indicator are flight instruments present in most aircraft. Much variation exists for these instruments, which is explained throughout this chapter. Over the years, flight instruments have come to be situated similarly on the instrument panels in most aircraft. This basic T arrangement for flight instruments is shown in Figure 10-4. The top center position directly in front of the pilot and copilot is the basic display position for the artificial horizon even in modern glass cockpits (those with solid-state, flat-panel screen indicating systems).

Original analog flight instruments are operated by air pressure and the use of gyroscopes. This avoids the use of electricity, which could put the pilot in a dangerous situation if the aircraft lost electrical power. Development of sensing and display techniques, combined with advanced aircraft electrical systems, has made it possible for reliable primary and secondary instrument systems that are electrically operated. Nonetheless, often a pneumatic altimeter, a gyro artificial horizon, and a magnetic direction indicator are retained somewhere in the instrument panel for redundancy. [Figure 10-5]

Engine InstrumentsEngine instruments are those designed to measure operating parameters of the aircrafts engine(s). These are usually quantity, pressure, and temperature indications. They also include measuring engine speed(s). The most common engine instruments are the fuel and oil quantity and pressure gauges, tachometers, and temperature gauges. Figure 10-6 contains various engine instruments found on reciprocating and turbine-powered aircraft.

10-4

Figure 10-7. An engine instrumentation located in the middle of the instrument panel is shared by the pilot and co-pilot.

Figure 10-5. This electrically operated flat screen display instrument

panel, or glass cockpit, retains an analog airspeed indicator, a

gyroscope-driven artificial horizon, and an analog altimeter as a

backup should electric power be lost, or a display unit fails.

XPDR 5537 IDNT LCL23:00:34

VOR 1

270

2

1

1

2

4300

4200

4100

3900

3900

3800

4300

20

804000

4000 130

120

110

90

80

70

1 100 9

TAS 100KT

OAT 7C

ALERTS

NAV1 117.60 117.90NAV2 117.90 117.60

132.675 120.000 COM1118.525 132.900 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _ TRK 360

N-S E-W

VOLTS

27.3

2090

NAV1 117.60 117.90NAV2 117.90 117.60

132.675 120.000 COM1118.525 132.900 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _ TRK 360MAP - NAVIGATION MAP

Figure 10-6. Common engine instruments. Note: For example purposes only. Some aircraft may not have these instruments or may be

equipped with others.

Reciprocating engines

Oil pressure Oil pressureOil temperature Exhaust gas temperature (EGT)Cylinder head temperature (CHT) Turbine inlet temperature (TIT) or turbine gas temperature (TGT)Manifold pressure Engine pressure ratio (EPR)Fuel quantity Fuel quantityFuel pressure Fuel pressure Fuel flowTachometer Tachometer (percent calibrated) N1 and N2 compressor speedsCarburetor temperature Torquemeter (on turboprop and turboshaft engines)

Turbine engines

Engine instrumentation is often displayed in the center of the cockpit where it is easily visible to the pilot and copilot. [Figure 10-7] On light aircraft requiring only one flight crewmember, this may not be the case. Multiengine aircraft often use a single gauge for a particular engine parameter,

but it displays information for all engines through the use of multiple pointers on the same dial face.

Navigation InstrumentsNavigation instruments are those that contribute information used by the pilot to guide the aircraft along a definite course. This group includes compasses of various kinds, some of which incorporate the use of radio signals to define a specific course while flying the aircraft en route from one airport to another. Other navigational instruments are designed specifically to direct the pilots approach to landing at an airport. Traditional navigation instruments include a clock and a magnetic compass. Along with the airspeed indicator and wind information, these can be used to calculate navigational progress. Radios and instruments sending locating information via radio waves have replaced these manual efforts in modern aircraft. Global position systems (GPS) use satellites to pinpoint the location of the aircraft via geometric triangulation. This technology is built into some aircraft instrument packages for navigational purposes.

10-5

Pointer linkage attaches here

Spur gear

Pressureentrance

Pressure in

Sector gear

Free end

Fixed end Bourdon tube

Figure 10-9. The Bourdon tube is one of the basic mechanisms for

sensing pressure.

XPDR 5537 IDNT LCL23:00:34

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2

1

1

2

4300

4200

4100

3900

3900

3800

4300

20

804000

4000 130

120

110

90

80

70

1 100 9

TAS 100KT

OAT 7C

ALERTS

NAV1 117.60 117.90NAV2 117.90 117.60

132.675 120.000 COM1118.525 132.900 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _ TRK 360

N-S E-W

NAV1 117.60 117.90NAV2 117.90 117.60

132.675 120.000 COM1118.525 132.900 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _ TRK 360MAP - NAVIGATION MAP

77 IDNT LCL23:00:34 T

2

1

1

2

4300

4200

410020 20

4000

4000 130130130

120

OAT 7C

ALERTS

V1 117.60 117.90V2 117.90 117.60

WPT _ _ _ _ _ _ DIS _ _ _ ._ NM DTKMAP - NAVIGATIO

VOR 1

DME TUNING DME MODE NAV1

120

11011

100NAV controls

120.0001132.32.900

4000

COM frequency window

0 111171770 111111777

132132.675 5 1118.525 11

7 97.97.99000077 67.60.60

4000

WPT _ _ _ _ _ _ DIS _ _ _ ._ NM DTK _ _ _ _ TRK 360

NAV frequency windowNAVNAV

COM controls

Com sectionaudio panel

NAV sectionaudio panelXPDRDR XPDXP 5537

DME tuning window

270270

3390003

3383800

80804000

70707070TAS 100TAS 1AS 100100T KTKTKT

90

808080

100V controls

Glideslope indicator

132 6132 6132.6132.6757575755 120 0120.0120.0000000 COMCOM1OM1118.525 132.900 COM2

K _ _ ___ _ TRK TRK K 360360360ON MAPP

Moving map

Figure 10-8. Navigation instruments.

Many of these aircraft navigational systems are discussed in chapter 11 of this handbook. [Figure 10-8] To understand how various instruments work and can be repaired and maintained, they can be classified according to the principle upon which they operate. Some use mechanical methods to measure pressure and temperature. Some utilize magnetism and electricity to sense and display a parameter. Others depend on the use of gyroscopes in their primary workings. Still others utilize solid state sensors and computers to process and display important information. In the following sections, the different operating principles for sensing parameters are explained. Then, an overview of many of the engine, flight, and navigation instruments is given.

Pressure Measuring InstrumentsA number of instruments inform the pilot of the aircrafts condition and flight situations through the measurement of pressure. Pressure-sensing instruments can be found in the flight group and the engine group. They can be either direct reading or remote sensing. These are some of the most critical instruments on the aircraft and must accurately inform the pilot to maintain safe operations. Pressure measurement involves some sort of mechanism that can sense changes in pressure. A technique for calibration and displaying the information is then added to inform the pilot. The type of pressure needed to be measured often makes one sensing mechanism more suited for use in a particular instance. The three fundamental pressure-sensing mechanisms used in aircraft instrument systems are the Bourdon tube, the diaphragm or bellows, and the solid-state sensing device.

A Bourdon tube is illustrated in Figure 10-9. The open end of this coiled tube is fixed in place and the other end is sealed and free to move. When a fluid that needs to be measured is directed into the open end of the tube, the unfixed portion

of the coiled tube tends to straighten out. The higher the pressure of the fluid, the more the tube straightens. When the pressure is reduced, the tube recoils. A pointer is attached to this moving end of the tube, usually through a linkage of small shafts and gears. By calibrating this motion of the straightening tube, a face or dial of the instrument can be created. Thus, by observing the pointer movement along the scale of the instrument face positioned behind it, pressure increases and decreases are communicated to the pilot.

The Bourdon tube is the internal mechanism for many pressure gauges used on aircraft. When high pressures need to be measured, the tube is designed to be stiff. Gauges used to indicate lower pressures use a more flexible tube that uncoils and coils more readily. Most Bourdon tubes are made from brass, bronze, or copper. Alloys of these metals can be made to coil and uncoil the tube consistently numerous times.

Bourdon tube gauges are simple and reliable. Some of the instruments that use a Bourdon tube mechanism include the engine oil pressure gauge, hydraulic pressure gauge, oxygen tank pressure gauge, and deice boot pressure gauge. Since the pressure of the vapor produced by a heated liquid

10-6

Sector

Set screw

Pinion

Spring stop screw

Socket assembly

Bourdon tube

Figure 10-10. The Bourdon tube mechanism can be used to measure

pressure or temperature by recalibrating the pointers connecting

linkage and scaling instrument face to read in degrees Celsius or

Fahrenheit.

Pressure diaphragm

Spr

ing

actio

n

Aneroid

Figure 10-11. A diaphragm used for measuring pressure. An

evacuated sealed diaphragm is called an aneroid.

or gas increases as temperature increases, Bourdon tube mechanisms can also be used to measure temperature. This is done by calibrating the pointer connecting linkage and relabeling the face of the gauge with a temperature scale. Oil temperature gauges often employ Bourdon tube mechanisms. [Figure 10-10]

Since the sensing and display of pressure or temperature information using a Bourdon tube mechanism usually occurs in a single instrument housing, they are most often direct reading gauges. But the Bourdon tube sensing device can also be used remotely. Regardless, it is necessary to direct the fluid to be measured into the Bourdon tube. For example, a common direct-reading gauge measuring engine oil pressure and indicating it to the pilot in the cockpit is mounted in the instrument panel. A small length of tubing connects a pressurized oil port on the engine, runs though the firewall, and into the back of the gauge. This setup is especially functional on light, single-engine aircraft in which the engine is mounted just forward of the instrument panel in the forward end of the fuselage. However, a remote sensing unit can be more practical on twin-engine aircraft where the engines are a long distance from the cockpit pressure display. Here, the Bourdon tubes motion is converted to an electrical signal and carried to the cockpit display via a wire. This is lighter and more efficient, eliminating the possibility of leaking fluids into the passenger compartment of the aircraft.

The diaphragm and bellows are two other basic sensing mechanisms employed in aircraft instruments for pressure measurement. The diaphragm is a hollow, thin-walled metal disk, usually corrugated. When pressure is introduced through an opening on one side of the disk, the entire disk expands. By placing linkage in contact against the other side of the disk, the movement of the pressurized diaphragm can be transferred to a pointer that registers the movement against the scale on the instrument face. [Figure 10-11]

Diaphragms can also be sealed. The diaphragm can be evacuated before sealing, retaining absolutely nothing inside. When this is done, the diaphragm is called an aneroid. Aneroids are used in many flight instruments. A diaphragm can also be filled with a gas to standard atmospheric pressure and then sealed. Each of these diaphragms has their uses, which are described in the next section. The common factor in all is that the expansion and contraction of the side wall of the diaphragm is the movement that correlates to increasing and decreasing pressure.

When a number of diaphragm chambers are connected together, the device is called a bellows. This accordion-like assembly of diaphragms can be very useful when measuring the difference in pressure between two gases, called differential pressure. Just as with a single diaphragm, it is the movement of the side walls of the bellows assembly that correlates with changes in pressure and to which a pointer linkage and gearing is attached to inform the pilot. [Figure 10-12]

10-7

Pressure entrancePressure entrance

Bellows Bellows

Figure 10-12. A bellows unit in a differential pressure gauge

compares two different pressure values. End movement of the

bellows away from the side with the highest pressure input occurs

when the pressures in the bellows are not equal. The indicator

linkage is calibrated to display the difference.

Diaphragms, aneroids, and bellows pressure sensing devices are often located inside the single instrument housing that contains the pointer and instrument dial read by the pilot on the instrument panel. Thus, many instruments that make use of these sensitive and reliable mechanisms are direct reading gauges. But, many remote sensing instrument systems also make use of the diaphragm and bellows. In this case, the sensing device containing the pressure sensitive diaphragm or bellows is located remotely on the engine or airframe. It is part of a transducer that converts the pressure into an electrical signal. The transducer, or transmitter, sends the signal to the gauge in the cockpit, or to a computer, for processing and subsequent display of the sensed condition. Examples of instruments that use a diaphragm or bellows in a direct reading or remote sensing gauge are the altimeter, vertical speed indicator, cabin differential pressure gauge (in pressurized aircraft), and manifold pressure gauge. Solid-state microtechnology pressure sensors are used in modern aircraft to determine the critical pressures needed for safe operation. Many of these have digital output ready for processing by electronic flight instrument computers and other onboard computers. Some sensors send microelectric signals that are converted to digital format for use by computers. As with the analog sensors described above, the

key to the function of solid-state sensors is their consistent property changes as pressure changes.

The solid-state sensors used in most aviation applications exhibit varying electrical output or resistance changes when pressure changes occur. Crystalline piezoelectric, piezoresistor, and semiconductor chip sensors are most common. In the typical sensor, tiny wires are embedded in the crystal or pressure-sensitive semiconductor chip. When pressure deflects the crystal(s), a small amount of electricity is created or, in the case of a semiconductor chip and some crystals, the resistance changes. Since the current and resistance changes vary directly with the amount of deflection, outputs can be calibrated and used to display pressure values.

Nearly all of the pressure information needed for engine, airframe, and flight instruments can be captured and/or calculated through the use of solid-state pressure sensors in combination with temperature sensors. But continued use of aneroid devices for comparisons involving absolute pressure is notable. Solid-state pressure-sensing systems are remote sensing systems. The sensors are mounted on the aircraft at convenient and effective locations.

Types of PressurePressure is a comparison between two forces. Absolute pressure exists when a force is compared to a total vacuum, or absolutely no pressure. It is necessary to define absolute pressure, because the air in the atmosphere is always exerting pressure on everything. Even when it seems there is no pressure being applied, like when a balloon is deflated, there is still atmospheric pressure inside and outside of the balloon. To measure that atmospheric pressure, it is necessary to compare it to a total absence of pressure, such as in a vacuum. Many aircraft instruments make use of absolute pressure values, such as the altimeter, the rate-of-climb indicator, and the manifold pressure gauge. As stated, this is usually done with an aneroid.

The most common type of pressure measurement is gauge pressure. This is the difference between the pressure to be measured and the atmospheric pressure. The gauge pressure inside the deflated balloon mentioned above is therefore 0 pounds per square inch (psi). Gauge pressure is easily measured and is obtained by ignoring the fact that the atmosphere is always exerting its pressure on everything. For example, a tire is filled with air to 32 psi at a sea level location and checked with a gauge to read 32 psi, which is the gauge pressure. The approximately 14.7 psi of air pressing on the outside of the tire is ignored. The absolute pressure in the