Fundamentals of Air Traffic Control (Fifth Edition) PDF

FUNDAMENTALS OF AIR TRAFFIC CONTROL FIFTH EDITION This page intentionally left blank FUNDAMENTALS OF AIR TRAFFIC CONTROL FIFTH EDITION Michael S. Nolan Purdue University Australia • Brazil • Japan • Korea • Mexico • Singapore • Spain • United Kingdom • United States This is an electronic ve...

FUNDAMENTALS OF AIR TRAFFIC CONTROL FIFTH EDITION This page intentionally left blank FUNDAMENTALS OF AIR TRAFFIC CONTROL FIFTH EDITION Michael S. Nolan Purdue University Australia • Brazil • Japan • Korea • Mexico • Singapore • Spain • United Kingdom • United States This is an electronic version of the print textbook. Due to electronic rights restrictions, some third party content may be suppressed. Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. The publisher reserves the right to remove content from this title at any time if subsequent rights restrictions require it. For valuable information on pricing, previous editions, changes to current editions, and alternate formats, please visit www.cengage.com/highered to search by ISBN#, author, title, or keyword for materials in your areas of interest. Fundamentals of Air Traffic Control, 5th Edition Michael S. 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Printed in United States of America 1 2 3 4 5 XX 12 11 10 CONTENTS Preface xv Chapter 1 History of Air Traffic Control 1 1903–1925 2 Early Aviation Developments 2 Development of Airmail Service 2 The Morrow Report 3 1925–1934 3 Air Commerce Act 3 Evolution of Air Traffic Control 4 1934–1945 10 Establishment of the Bureau of Air Commerce 10 En route Air Traffic Control 11 Copeland Committee 14 Civil Aeronautics Act of 1938 15 1940 Reorganization of the CAA 16 The War Years 17 Civilian versus Military Air Traffic Control 18 1945–1955 19 RTCA Special Committee 31 Report Air Traffic Congestion 20 19 1955–1965 22 Implementation of Radar 22 Budget Cutbacks 23 The Question of Airway Safety 24 Creation of the Federal Aviation Agency 25 vi / Contents The New York City Disaster 27 Project Beacon 28 Controller Unionization 30 1965–1981 31 Department of Transportation Continued Labor Unrest 32 Airline Deregulation 33 Controllers’ Strike of 1981 34 31 1981–2001 36 September 11, 2001 37 ATC Privatization 39 ATC Modernization 39 En route Automation Modernization Air Traffic Controller Staffing 40 Chapter 2 Navigation Systems 40 44 Visual Navigation 46 Pilotage 46 Aeronautical Charts 46 Dead Reckoning 49 Flight Planning 49 Aircraft Instrumentation 49 Magnetic Compass 49 Heading Indicator 52 VFR Navigation 53 Instrument Flying 55 Electronic Navigation 56 Four-Course Radio Range 56 Introduction of Marker Beacons 57 Nondirectional Beacons 58 Automatic Direction Finder 58 Compass Locators 59 Visual Aural Range 59 VHF Omnidirectional Range (VOR) 60 Airway Altitudes 66 Airway Designators 67 Aircraft Positioning Methods 67 DME Position Determination 70 Tactical Air Navigation (TACAN) 72 VORTAC 73 Contents Area Navigation 75 Doppler Radar 75 Course-Line Computers 77 LORAN 79 LORAN-C 80 Global Navigation Satellite System 84 Global Positioning System 84 Receiver Autonomous Integrity Monitoring 86 GNSS Augmentation 87 Wide Area Augmentation System (WAAS) 87 Ground-Based Augmentation System 87 Inertial Navigation System 89 Performance-Based Navigation 90 Required Navigation Performance 90 Special Aircraft and Aircrew Authorization Required Instrument Approach Procedures 92 Segments of an Instrument Approach Procedure 92 93 Approach Navigation Aid Classifications 101 Terminal VOR 101 Instrument Landing System 102 Simplified Directional Facility 119 GPS-Based Instrument Approaches 120 GPS Approach Waypoints 120 Approach and Landing procedures 121 Lateral Navigation (LNAV) 122 Approaches with Vertical Guidance 122 Lateral Navigation/Vertical Navigation (LNAV/VNAV) 122 Localizer Performance with Vertical Guidance (LPV) 122 Runway and Approach Lighting 123 Runway Lighting 123 Approach Lighting Systems 126 VFR Approach Lighting Systems 131 Chapter 3 Air Traffic Control System Structure 138 Airspace Classification 139 General Categories of Airspace 139 Controlled versus Uncontrolled Airspace 140 Airspace Review 140 IFR Flight in Controlled Airspace (Class A, B, C, D, and E) Air Traffic Control Clearance 144 141 / vii viii / Contents IFR Flight in Uncontrolled Airspace 153 VFR Flight in Controlled Airspace 153 VFR Flight in Uncontrolled Airspace 155 Airspace Classes 155 Class A Airspace 163 Class B Airspace 165 Class C Airspace 169 Class D Airspace 172 Special VFR 174 Class E Airspace 174 Federal Airways 176 Flight Levels 176 Airway Dimensions 180 High-Altitude Redesign Project 180 Navigation Reference System 181 Tango Routes 182 Class F Airspace 182 Class G Airspace 182 Special Use Airspace 184 Nonregulatory Special Use Airspace 186 Airport Advisory Areas 187 Military Training Routes 187 Chapter 4 Airport Air Traffic Control Communications: Procedures and Phraseology 190 Radio Communication 191 Simplex versus Duplex 191 Frequency Assignments 193 Radio Operation 194 Standard Phraseology for Verbal Communications ATC Communications Procedures 204 Clearance 205 Aircraft Identification 206 Destination Airport or Intermediate Fix 210 Departure Instructions 210 Route of Flight 211 Altitude Assignment 211 Required Reports 214 Holding Instructions 215 Additional Communications Phraseology 217 195 Contents Chapter 5 Air Traffic Control Procedures and Organization 220 Separation Responsibilities in Controlled Airspace 221 Air Traffic Control Procedures 224 Military Use of Civilian Airspace 224 Air Defense Identification Zones 225 Foreign Air Traffic Control Services 228 Privately Operated ATC Facilities 228 Delegation of Responsibility 229 Handoff Procedures 230 Preferential Routes 234 Approval Requests and Coordination 234 Controller Duties in an Air Route Traffic Control Center 237 Flight Data Controllers 237 Radar Controllers 237 Radar Associate/Nonradar Controller 237 Air Traffic Control Tower Responsibilities 237 Ground Control 238 Local Control 239 Approach and Departure Control 239 Chapter 6 Control Tower Procedures 241 Control Towers 242 Flight Data Controller Duties 242 Receiving and Relaying IFR Departure Clearances 243 Operating the Flight Data Processing Equipment 246 Relaying Weather and NOTAM Information 248 Clearance Delivery Controller Duties Ground Controller Duties 252 Preventing Runway Incursions 252 Protecting Critical Areas 255 Local Controller Duties 256 Runway Separation 256 Arriving Aircraft 260 Land and Hold Short Operations Spacing Aircraft 266 Spacing Instructions 267 Runway Selection 270 Runway Use Programs 270 265 250 / ix x / Contents Helicopter Operations 271 Wake Turbulence 272 Chapter 7 Nonradar En Route and Terminal Separation 279 Design of Separation Procedures 280 Airspace Dimensions 283 Separation Procedures 285 Vertical Separation 285 Lateral Separation 290 Holding Patterns 294 Longitudinal Separation 300 Initial Separation of Aircraft 308 Visual Separation 315 Chapter 8 Theory and Fundamentals of Radar Operation 318 History of Radar 319 Development of Pulse Radar 320 Components of Radar Systems 322 Ground Clutter 328 Transmitter Frequency 328 Receiver Controls 329 Receiver Gain 329 Moving Target Indicator 330 Moving Target Detection 336 Merge/Tracking 337 Sensitivity Time Control 337 Transmitter Controls 338 Display Controls 339 Range Select 339 Range Mark Interval and Intensity Receiver Gain 339 Video Map 340 Sweep Decenter 341 339 Types of Air Traffic Control Radar 342 Precision Approach Radar 342 Airport Surveillance Radar 344 Contents ASR-9 345 ASR-11 346 FPS-20 347 ARSR-1 347 ARSR-2 347 ARSR-3 347 ARSR-4 348 Airport Surface Detection Equipment 348 ASDE-X 348 Precision Runway Monitor 350 Air Traffic Control Radar Beacon System 351 Development of ATCRBS 352 ATCRBS Display 354 Secondary Radar System Deficiencies 355 Mode-S 357 Traffic Collision and Avoidance System 358 Traffic Information Service 359 Computerized Radar Systems 360 Automated Radar Terminal System 361 ARTS-III 363 ARTS-IIIA Operational Characteristics 366 Versions of ARTS-III 369 ARTS-II 370 Common ARTS 371 STARS 372 Radar Data Processing 373 Display System Replacement 375 User Request Evaluation Tool 376 ERAM 377 Enhanced Backup Surveillance 379 Center Radar ARTS Presentation 379 Chapter 9 Radar Separation 381 Aircraft Identification 382 Primary Radar Identification 382 Secondary Surveillance Radar Identification Transfer of Radar Identification 386 Handoff Procedures 387 Point Out Procedures 389 Basic Radar Separation 390 Separation Standards 391 383 / xi xii / Contents Radar-Assisted Navigation 399 Radar Arrivals and Approaches Approach Gate 403 Arrival Instructions 403 ASR Approach 405 401 Radar Traffic Information 408 Use of Automation Tools 412 User Request Evaluation Tool 412 Chapter 10 Operation in the National Airspace System 417 Overview of an IFR Flight 418 Flight Planning and IFR Clearances 418 Coded Departure Routes 418 Traffic Flow Management Programs 420 Alternative Routes 424 Clearance Delivery 424 Phoenix Airspace 429 Ground Control Coded Departure Routes 431 Local Control 433 Departure Control 435 En route Separation 438 Miles in Trail Restrictions 443 Metering 443 Delay Techniques 443 Approach Control 445 Indianapolis Approach Control 445 Local Control 451 Example of a VFR Flight 453 Lafayette to Champaign 453 Overdue Aircraft 460 Chapter 11 Oceanic and International Air Traffic Control 463 International Air Traffic Control 464 Canadian Air Traffic Control International Airspace 466 Airport Identifiers 467 465 Contents European Air Traffic Control 469 Atlantic Ocean Air Traffic Control 470 North Atlantic Separation 471 MNPS Airspace Operations 472 MNPS Airspace Separation 477 ATOPS/Ocean 21 480 Trans-Polar Flights 480 Alternate Airports and Fuel Temperature 481 Communication and Navigation 482 Chapter 12 The Future of the National Airspace System Automated Air Traffic Control 486 Procedural Separation Standards 487 ATC Modernization 488 Current ATC Initiatives 489 Departure Delay Program 489 En route Metering Program 489 En route Sector Loading Program 490 Procedural Changes 491 National Route Program 491 CNS Improvements 491 Communications System Changes 492 Required Navigation Performance 494 Navigation Security 495 Surveillance Systems 496 Air Traffic Management 497 Hardware 498 Next Generation Air Traffic Control (NextGen) Major Components of NextGen 499 Trajectory-Based Operations 499 Flexible Airspace Management 500 Collaborative Air Traffic Management 500 Negotiated Routes 503 Improved Aircraft Separation 504 Additional ADS Functions 504 En route Automation Modernization 505 498 485 / xiii xiv / Contents Chapter 13 The Federal Aviation Administration 507 Administrative Structure 508 FAA Operations 508 FAA Organization 508 Administrative Structure 508 Administrator and Deputy Administrator Associate Administrators 510 FAA Regional Offices 511 Air Traffic Organization 512 510 Getting Hired by the FAA 515 Controller Hiring Sources 515 Certified Controllers 515 Approved College Programs 515 Medical Examination 517 Security Investigation 517 Application Process 518 FAA Academy Training 518 Field Training Program 519 Salaries 519 Locality Pay 523 ATC Facility Classifications 523 FAA Air Traffic Control Facilities 523 Federal Contract Air Traffic Control Services Flight Service Stations 540 Appendix A IFR Aeronautical Charts 543 Appendix B Aircraft Models and Performance Appendix C Three-Letter Identifiers Glossary 603 Common Abbreviations 634 References 638 Photo Credits Index 641 640 524 599 589 PREFACE This book was started over 20 years ago after having searched long and hard for an appropriate college-level textbook on air traffic control. Various Federal Aviation Administration publications have been available for years, as have commercial introductory texts. However, most of these books either describe rules and regulations or take a simplistic approach to how the air traffic control system works. No text has described how the ATC system works and why it operates the way it does. This book remedies that situation. It describes the background and history of the development of the air traffic control system, emphasizing why things are done the way they are, instead of simply repeating rules and regulations. Throughout the text, appropriate real-life examples are used to illustrate the reasoning behind procedures used by air traffic controllers. The liberal use of figures and example phraseology assists the student in achieving an overall understanding of the air traffic control system. It is hoped that with this knowledge, future air traffic controllers will have a far better understanding of their chosen profession and can make the appropriate decisions that will lead aviation into the next century. There are many unique features to this textbook that are not found in any other text on air traffic control. These features include the following. What’s New in This Edition • New, required performance-based operation standards including navigation, communications, and surveillance • Examples of RNP in both the en route and terminal environment • Information on LNAV and VNAV approaches as well as similar variants • Updated Atlantic, Pacific, and Arctic navigation procedures • 9/11 history and required security changes to air traffic control • Updated flight examples including the use of traffic flow management • New ATC systems including ASR-11, STARS, and ERAM • NextGen operations and timeline xvi / Preface History and Background The history of the development of the air traffic control system and many of its components is included throughout the book. This history is not intended to be a dry repeat of names and dates but rather an explanation of past decisions that dramatically affected the current air traffic control system. Illustrations, Charts, and Photographs Abundant illustrations, charts, and photographs are provided in this textbook. Air traffic control is a three-dimensional, visually oriented profession that cannot be explained simply through the use of text. These illustrations were designed to supplement the text, further explaining concepts and ideas that are difficult for the inexperienced student to visualize when simply reading about them. Examples and Phraseology One of the most important tasks facing a controller is the proper use of phraseology. The air traffic control system is based on comprehension and usage of strange and sometimes hard to understand wording. In addition to explaining the proper use of terms, the text includes numerous examples of the proper usage of phraseology. Real-Life Examples Throughout the text, examples found in real life are used to further explain the concepts introduced. In addition, one entire chapter is dedicated to the actual operation of the air traffic control system. “Behind the scenes” activities and coordination are described, using sample flights through actual airspace. Such examples reinforce the material introduced in earlier chapters, further clarifying and explaining some of the complicated procedures used to separate air traffic above the United States. The first four chapters of this text prepare the student for understanding the intricate procedures used in controlling air traffic. These four chapters cover fundamental topics, such as history, navigation, and phraseology. Chapters 5 through 11 detail the separation of aircraft in the ATC system. Chapter 12 takes an in-depth look at the future of air traffic control, and Chapter 13 discusses employment opportunities for air traffic controllers. At the conclusion of the text is a detailed glossary of terms introduced in the book. Collegiate Training Initiative This textbook has been designed with the Federal Aviation Administration’s College Training Initiative in mind. This program was developed to provide education to future FAA controllers. The material in this textbook provides much of the knowledge needed by tomorrow’s air traffic controllers. Acknowledgements I would like to thank the following individuals who have made this textbook possible. Without their gracious help and assistance, it would have been impossible to complete this book: Juanita Hull, Federal Aviation Administration; James Cheesman, SRSA Corporation; Mike Pearson, aviation attorney, professor, and air traffic controller; Jeff Berry, ZID controller; Denise Mason from IND tower; and the entire staff and management of the Champaign, Lafayette, and Phoenix ATCTs as well as Indianapolis ATCT and ARTCC. Over the course of the development and maintenance of this book, many reviewers have made helpful suggestions: Roger Bacchieri, Daniel Webster College; Peter Bailey, Wilmington College; Peggy Baty, Embry-Riddle Aeronautical University; Terry S. Bowman, Southern Illinois University; Jeffry B. Burbridge, Preface / xvii Catonsville Community College; Jonathan R. Burke, Metropolitan State College of Denver; Veronica T. Cote, Bridgewater State College; Michael Farley, Bridgewater State College; Bruce D. Hoover, Palo Alto College; Roger Matteson, Central Washington University; Patrick K. Mattson, St. Cloud State University; Mary Ozimkowski, Metropolitan State College; Keith Parkman, Embry-Riddle Aeronautical University; Martha Pearce, Arizona State University; Michael J. Polay, Embry-Riddle Aeronautical University; Robert Rogus, Mt. San Antonio College; Jose Ruiz, Southern Illinois University; Robert H. Ryder, Delta State University; Thomas Teller, Daniel Webster College; and Henry Whitney, Mt. San Antonio College. This edition was reviewed by David West, Mt. San Antonio College; Les Wilkinson, Aims Community College; Trena M. Mathis, Minneapolis Community & Technical College; and Dr. Jose R. Ruiz, Southern Illinois University, Carbondale. Thank you everyone. The air traffic control system in the United States is truly a system, which means that it requires the efforts of many individuals in order for it to work. I’ve found that publishing a textbook is much the same. Although my name is on the cover, only the concerted efforts of a diligent, professional, and very talented group of people made it possible for this book to be published. Everyone involved was just as important as everyone else, as is the case in any system. We should all be very thankful for their work and effort. I sure am. The first edition was completed in 1990 through the efforts of a group of individuals at both Wadsworth and Delmar Associates. Although many of them are no longer connected with this project, their legacy lives on, and I remember them fondly. They include Anne ScanlanRohrer, aviation editor at Wadsworth, and her editorial assistants, Leslie With, Karen Moore, and Cathie Fields. Jackie Estrada, Richard Carter, Detta Penna, Robin Witkin, and Nancy Sjoberg developed the layout and most of the illustrations for the first edition. Thanks to one and all. The second edition was coordinated by Ruth Cottrell of Ruth Cottrell Books and Jennie Burger of Wadsworth, assisted by Barbara Britton and Charles Cox; and the third edition by Tobi Giannone of Michael Bass Associates and Marie Carigma-Sambilay of Wadsworth, assisted by Hal Humphrey and Karen Hunt. The fourth edition was coordinated by Andy Sieverman of G&S Typesetters and Carol Benedict of Wadsworth. They were assisted by Belinda Krohmer and Jessica Reed. The fifth edition was led by David Boelio, executive editor; Jillian Borden, editorial assistant; Sharon Chambliss, senior product manager; and Barbara LeFleur, content project manager. I can never thank all of these people enough. They continually teach me how to revise and edit this text in an attempt to keep it up to date. They are the book experts, responsible for the ultimate product you see before you. They were indispensable members of our system. Without them, this project could never have been accomplished. And, of course I must thank my wife, Barbara, and my three children, Linda, Erin, and David, who gave up a lot of their time with Daddy so he could publish this text. It started before they were born and now they are reading it in college! I am indebted to each and every one of you. Mike Nolan xviii / Preface Michael S. Nolan (B.S., Industrial Technology, Illinois State University; M.S., Instructional Development and Educational Computing, Purdue University) is a former air traffic controller and holds licenses and certification as a commercial pilot, flight instructor, instrument instructor, tower operator, airframe and powerplant mechanic, and aviation weather observer. He has taught a variety of aviation courses at the University of Illinois and at Chanute Air Force Base as well as at Purdue University, where he currently teaches in the Aviation Technology Department. 1 History of Air Traffic Control Checkpoints After studying this chapter, you should be able to: 1. Discuss the significance of the Airmail Act of 1925. 2. Describe how the federal government became involved in air traffic control. 3. Discuss the history of the various federal agencies involved in air traffic control. 4. Discuss the formation of organized labor unions as they pertain to air traffic control. 5. Identify the organizations currently involved in the air traffic control system. 6. Identify the various organizations that have represented air traffic controllers. 7. Identify some of the methods air traffic controllers used in the past to separate aircraft. 8. The effects of 9/11 on the air traffic control system. 2 / CHAPTER 1 1903–1925 Early Aviation Developments When the Wright brothers’ experiment in flight succeeded on December 17, 1903, the world took little notice. Newspapers of that era either did not believe or belittled the accomplishments of the two brothers on that cold, blustery morning. At the start of the twentieth century, most people regarded aviation as a pastime for experimenters and daredevils. It was hard to believe that the tiny, underpowered aircraft of that era would ever evolve into a useful form of transportation. In this early period of experimentation, anyone with a mechanical aptitude could design, build, and fly an aircraft without passing any type of test or possessing any type of license. Without regulation or certification, people began to build and quite regularly crash these early flying machines. The general public was frightened by the machines and believed that only fools would fly in them. Potential investors in this new industry were fearful of risking their capital to finance an unproven and apparently dangerous industry. In spite of this climate of fear and distrust, aviation pioneers began to demonstrate the usefulness of their primitive flying machines. As early as 1911, the first mail was carried by air. By the time the United States became involved in World War I, the airplane had demonstrated its usefulness as an observation platform and as a crude weapons delivery system. After the war, numerous additional uses were found for the airplane. The Post Office Department began to offer routine airmail service in 1918, using U.S. Army pilots and aircraft. In 1919, the U.S. Department of Agriculture initiated experiments that would lead to the commercial use of aircraft for the application of pesticides. The first transatlantic crossing was made that year, which also saw the first experimental use of radio as a navigation aid. Development of Airmail Service Between 1918 and 1925, airmail service was expanded by the Post Office Department until full transcontinental service was finally achieved. Until 1923, most of the mail was flown during daylight hours, since a safe, reliable form of nighttime navigation had not been developed. In 1921 the first experimental night flight was conducted, using bonfires located along the navigation route. These bonfires were replaced in 1923, when a 72-mile stretch of airway between Dayton and Columbus, Ohio, was experimentally lit with electric and gas arc lighting. The experiment proved successful, and airway lighting was soon introduced across the country. By 1924 the portion of the transcontinental airway between Cheyenne, Wyoming, and Chicago, Illinois, was lit, and routine night flights were being conducted along this section of the airway. By 1925, the commercial potential for aviation had been established, and the Post Office Department found itself under pressure to expand airmail service at a faster rate than was possible for a government agency. Since aviation appeared to be a commercially viable industry, it was felt that airmail service could now be handled by private airline companies. A resolution to permit History of Air Traffic Control / 3 private contracting, introduced by Congressman Clyde Kelly of Pennsylvania, was signed into law on February 2, 1925, and became known as the Airmail Act of 1925. The Airmail Act authorized the postmaster general to contract with private individuals and corporations for the purpose of transporting airmail. Between 1925 and 1927, airmail contracts were bid to private corporations, and commercial aviation became a reality. After this act was signed into law, many companies that had been sitting on the sidelines earnestly jumped into the aviation field. Boeing, Douglas, and Pratt and Whitney were just a few of the companies that bid to supply aircraft and engines to the budding airmail industry. Even the great Henry Ford entered the picture, producing the famous Ford Trimotor and operating an air cargo airline between Detroit and Chicago. The Morrow Report With this increase in air activity came an increased desire for some type of national regulation of the industry. Prior to this time, individual states had reserved the right to test and certify pilots, but many were hesitant to exercise this authority. The aviation industry was still fragile, and public sentiment favored federal government regulation to unify the industry through a common set of rules, procedures, and certifications. It was felt that government regulations were needed if the aviation industry were to grow and prosper. Without this regulation, the public’s trust could not be gained. A joint congressional committee recommended the formation of an advisory board composed of prominent businessmen to recommend the possible extent of federal involvement in the aviation industry. In 1924, President Calvin Coolidge appointed Dwight Morrow to head this board and make recommendations as to future government policy. The Morrow board presented its final report to the president on December 2, 1925. The Morrow Report recommended that military and civilian aviation operate separately, with the Department of Commerce to be given the responsibility for the promotion and the regulation of the civilian aviation industry. 1925–1934 Air Commerce Act President Coolidge endorsed the findings of the Morrow Report and passed it along to Congress. He requested that the board’s recommendations be implemented as soon as possible. After the inevitable discussion and negotiations, Congress approved, and President Coolidge signed the Air Commerce Act into law on May 20, 1926. As Senator Hiram Bingham, who introduced the Air Commerce Act into the Senate, explained, the purpose of the act was “not so much to regulate as to promote civilian aviation.” The Air Commerce Act made it the duty of the secretary of commerce (at that time Herbert Hoover) to encourage the growth of the aviation industry through the establishment of airways and navigation aids. In addition, the secretary was authorized to regulate the industry 4 / CHAPTER 1 as necessary to elevate the public’s perception of aviation as a safe mode of transportation. To this end, Hoover instituted a program to license pilots and mechanics and to regulate the use of these airways. These responsibilities were delegated to the Aeronautics Branch of the Department of Commerce, which was headed by the new director of aeronautics, Clarence M. Young. In May 1927, Charles Lindbergh captured the attention of the nation with his daring flight across the Atlantic. During that same year, the first groundto-air experimental radio was installed in an aircraft. In 1928, the first seven airmail-route radio stations were installed. Many of today’s airlines were born in this era. Colonial Airlines (American), Western Express (TWA), Northwest Airlines, and United Airlines were all formed during this exciting period of air transportation growth. Evolution of Air Traffic Control Prior to the early 1930s, there was little need for an organized system of air traffic control in the United States. Almost all of the aerial traffic in this country was conducted in daylight with clear flying conditions. Advances in aircraft control and navigation that would permit flight at night or during periods of restricted visibility had yet to be made. The practice of “see and be seen” became the principal method of traffic avoidance. This meant that pilots could fly only in conditions that would permit them to see other aircraft and alter their flight path in time to avoid them. According to this principle, pilots were required to fly clear of any clouds and only in areas where the visibility was at least 3 miles. These rules have been only slightly modified since then and are now known as visual flight rules (VFR). (A discussion of the current version of these flight rules is presented in Chapter 3.) Since the aircraft used by the airlines in the 1930s were relatively slow and the pilots could readily see and avoid other aircraft, the establishment of an organized air traffic control system was not deemed necessary. But by the late 1930s, the capability of aircraft to fly at night and in marginal weather conditions had improved tremendously. Instrumentation that would permit pilots to control the aircraft without visual reference to the natural horizon had been designed. In addition, a system of ground-based radio navigation aids (navaids) was being constructed to permit pilots to navigate without ground reference. When this equipment was installed, pilots were able to take off, cruise en route, and land in weather conditions that would not permit them to see and avoid other aircraft. Because all of these aircraft eventually had to land at an airport, it was inevitable that the airspace within the immediate vicinity of busy airports became congested, and some form of local air traffic control would soon be needed. The problem of airspace congestion was compounded by the fact that the airports of that era only remotely resembled the airports of today. An airport in the 1930s rarely had designated runways. It usually consisted of a large, rectangular plot of land covered with either sod or cinders. After flying over the airport to observe the wind direction, local traffic, and runway conditions, the pilots themselves decided in which direction they wished to land. During the approach and landing, the pilots were kept busy History of Air Traffic Control / 5 trying to spot other aircraft, decide who had priority, and maneuver their planes behind the others, allotting sufficient time for a previous plane to land, brake to a stop, and taxi clear of the runway prior to their arrival. In addition, pilots needed to constantly scan the airport surface area to detect aircraft taxiing for takeoff. To decrease ground roll distance, pilots usually maneuvered their aircraft to land or take off into the wind. On windy days, this forced most of the pilots to land and take off in the same direction. But on calm days, aircraft could be seen landing and taking off in every direction. It was immediately apparent that some form of air traffic control would have to be initiated around airports or accidents would begin to occur at an increasing rate. FAA Air Traffic Controllers The earliest method of regulating takeoffs and landings required an air traffic controller to stand in a prominent location on the airfield and use colored flags to communicate with the pilots. If the controller waved a green flag, it meant that the pilots were to proceed with their planned takeoff or landing. But if the controller waved a red flag, the pilots were to hold their position until the controller had determined that it was safe to continue. At that time, the controller would wave the green flag, advising the pilots that they could proceed. The first airport to hire this type of air traffic controller was the St. Louis Airport in Missouri. In 1929, St. Louis hired Archie League as the nation’s first air traffic controller (see Figure 1–1). Figure 1–1. The first air traffic controller, Archie W. League, shown in his winter clothing at the St. Louis Lambert Municipal Airport in 1929. 6 / CHAPTER 1 FAA Before taking on this role, League had been a barnstormer, a mechanic, and the operator of a flying circus. League controlled air traffic from a wheelbarrow on which he had mounted a beach umbrella. In the morning, he would pack the wheelbarrow with a beach chair, water, a note pad, a pair of colored flags, and his lunch. He would wheel his equipment out to the approach end of the runway, where he would use the flags to advise the pilots to either continue their approach or hold until the traffic was clear. At the end of the day, League would repack his equipment into the wheelbarrow and return to the terminal. He performed these tasks both winter and summer, beginning a 36-year career in air traffic control (see Figure 1–2). Other large cities soon saw the advantages of this system and began to employ air traffic controllers at their own airports. Although workable, this early, crude form of air traffic control had many obvious drawbacks. Since the controller usually stood near the approach end of the runway, he was far more likely to attract the attention of departing rather than arriving aircraft. Pilots inbound for landing found it difficult to determine which direction to land and to see the air traffic controller’s location. And if more than one aircraft was inbound, it became difficult, if not impossible, for Figure 1–2. Archie League standing next to a spotlight while guiding down an aircraft during IFR weather. History of Air Traffic Control / 7 FAA the air traffic controller to give different instructions to each plane. It was also difficult for the controller to determine whether the pilots had actually received and understood the intended instructions. And it was impossible to use this system of communication at night or during stormy weather. Fortunately, at that time few aircraft flew during such weather conditions. Light Guns In an attempt to rectify some of these problems, the controller’s colored flags were soon replaced by light guns. A light gun is a device that permits the controller to direct a narrow beam of high-intensity colored light to a specific aircraft (see Figure 1–3). Light guns were equipped with a gunsight that let the controller accurately aim the beam of light at one particular aircraft. The gun was also equipped with different-colored lenses to permit the controller to easily change the color of the light. The controller operated the light gun either from a glassed-in room on top of a hangar, called a control tower, or from a portable light gun station located near the arrival end of the runway. The light gun signals used by the early controllers resembled the colored-flag system. A red light advised the pilots to hold their aircraft, whereas a green light advised them to proceed. Most of the busy airports soon built control towers and installed these light guns. The control towers were usually placed on top of one of the highest structures at the airport. Controllers working in the tower now had an unobstructed view of the airport and the surrounding airspace. They no longer had to stand out next to the runway, exposed to the elements. Light guns are still used today at most control towers. They are used to communicate when either the radios in the control tower or the aircraft Figure 1–3. Using a are inoperative or when an aircraft is not radio equipped. The light gun light gun signal. code has not changed significantly since the 1930s. The official light gun signals in use today are listed in Table 1–1. Table 1–1. Light Gun Signals Color and Type of Signal Meaning with Respect to Aircraft on the Ground Meaning with Respect to Aircraft in Flight Steady green Cleared for takeoff Cleared to land Flashing green Cleared to taxi Return for landing (to be followed by a steady green at the proper time) Steady red Stop Give way to other aircraft and continue circling Flashing red Taxi clear of runway in use Airport unsafe, do not land Flashing white Return to starting point on airport Not applicable Alternating red and green Exercise extreme caution Exercise extreme caution 8 / CHAPTER 1 Although the light gun was an improvement over the colored-flag system of air traffic control, a number of important deficiencies still remained. When inbound to the airport, the pilots were usually busy flying their aircraft and were unable to maintain a constant lookout for changing light gun signals. As a result, the controller might not be able to transmit critical instructions to pilots who were performing some other task and whose attention was diverted. The light guns were also useless in bad weather, since airborne particles of dust and moisture easily diffused and refracted the light beam. Furthermore, the controller could never be quite sure whether the pilot had received or properly interpreted the light gun signal. The controller could give instructions to the pilots, but the pilots had no means for communicating to the air traffic controller. It was apparent that a reliable, two-way communications system would have to be developed. Radio Communication The modern system of air traffic control was born at the Cleveland Airport in Ohio. The city of Cleveland constructed a control tower on top of an old hangar and equipped this facility with radio transmitting and receiving equipment. The communications transmitters were 15-watt radios that permitted voice communication with pilots over a distance of approximately 15 miles. Using this primitive radio equipment, the air traffic controller could communicate directly with the pilots of properly equipped aircraft. In addition, the pilots could respond to these instructions or initiate communication with the controllers. This system permitted the controllers to issue traffic instructions, weather information, and airport landing conditions to the pilots of radio-equipped aircraft. This voice communication could be maintained night and day, in good weather or in bad. The control tower was also equipped with light guns to permit controllers to communicate with aircraft that were not radio equipped. The light guns were also used for backup communications in case the radio equipment in either the control tower or the aircraft malfunctioned. By being located on top of the highest structure at the airport, the controllers had an unobstructed view of the airport surface area and the approaches to the landing area. This permitted the controllers to issue instructions that would properly sequence aircraft inbound for landing with those attempting to depart. Most of the busy airports around the country followed Cleveland’s example and constructed radio-equipped air traffic control towers (see Figure 1–4). Despite the dramatic safety improvement that these towers offered, their effectiveness was limited, since the primitive radio equipment was heavy, clumsy to use, unreliable, and relatively expensive. The airlines were hesitant to install this equipment on planes since it would replace valuable, revenue-producing space on the aircraft. Furthermore, most of the small aircraft in use during this era were manufactured with electrical systems that provided insufficient power to operate the radios, and the owners were often unable to afford the expensive electrical system modifications that would permit them to benefit from this advance in air traffic control technology. / 9 Michael Nolan History of Air Traffic Control Figure 1–4. The control tower at Indianapolis’s Stout Field. Air traffic controllers and pilots were also severely handicapped by the lack of a standardized set of rules or phrases to be used when communicating with each other. Some pilots contacted the control tower when they were 5 to 10 miles away from the airport, whereas other pilots neglected to contact the controllers until they were almost ready to land. Even though the air traffic controllers were federally certified, they were still airport employees, and pilots had no legal obligation to contact them. And if radio contact was established, there was little agreement on the phraseology that should be used. Many pilots simply did not understand the instructions that were being transmitted to them. Despite these serious limitations, this early form of air traffic control worked remarkably well. Radio permitted the controllers to pass along valuable information and control instructions to the pilots of properly equipped aircraft, and the pilots could acknowledge receipt of these instructions and make accurate position reports to the controllers. Instrument Flying At the same time that control towers were being constructed, aircraft designers were beginning to produce a new generation of faster, higher flying transport aircraft specifically designed for airline operation. These aircraft were equipped with advanced instrumentation and radio navigation equipment that would permit their pilots to fly in weather 10 / CHAPTER 1 conditions that had made navigation impossible just 10 years ago. Using these instruments and the ground-based radio navigation aids installed by the federal government, the airlines began to routinely conduct flights of hundreds of miles through cloud and fog with no outside reference. These flight conditions, where aircraft control and navigation are conducted solely by reference to cockpit instrumentation, are known as instrument meteorological conditions (IMCs). Pilots of properly equipped aircraft could now fly in conditions where in-flight visibility might be measured in feet instead of miles. Pilots were able to land when visibilities were less than 2 miles. Certainly in these flight conditions, the “see-and-be-seen” concept of aircraft separation was inadequate. In addition, as the airlines introduced newer airliners into service such as the DC-2, DC-3, and Boeing 247, the wide disparity in performance between these aircraft and the older planes in service became more readily apparent. This mix of aircraft with different cruising airspeeds and flight characteristics increased the complexity involved in separating aircraft and made it much more difficult for the air traffic controller to properly and safely sequence traffic inbound for landing. The only reason that midair collisions occurred infrequently was that few aircraft were flying in reduced visibility conditions at the same altitude, on the same route, and at the same time. By the early 1930s, the airspace around major airports had become increasingly crowded; people living around these airports felt that the risk of midair collisions had increased and feared that colliding aircraft might crash into their neighborhoods. These residents began to pressure the states and the localities around the major airports to pass laws restricting air travel over their jurisdictions. It was apparent that utter chaos would result in the aviation industry if every state enacted legislation restricting or banning flight over certain areas. These restrictions would retard the growth of the airline industry and might jeopardize its very existence. 1934–1945 Establishment of the Bureau of Air Commerce In response to this threat to the nation’s interstate commerce, in 1934 Congress created the Bureau of Air Commerce (part of the Department of Commerce) as the agency responsible for the regulation of traffic along the nation’s airways. This act made the federal government responsible for the licensing of pilots, the establishment of airways and navigation aids, and the actual separation and safety of the aircraft using these airways. In 1936, the Bureau of Air Commerce established rules to be followed by pilots when flying on the airways in instrument meteorological conditions. These rules are known as instrument flight rules (IFR). Because most of the major airports had already constructed and staffed air traffic control towers, the most pressing need facing the aviation industry History of Air Traffic Control / 11 was for the separation of aircraft flying between airports. The airways in the eastern United States had become increasingly congested, and during periods of IFR weather, near misses began to occur with increasing frequency. Some form of traffic control on these busy airways would have to be established as soon as possible. As a result of Depression-era budget restrictions, the Department of Commerce was unable to quickly form an air traffic control system and requested that the major airlines themselves take the initiative and develop a number of airway traffic control units (ATCUs) that would separate aircraft operating on the federal airways. The federal government promised that it would take possession of and operate these facilities at a later date. On December 1, 1935, TWA, American, Eastern, and United Airlines formed the first experimental airway traffic control unit at the Newark (New Jersey) Airport (see Figure 1–5). The responsibility of the ATCU was to separate traffic operating on the airway during periods of IFR weather. During VFR weather, pilots flying the airways would still separate themselves using the see-and-avoid principles of air traffic control. En route Air Traffic Control FAA Following the operational success of the first ATCU, the four airlines were encouraged by the Department of Commerce to open additional units in Figure 1–5. Controllers at the Newark ATCU separating en route traffic using maps and shrimp boats. 12 / CHAPTER 1 Chicago, Cleveland, Pittsburgh, and Oakland. These ATCUs were opened a short time thereafter and were staffed by employees of the airlines. By mutual agreement, each of these ATCUs assumed responsibility for separating IFR traffic within a selected area of airspace. It was not mandatory that every pilot contact the ATCUs, however. Military and noncommercial civilian aircraft were not required by law to contact the ATCUs. Fortunately, most of the IFRcertified aircraft were operated by the airlines. Because of the technical limitations of 1930s radio equipment, all communication between the pilots and controllers was accomplished through an intermediary, either an airline dispatcher or a radio operator. Whenever pilots planned to fly in poor weather conditions, they filed an instrument flight plan with an airline dispatch office. This flight plan included the type of aircraft to be flown, the names of departure and arrival airports, the estimated departure time and time en route, the airline flight number, the requested route of flight, the aircraft’s cruising airspeed, and the requested cruising altitude. The airline dispatcher on duty forwarded this information by telephone to the ATCU with responsibility for the departure airport. The air traffic controllers on duty determined whether the route and altitude requested by the pilot might conflict with other aircraft and modified the flight plan as necessary to ensure the safe separation of aircraft. The controllers then issued an air traffic control clearance to the dispatcher that was to be relayed to the pilot. This clearance included the departure time, route of flight, and cruising altitude. The dispatcher relayed this information to the pilot, either in person or by radio. The air traffic controllers in the ATCU wrote the appropriate flight plan information on a chalkboard and on a note card. This card was then attached to a brass holder that was called a shrimp boat by the controllers because of its resemblance to a small fishing boat. These shrimp boats would be moved along an airway map, indicating the approximate positions of the aircraft as they flew toward their destinations. As each plane progressed through the ATCU’s airspace, the pilots would transmit their position to an airline company radio operator, who then relayed this information to the ATCU controller by telephone or telegraph. The ATCU controllers updated the aircrafts’ information on their blackboard and note cards and continued to move the shrimp boats along the map indicating each plane’s approximate position. If a controller detected a potential conflict between two aircraft, appropriate route or altitude changes would be issued to one or both aircraft. These instructions were telephoned to the airline radio station nearest the last reported positions of the aircraft. The airline radio operator would then try to relay this information to the pilots. If the radio operator was unable to contact the aircraft, the ATCU controller would telephone other airline radio stations and ask that they try to make contact with the aircraft. Because of the problems inherent with the frequencies used by radio transmitters and receivers of that era, the controller might be required to telephone a number of radio operators before one could be found who could establish contact with the desired aircraft. Under certain adverse weather conditions, the History of Air Traffic Control / 13 radio operators might not be able to make contact with a particular aircraft for hours at a time. Normally, three air traffic controllers were on duty in the ATCU at any one time. Each controller was assigned different job responsibilities. The “A” controller was responsible for the safe separation of all the participating aircraft operating within the ATCU’s area of jurisdiction. Using the information provided on the flight plan and gathered through position reports, the “A” controller determined whether potential conflicts existed and undertook corrective action. The “A” controller communicated with the airline radio operators by telephone and issued the clearances that were then relayed to the pilots. As position reports were obtained from the pilots, the “B” controller was responsible for moving the shrimp boats across the airway map. In addition, the “B” controller received updated weather reports and was responsible for disseminating this information to the pilots. Using position reports obtained from the pilots, the estimated airspeeds from the flight plans, and the estimated winds aloft, the “C” controller calculated the future location of each aircraft. The “C” controller wrote this information on the blackboard and on the note cards attached to the shrimp boats. During periods of reduced staffing (such as evenings, weekends, and holidays), there might be two or possibly only one controller staffing the ATCU, and the responsibilities were divided evenly. During periods of good weather, when pilots could legally fly under the existing VFR flight rules, the ATCU controllers exercised passive control of the aircraft. Passive control means that the controllers would track and update the flight path of each aircraft and would advise the pilot of the presence of other aircraft only if they were predicted to be within about 15 minutes’ flying time of each other. The controllers would not issue any instructions to try to separate these aircraft unless either pilot requested this service. Since the weather was VFR, it was assumed that the pilots could see and avoid each other. Whenever adverse weather conditions existed and the pilots were unable to operate in VFR conditions, the controllers began to exercise active control of air traffic along the airways. Active air traffic control assumes that the pilots cannot see and avoid each other, and the controllers must issue instructions to ensure that all participating aircraft remain safely separated (see Figure 1–6). Although the air traffic control units were successful in accomplishing the initial objective of separating aircraft along the busiest sections of the airways, a number of problems were immediately apparent. Many airline companies were operating in the United States, but only four of them were chosen to operate the ATCUs. Any pilot who wished to participate in the air traffic control system was required to file a flight plan and receive a clearance from the controllers at the ATCU. The fact that the controllers were all employees of the four airline companies led to numerous complaints of favoritism and of unjustified holding of competing and privately owned aircraft. In addition, the legal authority of the ATCUs and their controllers was questionable. Pilots were not required by law to file flight plans until August of 1936. An additional problem was that few established or standardized procedures existed for the separation of aircraft operating along the airways. FAA 14 / CHAPTER 1 Figure 1–6. Controllers at the St. Louis Center in 1939 separating en route aircraft using flight progress strips. There was also little agreement as to how the transfer of control would occur when the aircraft entered the local area around the airport. Since the air traffic control towers were operated by the cities, whose controllers did not even have to be federally certified, little agreement or coordination occurred between the towers and the ATCUs. On June 6, 1937, the Department of Commerce began to acquire the ATCUs from the airlines and staff them with federally certified controllers. The federal government renamed these facilities airway traffic control stations (ATCSs). Many of the ATCU employees transferred from the airlines to the government. In most cases, these employees took a considerable pay cut to do so. With the acquisition of the ATCSs, the Department of Commerce began to implement standardized air traffic control procedures. In May 1938, the Department of Commerce also became the licensing authority for all civilian air traffic controllers, both those employed in the ATCSs and those operating the air traffic control towers. Copeland Committee On May 6, 1935, a TWA airliner crashed outside of Kansas City, killing five persons including Senator Bronson M. Cutting of New Mexico. This accident and a number of other factors prompted Congress to commission a report on History of Air Traffic Control / 15 air traffic safety and the operation of the Bureau of Air Commerce. The Senate appointed Royal S. Copeland, the chairman of the Commerce Committee, to head the commission. The preliminary report issued by this committee (known as the Copeland Committee) was released on June 30, 1936. The report was a scathing (and in retrospect very biased) indictment of the Bureau of Air Commerce. As a subordinate bureau in the Department of Commerce, the Bureau of Air Commerce had become enmeshed in politics and had found it difficult to improve the airway system in the midst of the Depression. The report blamed the bureau for providing insufficient funding and maintenance of airway navaids. At the same time, a Bureau of Air Commerce accident report placed the blame for the crash on the pilots of the TWA aircraft. The controversy that ensued harshly pointed out the problems in the nation’s air traffic control system. Both Congress and President Franklin D. Roosevelt decided that something needed to be done. Civil Aeronautics Act of 1938 In a move to eliminate the Bureau of Air Commerce, on June 23, 1938, Congress passed the Civil Aeronautics Act, which in turn created the Civil Aeronautics Authority (CAA). The CAA became the only independent authority in the U.S. government at that time. One of the Copeland Commission findings was that the Bureau of Air Commerce had been assigned contradictory responsibilities. On the one hand, it was supposed to promote aviation, yet on the other hand, it was supposed to regulate it. The bureau was responsible for operating many components of the air traffic control system, but it was also responsible for investigating accidents that might be caused by deficiencies in the air traffic control (ATC) system itself. To try to solve some of these problems, the Civil Aeronautics Act divided the functions of the CAA into three groups. A five-person C