Forecast of the general aviation air traffic control environment for the 1980's

TABLE OF CONTENTS Section Page .

v * 0 1 . 1 General Aviation Background . . . I . . . 1 1.2 NASA General Aviation Advanced Avionics System Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1 . 3 Obiectiva~ of ATC Environment Forecast + . * a . * 5

1.4 Outline of the Report . . . . . . . . . . . . . . . . . . . . . . . 7 * * * AIR TRAFFIC CONTROL FOR THE 1980'5 * 0 9 2 . 1 Historical Perspective 9 . . . . . . . . . . . . . . . . . . . . . . .

2.2 The Upgraded Third Generation ATC System . . . . . . . . . 30 2.2.1 Discrete Address Beacon System (DABS) . . . . . . . 11

2.2.2 : . ircrcrfr Separation Assurance . . . . . . . . . . . . . . 15

2 .2. 3 Area Navigation (RNAV) 21 . . . . . . . . . . . . . . . . .

. . . . . . . . . . . 2 . 2 . 4 Microwave Landing System (MLS) 27 2 .2.5 Upgraded ATC Automotion . . . . . . . . . . . . I , . . 29 2.2.6 Airport Surface Traffic Control (ASTC) . . . . . . . . 31 2.2.7 Wake Vortex Avoidance System (WVAS) . . . . . . . 32 2 . 2 . 8 Flight Service Stations (FSS) . . . . . . . . . . . . . . 33 2.2.9 Aeronautical Satellite (AEROSAT) . . . . . . . . . . . 34 2 . 3 Additional Pofentiul Features Beyond the UG3RD . . . . . . 36 2 . 3 . 1 Ground Proximity Warning System (GkWS) . . . . . . 36 2.3.2 Airborne Traffic Situation Display . . . . . . . . . . . 39 2 . 3 . 3 NAVSTAR Global Positioning System (GPS) . 4 1 2.3.4 Digital Data Broadcast System (DDBS) . + 8 . 43 2.3.5 OrnegaBLF Navigation . . . . . 44 v &DiIH@ PAGB BLhPJg 7'. . " .

AERDB PAC&! I Y B T E M B . INC . ONE VINE BROOK PARK r BURLINGTON . MIBBAGHWBETTE 01803 * (1'17) EX72-7M7

TABLE OF CONTENTS (Continued) Section Page 2.3.6 Loran-C . . . . . , . . . . , . . . . . . . , , , . . , . . .

2.3.7 Integrated Cockpit . . . . . . . . . . . , . . . . . , . .

GA Avionics Growth Projecrions . . . . . . . . , . , , , . . .

2 . 4 G E N E R A L AVIATION AVIONICS REQUIREMENTS IN

THE 1980's . . . . . . . . . . . . . . . . . . 57

. , . . , . , . . , . . . , 3.1 Avionics User Groups , . , , , , , , , , . . , . . . . . . . . . .

3.2 Air Traffic Control Scenarios for the 1980's , , . , . . . 68

3 . 3 GA Avionics Requirements for the 1980's . . . , . . . . . . . 69

3.3.1 R e q u i r e m e n t s F n r t h e L J G B R D * * + - . . . ~ ~ 71 3 . 3 . 2 Additional Desired Equipment for the UG3RD 1 73 3 . 3 . 3 Additional Desired Features Beyond the UG3RD . 76 4 PARAMETERS FOR AVIONICS COMPONEN'TS * * * 78 * + G A ALTERNATIVES FOR THE UG3RD 101 SeparatedATCforGA b 0 0 . 4 * . - .

5.1 101

5,2 Changes to the UG3RD to Maximize GA Benefit b . a 0 * 104

6 CONCLUSIONS AND RECOMMENDATIONS + * * - 11 1

6.1 Conc\uaions + . . . . . . . . . . . . . . . . . . . + , * + . t . o . 1 1 1 v i A E ~ Q 1 P A G E I Y B I I M B , lNca ONE VINE BROOK PARK BURLINOTON, MASSACHUBETTB 018133 (8'17) Z!7~-7617 LIST OF TABLES Table No .

Page .

Performance Characteristics for Typical General Aviation

Aircraft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

ATC Generations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Comparison of DABS vs ATCRBS Characteristics . . . . . . . . . 13

Projected Irnplsmtrntation Schedule for DABS . . . * . . . . . . . 14

Area Ntlvigation Features and Potential Benefits . I . . . . * . 22

General Aviation Avianics User Groups . . . . . . . . . . . . . .

Typical User Group Avionics Requirements . . . . . a . a . . . .

Current Distribution o f G .A . Users by Avionics Category.

Percent of Fleet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

1980'5 Distribution of G .A . Users by Avionics Category.

Percent sf Fleet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

General Aviation Proiections for the 1980 Period . . . , . . . .

ATC Scenarios for 1980's . . . . . . . . . . . . . . . . I . p . . . . 65

Changes to GA User Group Avionics Requirements (By

Approximate Year of Introduction) . I . I + . 1 70

+ 71

New Avionics Requirements for UG3RD . . . 0

New Equipment Desired for UG3RD . . . . . . . . . . . . . . . . . 74

Additional Desired Features Beyond UG3RD . . . . . . . * . . . . 77

Critical Parameters for VHF Communications Transceiver* 0

Critical Parameters for ELT . . . . . . . . . . . . . . . . . . . . . . 81

Critical Parameters for VOR Navigation Receiver . . . . - . . a 82

Critical Paramehers for ILS Localizer Receiver . . . . . . . . . . 82

* . .

Critical Parameters for Marker Beacon Receiver . 84

vi i AE R O 8 P A C @ m'CCCITEMB, INC. ONE J I N E BflOOK PARK OURCINQTQN. MABBAOHUBBTTO 01BLJQ * (017) P7P-7017 LIST OF TABLES (Continued) Page Table No,

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Critical Parameters for ILS Glide Slope Receiver . . , . . . . . .

2 1 22 Critical Parameters for DME . . . . . . . . . . . . , . . , . . . . . .

23 Critical Parameters for RNAV . . , . . . . . . . I . . . . . . . . . .

24 Critical Parameters for ATCRBS Transponder , , , , , , . . . , , , 2 5 Critical Parameters for Encoding Al timeter . . . . . . . . . . . . .

Critical Parameters for Horizontal Situation Display . , , . . . .

Critical Parameters fbr Autopi lots , . , , , . , , , , , . . . . . .

2 7 9 1 Critical Parameters for Radar Aitimeters , , . . , . , . . . . . . .

2 9 Critical Parameters for Weather Radar . . . , , . . , . . . , . . . .

30 Crr tica! Parameters for DABS Transponder , , , , , . , . . . , . , .

Critical Parameters for IPC Display . I I . . . . . . . . . . . . . . .

Critical Parameters for GPWS . . . . . . . . . . . . . . . . . . . . .

Crifical Parameters for MLS Receiver . . . . . . . . . I I I 96

Critical Parameters for HF Communications Transceiver * .

9 8 Avionics Cost Drivers and Possible Research Areas 36 Pros and Cons of Segregated Airspace + 0 .

v i i i A E R e a P A C e @ Y 6 I E M B , #NG. ONE VINE BROOK PARK * EURLINOTON. MABOACHUBETTB 01P03 (8'17) 278-7B17 LIST OF ILLUSTRATIONS Figure No.

Page L__

1 U.S. Aircraft Operations , , . . . . . . . , . . I . , . . , 3

2 3 G.A, Hours Flown by Aircraft Type . . , . , , . , . . , , ,

General Avlation Growth , . , . , . , . . . . . . . . . . . . , 3

4 I P C Display, . . . . . . , , . . . . . . . . . . . . . . . . . . . .

1 9 National Plan for Developing the Microwave Landing System . . . . . . . . . . . . . . . . . . , . . . . . . . , . . . . .

Schemattc Conception of Future FSS Network . . . . . . .

Omega Navigation Signal Format . , ,, . . . . , , . . . , . , Projected Growth of Various Avionics Equipment5 , . . .

Typical Airspeed Capabilities . . . . . . . . . . I , . , . . .

NOMENCLATURE ACAS Airborne Collisfon Avoidance System ADF Automatic Direcfion Finder A/G A i r to Ground ARTCC Air Route Traffic Control Center ARTS Automated Radar Terminal System ASA Aircraft Separation Assurance ASDE Airporr Surface Detection Equipment AS1 Aerospace Systems, Incorporated A STC Airport Surface Traffic Control ATC A i r Traffic Control ATCAC Air Traffic Control Advisory Committee ATCRBS A i r Traffic Control Radar Beacon System ATS D Airborne Traffic Situation Display AWANS Aviation Weather and Notam System BCAS Beacon Collision Avoidance System C A Conflict Alert CAT Category (for precision instrument approaches) CRT Cathode Ray Tube DABS Discrete Address Beccon System Experimental DABS Faci i i t y DARSEF DDBS Dig! tal Data Broadcast System DME Distance Measuring Equipment EADl Electronic Attitude Direction lndicator EHSl Electronic Horizontal Situation lndicator PJ~WQW~' PAGE M Q T ~FPLMIw xi fiP?ROO P A C @ l Y m f EMbl INC. . ONE VlNB BADOK PARK BURLINUTON, MQSSAGHUBeTTU 01803 (817) R7R.7817 NOMENCLATURE (Continued) ELT Emergency Locator Tronsmi tter ESA European Space Agency ETS Electronic Tert Set FAA Federal Avia tlon Administration FSS Flight Service Statlon FY Fiscal Year GA General Aviafion GCA Ground Control led Approach Global Positioning System (Navstar) G PS GPWS Ground Proximity Warning System Glide Slope GS H F High Frequency IAS Indiea ted Airspeed International C i v i l Aviation C ,+gr,nization ICAO Instrument Flight Rules I FR 11s Instrument Landing System Interim Microwave Landing System 3 MLS IMU Inertial Measurement Unit INS Inertial Navigation System lnput/Outpu t

t/o

IPC In termittant Positive Control LED Light Emitting Diode Loca l izer LOC Massachusetts Insi-i tute of Technology M I T xi i AE R 0 a P ACE EYBTEIUY6, INGO . ONE VINE aROOK PARK BURLINOTUN, MAP64CHUBeTfB Ol0Oa ( e l l ) P7P-7al7 NOMENCLATURE (Continued) M LS Microwave Landlng System I q ~ t Applicable N/A NAFEC FAA Natlonal Aviofion FacIli ties Experimental Center (Atlantic City, NJ ) NAS National Airspace System NASA Nafional Aeronautics and Space Admlnistra tion NDB Non-Directional Beacon NOTAM Notice to Airn~en PA LM Precision Al t i tude Landing Monitor PCA Positive Conh-ol Airspace PWI Proximity Warning Indication R,CVR Receiver RNAV Area Navigation Radio Technical Committee for Avionics RTC A SAS Separation Assurance Sys tern S E Singlo Engine SID Standard Insl.rurnen t Departure Route Standard Terminal Ar, ival Route STAR S T 0 L Short Take Off and Landing Tactical Air Navigu tion TACAN TAGS Tower Automated Ground Surveillance TCA Terminal Control Area Terminal Radar Approach Control TRACO N TSO Technical Standard Grder Transrni tter TX xii i A B PACE BYBTEMa, INC. ONE VINa aROOK PARK * EURLINOTON, MAEIBAOUUME7TO 016DB * (0371 R 7 P - 7 6 1 7 NOMENCLATURE (Continued) UG3RD Upgraded Third Gcnaration ATC Systam UHF Ultra High Frequency (300-3000 MHz) VFR Visual Flight Rules VHF Very High Frequency (30-300 MHz) VLF Very Low Frequency (3-30 MHz) 3D Area Navigation (includes vertical naviga tlon) VNAV VOR VHF Omnidirectional Range VORTAC Co-located VClR cnd TACAN Stations Vertical Take Off and Landing VTO t WVAS Wake Vtlrtex Avoidance System W X Weathe * 2D, 3D, 4D Twen, Three-, and Four-Dimensional RNAV xi v Ann0 I P A C E m Y m I B M I , INC, ONE VlNa BROOK PARK . aURLINWfON, MA1IQAOHUBETTB DZBQO (817) D7P.7017

SECTION 1 1NTRODUCTION 1 . 1 GENERAL AVIATION BACKGROUND Thc !arm Ganeral Aviation (GA) includes all aircraft, pllots and oparations othor tbun tho military, and tha schedulad and supptemental uir carriers. This includes such varied services as air taxi, ail -wqo, industry, agriculture, businass, personal, instructional, rasearch, patrol, and sport flying, Consequent1 y, tho spectrum of vehicle types ranges from four engine turbo jets to simple spot+ gliders and balloons.

Tuble 1 illustrates tho broad range of vehicle characteristics associated with the abave Flying categories.

Table 1 . Performonce Chat .lc! ~r:s:jl;s for Typical General Aviation Aircraft, - - - , .

Gross Thrust or Cruise Speed Range (mph) (stat .mi .)

I Twin Otter 12,500 2 x 6 5 0 '44. 7 ' 8 0

I Air Taxi

Air Cargo Electra S-14 Sky Crane l ndushy (He! icopfer)

1 Personal I Bonanza

I Instructional Cessno I50

I I

Patrol Bell Jet Ranger (Helicopter) Sport Ci tabrici

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A 0 ?) P Ace BYmTE!Ma, INC. 1 O N B VlNlr a R O o K PARK . EURL'YOTON, M A I I S A G H U S E l T B 01803 (017) 171*7Lll7 The GA fleet numbers over 162,000 aircraft, compared to the air carrier fleet o f approximately 2,300. Thus, GA makes up 98.5 percent of a l l the c i v i l air- craft i n the U.S. At the end of 1974 the turbine-powered GA fleet alone numbered about 3,500 as opposed to 2,200 for the airlines. By 1984 the GA fleet i s projected to grow to 8,200 while the air!ines wilt number 3,500. Single-engine piston aircraft, numbering over 100,000, dominate the general aviation fleet, and i n the 1980's these are expecfed to aggregate more I han 200,OCIO planes. Figures 1 to 3 illustrate several FAA projections o f the growth of qeneral aviation durins the next decade (References 27 and 28).

General rrviation carries one In every three intercity air passenger; and i s the only air link to more than 19,000 incorporated American communities; 379 of these cities have populations of 25,000 to 100,OQO buf no other kind o r air service, By 1980 general aviation aircraft w i l l be making two-thirds as man,) IFR (Instrument Flight Rules) flights as the scheduled airlines. With continued improvements i n pilot training, basic aircraft safety, arid low-cost Air Traffic Control (ATC) and navfgational avionics, the general aviation aircraft w i l l be used ever mare effectively i n airspace where tb ~y w i II "mix" with airlines and military aircraft, These heavily trafficked areas of mixed populations of airspce users generate the knottiest problems.

1.2 NASA GENERAL AVIATION ADVANCED AVIONICS SYSTEM PROGRPNi The overall objective o f this program i s to provide the critical information required for the design of a reliable, low-cost, advunced avionics system which would enhance the safety and utility of this mode of transportation. Sufficient data w i l l be accumulated upon which industry can base the design of a reasonably priced system having the capability required by general aviation i n and beyond the 1980's. It i s presumed that the orchitech~re of this advanced system would be quite different from A EAeJ m P AeLI mYITIMVII, IN=. QNE VINE BROOK PARK EURCINDTON, MAPBACHUSM70 OlEOD (517) a- P-7U77 M I L L I O N S

r A I R I

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T A X l AIR C A R R l ER GENERAL A V I A T I O N

Figure 1 . U .S. Aircraft Operations

Figure 2. G .A. Hours Flown by (Reference 27). Aircraft Type (Reference 27).

-

A I R C R A F T OPERATIONS

- - ACTUAL F O R E C A S T -

I

- 0

0.0*/ HOURS

, 5 . '

FLOWN\- _, , .

----

-,-,-.---*'\ ACTIVE A I R C R A F T A I R C R A F T PRODUCTION I I I I I 1 I I I 1 I I I 1 I I I I I I 1965 1970 1975 1980 Figure 3. General Aviation Growth (Reference 28).

I , ~ R o P u c r e n ; ~ ~ OF m h

,131i3WAxl PAGE l.8 POOR AESRPLSPACE EYeTEMs, INC. ONE VrNe BROOK PARK BURLINGTON, MABBPCHUEETTE a1003 (8173 127Q.7eI7 current general aviation avionics. The prcgrslrn w i l l attempt to establish the technology for a total avionics system design (i .em, navigation, guidance, control, powerplant management, displays, e t c . ) rather than singling out a particular subsystem, or function upon which to concentrate the research effort.

Since general aviation accounts for the vast majority of c i v i l aircraft opera- tions, as well as a substantial fraction of the passenger miles flown, it has a significant impact on the natiorr's economy and on the international balance of payments. Con- sidering the future, this segmant of c i v i l aviation can and should play an even more important role in transportation and i n the nation's economy. However, a number of

formidable obstacles exist. Operating procedures are cornpl icated . Regulations ere

comprehensive and restrictive. There are the ever-increasing demands of the National Air Traffic Control syskm. These requirements cause an increase i n the com- plexity of the onboard avionics with an associated increase in avionics systems cost.

A related result i s greater demands on the pilot i n terms of training and proficiency i n order to avoid any degraciation in operational safety.

To help overcome these obstacles, NASA has undertaken a general aviation avionics research and technology program. This program w i l l ufil ize recenf. advances in microeIectronics t o make significant advances i n general aviation systems and opera- tional capability. I t s compl etion i s kayad tn providing the informati on required for the design of low-cost integrated avionic systems needed to enable general aviation t o fulfill its role i n the 1980's.

Specific objectives of the program are as follows: a. In FY75, initiate the formulation of an advanced airborne avionics system concept. This design would emphaisze efficient integration of all elements of the onboard avionics system, with the aircraft, with the ATC, and with the ground navigation systems.

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A E R P B P A C E BYBTEMB, INC. O N E VINE BAOOK PARK BURLlNGTON, MPSfiACHUBE7TB 01803 (817) L171.7S17 b. I n Fk76, define preliminary specifications and performance requlrernents for the experimental avionics system.

c . By FY77, identify optimal subsystems resulting from a tradeoff OF candidate systems design as a Function of: 1. Cost 2 . Reliability 3 , Expandabilify 4, Flexibility 5 . Maintainability 6. Simplicity o f Operation 7. Perfom~nce These cost-benefits-analysis studies w i l l make visible the many trade-offs between system requirements and s stem architecture.

r These sfudies w i l l also evaluate the technica risks assaciated

with the prt'icular systems design-app-oach and the associated electronics technology used i n the design o f the system elements, i .e., sensors, displays, actuators, etc.

d . In FY78, provide specifications and performance requirements for a r'ina t systems design.

e, In FY79 complete final systems design. System fabric 'ion and flig/lt investigations are to be conducted to excimive acceptability and performance, Five years w i l l be required 1.0 complete the program activities. The first Four years w i l l be primarily concerned with the development and validation of design informufion, upon which the final system specifications w i l l be based. The last year of the program w i l l emphasize the final systems dexign and an examination of its per- formance and suitability using the NASA Cessna 4028 aircraft.

1.3 OBJECTIVES OF ATC ENVIRONMENT FORECAST The obiective of this particular study i s to Forecast the ATC environment for general aviation i n the 1980's and beyond. I f . i s recognized that the FAA i s proceeding with fhe development of the "Upgraded Third Generation ATC System" (UG3RD) which i s scheduled for use in that time frame. General aviation aircraft, of course, w i l l be operating in that system. To support the Advanced Avionics Program, NASA desires t o know what requirements w i l l be placed on general aviation aircraft operating in the UG3RD system. Any changes i n the methods used to accomplish the four primary functions of ATC (control, navigation, surveillance, and communication) could have an impact on the onboard avionics system design.

In the course of this sfudy, AS1 performed the following tasks: a Task I. Since general aviation covers a broad spectrum of users, s u c h 5 air taxi service, business travel, personal travel, recreafional flying, agricultural applications, and police surveillance, to name only a Few, the avionics requirements 1.0 operate in the future ATC system w i l l undoubtedly differ. We have there'fore attempted to categorize the different users of general aviation based on avionics requirements.

Task I I . The UG3RD ATC system being developed by the FAA has n i n e e y features as listed below: Discrete Address Beacon System (DABS) Separafion Assurance System (SAS) Area Navigation (RNAV) Microwave Landing System (MLS) Upgraded ATC Automation Airport Surface Traffic Conhol (ASTC) Wake Vortex Avoidance System (WVAS) Flight Service Sfations (FSS) Aeronautical Sate! I i tes (AEROSAT) AS I has assessed the avionics requirements laced on each of the use

categories identified i n Task I by each of t R e nine features of the

UG3RD system, particularly those feafures of the UG3RD ATC which w i l l make new or modified avionics equipment either required or desirable. Avionics that w i l l be required have been identified separately from those that w i l l be desirable, but not required.

- 6 - AE R m PACE EYBTEMB, INC. * ONE VINE mROOK PARK BURLIN~TON, MASGACHUS[fTTB 01803 (~17) e?zz.;raiY Task Ill, For each use category, the critical parameters that are necessary for component design have been identified, Examples include the following: the frequency range and spacing of com- munications channels; the range and accuracy required of the various navigation and communicatian systems; the ty e and

format of informotion that w i I l be available through ata-link 8

systems.

a Task IV, Although the FAA i s proceeding with the UG3RD as

aafined i n Task I, it i s also recognized that certain deviations

from this p!an are being investigated. An example of these deviations i s the use of the Airborne Traffic Situation Display (ATSD) for col lision avoidance. Consequent1 y, we have surveyed all possible deviations from the UG3RD plan and assessed the im- pact of these deviations on the avionics requirements for general aviation aircraft, Task V , The UG3RD system appears to be headed toward more mixing of commercial and general aviation aircraft in the ATC system, but the possibility remains that ATC for commercial and at least certain segments of general aviation aircraft could be more separated i n the future. The possibility or feasibility of this situation has been assessed.

Task VI, Finally, features o f the UG3RD that could be changed to minimize the avionics requirements for the different use cate- gories of general aviation, without changing the obiectives of the UG3RD system, have been identified.

OUTLINE OF THE REPORT Section 2 o f the report discusses the air traffic control environment in the 19801s, iricluding the upgraded third generation ATC system and several potential additions to i t , A series of general aviation user groups based on increasing avionics requirements i s defined, and specific ATC scenarios are hypothesized i n Section 3; the associated avionics requirements are then presentec' Sr each group. Section 4 sum- marizes critical system design parameters for the various uirborne equipments. The possibility o f some general aviation alternatives to the presently envisioned UG3RD are discussed i n Section 5, Conclusions and recommendations are presented in Secfion 6.

Finally, the Bibliography contains a variety o f pertinent documents which were consulted during this study. Individua! rel'erences in the text of the report are citations from the Bibliography.

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SECTION 2 AIR TRAFFIC CONTROL F O R THE 1980's 2.1 HISTORICAL PERSPECTIVE The air traffic control {ATC) system currently operated by the FAA i n the United Statesf National Airspace System (NAS) i s the result of an evolutionary process.

Improved capabilities, based on technology advances, have been introduced into the system to support the increasing utilization of the ATC services, Significant levels of evolutionary progress in the ATC system have been loosely identified as successive generations, as shown i n Table 2 (Reference 11 1).

The earliest air traffic control system, or first generation, relied solely on manual operating procedures, with aircraft separation based on pilot position reporting. Radar and other advanced technological concepts developed during World War [I were adapted for the post-war air traffic; control system, resulting i n the second generation ATC system.

Table 2. ATC Generations (Reference 1 1 1).

Generation Time Period Key Features

-

First Procedural Control - Flight Stri s

'1 936-1 960

- Limited Control - Mostly by ~ / b Radio

-

Radar Control Introduction of ATCRBS Second 1960-1 970

- Limited Flighf Strip Printing

-

1970-1 97% NAS Enroute and ARTS Automation Third

- Increased Use of ATCRBS

- Centralized Flow Control

Upgraded 1 975-1 995 - Upgraded ATC Automation

-

Third DABS, ASA, RNAV, MLS etc.

Fourth 1 995-? - New System Organizafion

- More Automation

- New Surveil lance, Communications, and Navigation Systems I

W4EXDPJG FAGS J~LAN~! - 9 -

L \ @ f t a m P ACE BYBTEMB, INC. ONE VINE 8 A O D K PARK BURLINCITtlN, MPBBACHUPETTE C 1 1 1 0 3 (017) ;t7P*fBl7 Additional technical progress, particularly in automation and other forms of electronics innovations, resut ted i n what i s recognized as the existing third genera- tion ATC system. Based on the results of Project Beacon (Reference 23), the third generation system constitutes the first stage ot automation for ATC operations and utilizes secondary radar to augment the surveillance function. This initial step of auto- mation consists of two subsystems: NAS Stage A, which is operational at all 20 Air Route Traffic Control Centers providing enroute control over the entire conterminous United States; and ARTS Ill, which i s used at 61 of the busiest terminals. In addition, a slightly scaled-down version of ARTS Ill i s scheduled for implementation a+ a number o f terminal areas of lower density traffic activity by 1980.

In 1969, the Department of Transportation's Air 'Traffic Control Advisory Commi ttee's (ATCAC) report was issued (Reference 22). I t s primary conclusion was that continued upgrading of the ATC system would be necessary even after the Proiect Beacon recommendations were implemented, in order to meet the projected demands for ATC service in the late 1970s and beyond. Specific recommendations were made for an evolutionary upgrading of the system, Accordingly, the term "upgraded third generation systemu was applied to the resulting configuration, This i s the system intended for operational use through the 1980s and into the 1990s.

2.2 THE UPGRADED THIRD GENERATION ATC SYSTEM Upgrading of the present ATC system w i l l continue through the late 1970s and well into the 19805, The upgraded third generalion (UG3RD) system has nine major features which are under development to satisfy four important system needs: improved safety, iricreased capacity, lower user costs, clnd lower operating cost. The nine principal elements of the UG3RD are described briefly i n this subsection. It must be recognized, however, that although development activities have started on all nine,

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A E R a a P A C E l Y B T E M B I #NC. O N E VlNE BROOK PARK aURLINOTONl M A B B A C H U I E T t O 0111133 (017) 2 7 R . 7 0 1 7 implementation decisions have not been made on most and w i l l not be made until com- prehensive costbenefit analyses are completed, The development and ;mplementation schedules presented are based on FAA program plans (Reference 7), and the latest reported milestones (Reference 1 11).

2.2.1 DISCRETE ADDRESS BEACON SYSTEM (DABS) The DABS was a major aspect o f the ATCAC recommendations (Reference 22) to provide intermittent positive con trol (IPC) for aircraft separation assurance. The ground-based IPC service was expected to be completely automatic, based on computer

processing of surveillance da ta , detection o f impending conflicts, and the generation

of the necessary data link messages. The transmission o f information to/from the air- craft required that the discrete address beacon system have the capability for a data link. The objectives of the DABS development, therefore, are to provide the basis for the IPC function through improved surveillance and accuracy, plus an integral data link between the ground and the aircraft.

An additional objective of the DABS system i s to interrogate aircraft indi- vidually to avoid a situation known as synchronous garble, The present air traffic control radar beacon system (ATCRBS) generates about Forty replies from an aircraft during the time that the beam i s illuminating the target. Synchronous garble occurs when two aircraft are at the same range and the same bearing, but not at the same altitude. This causes their replies to overlap, making i t difficult to identify the individual replies. The discrete address beacon system would use a single coded interrogation for each aircraft; since only fhat aircraft would reply to the interro- gation, the problem o f synchronous garble would be eliminated. Another major advantage of DABS i s its ability to limit interrogations to only those targets for which it has surveillance responsibility, rather than continuously inferrogatc a l l targets within line-of-sight. This prevents surveillance system saturation caused by all trans- ponders responding to all interrogators wi thin line-of-sight.

An important consideration i n the design of DABS i s the ability tcr implement i t on a time scale and at a cost acceptable to the aviation community, By the time deployment of DABS could begin, there w i l l be on the o. -!qr of 200,000 aircraft equipped with ATCRBS transponders and approximotely 500 grourid interrogators. DABS must be designed to operate in this environment and in a way which permits a graduai, economic transition to an all-DABS operation over a 10- to 15-year period, This has been achieved by providing a high degree of compatibility betweon DABS and ATCRBS, DABS uses the same interrogation and reply frequencies as ATCRBS, and the signal formats have been chosen to permit substantial commonality in hardware.

This degree of cornpakibility permits economic realization of two essential elements of a smooth transition: DABS interrogators provide surveillance of ATCRBS-equipped aircraft; a.

DABS transponders reply to ATCRBS interrogators.

b, Thus DABS equipment, both on the ground and i n aircraft, can be introduced gradually and continue to operate with existing systems during an extended transition phase, Table 3 presents a comparison of DABS and ATCRBS characteristics and accur~cies.

The development o f DABS was assigned to MIT4s Lincoln Laboratorry as the system design contractor. The basic design and breadboard verification of DABS i s essentially complete, and an experimental DABS facility (DABSEF) i s currently i n opera- tion at Lincoln. The DABS design i s now being tested together with the IPC concept by Lincoln Lab, and the FAA i s currently testing sensors and transponders at NAFEC. A contract for three protoinype ground sensors and 30 airborne tra1.1sponder.s was recently awarded by the FAA, with the first ground installation scheduled for late 1977. The Toblo 3, Comparlron of DABS vs ATCRBS Characteristics.

PARAMETERS DABS ATCRBS 1030 MHz 1 030 MHz Frequeqcy Up Frequency Down 1090 MHz 1090 MHz Range Accuracy ( 3 4 100 fl-. 1000 ft, Azimuth Accuracy ( 3 4 0. l o 0.75O Altitude Accuracy (34 125 ft, 125 ft, Addresses 16 M i l l i o n (224) 4096 Uplink Messuge Length 32.5 psec 8 to 21 psec 3 bits 112 bits Down 1 ink Message Length 20.3 psec

1 : ; e;tc

15 bits Data Link Messages UnI im: . ~ d Limited to Aircraff Ground-Air -Ground I .D. and Altitude- Downlink Only Surveillance Capacity 2000 A/c Per Sensor Garble Limited Coverage ATC Facility can draw ATC Faci l i ties use on any sensor i n its only their own airspace sensors implementation decision w i l l follow nearly two years of operational testing, with 1981 being the earliest possible implementation date. Table 4 presents a summary sf the latest development/irnplemen tation schedule for DABS.

Although the development of DABS i s well underway, its eventual imple- mentation remains uncertain. This decision still depends strongly upon the future of intermittent positive control, which at the present time i s an unproven concept.

Moreover, the IPC function could potentially be achieved with the existing ATCRBS, providing the accuracy were enhanced and a separate data link were utilized. Equiva- lent accuracy to that provided by DABS might possibly be obtained by upgrading the Table 4, Projected Implementation Schedule f w DABS.

Date Milestones Through 1975 Basic design and signal format.

Experimental facility operational at MIT Lincoln Laboratory, March 1976 Con tract to Texas Instruments for three prototype ground sensors.

Subcontract to Collins Radio for 30 prototype airborne transponders.

Summer 1976 National standard for airborne transponder, 0 ctober 1977 First prototype ground sensor installation at NAFEC, December 1 977 Begin year of mu1 ti-site testing, Followed by year of tests ot field facilities.

January 1978 Second ground sensor installation at Philadelphia.

April 1978 Third ground sensor instaliation at Elwood, NJ.

1979 lmplemen tation decision.

Earl jest date for system implementation.

I

existing ATCRBS transmitters to use rnonopulse techniques instead of beam-splitting, However, the synchronous garble problem could not be avoided without discrete addressing. The magnitude of this problem i s difficult to evaluate because i t i s so strongly linked to the density of aircraft, which has not increased as rapidly as pre- dicted, The establishment of terminal control areas (TCAs) has discouraged large num- bers of VFR aircraft From utilizing the terminal air space. In addition, commercial traffic growth has diminished partially due to the increased use of wide-body jets and a general decrease i n the demand for air carrier services.

If the discrete address beacon system i s implemented, i t w i l l require a new transponder which i s fargeted to cost slightly more than the present ATCRBS transponder and encoding altimeter, 1st addition, an I PC d~sploy probably would be required.

Those sophisticated usors who desired to use the data link From air to ground would requlre an optlonal on-board console. Although such consoles for DABS havn not Sean developed yet, they could be expected to cost i n the neighborhood of $20,000 or more, The cri tical system cost alemen t w i l l be the ground sensor and associafed software, Although DABS' primary function i s to provide surveillance and air-ground communication service to air trafflc control fcrcili+ies (including IPC), an air-to-clr anode, termed Synchro-DABS (Reference 88), could operate as backup to the graund- based IPC Function. O y proper timing of the interrogations to a l l DABS-equippod alrcrafr, suitably equipped aircraft could utilizo the DABS replies from other nearby aircroft to perform onboard proxirrbity vfs;lrn;ng indication (PWI) and conflict detection.

2.2.2 AIRCRAFT SEPARAT1O1\l ASSURAbICE t h e aircraft separation assurance program consists of five separate but related activities: 1. Conflict Alert (CA) 2 . Extended Flight Plan Requirements Expcnded Al tifude-Reporting Transponder Requirements 3, 4 . Beacon Coll ision Avoidance System (BCAS) 5.

Intermi ttcnt Posi five Control (IPC) These span a period of time from those which are being implemented immediately to those which may be implemented over a number of years. Included also i s a mixture of software and hardware techniqces.

2.2.2.1 CONFLICT ALERT (CA) A near-term activity involves the upgrading of the enroute and terminal automafion software to alert the controller of impending conflicfo. This automatic

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A E R a P A C E % Y & l G M 6 , QNE WNC EAaOK PARK * BURL l N Q T d N MASBACHUSKTTP DIE03 b l 7 ) Q7P-7817 backup alarm for conflicting traffic i s a software program uslng existing computers to profect the flightpaths of transp~nder-equip~ed aircraft for the novf two minutes. I t w i l l alert controilars of a potential conflict so that thoy can take the necessary action via radio to warn the pllots. Tlris activity i s now completed i n 20 domestlc air route traffic control centars for airspace abovo 12,500 feet, A similar capability Is baing developad for automated terminal systems with a planned installation a t the 60731~s airports during 1977.

2 . 2 , 2 , 2 EXTENDED FLIGHT PLAN REQUIREMENTS New flight-plan requirements w i l l be established for passenger-carrying aircraff. These aircraft w i l l include air taxis, commuter airlines, and the executive corporate fleet. The new scheme requires these iypas o f aircraft to file a flight $an and operate under IFR to ensure continuous moni tcring by ATC, 2 . 2 . 2 . 3 EXPANDED AL'TITUDE REPORTING TRANSPONDER REQUIREMENTS Automatic iden t i ty and altitude reporting transponder equipment w i l l be required for a l l aircraft flying in certain control led airspace, The alfitude/identi ty informotion i s displayed directly on controllers' radarscopes, giving them a more complete picture of the traffic under their control. The altitude-reporting transponder will be the key to the enhancement of both CA and the upcoming BCAS, 2,2.2,4 BEACON CQLLlSlOPl AVOIDANCE SYSTEM (BCAS) The beacon collision avoidance system was recently selected by the FAA as the preferred airborne system to detect and resolve conflicts independent of the present ATC system. BCAS was chosen aver the cooperative airborne collision avoidance system (ACAS) 0 5 the quickest and least expensive way to provide an independent backup capability for the ground-based ATC system, By its nature,

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A E m a P ACE? OYBTZ:.':3, INC. . O N E vlNS 6FloaK PARK r BURLINOTON, MAEBADWUSETTU 01800 . b17) a7P-7n37 BCAS wIll make the ATC transponder with altitudo reporting an essential equipment need for aircraft operating i n certain airspace, particularly that used by the air carriers, The two forms of BCAS, actTve and semiactive, are still i n competition for the final selection. The active BCAS concept was originally conceived several years ago for use over oceans, but was not pursued because of the potential interference by the airborne interrogator/transponders with the ground surveillance system. An active BCAS emits a conventional mode C interrogation once each second. Antennas are necessary both on the top and an the bottom o f the fuselage to avoid masking by the airplane; presumably, the interrogation would be alternated between antennas, The active BCAS signal elicits a reply from all transponder-equipped aircraft within range.

From each reply the airborne system measures the separation distance using the round- trip transit time, and also receives the identity and the barometric altitude of each responding aircraft. By differencing the measured slant ranges the active BCAS defer- mines the range rate. The system can determine from this information whether a threat exists, and whether a climb, descend or Ievel-ofF evasive tnaneuver i s appropriate.

The semiactive BCAS (Reference 85) usas an active mode only when there

are inadequate ground interrogators i n the vicinir) . The passive measurernsnf involves

listening to the responses of other airborne transponders to the ground interroga:ions.

When two ground interrogatorr .are within range, sufficient information i s available to determine range and bearing to a transpor~der, This system does revert to an active mode when there are insufficient grcund interrogators in the aircraflls vicinity. Since the serniacfivo system provides the pilot an indication of the direction as well as the rmge and ill ti tude OF a threat aircraft, i t provides the option of a horizontal, vertical or combined maneuver to avoid a col [ision. In contrast, the active BCAS i s restricted to only vertical maneuvers.

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A E R O B P A C E BvSTE#t6, Il'JC. * ONE VINE BROOK PARK BURLINGTON. MAlEACHU8E7TE 0?003 (817) 8 7 P . 7 5 3 7 J I A t the present time, the semiactive BCAS appears to offer more advantages than the active system. But since both techniques rely upon signals received from aircraft transponders, they are not mutually incompatible. Conceivably, a combina- tion of the two techniques might emerge as the optimum design. The active BCAS has been demonsbated in fllgbt by the FAA and i s considered feasible, The semiactive system i s about to undergo a similar flight evaluation program at NAFEC, A final BCAS system design should be available early in 1978.

Preliminary FAA planning i s to seek mandatory installation of BLAS on a l l aircraft capable o f transporting ten passengers or more, which would exclude most 9f the GA fleet as well as much of the military fleet. Current estimates are that an active BCAS would sell For a b ~ . .. . 4 10,000, in production quantities, with the serni- active version costing s l jgf~fly more.

2,2.2,5 INTERMITTENT PC;SIT\ 4E CONTROL (IPC) Intermittent positive control i s still the FAA's preferred, long-range solution to the separation assurance problem. IPC was first conceived as a cornerstone of the 1IG3RD by the ATCAC report, and has only recently been augmented by BCAS, This technique protects both VFR and I FR aircraft, provides more Flexi b i i i ty for conflict resolution through use of hurizontal maneuvers, a ~ d assures maximum coordination with air traffic control i n resolving conflicts. Advisories and collision avoidance commands w i l l be ground-determined and transmitted via a data link to the aircraft, This data l ink can be provided by the discrete address beacon system.

The present experimental version of I PC involves a cockpit display of proxim- i t y warning lights and ground derived commands (Figure 4) which indicate avoidance maneuvers or restraining advisories (negative commands). An extremely cornpl icatad logic determines when the various commands are issued, depending on such things as: AEFlo6PAcP 6 f 6 T E M B I IN=. a O N E VINE BROOK PARK SUALINOTON, MASBACHUSEFTB 0tQ03 (847) 27P-70lf Figure 4. IPC Display a whether the aircraft ate DABS or ATCRBS equipped whether the aircraft are under IFR or VFR flight plans e the grouncjspeed o f the aircraft the predicted time to point of closest approach the relative geometries o f the conflict situation whether the aircraft responds to initial commands, The experimental proximity warning indicator in Figure 4 provides the relative bear- ing to the nearest 30 degrees (clock code), and the relative altitude (high, level or low) which i s quantized to about 500 feet, Because the warning lights come on at different times under different situations, the unit provides effectively no range

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AEROmP Ace BYHTEMB, INtZ. + ONE VINE BROOK PARK BURLlhlDTON, MABIIACHUSETTS O l Q 0 3 (517) a7P-7B17 information, Several pilots have expressed a desire to have the range information dis- played since i t i s available from the computer, I f IPC i s implemented, a DABS transponder and a display w i l l be required to receive protection from al I al tltude-encoded, transponder-equipped aircraft. An input/crutput device would be required to use the data link For other messages. Corn- pared to the present cost of' a GA ATCRBS transponder o f about $750, a future DABS transponder with IPC cockpit disploy i s estimated to sell for about $2,000, excluding the cost of the altitude encoder.

The IPC concept i s currently under test using the Lincoln Laboratory DABSEF facility and a Fleet of general aviation aircraft equipped with the DABS transponders.

Evaluation flights with general aviation subject pilots have been conducted regularly for several months to evaluate kheir response to commands, and their reaction to the system. Preliminary conclusions show that the proximity warning i s univeraolly received with enthusiasm, However, the positive and negative commands are generally less favorably accepted, partially because the commands are frequently inconsistent with normal evasive practices when the intruding aircraft can be seen vtsually.

As previously discussed, a prerequisite for the IPC service i s the imple- mentation of the Discrote Address Beacon System. A prototype test of IPC i s scheduled for late 1977 at NAFEC, using the first DABS ground sensor. The first operational IPC service i s scheduled to begin in Philadelphia in 1979.

If BCAS and DABS are both implemented, a question arises as to which would be the primary means o f assuring separation. Some think that the DABS IPC should be the principal separation assurmce system i n areas where coverage i s available, and that BCAS would protect in areas where there was no DABS coverage. This would probably require that the acfive BCA5 be deactivated i n areas where DADS coverage A E m P 6 PACE BYBTEMS, JhIC, O N E VINE BROOK P A A K . BURLINGION, MASBAEWUSETTB 01803 ( ~ 1 7 ) 272-7617 was availabl+ to prevent possible conflicts i n evasive maneuvers prescribed by the two systems. Also, with the implementation o f DABS it w i l l be necessary for active air- borne transmitters to interrogate other aircraft i n both a DABS and an ATCRBS mode.

Once communication between aircraft using the DABS equipment is established, many interesting p o s s i b i l i ~ i ~ s exist, such as having one aircraft advise the other of an escape maneuver, Conceivably, the aircraft could effectively have "turn signals" that would be flashed to equipped aircraft whenever the pilot intended to change direction or altitude.

2.2.3 AREA NAVIGATION (RNAV) The exisfing structure of enroute airways and routes within terminal areas consists of flight segments defined by radials of the existing VORTAC n e ~ o r k . This limitation to radial segments has imposed extra mileage between certain terminals and has limited the number and capacity of air routes. Area navigation systems give air- craft the capability to follow predetermined altitude and time schedules i n proceerling from one navigational waypoint to the next, unconstrained by the location of the navigation station. These RNAV routes permit possible traffic segregation by speed classes and separation o f trcrffic bound for metropolitan areas according to the airport of destination. Vectoring by the ground cont-oller w i l l be reduced, and aircraft operating cosfs w i l l be lowered by more direct routes and optimum climb profiles.

Table 5 presents a detailed outline of the potential benefits of RNAV (Reference 7).

The problems associated with RNAV are primarily due to the integration of the new routings into the present air traffic control system. The existing NAS enroute system does not readily accept flight plans with direct routings, because i t i s difficult for the human controller to handle RNAV direct traffic when the majority of the traffic i s following the established airways. However, the 1980'5 undoubtedly w i l l see AEAOBPAEE! I Y a T E i M B , INC. ONE VINE BROOK PARK BURLINGTON, MASSACHUBEffB 01803 ( B I T ) 872-7517 Table 5. Araa Navigcrfion Features and Potential Benefits, I. RNAV (2D) A. Designated Routes Efficient Restructuring of Terminal Alrspace for Departures Efficient Restructuring of Terminal Airs ace for Arrivals

B

Shorter Standard Instrument Arrival an Departure Routeb PIlot-Navigated Nolse Abatement Arrival and Departure Routes Segregation of Traffic by Speed/Clirnb/bescent Capabilities Replace Some MeterIng and Spacing Vecforinp Shorter Low A l f i tude Routes High Altitude Great Circle Routes Optirnizecl H igh Altitude Weather Routes More Favorable High A1 t i tude Flight Level Assignments More Optimum Routes through Restricted Areas When Nor in Use Fewer VOR/bME8s to Support Exporrded Route Structure Fewcr VOR1s to Provide Instrument Approaches Fewer Duar VOR/DME1s Required Increased Continuity of Service Many Non-ICNAV Users Will N o t Require 50 kHz Frequency Spacing Change Route Structure Without Moving VOR,hME1s VFR Guidance Airport to Airport 0 . Parallel Routes 1 . Convenience of Parallel Offset 2. Simpl ified Passing Procedures 3. Simple Spacing Procedure C, lrnnrom~fu Routes Severe Weather Avoidance with Pilot Navigation 1 .

Direct to Next. or Other Waypoint Navigation 2.

Metering and Spacing Appl icafions 3.

D . Pro-Planned Routes

lnstrumenf Operations tao Non-ILS or VOR Instrumented Runways E.

-- "

1. Separate Approach Paths for STOL and General Aviation 2. "Straight-l n If Approaches R N A V D N A V lnstrumenf Operations When I LS Inoperative 3.

A 0 6 P A C E B Y s r e M B , IN=. ONa VINE BROOK PARK BURCINOTUN, MASSACHUBETTB 01803 * (a171 P7P.7Bl7 Table 5 . Area Navigation Features and Potential Benefits (Continued).

F. Pilot Navigation Instead OF Vectoring 1 , Pilof Awareness Back-up Following Radar or ARTS Failures 2 .

G. Improved Navigation Performance -

Linear, Smoothed Course Indications 1 .

2. Reduced Airborne VOR Error 3. Improved Lateral Navigation Accuracy 1 1 . VNAV (3D) A . Designated Routes

1 . Inclined Tunneling

2, Mare Econarnic Descent Profiles 3. Inclined Plane Floor/Ceiling Boundaries 4. Parallel, Precise Climb/bescent Paths Vertical Guidance for Instrument Approaches B,

1 . Lower Minimums Than with RNAV

2. Two-Segmen t Approaches I I I . TNAV (4D) A. En Route and Transition Application B, Terminal Area Application k

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A E R a a P A t a B y H T E M B , IN=. ONE VINE BROOK PARK EURLtNOTON, MASEACHUSETT6 01EaD (~17) PIP-Pal7 additional use of RNAV, first at the hlyher altitudes, then i n the mare densely- populated terminals, and Finally over most of the airspace.

Equipment for area navi- gation already exists, and i s in operation in many general aviation aircraft. In the future, certain airspace such as the present fermina! control creas may only be avail- able to RNAV-equipped aircraft.

Navigation equipments most likely to be used i n an RNAV structure include: VOR/bME, Ornega/VLF, Loran-C, and inertial navigation systems, NAVSTAR, the military satellite Global Positioning System, i s also a candidate, although i t i s not scheduled to become operationally available until after 1984, and initially may find only limited c i v i l use. VOR/bME area navigation has several disadvantages despite the fact that i t i s presently the primary navigation system. One major disadvantage i s that the bearing accuracy of the VOR i s relatively poor, of the order OF 3-4 degrees, which leads to large position errors at significant distances from the VOR facility.

DME i s more accurate, having a random bias error of 500 feet ( 1 ~ ) . Consequently, for more accurate RNAV, multiple DME holds much more ~rornise than VOR/bME, and it i s reasonable to expect a multiple DME RNAV to provide position accuracies of 0.1 nm (10).

Another problem assoc;ded with VOR/bME area navigation i s coverage.

Because VHF and UHF signals propagate along a straight line, a large number of sta- fions i s needed to provide uninterrupted coverage, especially at low altitirdes.

Because individual ground stations cost severat hundred thousand dollars each, VOR/ DME coverage over the entire United States at all altitudes i s a very expensive way of providing area navigation capability, mega, on the other hand, i s a much lower cost RNAV system, in thaf only eight stations are required to provide complete world-wide coverage. The eight stations The accuracy of Omega i s normally are already funded and most are operational.

A E m 0 8 P Ace BYSYEMB, I N e . ONE VINE BAOOIC PARK SURLINOTON, M A S B A t H U B e T T B 01003 (a171 P7R-7017 considered to be one mile i n the daytime and two miles at night, Improved accuracy of the order o f 2,000 feet could be obtained using differential Omega, but this would require differential ground stations located every few hundred miles. However, tho cost of these stations would s t i l l be extremely inexpensive relative to the cost of pro- viding a complete VORDME RNAV network.

Loran-C lias an intermediate cost between Omega and VORDME. Loran-C stations cost about five million doflars each, but the usable rangeextends out to ~~pproximotely 1,000 miles, which i s about an order of magnitude greater than for

VOR/bME . Like Omega, Loran -C i s a low frequency system and provides coverage

all the M'ay to the ground, Over the total area of coverage i t would be reasonable to expect accuracies of a tenth o f a nautical mile. However, under the best geometry Loran-C has the potential of significantly enhanced accitracy, with a repeatability of the order o f 100 feet. A t the present time, the FAA i s studying the possibility of using Loran-C as the standard navigational aid to replace the present VOR/bME system. In addition to its potential cost savings, the Department of Transportation has specified Loran-C in the National Plan for Navigation i n the coastal confluence area, Loran-C chains are presently operating on the East Coast and in the Great Lakes, and a West Coast chain w i l l seen be commissioned. Relatively few additional stations would be needed to provide complete Loran-C coverage over the conterminous United States.

Inertial navigation systems (INS) w i l l probably be limited to the more sophisticated users because o f their high cost, on the order of $100,000. However, low cost versions for GA ore forecast to eventually cost dround $30,000 or less. The accuracy of an inertial navigation system i s typically one nautical mile per hour. A significant advantage of inertial navigation systems i s their complete independence from ground stations. Recently, general aviation aircraft have been certificated For use of inertial navigation under IFR.

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A ERa a P A C E 8 V B f eM8, LNG. * O N E VINE ERClElK PARK BURLINQTUN, MABBACHU8ETTB DIBD3 (017) P7R.7017 It i s djfficul t to spaculat.e osi which of the navigation systems w i l l become the primary system far general aviation use inasmuch as the outcome depcnds largely on political decisions to be made by the FAA, by the Congrass, and by ICAO, /,I1 of the navigation systems discussed above are presently in operation and none can be completely eliminafad i n the time span under consideration, since a large number of alrcraft are and wilt be equipped with the raspectlve avionlcs and dependent upon the ground stations, Modifications to t h e ATC system can only be undertaken if they w i l l be compatible with existing equipment, As a consequence, additional new systems wiil be slow in implemrtntation, and those which are in existence w i l l remain in opera- tion long after their shortcomings are recognized. The most probable situation for the 1980s i s that a l l of the systems w i l l have found some use and that the ATC system w i l l accept any OF the various RNAV equipments that can achieve sufficient accuracy, which i s presently specified in t h e FAA Advisory Circular 90-45.

One Important factor in the design of RNAV equipment i s the pilof workload created by its use in h e terminal area, Since manually changing from waypoint to waypaint can produce significant workloads, stored waypofnts that have been preset prior to flight w i l l prauably be necessary, at least for high dansify terminals, In addition, the system has to be designed to minimize the possibility of operator errors i n setting the waypoints. For example, i t i s relatively easy to inadvertently transpose digits in specifying a latitude and longitude or a bearing and distance: hence, some kind of cross-check i s desirable, The implementatian of RNAV has proceeded at a very low level during the past Few years, However, the implementation rate i s expected to accelerate during the remainder of this decade and into the early 1980's. Considerable effort has been spent in configuration studies and avionics standards, and a decision on major imple- mentation i s expected within a year. It i s possible that the high altitude enroute

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A R m P A c e BYBTEMB, INC. 4 PNII; VINE BROOK PARK * DURLINQTBN, MA#iTPCHUBlltTO 01803 (817) R7P-7077 / airway structures and certain dense terminal areas w i l l require RNAV capabiliv by 1980-82. By 1985, RNAV w i l l likely be used exclusive\y at all medium and high density terminals (at least during peak traffic periods), as well as i n the hlgh altitude snrovte structure, 2.2.4 MICROWAVE L A N D I N G SYSTEM (MLS) The universal microwave landing system now under consideration by ICAO i s in tended to provide more flexible yet more precise approach and departure paths than the existing VHF,/UHF instrument landing system. The basic system 1s being developed fo satisfy both c i v i l and military requirements, with variations in several versions adapted to the porticulur needs of each. The c i v i l version w i l l be designed for both commercial air carrier and general aviation requirements, The high cost of site prepara- tion kequently required for the ILS w i l l be significan fly lessened, and installations w i l l be possible at sites where the co~ventional ILS i s not now practical, Improved fiexibil- i t y w i l l be provided in the form o f multiple glide slope selection and curved approach capability, which could have a marked impact on reducing noise i n areas immediately surrounding the airport.

The development program F o r MLS has been underway for a number o f years.

Many MLS systems are already in operation, and the problem i s to select one universal system for the international community. The United States has chosen the time reference scanning beam MLS technique as its proposal to ICAO, after a close competition with the Doppler scanning technique which the United Kingdom i s promoting. The Federal Republic OF Germany i s proposing a system involving interferometer measurements with 1,-Band DME, Therefore, i t i s not clear which MLS concept w i l l eventually be selected by the international community.

I n the interim, several MLS systams are already tn operatlon: the Canadians are operating a C-Scan system; MADGE (microwave aircraft digital guidance equipment) has been recommended for adoption by NATO, and i s being supplied to the UK Ministry of Defense; and each o f the U, 5 . mill tary sarvicas has a different MLSsystem i n current operation, The FAA has dasjgnated Tul! Aviation's system as the official interim standard MLS, and a few installations have been cammissioned, Individual organizations, such as Rocky Mountain Airways, are operating w l th the TALAR system and others. Consequently, there i s s t i l l some doubt as to the form that MLS w i l l take, since there i s no international agreement yet, and by practice there i s a proliferation of interim MLS systems.

It i s conceTvable that MLS w i l l not be implemented i n Its complete Form, sfnco It i s only needed at airports wlth siting problems or where steep and curved approaches are required, Impiementation of just tho glide slope portion of MLS couid meet these requirements. I t would be relatively easy to add or substitute iust the MLS glide slope to existing ILS facilities, since the conventional UHF glide slope i s entirely indopendent o f the VHF locallror. The conventional ILS glide slope i s often difficult to form since i t normally requires reflection of the radicted energy off the ground plane, and i t i s limited to approximately 3 degrees which does nof permit steep approaches.

However, pilots have shown reluctance to make steep approaches that do not level off to the conventional 3 degree approach prior to the final flare, Also, they have expressed reluctance to fly curved approaches beyond the same point whc;e the glide slope shallows to 3 degrees. The steep and curved portions of these approaches can probably be flown with area navigation equipment with interception of a conventional 3 degree glide slope at the point 400 to 600 feet above the runway.

Furthermore, a number of technical improvements could be made to the existing ILS to make i t a strong competitor for remaining as the primary landing system.

The majority of VOR navigation receivers process the ILS localizer signals as a standard feature. Conventional I LS has been accepted by lCAO and i s used at airports around A E R d 8 P A C E BYBIEMS, I NC. . ONE VINU .ROD% PARK EURLINPTON MASSPCHUII!TTE a i ~ 0 3 (~117) 8 7 1 - 7 ~ 1 7 the world. Airport operators w i l l tend to install a conventional ILS before a new MLS because very few users are equipped to use the MLS, and the form of the universal MLS i s still in doubt. Since a new MLS would generally be located where an ILS i s also instal lad, there t s l i t t l e advantage to providing two localizers I f the VHF ono i s satisfactory. Simltttrly, thero I s little reason to initiate a new C-band DM€, which i s planned as a part of the scanning beam MLS, when we already have L-band DME, MLS probably w i l l be most i m p o r t ~ n t for Category Ill landings where higher accuracy for flare I s required. Again, the MLS glide slope w i l l probably be aligned with the conventional 115 and be used prIrnarily by those aircraft which need Category I II capablli ty. I t should be pointed ouf that the conventional UHF glide slope Is inadequate for flare guldance because i t does not intersect the runway, Instead it has a hyperbolic share near the ground, typically rounding off some 10 to 20 feef i n the air depending on the distance of khe antenna mast from the center of the runway.

The main reason for not placing the UHF glide slope antenna closer to the runway center line i s that i t becomes an obstacle for landing aircraft.

However, fjexible antennas have been developed to reduce the hazard to landing traffic,

Despite considerab!.; controversy, the U . S. MLS development program has

proceeded nearly as scheduled (Figure 5). T h e U. S . choice of a scanning beam system has been flight demonstrated i n the NASA TCV aircraft and sdbmitted for ICAO consideration, T h e ICAO i s scheduled to specily one of t h e competing syskems as the univers~! MLS by the fall of 1977, Commencement of international opercltions with the universal MLS i s expected by the beginning of the 19801s, 2.2.5 UPGRADED ATC AUTOMATION T h e specific objectives of the UG3RD automation development program

apply to a l l rnaior portions of the ATC system, i . e,, enroute, terminal, and central

A E R o f l P A C E BYBTBMS, INC. * ONE VINE ERaOK PARK EURLINGTDN, M A S E A C H U S t f T t O Ole03 (817) P I P - 7 0 1 7 I UOVBRNMLNT EVALUATION INDUSTRY SYSTEMS DEVELOFMBNT PROGRAM SUPPORT I N 1 3 COVERNMENT PllQOAAM IDOTlDODlNASAl Figure 5. Natianal Plan for Developing the Microwave Landing System, flow control. These objectives are: improve management of air traffic flow through the ATC system to reduce costs of airborne delays; increase productivity o f ATC con- trollers to stabilize or reduce the numbers of required personnel; maintain or improve the current level of safety for controlled aircraft; increase airport capacity; provide the automation hardware, software, and control procedures needed to operate with other features of the UG3RD; and improve automation system re! icrbility.

Many improvements w i l l be provided by additrons or rnodificcltions to the existing NAS and ARTS computer programs. A few of the basic additions which w i l l assist in the transition to automatic air traffic management are: flight profile genera- tion; sector clearance planning; flight progress monitoring; automatic clearance delivery timing; improved aircraft tracking (radar and beacon); metering and spacing;

m u conil ict prediction and solutlon . Same longer term automation functions w i l l rely

heavily on the avoilabiliiy of an automatic data link for the exchange of ATC mes- sages with airborne aircraft, The system i s planned to move from a labor-intensive to a machine-i,ltensive base, with the air traffic controller ultimately becoming a system manager.

Implementation of several elements of the increased automation i s already well underway, while other aspects are inseparably linked ta other features of the

UG3RD . The confl lct alert system, dlscussed i n Subsection 2.2.2.1, hus been opera-

tio;ral above 12,500 Feet for several months, but has a problem with numerous false alarms. A minimum safe al tituda v,arning feature i s being implemented a t the ARTS facilities. Despite significant research, a l l metering and spacing systems tested to date hove been unacceptable, In general, increased ATC automation w i l l not involve additional avionics beyond those required by the other UG3RD features (DABS, RNAV, IPC, etc,).

2 . 2 . 6 AIRPORT SURFACE TRAFFIC CONTROL (ASTC) Growing traffic loads, increased all-weather operations, and new airport construction which blocks the visibility of airport facil ities From many control towers result in now requirements For handling traffic G;I the airport surfaces. Three needs have been identi Fied: a Improved survei llanse of the airport surface Guidance information for aircraft, and a Improved control O F the airport situation.

To improfe surveillance, the current airport surface detection equipment (ASD E) i s beiris modified, and new ground surveillance radars are being devoloped with the goal of achieving automatic tracking o f aircraft and surface vehicles from enhanced radar preset~tations, The use of discrete sensors such as magnetic !oops placed i n runway and taxiway surfaces has been analyzed, and completely automated and integrated control systems using hundreds of intersections have been considered, A major research effort i s being devoted to a beacon trilateration system, using ATCRBS at first and eventual! y DABS, for surveillance of the airport surface (Reference 94). This TAGS (Tower Automated Ground Surveil lance) technique wil l involve additions and modifications to the ground-based beacon system, but fortunafely w i l l not require addi tional avionics aboard the aircraft. Experimental equipment using two phased array antennas has been built by Bendix and recently demonstrated the feasibility of t h ~ cot~cept at NAFEZ (Reference 82). An implementation decision on this system i s not expected for at least two years.

Trailing wake vortices, especially tl.om large aircraFt on approach and land- ing, present hazards to aircraft following too closely behind. f his i s particularly true for general aviation aircraft. Increased long! tudinal separations (up to four and five miles behind "heavy" aircraft.) provide safety, buf signiFicantly reduce airport capaci1.y and introduce delays, Beyond efforts to minimize the size and effects of these vortices by aerody- namic means, the FAA i s working on ground-based systems to detect and avoid these vortices. I t has now been demonstrafed that pulsed and Doppler radar-like devices operating at acoustical frequencies can detect and track these wake vertices, and development and test o f these devices continues on an expedited basis. Given improved

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AER 0 B PACE! SYGrTEMB, [NCa aN@ VINE ElFIUOK PARK B U R L t N G T O N , M A S 6 A C H U S E T T I 0 1 f l O I (8171 127R 7017 knowledge of the movement and effect of vortices on aircraft, such a sensor might be the central factor ir, a system which would detect the presence of vortices, predict their behavior and intensity, and present this information in a suitable fashion to ground controllers who can appropriately adjust aircraft spacings. O n a longer term basis, i t i s planned to couple this system directly into automatic metering and spacing programs, I t i s possible that the DABS data link could be used to issue wake vortex warning advisories on Final approach, Wake vortex data collection efforts have been conducted at Heathrow, Stapleton, and Kennedy airports, and an experimental Meteorologi cat Vortex Advisory System has been installed at O1Hare for testing. However, no advanced implementation plans for WVAS Iiave been released.

Because severe wind shear was a contributing factor i n some recent accidents, a prograni to dzvelap a detection method i s receiving priority attention from the FAA.

Wind shear pressure sensors to predict the approach OF thunderstorms are being evalu- ated at C'Hare, and wind shear equipment i s to be installed at Dulles this summer.

Research efforts at Stanford Research Institute and elsewhere are aimed at developing airborne equipment to detect severe :,;;nd shears.

2.2.8 FLIGHT SERVICE STATIONS (FSS) The FAA currently operates a network of some 400 Flighf Service Stations (FSS) at which general aviation pilots (the primary users) may obtain face-to-face or telephone weatl~er briefings from FSS personnel and File their Flight plans. This net- work of stations i s technologically and functionally the same as i t was in the 1940's; most facilities and equipment are deteriorating and obsolete, and the system i s labor- intensive and unable lo meet the present demands For flight services.

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A E P ACE BYBTEMEI, INc. + ONE VlNa a R o o K P A n K nURLINETDN, MASBACHUBICTTB 01003 ( 8 7 7 1 &'78'.7017 A new automated Flight Service Station concept, developed by a joint study team of FAA and the Department of Transportation, proposed three basic elements (Figure 6): a A central processing facility a 30 to 50 full-time, manned hub stations a A nationwide total of s o m e 3,500 unmanned, pjlot-self- service terminals at approximately 2,500 locatrons.

When this network i s com~leted, virtually all pilot requests for preflight service (i.e., weather briefings and flight-plan-filing)# should be fulfilled through unattended, auto- mated terminals (Reference 34). A touchtone telephone system data link or the DABS data link might be used to access automated services, However, there w i l l probably s t i t ! be voice response to airborne requests far into the foreseeable future A demonstration AWANS (Aviation Weather and Notam System) i s in spera- tion at Atlanta and w i l l be installed at Leesburg, Virginia. This system uses a computer, keyboard and display scopes to improve the efficiency of the FSS weather briefer, The next stage i s the development of the Baseline system which w i l l permit the user to bypass the briefer For weatller information or to file a fright plan. Specifications are expected to be issued before the end of 1976; the first system w i l l be installed at N AFEC i n mid-1979; and tlie first operational system i s scheduled for implementation by mid-1980.

2.2.9 AERONAUTICAI, SATELLITE (AEROSAT) Oceanic air traffic control and air carrier communications are prosenfly conducted over high-frequency radio circuits which are of relatively low reliability and approaching saturation i n the North Atlantic and eastern Pacific. Surveillance of the oceanic airspace i s non-existenf; separation and control are based on pilots' reports

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A E R 0 P ACE B Y a f I NC. UNE VINE BROOK PARK BURLtNQTON, MASBACHUBETTB 01803 (817) P7R.7817 D I R E C T D I A L I N G TO HUBS WEATHER O B S E R V A T I O N n ST,,,,,, Figure 6 . Schematic Conception of Future FSS Network.

of their aircraft positions as determined from an-board navigation equipment. Improved conmunicutions and surveillance w i l l be required to handle the reduced aircraft separations necessary with traffic loads forecast for the 1980's; the alternative w i l l be lengthy ground delays or the use by some aircraft of less advantageous flight tracks.

Since these over-ocean flights tend to originate at the major hub airports, such ground delays would also contribute to surface congestion to some degree.

The Aerosat program i s exploring the u t i l i t y of satellites for expanding the

availability of or improving oceanic communications, and providing complete surveil -

lance to reduce oceanic separation standards, The program i s jointly sponsored i n a formal agreement with Canada, the European Space Agency (ESA), and the United States. The objective i s to establish the design o f a future operational system and international agreement on standard operating procedures to be followed i n i ts use.

The present configuration i s illustrated i n Figure 7.

The Aerosat Council (U. S, , Canada, ESA) has agreed to launch two satel-

lites for fest and evaluation o f satellite communications for oceanic ATC. The first launch i s expected i n late 1979, with a second to follow a few months later. Equip- ment decisions for any operational system are still uncertain and a long time away, Aerosat w i l l probably not have a maior impact. on general aviation because it applies primarily to over-ocean flights.

2.3 ADDITIONAL POTENTIAL FEATURES BEYOND THE UG3RD 2.3.1 GROUND PROXIMITY WARNING SYSTEM (GPWS) Federal air regulations require e GPWS on a l l turbine powered air carrier aircraft after September 1976. The system i s required to operate i n four different modes: 1) excessive rafes of descent; 2) excessive closure rate close to the terrain; 3) negative climb rate after takeoff or missed approach; and 4) flight into terrain when the aircraft

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A E R O 6 P A C E BYEITEMB, INC. . ONE VINE BRODK PARK BURLINGTON, MAIISACHU6Efffl;t M803 (817) 2 7 R . 7 0 1 7 I SPACE SEGMENT I I * TWO SATELLITES I

- S C F

I I I I AIRBORNE SEGMENT A V I O N I C S , t-BAND a VHF I T E S T AIRCRAFT : I COMMERCIAL AIRCRAFT I 1 INPUT/OUTPUT DEVICES .

I ' /i// G R O U N D SEGMENT

$ 1 - I/L ASET

- - . - A S C C (AOCC] a A l R L l N E S LEGEND A 0 CC AUTOMATED OCEANIC CONTROL CENTER 1 ASCC AERONAUTICAL SATELLITE COMMUNICATIONS CENTER 1/2 ASET ONE HALF OF AN AERONAUTICAL JERVlCES EARTH TERMINAL A T C AIR TRAFFIC CONTROL E T S ELECTRONIC T E S T S E T SMALL,REMOYE EARTH TERMlNAL FOR L - BAND 8 VHF ACCESSING

MINI - ASET

SCF SATELLITE CONTROL FAClLlTY Figure 7. Aerosat Configuration, i s not i n the landing configuration. A fifth mode, expected to be required i n the future, warns if the aircraft i s below safe limits during an ILS approach, I n this mode an advisory alert i s sounded when the aircraft is slightly below the center of the glide- path beam, and a pull up warning i s announced i f the aircraft descends significantly below the glidepath, especially i f the aircraft should near terrain clearance of approxi- mately 150 feet. The GPWS provides the ~ i l o t with bath aural and visual warnings i n a l l modes, The FAA requirement for GPWS w i l l probably be expanded to include larger general aviation aircraft and eventually might become a general requirement for a l l aircraft operated under IFR, Other governments are making the ground proxlmify warn- ing system mandatory in foreign transport aircraft. Although there are few objections to the concept of a ground proximity warning system, the early implementation o f these systems has resulted in a number of false alarms which, unfortunately, have reduced p i l o t confidence i n the equipment. Clearly, some warning of ground proximity i s desirable For all instrumentqualified airclaft. The main constraint against irnplernenia- tion of such equipment i n all IFR general aviation aircraft is the cost. A radar altimeter would be desirable in aircraff which conduct low approaches in instrument weather, Ground proximity warning would also be valuable for any night operations conducted at low altitude.

Relafed to the GPWS i s the FAA's terrain warning program i n which fhe current NAS and ARTS computers are being modified to alert controllers whenever an IFR aircraft descends below a minimum safe altitude. However, the warning i s only avaiiuble to those aircraft operating i n radar contact under I FR control , Moreover, radar surveil lance provides al ti fude of equipped aircraff only to the nearest 100-Foot inc~ament, anc! the reporting function could be i n error even more than this value.

Although this technique w i l l provide some assurance to the general aviation p i l o t making an instrument approach at a major terminal, i t cannot help VFR pilots at night nor pilots making instrument approaches to remote airports beyarid surveillance or com- munication limits, 2.3.2 AIRBORNE TRAFFIC SITUATION DISPLAY A somewhat controvsrsial issue not currently part of the UG3RD program in- volves the airborne traffic situation display (ATSD), which enables the air crew to participate actively i n traffic management. Proponents of the concept maintain that VFR capacity levels are achievable under IFR conditions by introducing fhe ATSD.

Opponents argue that an aircraft cannot safely and efficiently determine what i t should do without reference to the intentions and locations of many other aircraft, and to dist.ribute such information i s technically difficult and expensive.

Far several years MI T has experimented wi th a cockpit simulation of the ATSD, and the results of that rerearc11 have been universally favorable. The display itself is a cathode-ray tube which shows the navigation routes, the surrounding traffic, obstructions, terrain, weather features, and ATC directives, I t permits the p i l o t to maintain his own separation on other aircraft and allows him to verify h e reasonableness of ATC directives. In the present system, the traffic information available to the i s obtained visually, or relayed via the air traffic controller on the ground. f i e MIT research shows that the traffic situation display i s an extremely effective way of tmns- ferriny complete traffic and other information 1.0 the pilot, In high density terminal areas, the information could be used to provide spacing; some metering would probably be p i l o t assisted, The ATSD would certtrinly be used for separation assurance or collision avoidance, and rnighf also be used to display air traffic control clearances, weather conditions, NOTAMs, runway condifaions, etc.

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A E R P 6 P f i c E BYBTEMB, I M C . D N I VlNE QRaOK PARK BURLINQTCIN, MABBACHUPET79 01603 (877) P Y Q . 7 B 1 7 The impact of ATSD on genera! aviation i s that many users w i l l want the equipment i f i t can be provided a t a reasonable cost, Early estimates o f rhe cost of a general aviation airborne traffic situation display are on the order of $'I ,000 to $2,000, A major consideration for general aviation i s whether or not to present heading information, The MIT simulation results have shown the pilots prefer tl, have the dis- play indicate heading up, but this requires that aircraft headings be made available to the display. Unfortunately, general aviation aircraft at the lower end of the spectrum usually do not have heading information clvcailable in a useful for^: A gyro heading reference with an electrical readout, slaved to tlie magnetic sensor wol~ld cost around $1 ,000.

Another somewhat radical possibility afforded by ATSD i s for uncontrolled I F I I operations. By giving an aircraft the ability to see other traffic independent of the ground controlier (such as with BCAS and ATSD), i t would be reawnable to permit an equipped aircraft to fly i n instrument conditions without being under the control of the ATC system. This would give general aviation considerable freedom to fly i n poor weather essentially i n the same mode that they currently operate under VFR flight rules, Although this concept i s probably nof feasible wi+hin h' 4-1 density areas, i t would be a major improvement for general aviation i n vic,nttics where flights now are often increased by 50 percent becuuse of segregated airspace like the New York City area. For example, on an I FR flight from Boston fo Atlantic City, the approved route i s either via Scrcnton, Pennsylvania, to avoid the New York Metroplex, or alternatively over water, which i s an uncomfortable operation for single engine aircraft. Although i t would not be feasible for an aircraft with its own traffic viewing capability to pro- ceed direct1 y through the New York Metropjex, i t would be {cry reasonable to proceed a few miles to the west of New York, fo~. example, This i s particularly true if a low altitude were maintained, which a t the presenf time wouId be below the coverage area of the ATC surveillance system,

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R 0 8 P A c e BYBTEMB, INe. O N E VINE BROOK PARK OURLINGTON. M A E B A C H U 8 E i T O 0 j 8 0 3 (817) 27P.7847 2.3.3 NAVSTAR GLOBAL POSIT1 ON1 NG SYSTEM (GPS) GPS i s the Department of Defenseis anticipated replacement for Navy%

TRANSIT navigation satellite system (References 40, 91, 106). Phase 1 of the

NAVSTAR program w i l l provide for the launch of six satellites into 12 hour, circular, high inclination orbits by August 1977. The satellites w i l l be so spaced that they w i l l provide up to 5-IF hours of test time periodically each day for receivers located i n the Continental United States and the coastal ocean areas. Control stations locatcd i n the U, S. w i l l update the atomic clocks and provide ephemeris data to the satellites.

During this first phase of the program, several types of user equipments w i l l be developed to meet the spectrum o f future needs by the military services. A decision to proceed with the fuIl scale development o f the system worldwide wif l be based on the demonstrated achievement of two goals: high positioning accuracy and moderate cost of the system. The user must be able to position himself quickly to an accuracy of approximately 10 meters (24 i n three dimensions, and the user's eqtiipment should be comparably priced or less expensive than the other less accurate military navigation systems available today. Present unit cost projections for user sets range from under $10,000 to $40,000 for the most elaborate NAVSTAR equipment. The decision date to determine i f the system w i l l proceed beyond Phase I of the program has been scheduled for the spring of 1978, The first satellite, NTS-I containing the prototype rubidium clocks and a transmitter with the NAVSTAR frequency and type of signal coda, was launched i n 1974 and had limited experimental success before developing a stabilization problem.

A second satel life, NTS-2, i s under development and i s scheduled for launch i n late 1976. 1 t w i l l contain two cesium clocks and w i l l be the first. satellite launched as In early 1977, the first o f five part of the six satellite demonstration constellation.

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A E n 0 9 P A C E BYeTEMEI, iNC. ONIS VINR BROOK PAAK BURLINGTON. MASBACHUPETTB 03803 * (817) P7P 7B¶7 commercially b u i l t satellites w i l l be launched, The fifth commercial satellite should be in orbit by August 1977 and w i l l bring the constellation to the required total of six.

I f the decision i s muda to deploy NAVSTAR as a worldwide systern, then a second generation o f satellites w i l l be developed. The clocks on the second generation satellites w i l l be based on the demonstrated performance o f the NTS-2 cesium clock standards developed by the Navy and tested i n Phase 1, which should reduce the fre- quency of updating required by ground stations to once per day per sat ell it^ for a worldwide system. The second generation w i l l have an ability to secure telemetry arid data channels and may be powered by radioisotope tLernial e!ectri c power sources, Another difference will be i n the satellite l i f e oxpectancy, While the Phase 1 satel- lites are being built with Q design life oxpectancy of four years, [ha Phase 2 strtollites should have nearly doubie that. iongevify.

Once the decision is made to proceed with the system development in Phase 2, the satell Ftes w i l l be b u i f t and launched t.o expedite a two dimensional, worldwide

capability (assuming program approval i n early 1978) i n 1981 . As more sctelli tes are

added, the two dimensional system w i l l have increasing periods where three dimensional capability i s available. These periods w i l l gradually be extended until a cnntinuous, 3-D availability i s achieved by 1984.

The user sets consist of an antenna, receiver, data processor and control/ display. There are three basic receiver configurations for the NAVSTAR development and concept validation phase. The first configuration (model X) receives signals From four satel l i tes simultaneously, which requires four channels i n the receiver and the largest data processing capability. I t would be used in a highly dynamic platform or where minimum fix time i s esse-.ltial. The second configuration (model Y) would have one or two channels, time sharing them among the four satellite signals required, The

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A E R O B P A C E BYBTEMB, INC. O N E V1NK BROOK PARK BURLINGTON. MASfAGHUOETTB 01803 (a%') P7P.7a17 planned would establish a standard system of RNAV waypoints, based on bearing and distance from each VORTAC. Unfortunately, this concept would marry the RNAV route structure to the existing VORTAC ground system, rather than providing for a flixible waypoint definition based on general lati tude and longitude coordinates, 2.3.5 OMEGAflLF NAVIGATION Omega i s a very low frequency (VtF) hyperbolic navigation system designed for worldwide navigation coverage with eight grrund stations, transmitting on frequencies of 10.2, 11 ,33, and 13.6 kHz alternately, A t the present time the continental United States has complete Omegu coverage, Signals are being transmitted on all eight trans- mission segments (Figure 8). Seven o f these are from the permanent Full power (10 kw) stations. The G segment i s being used by Trinidad a t 1 kw awaitfng commissioning of the Australian station. Omega i s extremely significant to general aviation because i t has the potential for providing remote area and worldwide area navigation coverate a t extremely low cost, STATION 0.9 0 . 2 1.0 0.2 1.1 0.2 1.2 0 2 1.7 0.2 0.0 0 2 1.2 0.2 1.0 w ~ : NORWAY LIBERIA

NORTH D A K O T A D I \

L A REUNION E 1

I

ARGENTINA F

I

J A P A N ki * Trinidad w i l l ultimately be replaced by Australia.

Figure ,a, O m e g a Navigation Signal Format.

The transmitted signals are sinusoidal witri tight phase talsronces maintained by quadruple cesium stcndards. The only modulation i s the turn on and turn off of the transmitter. The signals travel i n the waveguide formed by the earth's surface and the ionosphere, As the height of the ionosphere varies diurnally, the effective speed of propagation varier, and so does the phase of the signal a t the receiver. Propagation variations are a function o f specific path, time o f day, and time of year, Sky-wave correction models which can reduce the positioning error to less than one nm can be applied automatically using a small computer at the receiver.

Distances are derived from differential phase measurements, which have an ambiguity of one cycle, Thus, when obtaining a position fix with the 10.2 kHz sig- nals, the position estimate w i l l be accurate to one or two miles, but. with an ambiguity

of approximately 8, 16, 24, . ., nautical miles. For most applications, many measure-

ments w i l l be taken before the vehicle has trciveled eight miles, and the receiver w i l l not lose track of the number of eight mile lanes i t has crossed, Receivers utilizing a l l three frequencies sbserve ambiguities spared approximutely 72 miles apart.

Differential Omega i s a proposed technique for further reducing the magni- tude of Omega propagation errors. Ground stations at known geographic locations would measure the Qrnega propagation error and broadcast a current correction to local aircraft, in the same manner as loccil barometl.ic pressure i s provided for altimeter corrections, The error due to propagation variation would be reduced to the difference i n the error a t the aircraft and at the reporling station, which i s on the crder of a half mile at a distance of 200 miles. This correction could improve the absolute Omega accuracy from about 19,000 feet to approximately 1,000 feet.

In addition to the Omega navigation transmitters, several U. S. Navy com- munications stations broadcast VLF s' jnals with phase stability sui tabla for ~~avigation.

A E A a B P A C E BYBTEF a, INC. ONE VINE BROOK PARK BURLINQION, M A S S A C H U S l n B O j C : . J (017) E17P-7M37 These signals are ten to 100 times cs as the Omega fransrnissions and have a 100 percent duty cycla. Global and Ontruck VLF receivers are now operational using both Omega and communication station signals simultaneously. Equipment cost i s about $25K.

2 . 3 . 6 LORAN-C Loran-C i s a hyperbolic navigation system which operates in the 90-1 10 kHz Frequency band. I t can achieve position accuracy better than 100 feet by using phase information i n addition to timing pulses, and i s therefore very attractive for area navigation. Each pulse i s designed to build up and dccay slowly to keep 49 percent o f the radiated energy within the assigned frequency band, Skywave contamination becomes significant abouf 30 psec after the beginning of the pulse so only the first three cycles gre generally used for navigation. The receiver must have a very high effective selecfivity because the first. three cycjes may be contaminated by atmospheric noise and other interference, Selectivity i s obtained by tracking the received signal with a servo loop +~ut has a long characteristic response time. For use i n aircraft the receiver must have velocity inforrnaiior; to keep the servo loop locked onto the signal.

Modern Loran-C receivers using integrated circuifs feature automatic search, weigh about 25 pounds, and use about 200 watts of power. Readout from the receiver itself i s i n time differences, requiring the navigator to transfer these to the corresponding hyperbolic lines on a chart, Digital computers are available which (at the price of doubling the size, weight, and cost) provide readout in latitude and longitude, together with left-right steering information and disruce along track. Exist- ing airborne Loran-C receivers are mostly military designs ~ n d are to expensive for general aviation, A \ though several low cost Loran -C recei-:err 50; a L-7~7 4sveloped for marine use, they do nof allow for the introduction of WQ;~:~ ,I.-.: . :*..I afcrmation .,, . : : > Y G , of hyperbolic position information into cruise and deviation ,.

A E R O a P A C E B Y 8 T E M 1 , INC. ONE VINE BROOK PARK BURLINGTON, M A 8 6 A C W U B E T f 8 DtQ03 * (8'17) 272.7517 Atmospheric noise a t the receiver i s the maior source of error in the Loran-C system. The accuracy depends on the signal-to-noise ratio which varies widely with range, and on the respcnsa time of the servo tracking loop. For averaging times o f 100 seconds a t medium runge, an error of 300 feet (lo) I s typical, TC.2 instantaneous accuracy could change by a factor of three i n either direction depending upon actual range. Loran-C i s not lirnifed by line of sight, and the high accuracy makes it particularly attractive for fhe 1980 period.

About 20 Loran-C stations are required to provide full U. S. coverage.

Relative to VOR DME, fhe system cost per square mile of coverage i s un order of

magnitude less and the average accuracy i s an order OF magnitude better. O n the

other hand, the system cost of Omega i s about one tenth that o f Loran-C, but the accuracy i s ten times lower. However, a modified form OF Differential Omega could be obtained by developmen+ o f a hybrid Loran-C/Ornega receiver. The cost of the hybrid receiver would probably 110t exceed the cost of a single receiver by more than 25 percent since both systems use common carnponenfs except for fhe receiver front end. The advon tages would be improved accuracy and improved reliability over that available by either component system alone. Loran-C would provide the differential update for Omega, while Omega would guarantee coverage over oceans or wherever there were coverag.: gaps c r outages o f the Loran-C.

2.3.7 l NTEGRATED COCKPIT The integrated cr,. k p i t i s a concept to reduce the proliferation of individual instruments, radios, and other subsystems that have grown i n the general aviation cockpit., Each of the individual instruments has a common need for data processing and display, which can be provided with current technology in an integrated manner such that the user receives mare benefits for an equivalent cost. O n c e the cockpit AERD B P A C E SYBTEMO, IN=. ONE VINE BROOK PARK BURL JGTON. MASBACHUBRTTB OlBC13 (017) 272.7U17 contains a CRT-type display and some computing capability, separate systems can be economically combined. The integrated cockpit should be modular because the typical general aviation user starts at the lower end o f the avionics spectrum and progresses up as he can afford i t . A t the lower end of the spectrum, the integrated cockpit would have the capability of providing the information associated with the basic flight in strum en:^, engine instruments, and navigational equipment, A t the high end of the spectrum i t might also include the information associated with RNAV, precision approach, weather radar, ground proximity warning, traffic situation, coll ision avoid- ance data link, and engine analyses, The particular information displayed would be selected at the pilot's option. Dual CRT1s would provide operational reliability through redundancy.

Current GA avionic systems consist primarily of independent electro- mechanical boxes for various functions, Each function i s handled by the combination o f a sensor, pilot. control, data processing and o display and/or actuator, 1ntegi.ation o f these functions using advanced avionics can be accomplished with a common data processor, common pilot control and common display. Individual sensors and actuators would still be required, However, they can be redesigned to give a better interface with the digital data processors, probably with advantages in cost and reliability.

In most current avionics installations, individual wires connect each o f the sensors, actuators and pilot controls with their associated data processors and display.

To minimize the wiring many of the electro-mechanical devices are housed behind the instrument panel close to the pilot control and display area. This location i s crowded, and access i s difficult for maintenance. A common display and control unit could free much of the space on the front of the instrument panel, while a common data bus could eliminate much of the convenf.iona1 wiring behind the panel. Further, the data processing functions could be shared and located i n areas which are more easily A E R P EI P A C E aY8TEMe, tNC. ONE VINE BROOK P P A K BURLINGTUN. MASBACHUBETTB O t B d l ( ~ $ 7 ) S 7 Z - 7 S l 7 accessible for maintenance. An a l l digital, integrated cockpit would creafe a complete departure frorr: the "separate box for each function" approach. During the 19801s, hardware for computing functions w i l l become relatively inexpensive. With sensors, actuators, displays and controls already integrated, the incremental cost of providing new functions w i l l be minimal . The major risk i s ti,:! danger o f common mode failures.

The design must make provisions for such effects as loss o f the prime electrical power source, failure of the common indicator, shorting of the dofa bus, or malfunction of the common pilot control. An emergency dropout generator on a separate power bus can provide backup protecfion against the loss of primary electrical power. Dual indicators and pilot control panels, one for the pilot and one for the co-pilot with cross-feed capability provides protection against a single failure of either. The data bus can be triplicated for redundancy with electrical isolation befween buses.

To simplify pilot. input/output, a substantial portion of the congested array of unipurpose indicators, switches, and knobs on the present instrument panel could be replaced with a sir~gls multipurpose alphanumeric keyboard-display unit. With a simple, but powerful, keyboard language, the p i lot could set frequencies, store RNAV waypoint coordinates, select operating modes for individual subsystems, and perform many oiher control and information management functions which today require separute 1/0 devices, Another improvement could be to integrate several conventional flight instruments whose functions overlap into two multipurp~se electronic displays, i .e ., an EAD I and an EH5I/ATSD combination, Many panel indicators, whose sole purpose i s to irldicate the status O F some aircraft system (engine, electrical, hydraulic, etc.)

could be eliminated, Today's p i l o t must monitor these indicators constantly to detecf abnormal conditions, whereas i n the advanced system, the central proceswr wi 1 l

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LIEROEPACE BYBTEMB, IfUC. O N E VINE BROOK PARK E U R C I N ~ T O N , MASBACHUSETTP 01603 (817) 27a-7517 assume this function, and only advise the pilot when an abnormal condition exists, To further reduce pilot workload the more sophisticated avionics system would provide bulk data storage easily accessed via the keyboard-display unit for enroute navigation, navaid frequencies, STARS, SIDs, etc.

2.4 GA AVIONICS GROWTH PROJECTIONS The future demand for various avionic equipment. has been projected i n Figure 9. These plots show the expected total number of equiprnents installed i n general aviation aircraft as a function of time, The projections are based on forecast growth in the GA Fleet and anticipated changes i n percentage of the Fleet that w i l l install each equipment. The growth i n VHF ftl and 82 communications transceivers, ELT, ADF, # I and 12 VORALS LOC receivers and marker beacon i s basically due to the growth i n the size of the fleet. The ILS glide slope receiver percentage w i l l reduce only slightly late i n trre period as MLS i s introduced. DME i s expected to show a percentage increase i n the near 80's but w i l l decrease later i n the 1980's as use of Loran-C becomes more common. VHF RNAV w i l l show only modest growth.

By the time that the rnaiority of general aviation moves toward RNAV, more common use of Loran-C and VLF i s anticipated. This i s reflected i n their growth i n the late 1980's. MLS will make only modest inroads on the ILS market until the late 1980's.

Aufopilot installations are expected fo increase i n both percentage and total numbers.

The number of ATCRBS transponders w i l l grow until the mid-1 980's and then level off cis DABS becomes operational early in the 1 480's. The altitude encoder w! I1 con- tinue to grow in use since i t i s used with either transponder and w i l l be a requirement for f l i g l ~ t in almost all the airspace, Weather radar, radar altimeter and GPWS w i l l increase considerably i n percentage, but the fraction of the total fleet will remain relofively small.

50 -

A E R 0 Ef P A C E SYBTEMS, INC. O N E VINE BROOK PnnK 6 BURLINGION, MASSICHUEETTE OlBO3 (817) 27Z-7U77 Figure 9 . Prole6 ted Growth of Varfous Avionics Equipmentr.

A D F Flgure 9 . Proiecfed Growth of Various Avionics Equiprnen ts (Continued).

r

MARKER BEACON I L S G S Figure 9 , Projected Growth of Various Avionics Equiprrrents (Continued).

D M E V H F R N A V A E R H P A c & BYBTEMa, INC. CNE VIIUK BROOK PARK EIURLINGTON. MASBACHUBRTTP 01805 (%17) P7P.7M17 Figure 9 . Pro jectod Growth of Various A t ion ics Equipmen t5 (Continued) , LORAN-C A U T O P I LOT

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A E R 0 B G . l E E BYBTEMB, INC. ONE VINE BROOK PARK . BURLINGTON, M A s 6 A C H U 8 l T T 6 01003 . (017) 27Z.7017 Figure 9 , Pro joctad Growth of Various Avionics Equipmen ts (Continued) , ATCRBS TRANSPONDER ALTITUDE E N C O D E R Ffgure 9. Proisctsd Growth of Various Avionics Eq*iipments (Continued).

W X RADAR RP-OAR ALTIMETER G P W S

SECTION 3 GENERAL AkIATION AVlON ICS REQUIREMENTS IN THE 1980's 3. I AVIONICS USER GROUPS General avlation users comprlsa a broad spectrum with widely varying avionics requirements. A t one end of the spectrum i s the sport pllot who operates his glider in the airspace with no avionics ~t all. A t the other end are the corporate flight operations which take wet I-equipped four-engine executive jets i n and out of international airports.

Some OF these general aviation aircraft contain more avionics capability than air car- riers because of their strong motivation for reliability and versatility. Cost i s the prime motivatI,,~ a t the lower end of the spectrum while safety and reliability are the prime rnakiva ttons at tho higher end. The cost i s relatively unimportant. when providing safe, reliable transportation for tho chief executive of a mu1 timil lion do1 lar corporation.

There are many possible dimensions for categorizing the users. One approach i s based on the standard FAA user categories which are related to the aviation applica- tions: a Business Transporkation--

Individual - Any use o f an aircraft not for compensation or

'Fijrc by an individual For the purposes of transportatiorr re- quired by a business i n which he i s engaged.

Corporate - Any use of an aircraft by a corporation, com-

pany, or other organization for the purposes of transporting its employees and/or property not for cornpenso tion or hire and employing professional p i lots for the opera tion of the aircraft.

Personal Flying-- Any use of an aircraft for personal pur- ~oses r ~ o t associated with a business or ~rofession. and not 'For hire. This includes travel, recreation and mdintenance of pilot proficiency.

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A E m e P Ace BYBTEMB, INC. ONE VINE 6RDDK PARK OUALINGTDN, MABBACHUBETTE O l D O J (817) 171-7077 Aarlal Application-- Aerial applicafion i n agricul lure con- a sists of those activities hat involve the discharge of materials from aircraft i n flight and a miscellaneous collection o f minor activities that do not require the distribution of any materials.

Instructional F I y i u - - Any use o f an aircraft For the purposes o f formal instruction with the maneuvers on the particular flight(s) specified by the Flight instructor, Commercial Operations--

A i r Taxi - Any use of an aircraft b the holder o f an A i r Taxi

U j Z 5 T i n g Certificate which i s out I orized by that certificate

(includes opera tior~b by scheduled comrnu ter air lines and non- scheduled air taxi operators),

A i r Ca= - Non-passeng er-carrying comrnerciu I transporta-

goods, materials, etc.

a Industrial 5 ecial-- Any use of an aircraft for specialized &nd!rs trial a s t i v i ty, excluding tranrportotion and aerial application (examples: pipeline patrol, survey advertising, swrch/rercue, photography, helicopter hoist!.

Other-- Any use o f an aircraft not accounted for by the previous user categories.

I n terms o f avionics, the most appropriate user categories are based on the types of o-=;ations conducted within the air traffic control environment.

VFR Operations a IFR Operations a Al I-Weather Operations The VFR operations category includes a l l those users whose avionics requirements are based on the fact that they only want to fly i n good weather. They have no need to fly under instrument conditions buf require basic navigation capability.

The IFR operations category includes a l l those ~ 5 ~ x 5 whose avionics require- ments are bused on the desire for an additional capability to Fly cn instrurn~nts i n margiral wocthn_r conditions. They are not, ho\faver, molivated rr, pay For the reli- a b i l i t y associated with complete all-weather capabi I i t y . There i s a general require- men t beyond the VFR category for basic surveil lance; i ,e., sorn;thing which provides the ATC system with position, altitude and identity. There i s also a requirement far approach capabiliry, A t the low end this means non-precision approach capability to typical minimum5 of'500 foot ceiling and one mile visibility. A t the high end i f means pracision approach capability to CAT 1 minimirms o f 203 foot ceiling and one-half mile visibility.

The All-Weather operations category includes thnse users who are primarily motivated by high rei iatii li!y, requiring redundat~cy through dual and backup sys!erns, weather protection through de-icing equipmenf and onbonrd radar, and lower minimums using flight directors and autopilofs. The lower end of this category requires CAT I I approach capability and the higher end needs CAT Ill approach capability.

The avionics required for these varied opera tians form a contiquous spectrum .

However, i f i s desirable to identify discrete categories within this spectrum just as we i d e n t i f ~ .;ezific colors within the s ~ ~ c t r u m of visible light, To that end we have separated ;lie users into six groups, which are id..ntified according t o their avionics requirements in Table 6.

A t the low end of the avionics spectrum (i . e . , for the VFR Only and I.i.ni!ed !FR Groups), tiie avionics requiremenks are dominated by cost; the user wants to accompti~.. the necessary functions a t minimum cost. In the middle portion of the spectrum (i.e., for the Standard and High Perfotamance IFR Groups), the avionics requirements are domirated by performance; fhe user wants to achieve the maximum

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A ER a P ACE BVBTEMFJ, INC. . ONE VINE BROOK PARK 4 QURLINQTON, MASSACHUBETTB 01803 (817) 27P-7mt7 Table 6 , General Aviation Avionics User Groups.

Avionics Requiremenls Co tegory

-

Grsup F Group E Group D Group C Group B Group A Objective VfR O n l y Limited Stondard High Per- A l l Highest I FR IFR formance Weather Rel iubility I FR Typical Approach VFK C o p b i l i ty Precision Typical Avionics Investment capability i n terms of landing conditions, routing, and availahl xts, A t the highest end of the spectrum (i . e . , for the Af l Weather and Flirt, i keliubili ty Groups), the avionics requirements are dominated by reliability; the user seeks maximum con- fidence that he can reach his destination and land safety despite the weather condi- tions, The typical avionics complemenb for each of khese groups at the present time are summarized in Table 7.

Table 8 shows the estimated current distribution of general aviation users by the avionics categories, The user categories in Table 8 follow the FAA application catqories, and the percentage breakdowns are based on ASI estirnatzs. N o t e thaf the percentages far a given user cafegory (e.g., business travel) total to 100 percent.

However, complete1 y accurate s ta tisbics are not possible becuuse, in practice, there i s significant overlap between the various groups selected for this study, For comparistn, A E R O a P A C E BYSTEMB, INC. . ONE VINE BROOK ='ARK 13URLIN6T0NI MASBACHUSETTB 01803 * ( ~ 1 7 ) 270-7637 Table 7. Typical User Group Avionics Requirements .

+ User Group Avionics Requireme~ts User Group Avionics Requirements Group F VHF Comm Group E 2 VHF Comm ELT E LT VOR 2 VOR A DF These equipmenk may not meet TSO or Marker Beacon FAA IFR certification requiremenk. Transponder Wing Leveler Group D 2 VHF Comm 2 VHF Comm Group C

-

E LT E LT 2 VOR 2 VOR ADF ADF Marker Beacon Marker Beacon GI ide Slope Glide S!:3;5*s DME DME Transpcnder R N AV Encoding Altimeter Horizontal Situation 2-Axis Autopilot Display Transponder Encoding Altimeter 3-Axis Autopilot Weather Radar Group A 2 VHF Comm Group 0 2 VHF Comm E LT E LT 2 VOR 2 VOR 2 ADF ADF Marker Beacon 2 Murker Beacon 2 G l i d e Slope 2 Glide Slope 2 DME DME 2 RNAV RNAV 2 Transponder Horizontal Situation Display 2 Encoding Altimeter Transponder 2 Hqrizontal Situation Dlsplay Encoding Altimeter Fl ight Director 2 Flight Director 3-Axis Autopilot 2 3-Axis Autopilof Auto Throttle Radar Altimeter Weather Radar 2 Radar Altimeter Wecfher Padar

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A ER P A C E BYBTEMB, INC. ONE VINE BROOK PARK BURLINGTON. M A 6 6 A C H U B E T T Q 011303 (017) P7P-7U17 Table 8. Current Distribution of G .A. Users by Avionics Category, Percen t of Fleet.

* Less khan 5 percent,

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A € R P ACE BYSTEMS, INC. ONE VINE BRODK PARK EURLIN~TON, M A S S A C W U B ~ ~ 01803 (917) 872.7m17 Table 9 shows the estimated 1980's distribution of general aviation users based on avi- onics category . The percentages sti I 1 tata I to 100 percent for each lrser category; however, the distribution has generally shifted toward the higher end of the spectrum, indicating a greater demand for more sophisticated avionics capability.

3.2 AIR TRAFFIC CONTROL K E N A R I O S FOR THE '1980's This section out1 ines three scenarios for the air traffic control environment in the 1980 to 1790 time span, to provide a basis for the anficipated avionics require- For perspective, Table 10 presents a few projected numbers on fleet sire and ments.

general aviation operations to show the extent of growth anticipated during the 1980's.

Table 1 l presents the scenarios for three times i n the 1980 period -- 1980

which i s only four years from the present date; 1985 which i s nine years i n the future; and 1990 which i s fourteen years hence. The bases for these scenarios are the FAA forecasts i n References 9 and 28. I n the near term, the rr,aior navigation change w i l l be the widespread introduction of area navigation. VOR/DME area navigation i s be expanded i n the very near future by e x - already i n limited use and w i l l tended use of 50 kHz sp;*=ing VOR stations which are paired with the channel Y DME.* Most of the newer VOWDME receivers are designed to accommodate this channel splitting. The expansion of RNAV i n the near future w i l l b e i n the high altitude enroute structure and i n the dense terminals to alleviate controller vectoring. Some three- dimensional RNAV approach and departure routes w i l l be introduced, In the mid 1?801s, the high altitude sector routes w i l l be exclusively RNXV as w i l l be those i n the high density terminals. A siandard grid of waypoints w i l l be established for area navigation to provide roufing f l e x i b i l i t y and to permit automatic * Channel Y DME operates on the same carrier frequencies as channel X, but uses different pulse spacing for discrimination, A C ) 6 P A C E SYSYEM8, ING. * ONE VINE BROUK PARK BURLINGTON, MAESACHUBETTS 01803 (017) 27a-7B17 Table 9 , 1980's Disfribukion of G .A. Users by Avionics Category, Percent of Fleet.

Avionics Requiremenis Category

F E D C B A

- - - -

High Hi hest Limited Standard VFR Perf. All ~e!ia- Only IFR I FR IFR Weather bi li ty I Business Transpor to tion *

*

Individual 5 60 35 0 * -~r

*

20 5 Corporate 75 Personal

*

10 2 0 40 30 0 Travel 25 5 25 15 0 0 Recreation

*

8 1 4 5 0 0 Aerial Application 15 I nstructioncll ; I 20 70 10 0 0 0 VFR

*

I FR i 0 0 50 4 5 5

Commerci a1 Operations

*

10 30 50 10 0 Air Taxi 15 5 30 4 5 5 0 Air Cargo ~ndustria~/Special 3 0 0 45 Survey 15 10 0 x 20 2 0 0 40 Patrol 2 0 40 5 0 20 ~earch/Rescue 10 25 10 0 0 70 Construction 20 0 * Less than 5 percent,

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k E 4 8 8 P ACE ' %*C&MB, lNC, ONE VINE BROOK PARK BURLINCTON, M&S6ACHUBEITB 01803 * (1317) 2 7 P - 7 O l 7 Table 10. General Aviation Projections For the 1980 Period, r 1990 1980 1985 275K 190K 230K Total GA Fleet 32K Peak Airborne Count 20K 2% llOM GA Operations 6 O M 85M GA Hours Flown 45M 60M 80M 900K 1400K Total Active Pilots 1 1 OOK Table 1 1 . ATC Scenarios for 1980's.

-

r ATC Feature 1980 198, 1990

.-

RNAV Initial use for high Exclusive use of RNAV the standard altitude enroute and RNAV in high navigation mode for dense terminals to altitude sector and ATC. 4-D RNAV alleviate vectoring. high density termi- approaches i n use a t den. terminats.

3-D RNAV Routes nals. Established for approach intro- grid of RNAV way-

duced . points. Automation

of waypoint inser- V~F/Ornega opera- tional.

approaches tion. 3-D RNAV standard.

GPS operatioilal i n GPS i n civil use.

Extended use of '

50 kHz VOR ar: I m i li t u y . Loran -C

channel Y DME. i n c i v ~ use. Mul- tIple DME RNAV in c i v i l use.

M LS Limited use of DME colocafed with Gradual replacement IMLS and MLS ILS & MLS. of ILS with MLS.

glide slope a t ILS & MLS colocated d i f f i c u l t sites and at moior for CAT I & I I MLS a t difficult sites.

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A ER m P ACE EiYETEMa, IN=. ONE VINE BROOK F&RK r EURLINDTON, M A 6 S A G H U E E 7 7 6 01803 (817) R 7 P - 7 1 1 7 Table 1 1 . ATC Scenarios for 1980's (Continued).

-

ATC Feature 1980 1985 1990 Surveil lance ATCRDS transponder A'TCi38S or DABS DABS transponder and encoding altirne- transponder with en-

and ]PC o r BCAS

ter required i n all coding a1 timeter required to fly in positive control required to fly i n control led airspace, airspace. Floor O F canhol led airspace.

enrov te posi ti ve con -

trol Inwerad to

12,500 Ff. . TCA1s

ex anded to include

mi f' itary oirFields

and ceilings raised to intersect enroute positive control airspace.

First DABS ground Mixed use of DABS DABS transpander facilities imple- and ATCRBS trans- a n d da tu link re- menfed. infrocluc- ponders. IPC service quired in posi tivo tion O F IPC service in expanded.

control airspace, limited areas, DABS transponders avoi lable:.

I

DABS survai I lance AgTS I! installed available at medium at medium d e n s i t y dcnsi I-Y terminals. terminals. Radar service available at a! l to)v.~er con- trolled fields.

BCAS in common BCAS introduced use as cost comes in air curriers and down.

high performance aircra Ft .

Introduction of data ' Common use O F data Introduction of 25 Gmmvnieafions link Tor ATC com- link (DABS or VHF).

kHz VHF channel

munications.

~nacing .

Use or' CUT i n cock- Possible implements- Test of Aemsat for tion of Aerasat pit For display O F oceanic c o m m u n i c ~ - although intraduction data l i n k information.

tions, BCAS reduces re- quiremen t for Aerosa t .

tncreased general aviation use O F radio telephone.

+ 3400 unmanned FSS. Communicafion with Implementation of FSS FSS by touchtone 30 manned FSS.

au tornated sfations.

data l i n k , A E R m 5 P A C E BYBTEMB, INC. ONE VINE BROOK PARK EaURLINBTON, MASSACHUBETTB 01803 (817) 878-7El7 insertion of waypoints. Ideally this grid w i l l be based on latitude and longitude, although other techniques have been studied (the DDBS concept using bearing and dis- tance from VORTAC stattons). By this time frame three-dimensional area navigation approaches w i l l probably be standard.

At the end of the 1980ts, 4-D RNAV approaches w i l l be i n use n ! . the denser terminals i n order to provide spacing of aircraft into the airports. Rau;;rrg k.y area navigation w i l l be standard at low and high a i titudes.

Although initial RNAV use w i l l be mostly wirh VOR/DME, VLF and Omega are also expected ro be uti Iized. VLF/Onleya has already been certificated for enroute use and i s avci~ IcSic in general aviation aircraft. By the middle of the 1980's i t i s anticipated that Loran-C w i l l be i n c i v i l use for air navigation, that multiple DM€ RNAV also w i l l be in use, and that tho global positioning system w i l l be operational in military aircraft. 1985 i s the expiration year of the existing ICAO regulations which specify VOR/DME as the standard navigation system, and some studies have exan-lined Loran-C as a replacement for VOR/DME a t that time. However, i t i s more likely that the RNAV system w i l l be predicated on accuracy without specification of what system i s used or provided. By the end of the 1980's the giobal positioning system i s expected to be available for c i v i l use.

Turning to the microwave landing system, l irni ted use of the standard interim microwave landing sys tern (IMLS) and the universal microwave landing systern l ide slope i s expected at sites requiring rnIcrowave glide slope and for Categories 1 1 and Ill in the early part of the 1980's. In the mid 1980'5, ILS and MLS w i l l ~ r o b a b l ~ be colocated a t the major terminals with MLS being used at difficult sites. DME w i Il probably be colocated w i f h !LS and MLS by 1985, but the DME i; more l i k e l y to be the existing DME than i t i s to be the new C-bund DME. By the end o f the 1980's one should

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A E R O S P A C E H Y B T S M B , lNdl ONE VINE ERDDK PARK * QURLINOTON. MAS6ACUUBET78 O t Q 0 3 ( ~ 1 7 ) P7il.7017 look for gradual replacement of ILS witi: MLS iT the univerzal MLS i s accepted by ICAO in the near future.

For surveillance in the near 1983's, {he ATCRBS transponder anci an encoding altimeter w i l l be required i n a l l positive control airspace, arid the floor of the enroute positive C O ~ ~ F O ~ airspace w i l l be lowered to 12,50a Feet in most regions. The terminal control areas probably w i l l be expanded to include mi!itary airfields, and the TCA ceilings w i l l b e raised to the floor o f rhe overlying enroute positive control airspace.

Implementation OF DABS w i l l begin i n the early 1980'5, and 1PC w i l l probably be intro- duced in limited areas. The ARTS I1 w i l l be instal led at medium densit) terminals and some form of radar w i l l be available a t essentially a l l tower controlled fields. BCAS w i l l be introduced by 1980, but its high cosF w i l l probably l i m i t its use 1 0 air carriers and high perforlnance aircraft.

I n the middle of the 19801s, the t~rlnsponder with encoding altimeter w i l l probably be required to Fly in any controlled airspace, and implementation o f DABS w i l l have produced a mixed use o f DABS and ATCRBS transponders. The IPC service w i l l be expanded to more areas and BCAS w i l l find greater use us the equipment. cosfs f a l l . By the end of the 1980'5, some form of collision avoidance system, either IPC o r BCAS, might be required in order to Fly in controlled airspace, The DABS trans- ~ o n d e r with a data link readout might be required in positive contrnlled airspace.

I n communications, channel splitting i n the VHF band w i l l b e utilized throughout the 1980's. Most of the new VHF comrnt~nications radios already have 25 kHz spacing, A data link utilizing either DABS or a dedicated VHF frequency w i l l probably b e introduced by the middle of the 1380'5, and by the end of the 1980's data link w i l l be in common use for air traffic control com,rlunications, There w i l l probably be considerably more general uviation use of the radio telephone as the cost declines A E R a a P A C E aYETEMa, INC. QNE VINE BROOK PARK BURLINGTON, MASBACHUPETTE 01803 (817) P7P-7Ul7 and the GA users discover its convenience. AerosaC i s to be tested in the early 1980's w i t h possible Implemen tation; however, the introduction of BCAS w i l l greatly reduce the requirement for an aeronautical satellite.

Flight service stations should begin automatlon in the early 1980's. By the mid 1980's the FAA forecasts that there w i l l be only 30 manned Flight service stations remaining, with 3,400 unmanned self-briefing stations.

By the end o f the 1 9 8 0 ' ~ ~ i t should be possible to communicate directly with the flight service station data links using touch-tone dialing and computerized voice synthesis.

3 . 3 GA AVIONICS REQUIREMENTS FOR THE 1980's Table 12 indicates the impact o f the preceding scenarios on the incremental avionics requirements beyond those shown in Table 7. In general, the rquiprnent Finds implementation at the highest level OF sophistication and tends to filter down 1 0 the lower levels as the cost reduces, as the advantage to the user i s demonstrated, and as regulations and common usage fend to force i t upon the less sophisticated user.

In the case of the Yrea navigation system, groups A, B, and C are already generally using area navigation i n varying degrees. Groups D, E, and F are expected to see major introduction of RNAV by the years 1980, 1985, and 1990, respectively. The particular fype of area navigation which the various user groups w i l l utilize w i l l probably be split among VOQ'DME, DME/DME, VLF/Omega, Loran-C and the Global Positioning System.

Inertial navigation w i l l probably not be used extensively outside of the more sophisticated general aviation users because of its high cvst relative to the other op tions.

The rest of this section discusses in more detail the avionics requirements which are dictated by the UG3RD, which are desired for the UG3RD or beyond the

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AEROBPACE BYBTEMS, INC. + ONE VlNE BROOK P A R K BURLINGTUN. MASGACHUUETTB 01803 + (817) 07P-?at7 Table 12. Changes to GA Usar Group Avionics Requirements.

(By approxima ta year O F 1r1 I, qduc tion .)

G '$ User Group

-

Avionics Change A 5 C D

- -

- -

VHF Comm. to 25 kHz Spacing Encoding A1 timeter DABS Transponder I PC Data Link Readout BCAS M LS VOR to 50 kHz Spacing DME to Y Channels RNAV VNAV VLF/OMEGA LORAN C DME/DME G PS x indicates change already exists.

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A E R O P A C E B Y B T E M B , INC. * OhlS VINE Q R a O U PARK BURLINGTON. M A l S A C H J S E T r O all303 * (817) P 7 t - 7 5 3 7 UG3RD. These discussions contain some repetition from previous sections since they are intanclod to bo self-contained explanations.

3 , 3 , 1 REQUIREMENTS FOR THE UG3RD Table '13 indicates how the ATC functions under the upgraded ~ h i r d genara- tior, system would aFFect the ~ a r i o u s ovionics user groups. For navigation oquiornent, the maior impact i s expected to be a requirement for areu navigation for a l l of the user groups t h a ~ operate 1 FK. As previously mentioned, i f i s an ticipafed that area nuviga- :ion structures w i l l be introduced into the air traffic co~ltrof system in he relatively near f u t ~ r e , and by the 1980 time period tho t portions of thc air space may be restricted to users with RNAV c a ~ a b i l i ty , Table 13. New Avionics Requirements For UG3RD.

t Avionics Requirements Category ATC Funckion Group B Group F Group A Group D Group E Grol~p C

- ---

Navigation

-VOll/~h. E or VLF/C~MEGA o r LORAN-C ..- o r - INS

RN AV

I 1 1 I

iviiS - S!Tclq Slopa -

Communications -

Data Link DABS Lata Link FL -. 4 Surveil lance A! t i tude Encoder A1 t i b d e

---

Reporting DABS IPC/BCAS

-71 -

A E R O S P A C E B Y a T E M S , 1 W C l O N E VINE BaOaI' PARK . OURLINGTON, MASBACHUHLPTrB 018U3 ( 1 1 7 ) Z72.7317 The type of RNAV equipment w i l l probably not be specified, except that i t must be certificated for operation i n the system. The criterla for certification aro ex- pected to remain sirnilur to FAA Advisory Circular 90-45. The p ~ ~ s i b l e types of RNAV are: VOR/DME, which i s alreudy available to tho gonercll aviation community; VLF/ Ornegu, which Is also available but has received only limited IFR cortification; Loran-C, which meets the accuracy requirements but has not received IFR cartificatisn; or INS, where some equipments have been certified For IFR operation.

Area navigation equipments using multiple DME or DME i n a fast-hopping mode may be preferable to VOR/DME RNAV since the accuracy of the DME i s better than VOR. The mu1 tiple DME equipments, however, are not yet general ly available at though there are a number of sets in a developmenf. stage. Cerfain problems arise with the pro- liferation of fasf-hopping DhEs in that a DME ground station can be saturated by over interrogation. The DME ground equipment i s designed to reduce tlta sensitivity of the receiver whenever the inFerrogation rate is too high to keep the number nf using aircraft at the level that rhe ground station can handle. Consequently, aircraft transmitters havlng the strongest received power at the ground station w i l l be the ones granted service.

Since +he received power depends on both the tiansrniffed power and the aircraft range, there i s some user advantage to transmitting at high power. Presently, a DME ground station can handle about 100 aircraff simultaneously. Potential improvements in the DME system could increase the number of interrogators by a factor OF about 8. Same of those changes involve slower interrogation rates on the part of the using aircraft and improved capability of the ground systems to handle the interrogations.

The requirement for the MLS glide slope is placea on the user groups w f ~ o I t i s anficipated that sorre airports w i l l seek very high reliability, Groups A and B.

provide only an MLS glide slope, and the user would be unable to make a precision MLS i s not instrument approach to that field withouf !he MLS glide slope receiver.

A E R S ~ I PACE! SYSTEMB, INC. . Q N ~ VINE E R ~ O K PARK ~URL~NP-ION. M A E B A C ~ U P ~ ~ T T S 01en3 (017) 871-7m7 considered as a requirement for any of the lowar user classes since the rnaiority of the airports wi l l provide precision approach capability through existing instrument landing systems. The possibility exists that the glide slope portion of the MLS w i l l be implc- ~.rlt,nked independent af the localizer portion, atsl be used essentially as a replacement for the UHF glide slope component i n t;lrr eiatldard I LS configuraticn. Consequently, an MLS loca!izer i s not seen as a requirement, The major new requirement for communications i s a data link v,etich w i l l most Jikely be the DABS data link. The du:a link would be requiraci for 0 1 1 aircrcft partisi-- pating in the IPC system, shown to include the four highest user groups.

Under surve;!lance, an a1 titude reporting capability w i l l be required of a l l user groups. Thertt i s a strong probability of a requirement far every user of the air- space system l o rrnnounce his identity and al titude with his radur position reply, The FAA i s already i r , i tia ting rule-muking proposals to require beacon transponders and reporting al tiinel-ers for a l l aircraft ope: tting i n control led airspace. 1 hir reauirement i s preJenf.ly i n existence for TCA's and Positive Control led Airspace, but can be waived a t the controller's discretion. The a1 ti tode encoder for the two loi*~est categories would be used in conjunction with the existing ATCRBS transponder. For those aircraft equipped with DABS, it. would be used in conjunction with the DABS transponder.

In summary, tlie major impact on requirements from the UG3RD i s anticipated to be some form o f RNAV capability for a1 1 of the users flying IFR, an MLS glide slope for the high reliability and a!!- eath her users, an altitude encoder for a l l aircratt in the s:~stern, and the DABS transponder data link and display for the four highs-r groups, 3.3.2 ADDITIONAL DESIRED EQUIPMENT FOR THE UG3RD Table 14 shows equipment which would be desirable as a result of the UG3RD.

These are equipmenfs 7 addition to those discussed above -which would be conside-ed essential .

- 73 -

N c w Equipment Desired for UG3RD.

Table 14, Avionics Requirements Category Aviclnics Group F Group E Group D Group C Group B Group A

. - -. .. . -----.-

- -

- - - - - - .

-DABS Troniponder w i 4-1 DABS Encodin$ A1 timeter Altimeter IPC D'spl{ry* , a

- - . I PC D'splay

I PC or FCAS

VLF/OME~A or VO DME

LLow-Cos t RNAV

RNAV*-4 Lo;.AN-C or C I s

CiS & L o & + -1MLS GS* MLS

M LS

. .

-

Data Linkq Automation

4 -

.-Do to L i n k - - . - A S K 4 - . D a b Link*- d WVAS t .,Touchbne

+ Data ~ f n k *

FSS TX/kCVR~ -e 'Aero Sat An tennu

I

* Indicates over and beyond required equipment, Tire DAGS iranspor-1lit.r w i t h erlcoding cjliirneter v~ovlci Lt! JesiraL1e fur ill!

aircraft in the system, whereas i t was considereJ iequired only for the four highesf zafkgories. The advantage O F having a l l aircraft DABS equipped i s that the IPC service would include a l l oircrcft ii. khe syslaern. The IPC display w i l l also be required; co~sequen fly, the IPC display i s extended fo cover all user groups.

Low cost crea navigation equipment would be desirable, even for Group F (VFR-only) users, inasmuch as i t ollov~s the user to f l y direcr routes and to locate air- pork not served by other navaids. Tire RNAV equipvent would not need to meet the requirements for IFR certification as outlined i n Advisory Ciscular 90-45, but should have i n accuracy o f the order of 2 miles. There is a good deal of promise for this low cost capability from ~ L ~ / O m e g a . The RNAV using VOR/DME i s probably not satisfactory for this purpose because i t does not provide coverage a1 low altitudes throughout the continental United States, whereas many of the Group F users typically operate in re- mote areas or a t low altitudes. Loran-C could serve this need except that a t the present time Omega sets cost less than Loran-C equipment because o f the simpler signal processing required. In the future, with advanced electronic components, O m e g a and Loran-C should approach the same cost to the user.

Under MLS, i t would be desirable for al I of the IFR users to be equipped with the MLS glide slope receiver to permit precision approaches to runways not served with the conventional ILS glide slope. For the highest reliability users, the availability of the MLS localirer would provide a back up fo '+he conventional ILS loca t izer and provide addi tionai accuracy and re1 iabil i ty for automatic approaches.

The UG3RD function o f uutornaf.ion leads to the requirement for some form of data link i n order that increased voice communiccrtions do not cancel the gains in traffic handling capability made possible through automation. Consequently, a data link capability for the aircraFt flying IFR i s desirable to achieve the full benefits of in- creased ATC automation.

Data link would also be desirable for airport surface traffic control. I t i s included for the t f ~ r a e highest user categories since they are more l i k e l y to operate at the high density terminals which require this surface con trot.

Duta link i s also desirable for providing advisories to aircraft as parf of the wake vortex avcidance system. The desirability of data link i s extended into the stasdard IFR group since the wake vortex avoidance system could be utilized to advant- age at many airporfs with insufficient traffic fa juskify surface control, A E R O Q P A C E aYSTEMB, I W C . ONE VlNE LfBDK P L R K r BURLINSTON, M A S S A C H U U E I T B OIBOS (817) 271.7817 A nluch lower cost form of data link could u t i l i z e the touch-tone system developed b y the telephone company for transmitting digital information over a voice channel. I t would be suitable for use i n connection with flight service stations which w i l l be usir,g automated weather information transmission over voice communications lines. Since a l l groups u t i l i z e khc flight service stations, the touch-tone data link would be a desirable feature for a l l users.

Aerosai only applies to the few GA users who would be flying oceanic routes. I F the system develops using carrier frequencies already available on the air- craft, the new requirement would be for an antenna with directional capability point- ing general1 y upwards towards the satellite. IF the carrier frequencies are different than those existing on current aircraft, then a dedicated transmitter and receiver would also i e desirable.

3 . 3 . 3 ADDITIONAL DESIRED FEATURES BEYOND THE UG3RD Table 75 suggests several additional desirec! avionics features for each user group beyond those called out i n the upgraded third generation system.

The Ground Proximity Warning Sys tern (GPWS) i s considered desirable for the four highest categories of IFR users. The GPWS w i l l be required by turbine- powered airliners after December 1976. The potentiol capability i s useful for a l l aircraft operating i n instrument weather or at night. GPWS would require a radar altimeter plus a warning system with p i lot display and asso~iated logic to drive the warning system. The requirements a s set out for the airliners might be relaxed for general aviation aircraft, but certainly the presence of a radar altimeter for low aFproacE,es ir. IFF? weather i s an extremely dzsirable feature.

The airborne traffic situation display would be extremely desirable for many of the users, since i t would place the traffic information i n the cockpit.

- 76 - R i?YRODUCTSILlTY OF THE

UK.IGWAL PAGE IS POOR A E R a 5 P A C E SYSTEMS, iNC. DNE VINE BROOK PARK BURLINQTON. MASS&CHUSETlR 01803 (817) P7P--El7 Table 15. Addi tional Desired Features Beyond UG3RD.

- -

I Avionics Requirements Category Avionics GroupF Group E Gmup D Group C Group B Group A

, I -

GPWS

ATS D 4 -

o M EGA/VLF 4

LORAN C INS Touchtone Datal inF- Fuel ~ ~ f i r n i z a t i o n G P S RCVR T X - b Three of the previous1 y mentioned RNAV sys terns are associa fed with user groups in Table 14. A VLF/Ornega system would require a low-cost receiver, compu- tation and display. The same i s true for Loran-C, and a l l user groups would be interested i n this form of RNAV. he INS system, because of i t s Cligh cost, would probably only be desirable for the more sophisticated user.

The touch-tone data link, which was mentioned sarlier, would amount r o a simple modulation on the VhF communications channel. It would be desirable for a l l users since i f could b e o major communications channel to flight service and srnoll fields not served by a tower.

Fuel o p t i m i ~ a ~ i o n is considered ,o be a flight management system feature i#.'nich would conserve fuel by flying a fuel optimum trajectory during letdown and landing with a

- 77 -

fi E R U 9 P A C E B Y B t E M a , ING* ONE VINE OROQK P A R K m BUFILINGTON. M A S S A t H U S m E I 01803 ( ~ 1 7 ) 272-73t7 programmed speed reduction and delayed flap extension. It would on1 y be reasonable to use this equipment on the higher performance aircraft and i s only listed, therefore, for the three highest categories.

The Global P o ~ i ~ i o n i n g System, if implemented, will provide an extremely accurate worldwide navigation capability. However, due to the l imi fed w e d for this copability and the cost of obtaining it, cnly the two most sophisticated groups are shown os potential users during the 1980's.

- 78 -

A E R 0 a P A C E ! BYBTEMB, INC. ONE VINE BHODK PARK BL'I3LLYGTDN, MASGACHUSETTE 01003 (Ell7) 272-78<7

SECTION 4 PARAMETERS FOR A V I O N ICS COMPONENTS A matrix of critical parameters versus avionics user group has been prepared for each major element of the avionics complement. The parameters are listed i n

approximate order of relative importance, Tables 16 - 34 present these parameters for

each of the following existing or future equipment.

VHF Communications Transceiver E1.T VOR/I LS Local izer Receiver ADF Marker Beacon Receiver ILS UHF Glide Slope Receiver DME RNAV ATCRBS Transponder Encoding A1 time ter Horizonfa1 Situation Display A u t o p i I ~ t Radar Altimeter Weather Radar DABS Transponder IPC Display GPWS MLS Receiver HF Communications Transceiver Each of these avionics components has been reviewed in an attempt to es~clblish which design features w i l l have the major effect on ~:qniprnent. cost. Tl~ese "cost drivers" and s t m e suggesfed research and development areas are summarized i n Table 35.

- 7 9 -

A E R 0 5 P A C E BYBTEMB, INC. aNE VINE t3ROoK PARK BURLINGTaN, MAS6ACWUBETTB 01803 ( ~ 1 7 ) 27=-7=17 Table 16. Cri tica f Pammeter.: for VHF Communications Transceiver.

High VFR Performance Limited Sfandard A1 1 Highest f a r a m e f e r O n l y I FR IFR IFR Weather Reliability Approximate Cost $500 $700 $2,000 $5,000 $1,000 $3,000 Power Output 5w 15w 2% 7w 1 Ow 2Ow Spectrum 1 118.000 t o 135.975MHz Channels 720 Number 720 360 720 720 25 kHz Spacing 50 kHz 25 kHz 50 kHz 25 kHz 25 kHz A M Mod~~lation AM AM A M AM [: Transmiff ing 175 n.m. 200 n.m. 125 n.m. Range 225 n.m. 150 n.m. I00 n.m.

TaLie 17. Criticuf Parame f o r ELT.

t High Highest A!!

f erforrnance Sfandard VFR Limited Weather ReIiobility IFR IFR I FR Paramef er Only Approximate Cost $150 $400 $200 $250 5300 $ 3 9 TSO C91 (Ref RTCA DO-1 45 5 Nov 1970) - - Frequency 121.5 and 243.0 MHz 500 mw 300 mw Power Outpuf 125 mw 200 mw (after 48 hours

I 7gmw

operation o f -2WC)

r'+

Modulation , Downward sweeping audio tone over at leasf 700 Hz between 160'3 and 300 Hz af

a repetition rote o f 2-4 times par second,

I 1 I I

Acf ivaf ion When longitudinal acczleration exceeds 5 (+2, - O ) g for longer than 17 (+5, -0) millisec f I 1 Table I & . Critical Parameters for VOR Navigation Receiver.

High Highest AI 1 Standard Performance Limited V FR ReIiabiIiiy Parameter Weather IFR I FR IFP, Oniy

I

Approximate Cost 5500 $1,000 $700 $2,000 53,000 15,000 Spectrum 4 108.00 to M H z - - - - 117.95

Channels I

I

200 (50 kHz Spacing) 200 200 1 200 200 200

1 O 0 1

Accuracy (2 cr ) 3 .oO 2O 2 . 9 1 . s "

-

Table 1%. Critical Parameters for ILS Localizer Receiver,

-

I

High Highest All Performance Limited Standard VFR Reliubiliiy Weather IFR I FR I FR Pararncfer Only

--

R e c e i v e r ) - - - - Approximate Cost +.(Part of VGR I !

-36c (Ref RTCA DO-131 15 ~ e c e m b e r 1965)- TSO

I

Frequency Range i - 108-1 12 MHz

- 1 Channels r- 40 (50 kHz r & c i n g ] - - - - - Table 19. Critical Parameters f o r ADF.

I

High Highest A1 I Performance VFR Limited Standard Re1iab;lity Weather IFR

Paramete, Otdy 1 IFR I FR

Approximafe Cost $5000 S l OOO 53000 S~oCIo N/A I I TSO C41 c C41 c C41 c C41 c (Ref RTCA DO-142 doted 8 January 1970) - - - Frequency Range - 200-1800 kHz I Quantization I 1 kHz .5 kHz - 5 kHz I

I !

. - - , Tuning * d i g i t a l - Rell~five Bearing

i

I

Accuracy (2 c ~ 1 2.50 2 O 2 O I I I i Mcunting Remote Remote Panel Panel Remote

t

Table 20. Critical Parameters for Marker Bwcon Receiver.

, High Highest All Performance Limifed Standard VFR Rel ;obi l ify Weather IFR I FR IFR Parameter Only .

I Approximofe Cost $200 $700 N/A $150 $200 $500 $ I

- 7

€ 3 5 ~ Ref R CA DO-143 dafed 8 January 1970

I

1 re:uency 75 MHz

--

Fi

--------------

Display Lights and Audio 1 Tone

Receiver Threshold No Selection Yes Yes Yes t Table 21 . Critical Parameters f o r 1LS Glide Slope Receiver.

High Highesr AI I L im i fed Standard Perfor-nonce VFR Ref iability Weather I FR I FR IFR Parameter On1 y Approximofe Cast 5500 $1000 N/A N/A $2000 5 2 5 0 I I TSO C34c (Ref. RTCA DO-138 June 27, 1968) and RTCA DO-132 March 15, 1966)

I

Frequency Range 3 2 9 - 3 3 5 M H z - ~ -

I

Channels 40 of* 0.15 MHz spacit-ig h ILS localizer frequ3ncy) Remote Mounting Yes Yes Yes Table 22. Critical Parameters for DM€.

High Performance AI I Standard Highest ReIiabi1iI-y Parameter Only IFR IFR I FR Weather I

I

$14,000 $7,000 $10,000 Approximate Cost $2,000 53,000 S4,500 400 n.m. ?OO n .m . 300 n,m, 3,SOn.m.

100n.m. 1SOn.m.

Rcnge 7 J h 3 0 0 ~ 500w Power Oufpuf 7Ow 1 ,OooW ' 5 0 ~

---

7 - -

960 t o 1215 MHz Specfrurn Number of Channels* 1 00 1 00 200 200 2 52 252 X only (X 8 '0 (X Y) (X a Y) Oc Y ) X only 660 660 64a 66a 660 66a TSO -4 n.m. -3 n .m. 0.2 n.m. 0.1 n.m, 0.1 n.m.

0.5 n,m.

Accurozy ( 2 ~ 1 or 3% or 2% or 1.53; or 1%

[R AV CompafibIe] --

F e ~ f u r e s Fast Hopping Capabil ityj- - " X Channels are paired with VOK rtcitio~s at 100 kHz spacing; Y Channeis are paired with VOR stations at M kHz spacing.

Table 23. Critical Parameters for RNAV,* High Hishest All Performance Limited Standard VFR Reiiobility Weather I FR IFR I FR Only Parameter Approximate Cost $4000 $7000 $2000 $ T 5,090 S30,OOa

I

As ~ e c i f i e d in FAA AC-9O145-- Accuracy 3-2 n. mi. e -( 0 ) Waypoin ts 'I 2 1 0 VNAV Capability N o N o Yes Yes Track Offset N o No Yes Yes

Display L / R & miles. L A SI miles L/R 8 miles Map B alpha-

fo go to go fo go numeric~

Wind Estimation No N o No Yes Yes ' yes

m F .

D/R CapaSi I ify No N o N o Yes Yes Yes n I

C -

ID m -I "Includes U H F B H F , OrnegaflLF, Loran-C, GPS.

0, O W

-

-a

-

R .J ?

u I!

.J Figure 24. Critical Parameters for ATCRBS Transponder, r High Performance A1 I Standard Highest VFR timifed I FR Wecther Reliability I FR Parameter Only 1 FR $1500 $600 $1000

$2m $moo Approximate Cost $6000

TSO C 7 k 1A 1A 1 B 2A %B Class 28 I = higher standard A = above 15,000' 2 = lower standard B = below 15,000' Power Output 500 500 250 250 75 T25 (Watts) A,B,C, A,B,C,D Modes A, C Arc A, C A,C D RTCA DCb138 UTCA DO-138 Environments!

Paragraphs 4.0 - 7 . 0 8 9 . 0 only

Stclndards (Temp-altitude-humidity shock, vibration, power '- tuf) I Frequency

I

I090 'I 090 1090 1090 1 090 1090 TX 1030 1030 1030 f 030 1030 ? 1 1 2 0 RCV 4096 4096 4096 4096 Codes 4096

""1

- Table 25. Critical Parameters for Encoding Altimeter.

-- - - High VFR Limited Standard Perfornunce A1 1 Highest Parameter On! y IFR IFR I FR Weather ReliabiIity Approximate C a s t $600 $1,000 $1,500 $2,000 $4,000 TSO (388 C88 C88 C88

Al tiiude Range - 1,000' f o - 1,000' t o -1,000' to -1,000' to -1,000' to

1 7,000' 'I 7,000' 25,000' 3 5,000' 50,000' Quantization

Accuracy -

Features -

I

Table 26, Critical Parameters for Horizontal Situation Display.

I High Highest A1 I Performance L irn i ted Standard VFR Reliobi l ii-y Weather IFR I FR 1 FR Only Parameter $2000 S 4 0 0 0 S o 0 0 Approximate Cost N/A N/A N/A - - .

Table 27. Critical Parameters for Autopilots.

High Hishest Performance All Standard Limi fed VFR Weather Rel iabi l iiy I FR JFR I FR Paramef er Only -, .

$1500 $3000 $700G Approximate Cost $800 $15000 N/A Stabi I ized Axes Roll Rol Iflaw R o l I/Yow/Pi+ch Rol I/Yaw/Pi tch Rol I/Yaw/Pitch Auto Throttle Bias Turn/Heading Turn/Heading/ Tum/Heading/ Command Capabi 1 i ty

T;;$;:;i7d Pitch Rate/ Pitch Rate

Altitude Airspeed Al tiiude V0R/RNAV/LOC VOR/RNAV/LOC VOR/RNAV/LOC.

Tracking Capability None VOR/LOC VNAV/GS VNAV/GS VNAV/GS C3b C3b TSO C9c C9s C9c

(Ref - SAE AS- 402A dated 1 February 1959)

Fl ight D irecior No No No Yes Yes Interface Missed Approach No Capability No No Yes Yes Table 28, Critical Parameters for Radar Altimeters.

I High Performance Limited Standard VF R Highest All Parameter Only Reliabilib I FR Weaiher IFR IFR $10,000 $4,000 $2,000 Approximate Cost 57,000

N/A N/A

C87 TSO C87 C87 C87

I

Al ii tude Range 0-2,000' 0-3,OOT 0-2,000' 0-3,000' Accuracy (2a) Below 100' 4 ' 2 ' 3' 5' 100-SO' 3% 2% 5% 4% 4% Above 500' 7% 6% 5% Power Oufput 35 rnw 70 mw 500 m w 150 mw 1 sec Eesponse T h e 1 sec . I sec 1 sec Yes Autopilot Outpuf No Yes Yes Noise Output Below 700'

(to Autopi :of) -- -25' .25' .25'

f o G PW,F]--------- --------------

Featu-es - [Adap to b I e -

Tab Ie 29.

Critical Parameters For Weather Radar.

High High& Performance A1 l Limited Standard VFR Weafher Reliability I FR IFR Only I FR Parameter

- -

Approximate Cosf $5000 $10000 $20000 N/A N/n N/A C63b (Ref. RTCA DO-134 dated 16 February 1967) TSO

I

Frequency X - B a n d - - l L - P Power Output 8 kw 15 kw (peak)

_ - 5 "

C R T - - - Display Runge 200 n.m. 300 n.m.

'100 n.m.

Bearing Accuracy 5" 4" 3O ( 2 4 Range Accuracy 6% 5 % 4% ( 2 . 1 Scan 9 0 ' 1 20° 180' Stabilization None 1 axis 2 axis I r Table 30. Critical Parameters for DABS Transponder.

r P High Performance AI I Highest VFR Limited Standard Reliability Parameter OnI y I f R IFR IFR Weather Approximafe Cost $800 TSO Class Address Codes

----

Environment Tabfe 3 1 . Critical Parameters for IPC Display.

I

High Highest All Performance Sfandord Limited VFR Reliability Weather IFR IFR IFR Parameter Only

Approxirnafe Cost $500 $700 $1 200 $2000 $3000 $m

Displayed lnforrnofion Audio Data Refresh Rah '9- 4 sec Table 32. Critical Parameters for GPWS.

High All Highest Performance Limited Standard VFR Weofher ReIiobilify I FR I FR IFR Parameter Qnl y Approximate Cost.

$1200 $2000 N/A N/A $3000 59L-- TSO 4 R I NC Characteristic

Mode 1 - Excessive

Sink Rate for A! titude Yes Yes Yes Yes

Mode 2 - Excessive

Terrain Closure Rafe Yes Yes Yes Yes

Mode 3 - Negof ive

Climb After Takeoff or Missed Approach N o Yes Yes Ye5 Mode 4-Flighf Info Terrain when nat in Landing Yes No N o Yes Configuratior;

Mode 5 - Below

ILS Glide Path N o No Yes Y er Visual Display 4 e d Warning Lighf I Audio Display -400-800 Hz Modulated T m e

- - -

1 .

I

I

Table 33. Critical Parameters for MLS Receiver. * * High A1 l Highesf Performance Standard Limited VFR Reliabilify Weather I FR I FR I FR Parameter Only Approximate Cost $1 5 1 3 0 N/A $2W $2500 $3000 N/A --p

Frequency Range 5 - 5.25 GHz -

I-

Z O O - - Channels i

1 i

Table 34- Critical Parameters for HF Communicaiions Transceiver.

High VFR Limited Standard Perform once High& A1 l Pararneier IFR Reliability Only IFR IFR Weather Approximate Cost $1,000 53,000 $4,000 N/A N / h 52, Power Output Sow lOOw 200 nr -.

1.5 to 30MHz Specfrum / Channels 20 5

t ::; -

Modulation AM AM -+ 558 AM + SSB AM + 558 C 3 1 C31 C3 1 C 3 1 T S 0 C32 I C32 C32 C32 Table 35. Avionics Cost Drivers and Pcssible Research Areas.

PossibIe R&D A& Cost Drivers Avi on i cs RNAV

. Low cost Loran-C/Ornega hybrid . Loran-C: extensive data processing

omega: phase locked loop tracking

receiver , at low signal/noise ,

. Logic chips for s h d a r d naviga t i c m

fwc tiam . DM~DME: transmitter

. Input-outperf displays for 3 3 d 4 D . INS: gyros

RNAV

. Atomic clocks for G A

Encoding Altimeter

. . OpficaI encoder

Packaged encoder f o r altitude, heading a irrpeed

- - --

Horizontai Situation . Gyro-stgbilized heading ; t . ? ~ r ~ n c e

. Low cost heuding rererenct

Display . Contrast at all ambient light leve!

. Low msf CRT, LED or liquid crystal

display

Autopilot . Gyro components

. low-cosf inerti~I pack-e

. Servo dl i v e instal lotion

. Low-cost digital s e r v o drives

Weather Radar

- Mu1 tipurpose disp k y ' . Disploy

. Antennc

, tow-cost phased-array anrenna

DABS . Dofa I ink output

. Low-cost input-output unit for data link

H F Communications . Antenna installation

Transceiver

I

I 1

Table 35. Avionics Cost Drivers and f ossible Research Areas (Continued), I I Cosf Grivers Possible RhD A ~ S Avionics

';'PF Conrnunica:*~ns . Re1 iaSili t y under high ambient heat protection

lure . Microprocessor r.f. generaw dzvelop-

Transceiver

. Frequency lo1 erance

. Manual frequency selection . Electronic switching

. Improved fideIity/noise aftmuation

. Baftery life . Alternate power so;lrce

EL?

. Inadvertent activation I . Improved decelnation detectors

. Additional features (identity, heft pm-

. Voice modulation

tection, etc.)

. Reliability under high amb:G,l; :empc,u- 1 . Avionics heat r3tection

d3R/l iS Local izer

ture I . Imp~oved rrlia ility under temperature P

Receiver

. Re1 iability under vibration and vibration

+ ---

. Low-cost, gyro-s fabi lized compuss

P.DF I . Accurate heading reference

. Sense cnd loop antenna consoIidation

with integral phase cowensation UHF circuitry more expensive than VHF :LS Gf ide-Slope .

Rece'ver

. Low-cost, high power, solid state

. HTghpower output

EM E fronsmi:fw Table 35. Gmponen t Cost Drivers and Pozsibie Research Areas (Continued) .

Avionics Cost Drivers Possible ?&D Arms

IPC . Special purpose display

. Lovr cost r n d tipurpose display

MLS* - Additional C-band DME

.

Glide slope converter t o drive ILS receiver.

* No l CAO agreement yet on final configuratian.

SECTION 5 GA ALTERNATIVES FOR THE UG3RD T l ~ i s section discusses possible variations i n the UG3RD ATC system insofar as general aviation i s concerned.

Specifically i t invectigates the possibility o f separated ATC for aviation and changes i n the UG3RD to minimize the Gk avionics requirements, or to rnaxirninze their utility.

5.1 SEPARATED ATC F O R GA A natural segregation of air traffic has developed over the years, but this separation Iias been based on capability and cost factors and i s not a segregation of general aviation as a whole, Aircraft perfotmance capabilities (r .g., high altitude versus low altitude or single engin0 versus multi-engine), equipment expenses (trans- ponder, altitude encoder, IFR versus VFR, etc.), and user costs (e.g., landing fees) are generic features which tend to discriminate part of the GA fleet from the air carriar's. While the air traffic control system either creates some of these differences or tends to reflect and emphasize them, airport operators are responsible for some discrimination.

I n the terminal area, a nafural segregation based on airspeed capability i s almost. unavoidabte in order to make maximum use of availabls runway capacity, It i s desirable t o hove all aircraft i n the landing queue flying the same airspeed so thot separation can be maintained without leaving gaps, However, the approach speeds for the larger turbojet aircraft are greater than the maximum cruise speeds of many smaller gel era1 aviation aircraft. Furthermore, the length of the landing roll and consequently the length of runway required i s a direct function of the landing speed, Therefore, i t i s desirabls not only to segregate the traffic by speed capability, during the approach, but also to direct them to different runways o f appropriate length.

A E R 0 P Ace BY STEMO, INC. O N E VINE BROOK PARK EURLINOTON, M A S 0 A C I . 1 U S E W B 01803 (817) P74.7E'17 Another consideration i s that more than one speed i s needed for each class of ahcraft i n order to permit metering and spacing by speed control , Also, the deceleration process takes place in stages from cruise speed to approach speed to landing speed.

Therefore, a range o f airspeed capability i s necessary for a l l aircraft i n u particular class. The typical airspeed capability for each avionics user group i s shown in Figure 10. Typical air carrier and helicopter capabilities are also shown f o r comparisorr. The upper bound of 250 kts indicated airspeed (IAS) i s the FAA established speed l i m i t at altitudes below 10,000 feet. The figvre shows clearly that two segregclted classes are necessary, with possibly a third class for VTOL , This segregation af aircraft w i l l continue during the 1980's as more of the airspace becomes restricted i n terms of equipment required and user flexibility (expand- ing TCAs, PCA, IPC, etc.). Unfortunately, segregation w i l l probably continue to expand as much to satisfy the ATC complex as out o f operational necessity. Although feasible alternatives exist to expedite mixed traffic flow, the evolution of responsibil i i y toward the ground system practically precludes pilot participation and resolution of mixed conflicts.

The air carriers are primarily motivated by schedule reliability into the courrtl-y's major airports to maximize their market profitability. However, GA Groups A and B are just as interested i n operational (schedule) reliability, with Group A being

perhaps more interested even than the air1 ines . General aviation corporate aircraft

take up where the airlines fail to provide reliable and timely service for executive transportation. The general aviation fleet as a whole i s becoming more sophisticated i n terms of performance and equipment. This w i l l continue during the 1980'5, partially as a result of new technology, but also due to availability of better equipment at moderate costs. Moreover, the limi f s o f th3 spectrum are expanding fhrough implernenta- tion of advanced vehicle designs i n many areas, such as VTOL, A ER O 5 P A C E SYaTEMB, INC. ONE VINE BPIDDK PARK BURLINDTON, M A B B A G H U S I Y T B O t 0 0 3 9 (817) 27P-7U47 USER GROUP LARGER AIR CARRIERS I H l G H SPEED - I APPROACH SPEED

/

I I 250 KT. Ll M l T S T O L

/ - /

' M A X I M U M

CRUISE SPEED I F VTO L

1 t I 1 !

I 1 INDICATED I I I I

0 5 0 100 150 200 2i0 AIRSPEED

KNOTS Figure 10. Typical Airspeed Capabi iities.

An enforced segregation of general aviation trafflc would be unfair to the contit ' l y expanding GA industry and woutd have significant economic repercuss/ons.

Many general aviatlon flights (including air taxis, corporate, and commuters) are connections to the air carriers for passengers or cargo. Also, a large number of general aviation operations are supplemental to the air carrier service at principal airports, serving the same market For passengers and cargo as well as the smaller airports not served by fhe air carriers. Some major pros and cons ragading segregated airspace are compared i n Table 36.

In summary, there i s a very strong possibility that segregation w i l l continue due to concentration of ground based authority in the air traffic control system, How- ever, i n terms of feasibility, continued segregation other than as described i s undesir- able. Tho utility of general aircraft can only be fully realized by providing adequate flexibility in operational capability. The future air traffic control environment should provide means to minimize or limit segregation through proper instrumentation and pilot participation in traffic management, 5 . 2 CHANGES TO THE UG3RD TO MAXIMIZE GA BENEFIT The following comments pertain to changes i n the UG3RD which would minimize avionics requirements for GA, o r which could offer additional services as a result o f avionics that w i l I be introduced i n the UG3RD. They include modifications or additional potential capabilities of IPC, RNAV, DABS and BCAS.

The IPC proximity warning display consists of 36 lights which indicate threafening traffic, using a clock code for azimuth and either high, level, or low for altitude; no range information i s provided. The collision avoidance commands w;l l consist of one of four positive commands, (climb, dive, turn left, turn right) or four negative commands (do not turn left, right, climb, or dive). The foremost .A ERQBP ACE BYBTEMB, IN=. O N E VINE BRaOK PARK BURLINBTON, M A B B A C H U B E V B [318a3 + (W7) 279-7Bt7 Table 36. Pros and Cons o f Segregated Airspace, Posi five Negative Reduced co!lision risk between

1 . 1 . Defeats flexibility designed

disoimi lar aircraft, into vehicles.

2, Requires stratificafion (hori- zontal boundaries) OF vertical boundaries requiring a certain degree of navigational sophisti- cation; horizontal boundaries restrict flexibility.

3. Requires constant monitoring of boundaries.

4. Requires evasion techniques after intrusion detection and the high performance aircraft must ad just.

5, Limits origin/destinafion (e. g . , intercity WTOL) , problem with IPC i s tho) the system w i l l attempt to accept responsibility for aircraft separation with as little as 30 seconds to go before a potential collision. Moreover, this i s to be done with relatively limited information, with no interaction batween the pi lots or the controllers, and with logic which has proven to be detrimental to the solution of the conflict i n some cases. A more attractive alternative to the tPC display i s to uplink the information about conflicting aircraft using the DABS data link i n a format such that range, altitude and bearing infomuf .n are available For the user to display i n whatever manner h e prefers. T h i s might involve purchase o f the protofype \PC disp!ay o r an alternative, such as an alphanumeric printout of the infor- mation, a mop display of the conflict, or as input to an airborne traffic situation dis- play. In any ease, the user could decide for himself how t h - utilize the information and display i t meaningful I y and economically F o r his avionics complement.

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AE R C) B P ACE ELYBTEMB, INC. ONE VtNB BROOK PARK BURLINQTDN, MAEEACHUBETTB O l B 0 3 (817) ~ 7 9 - 7 a l 7 Secondly, 1PC commands should be considered as advisories, I f the pilot were unable to see the other aircraft and resolve the conflict on his own, he C O U ! ~ then respond to the advisory command with confidence that i t would tend to improve the situation.

The logic for avoiding the conflict would have to be changed from i:s present Form so that i t could be relatively easily understood by pilots and so that i t would not create situations i n which the conflict i s aggrevated. These commands should also include the desired heading and/or altitude.

In the case of IFR controlled aircraFt, the proposed commands should be made available to the controller first to permif him the opportunity to resolve the conflict before the aircraft reacts on its own. In no case should the legal responsibility For separation of aircraff be exchanged with 30 seconds or less to go to a potential col lision , DABS, with i t s associated data link, has the potential for providing a number of valuable services to general aviation a t very low cost. These include area naviga- tion, ground proximity warning, terrain/obstacle avoidance, weather depiction, and

traffic information. A l l the necessary information to provide these services i s avail -

able from the DABS sensor and the ATC computer; the data link i s adequate to trans- mit the information to the cockpit, Unfortunately, the only planned use of this capability i n the UG3RD i s to drive the IPC display, Consequently, the general aviation user who i s forced to purchase a DABS transponder with altifudo encoder and IPC display w i l l not receive the maximum available benefit from his instruments.

Moreover, the ATCRBS transponder and encoding altimeter w i l l provide col I isian avoidance protection from at l control led aircraft and From those DABS-equipped un- control led aircraft. Therefore, the GA user would have little motivation to purchase the DABS transponder and IPC display, since he would gain additional protection only from those uncontrolled aircraft who are equipped with ATCRBS and the encoding altimeter. If the design were modified to include area navigation, then the user would gain more value for his investment,

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A E R a A P ACE SYBTEMB, INC. . ONE VINE BROOK PARK r BURLINWfON, MFIBGACHUBETTB OZE03 (817) ~ 3 ~ . f a i 7 One prlmary reason that the present IFC display was adopted (thereby limiting I t s capability to collision avoidance alone) was the desire to keep i t s cosf low. Consequently, the main deterent to modifying the UG3RD to reduce avionics requirements i s the absence of a low cost general purpose display. This i s the foremost weakness of the UG3RD; namely, that tho capability and potential of the DABS data link i s being used only t o provide IPC which i n its present form i s unsatisfactory.

A properly designed IPC display should be able to vector an aircraft using computer generated altitude and heading commands transmitted through the DABS data link with the same or better precision than a human controller using voice communications.

The general aviation user would then be able to utilize airspace requiring a 3-D RNAV capability whether RNAV equipped or not. With the addition of airspeed commands, the user would obtain a 4-D RNAV capability.

Another modification to the UG3RD concerns area navigation equipment.

A t the present time the term "area navigation" usually refers t o VOR/DME area navigation.

However, the RNAV system should be designed to accept any navigation- al equipment capable of positioning the aircraft to the accuracy requirements speci- fied in Advisory Circular 90-45. The RNAV structure should not be irrevocably tied to the location of the current VORTAC stations. A more universal and flexible approach is to establish waypoints on the basis of latitude and longitude, such t h d any of the available area navigation systems would be able to idenfify and store the waypoints easily. A proposal to uplink the waypoint inforrnafion using the VOR/DME system would clear1 y be detrimental to the possible implementation of systems such as Loran-C and Omega. The M~R/DME system i s noncompetitive in terms of providing area navigation coverage af low altitudes and i n remote areas critical to general aviation. The capital investment costs and the operational maintenance costs are an order of magnitude larger For VOR/DME coverage on a AER P ACE 8YaTEMBfi INC. ONE VINE BRODK PARK BURLINCTDN, MASEACHUBEfl6 01EC13 (817) 87P.7017 per square mile of coverage basis than arc those of Loran-C or Omega. Thbt i s not to say that the VOR/DME network should be abandoned; but it i s not cost effective to attempt to provide universal coverage at low altitude by pro1 iferation of the VOR/ DME system. Therofore, any steps taken to implement the RNAV systm should be independent of the VOR/DME network.

The SynchroDABS option could provide a subsiantial improvement i n the capability of the DABS system as it i s presently planned. The basic ingredient of

SynchroDABS i s to time he ground interrogations so that the aircraft always respond

at instants of universal time, This permits a one-way range measurement from any DABS equipped aircraft, since any aircraft i n the system automatically has a ctock kept at universal time, Consequently, each time an aircraft responds, all others which hear the reply can determine their range from it. If each aircraft, i n addition, is equipped with an antenna capable of determining the direction from which the trans- mission i s received, then bearing as well as range would be available for determining the location of any other transponder. This would enable an aircraft to obtain range

and bearing information from any arbitrary location , by merely placing a transponder

at the selected site. For example, transponders could be laced on obsf.ructions, on mountain tops, or at airports i n remote areas to provide a very low cost DME, i n addition to providing proximity warning or collision avoidance infbrrnation.

Similar possibilities exist with the semiactive BCAS system. Since the range and bearing to a transponder i s geometricol!y determined by the difference in i h e time of arrival of the direct signal and the signal via the transponding aircraft, it. i s possible to create a DME or a navigation beacon by placing transponders wherever they are needed. However, to be meaningful for general aviation, the BCAS must be low i n cost, high i n reliability, light i n weight, ctnd have a good mean time between failul'es.

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A E R O B P A C E BYBTEMB, INC. ONE VINE aROOK PARK BURLINSTON. MA96ACHUSET7E 01803 (017) P7P-7817 Another possible advantage to general aviation using the beacon system i s a technique known as PALM (precision altitude landing rnoiritor). The PALM system i s essentially another form of MLS where the position of the aircraft i s determined b y observing with rnonopulsd technology the direction from which the aircraft reply comes. Accuracy has been demonstrated by Lincoln Laboratory to 6.06 degrees, which i s more than adequate for precision instrument landings (Reference 108). Ihe major advantage of he PP.LM system i s the elimination of mu1t;puth; the time sequenc- ing of )he signal i s klown and reflections from other locations are not close enough i n time to contaminate the measurement to the aircraft. Azimuth and elevation inforrna- tion i s available on the ground and could be sent bock to the airplane over a dafa link, such as the DABS data link. This data could be presented directly through the IPC display which could give the general aviation user an fLS without having t o buy any additional equipment beyond the DABS transponder and IPC. The PALM system i s demonstrated hardware which operates similcrrly to the normal DABS interrogator, except that i f interrogates every 1/10 of a second insfead of every 4 seconds. I t also provides range information to an accuracy OF at least 250 feet at a distance of 30 miles. The same concept w m l d also work with the beacon transponder by uplinking the information on a VHF data link or by transmitting commands to the airplane similar to a normal GCA approach. Apparently, PALM has received limited publicity and enthusiasm from the FAA because i t i s competitive with the MLS system selected by the U. S. to submit to ICAO.

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A E R a a P A C E EIYBTEMB, INC. rn ONE VINE BROOK PARK BURLINQTON, MAS6ACHUSETTB 01803 a (o??) a72-7017

SECTION 6 CONCLUSIONS AND RECOMMENDATIONS This section outlines the rnaior conclusions and recommendations deterrnlned from the study.

6.1 CONCLUSIONS A proliferation of navigation systems w i l l continue to exist in t h ~ 1980's.

Any area navigation system meeting the provisions of Advisory Circular 90-45 or equivalent shouid be considered for operations in the RNAV network. Omega naviga- tion i s already available; the ground netwc.;k i s i n place and operational, and first genera tion Omega receivers are operational i n general aviafion aircrcft. However, Loran-C i s becoming a strong candidate for future RNAV use, and has been designated the primary navigution system for the U .S. coastal confluence zone. The East Coast chain i s i n place; the West Coast chain i s expected to be on the air in a matter of months; and new stations w i l l complete coverage in the Gulf of Mexico and the G r ~ l f of Alaska. Current construction together with existing Loran-C s totions w i l l provide inland coverage over two-thirds of the U . S . , and there are pressures to complete coverage to the internal U . 5 , Several studies have considered replacing the VGR/DME network with Loran-C after the ICAO commitment to VORTAC expires i n 1985. While DME offers an accuracy that i s equivalent to Loran-C, the cap: tal installation costs and tlie operating and maintenance cosfs are far more expensive. Since DME opercltes line-of-sight, i t i s of no value Far from land, in mountainous areas, or far from the transmitter sites. A1 though DME i s operational in high density areas, Loran-C has such promise that more consideration should be given to developing a generzl aviation Loran- C receiver.

The system fhat makes fhe most sense i s a hybrid L o r a n - ~ / ~ r n e y a receiver

because the two systems are complementary . They are both hyperbolic systems, and

PR&WWG PAGE BLANK IriWl' %Ml*;E) A E R P B P A c e BYBTEMB, INC, r ONE VINE MRODK PARK BUFILINOTON. M A 8 S A O W U B E T T E O W 0 3 * (017) Zl7R.7U17 about 80 percent of the components are common to both, The only malor difference i s in the front and; Loran-C operating at (00 kHz and Omega I n the 10 kHz band. Sinca O m q o has world-wlda coverage wlth an accuracy of about one rnlle, I t Is useful over water and as a backup to Loran-C In tho event of outages or luck o f coverage. Loran- C can provfde the differantial cupabfllty for Omega which i s necessary for Gmega to meet the requirzments of Advisory Circular 90-45. The combinotIon of Loran-C and Omega together would be better than either one alone I n terms o f both accuracy and reliability. The hybrfd receiver would also be valuable in providing nuvigation capa- bi lity during the transition from VOR/DME to Loran-C i F such a transition takes place.

For communications our conclusion i s that a low-cost general aviation dts- piay to operate with data link i s of extreme importance. The data link w i l l most likely be tho DABS data link; however, even i f DABS i s not implemented, a separate VHF data link w i l l probably be developed, in which case the display w i l l still be required, The display could have other uses, such as presenting IPC informafion or to present aircraft cctti tude and navigational information.

For ~urveillance, i t i s anticipated that DABS w i l l be implemented, although the IPC function as presently envisioned i s unsafisfactory for gcnerai aviation. I t could be improved as suggested earlier, 6.2 RECOMMENDATIONS The first rocommendation i s to conduci research to develop a low-cost, low- power, cockpit display for general aviation. This display could be used to show alpha- numeric information from the data link, to display ~ r o ~ h i c a l information iuch as a readout for area navigation, ar to display attitude information. At the present time, a cathode-ray tube i s the only viable display available which can present the informa- tion at all ambient light levels. However, the cafhode-ray tube requires high power and i s slightly undesirable from a safety siandpoint, in that i t requires high voltage and A E R P B PACIE! BYBTEMB, LNG. * ONE VtNe BROOK PARK . QUALINGTON, M A S B A G H U S Q T T ~ 01103 * (017) P73.7bl7 could suffer from implor ion In the avant of an accident. Also, i t i s a large device which requires considerubla space beyond tho instrument panel, The idoal choractaristics of a GA display are: a flat shape, taktng up relab'vrtly I f t t l o dupthy low cost, preferably under a few hundred dollars; lower powor, which might be ach;nved by using ambient light instead of providing its own light] and sufficient resolution to preaen t graphic information. Alternate displays availubJe now fail in one or more of these categories, Besides its imminent need with the data IInk, the cockpit display would be useful for urea navigation, for a traffic situation display, and for an in tagrated cockpit. The main reason that the prototype IPC display evolved as i t did was an attempt to keep the cost low. As a result, i t provides less than the total desired amount of information and prevents evolutionary changes to the concepL.

The second major recommenda?iotl i s the develapment of a Loran-C/Omega hybrid receiver for general aviation. This combination has been justified by a number of studies for their complementary features arid their considerable savings in common circuits. Omega i s operafional, and Loran-C implementation i s continuing; yet there i s no low-cost Loran-C and/or Omega reciever available for general avigtion.

The third recommendation i s that a front-end converter be developed which would receive MLS signals and transform them into convnntional ILS madulation, thus permitting general aviation users to utilize MLS with existing airborne equipment.

The converter should be so designed that the MLS/lLS gl ideslope and localizers could be selected i n combination.

A Fourth recommendation, which i s predicated on the availability of a cock- p i t display and data link, i s the development of a weather presentation for single- engine aircraft. At the present time, weather radars are only available to multi-engine aircraft, since the airborne antenna i s mounted i n the nose. A phased array weather radar has bean dasignod and b u i l t for single-engino aircraft, but production costs of Flnl ta alaments are too groat for cost-effective productton, Wt th a data link and a display, the weather depiction could be uplinked from the ground on request to show the weather as detected by the ground radar. At the present time, the single-engine pilot I~as to specifically ask the controller for radar weather information, and the request i s often denied because the con troller i s too busy.

0 ther useful Informotfan presently avai labla to the controller i s orally re- layed to the p i lot ~ n l y randomly or by specific request, An example i s the warning dlsplay ld to an ARTS controller when an aircraft descends below the minimum enrouta altitude for any flight segment, One accident hus already occurred in which the controllers were aware that the aircraft was too low for his position, but the informa- tion was not reported to the aircraft i;, a timely fashion. It should be possible ta uplink this information autornatica lly, so that the warning available on the ground i s also provided in the cockpit.

Another candidate for shared information i s the traffic itself; i t has already been recommended that IPC be modified to provide traffic information on confl i c ling aircraft to the general aviation pilot, I t i s also possible to uplink all the traffic in- formation so that the individual aircraft can selectively display that traffic which might be of intere:, ; o him even though i t does not constitute a threat. The uplinking of the information presents no technical ~roblcm; i t can be done simply OII a single VHF channel, The difficulty i s filtering and ~ i ~ c e s s i n g the data i n the aircraft in order to present information to the p i l o t in a relative format and in an altitude and range band r h a ~ he might select.

A t the component level the most important effort should bo to improve reli- ability in the Face of high temperature and vibration. The highest temperatures often occur when the aircraft i s parked and the equipment i s off. High power solid state transmitters are needed for DME, weather radar and beacon transponders. A low cost gyro-stabilized tnognetlc compass would be desirable in order to downlink heading.

B l BLl OGRAPHY 1. AATMS Program Office: Advanced Air Traffic Management System Study

0 verview . Department of Transportation, Transporta tion Systems Center

Report No. DOT-TSC-OST-75-32, June 1975.

Adarns, R. J.r Area Navigation Way oint Designation Standards. U.S.

2.

Department of Transports tion, Federu f Aviation Administration, Report No.

FAA-RD-75-122, July 1974 (Published August 1975.

3 , AGARD Conference Proceedings No. 105 on Air Traffic Control Systems.

AGARD-CP-105, June 26-29, 1972.

4. AGP.!?Dograph No. 209: A Survey of Modern Air Traffic Control - Volumes

I l n d I I . AGARD-AG-209-Vol. I, It, July 1975.

5. Air Traffic Cor,f.rol Association: A Compilation of Presentations Made a t the Air Traffic Control Association 17th Annual Meeting and Technical Program.

October 9-1 1, 1972. A i r Traffic Control Systems Committee: Future Air Traffic Control Systems. AGARD-CP-188 on Plans and Developments for Air Traffic Systems, May 1975.

6 . ALPA A i r Safety Forum: Cornpilation of Presentations made a t the Eighteenth ALPA A i r Forum and ALPA Steward and Stewardess Division Nineth Air Safety Forum, ALPA Air Safety Forum 1971, 20-23 July 1971.

7. Anon.: An Overview and Assessment of Plans and Programs for the Development of Upgraded Third Generation Air Traffic Control System. U.S. Department of Transportation, Federal Aviation Administration, Office of Systems Engineering Management, Washington, D.C. 20591, Report No. FAA-EM-75-5, March 1 975.

8. Anon.: Autornat;~ Piiots. Society of Automative Engineers, Inc., Aerospace Standard AS 402A, Issued August 1, 1947, Revised February 1, 1959.

9. Anon.: Aviation Forecasts, Fiscal Years 1976-1987, U .S. Department of Transportation, Federa I Aviai ion Administration Report No. FAA-AVP-75-1, September 1975.

10. Anon .: Avoid the Storms: Weather Radar for Business Aircraft. Fi ight Inter-

national, 17 January 1976.

11. Anon.: FAA Buys Automated Equipment to Improve Pilot Briefings, FAA De- partment of Transportation News, 76-14, February 24, 1976.

12. Anon .: FAA Lets $1 1.9 Million Contract for New Radar Beacon System, De- parhwn t of Transportation, Federal Aviafion Administration News, 76-20, March 4, 1976.

13, Anon*: FAA to Clarify Policy Toward Interim MLS. Aviation Week & Space Technology, March 22, 1976.

A E R P 6 P A c E m Y 6 f E M B t lNCr ONE VINE BROOK PARK + BURLINOTON, MASSACHUBETTE 01803 (017) 278.7S17

Anon .: Flight Directors (Reciproco king Engine Powered Aircraft), Soi;iety of

Automotive Engineers, lnc., Aerospace Standard AS 4206, Issued December 15, 1954, Revised March 15, 1962, Anon .: Fuel Flow-Fuel Managernen t Computer. Avionics News, January 1976.

Anon .: Green Light for Aerosa t.

Flight International, February 7, 1976.

Anan .: Kollsman Supplies JAL's Altitude Alerting Equipment, Journal of ATC, November-December, 1974.

Anon ,: Mi lfard Planning Additional Aerosa t Hearings, Business Aviation, February 23, 1976.

Anon .: New v L ~ / O r n ~ ~ a Navigator from Global. Flight Internationa I, 31 January 1976.

Anon.: Pan Am Conservation Program Saves 50 M i l l i o n Gallons of Fuel, Journai of ATC, July-September, 1975.

Anon .: Proceedings of the 1975 Annual Assembly Meeting, Washington, D. C., November 18-1 9, 1975, Radio Technical Commission for Aeronautics, Anon, : Report of Department of Transportation A i r Traffic Con h o l Advisory Committee, Vols. I and II, DOTr Washington, D .C., December 1963.

Anon .: Report of the Task Force on Air Traffic Control, Project Beacon, FAA, October 1961.

Anon. : Soviets Seen Accepting MLS Choice. Aviation Week 8, Space Tech- nology, March 1, 1976.

Anon.: TACAN/DME Digital Data Broadcast Design Plan - Vol . I - Opera-

tional Analysis; Vol, !I - Synthesis of the Data Transmission and Formatting

Techniques; VoI. Ill - Airborne Equipment; Vol, I V - Ground Equipment;

Vgl. V - Flight Test Program. U.S. Department of Transportation, Federal

Aviation Administration, Report. Nos. FAA-RD-74-151, I-V, September 1974, Anon . : Technical Development Plan for a Discrete Address Beacon System.

Department of Trarrportation, Federal Aviation Administration Report No.

FAA-RD-71-79, Ocbober 1971 .

Anon .: The National Aviation System Challenges of the Decade Ahead, 1977-1 986. Department of Transportation, Federal Aviation Administration, 1976.

Anon .: The Nationul Aviation System Plan, Fiscal Years 15'76-1 985. Deparf-

ment of Transportation, Federal Aviation Administration, No. 1000.27, Appen- dix 2, March 1975.

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A E R 0 a P ACE mYBTEMB, INo. ONE ViNE BROOK PARK BURLINGION. MASEACHUQET7e Ole03 (al7) 27R-7L17 29, Ashby, W. L.: Future Demand for A i r Traffic Services. Proceedings of the IEEE, Special Issue on A i r Traffic Control, Yol. 58, No. 3, March 1970.

30. Banks, J . R.: Collision Avoidance by the Seat of Your Pants. Journal of

ATC, October-December, 1975, 31 . Barrows, J. T.: DABS Downlink Coding, MIT Lincoln Laboratory, Report No.

FAA-RD-75-61, 1 2 Sep ternber 1975.

32. Belson, J .: Tomorrow's Flight Deck. Flight International, 6 March 1976.

33.

Beran, J. F.; and Bortz, J . E., Sr.: Omega - A System Whose Time Has

Come. AGARD-CP-188 on Plans and Developments for Air Traffic Systems, May 1975.

34. Berkowitz, S. M.: Flight Service Station (FSS) Automation. Journal of ATC, January-March, 1975.

35. Beukers, J . M .: A Review and Applications of VLF und LF Transmissions for

Navigation and Tracking. Presented at I .O. N . Radio Navigation Symposium, Washington, D. C., November 13-1 5, 1973.

36. Blade, N,A.;anJNelson,J.C.: AProjecti~nofFutureATCDataProcessing Re uirements. Proceedings of the IEEE, Special Issue on Air Traffic Control, Vo . 58, No. 3, March 1970, 37. Boltz, E.H.; Clark,W.H.; Stephenson,A.R.;Heine,W.; Solomon,H.L.:

Economic Impact cf Area Navigation, Volume I - Main Text; Volume II -

Appendices. U. S. Department of Transportation, Federal Aviation Administra- tion, Report Nos. FAA-RD-75-20, I and 11, July 1974 (Published: August 1975).

38. Bowes,R.C.; Dro~i1het~P.R.; Weiss, H.G.; andStevens,M.C.: ADSEL/DABS - A Selective Address Secondary Surveillance Radar.

AGARD- CP-188 on Plans and Developments for Air Traffic Systems, M a y 1975.

3 9 , Bramson, A.: Must We Endure These Fatal Accidents? Flight International, December 18, 1975.

40, Brentnall, 0.: Status Report on DoD Navigation Satellites. Journal o f ATC, O c tober-December, 1975.

41. Britting,K.R,,Hollisfer,W.M.,Howe~l,J.D.: FinalRaportInvestigation of A i r Traffic Control Navigation Systems, Measurement Systems Laboratory RN-71, ~ebruary 1972.

42. Broadbent, S.: Omega First Principles - No. 1: Theory. Flight International, 6 March 1976.

43, Broadbent, S .: Ground-Proximi th Warning Systems. Flight In ternotional, 27 March 1 976.

A fi Ace SYBYEMB, INC. ONE VINE BROOK PARK IUALINCTON, MASGACWUSETTB 01803 ( ~ 1 7 ) 271.7@??

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