Integrated Modeling of Air Traffic,
Aviation Weather, and Communication SystemsChuanwen QuanDissertation submitted to the faculty of theVirginia Polytechnic Institute and State Universityin partial fulfilment of the requirements of the degree ofDOCTOR OF PHILOSOPHYINCIVIL AND ENVIRONMENTAL ENGINEERINGAntonio A. Trani, Ph.D., ChairmanHanif D. Sherali, Ph.D.
Gerardo W. Flintsch, Ph.D.
Dusan Teodorovic, Ph. D.
Hojong Baik, Ph.D.
April 20, 2007Blacksburg, VirginiaKey Words: Air Traffic, Aviation Weather, Communication, Simulation, and ModelCopyright 2007, Chuanwen Quan
Integrated Modeling of Air Traffic,
Aviation Weather, and Communication SystemsbyChuanwen QuanAntonio A. Trani, ChairmanCivil and Environmental Engineering AbstractAviation suffers many delays due to the lack of timely air traffic flow management. These delays arealso caused by the uncertainty weather information; and the lack of efficient dissemination of weatherproducts to pilots. It is clear that better models are needed to quantify air traffic flow in three flightregions - en-route, in the terminal, and on the ground, to determine aviation weather information re-quirements at each region, and to quantify their bandwidth requirements. Furthermore, the results fromthose models can be used to select alternative future aviation communication this research, the ‘ITHINK’ and ‘MATLAB’ software packages have been used to develop a lumpedAir Traffic Flow Model (ATFM) and an Aviation Weather Information and Bandwidth RequirementsModel (AWINBRM). The ATFM model is used to quantify the volume of air traffic in each phase offlight in three flight regions. This model can be used to study navigation, surveillance, and communi-cation requirements. The AWINBRM model is used to study aviation weather information require-ments in different flight phases of flight. Existing and potential communication systems used fortransmitting aviation weather information are explored in this research. Finally, a usable and practicalcomputer model - Aircraft Impacted and Detour Model (AIDM) around an aviation weather system is
developed. This model is used to compare the costs between detoured flights around a weather systemand delayed flights at the purpose of this research is to study air traffic flow and aviation weather information and bandwidthrequirements through modeling. The ultimate goal of the models described here is to serve as a livinglaboratory where policies can be tried before implementing them into the real system. Moreover, thesecomputer models can evolve dynamically through time allowing decision makers to exercise policiesat various points in time to quantify results with research would be a first integrated model for combing air traffic flow and aviation weather re-quirements and determining the quantity of aviation weather information between pilot and groundservice centers. This research would be a guideline for aviation industry to build an efficient and timelyaviation weather information transmission system with minimum budget. Consequently, this researchwill reduce aviation delays and improve aviation
AcknowledgmentsI would like to thank my advisor, Dr. Antonio A. Trani, for his encouragement, professional guidance,and technical and financial support. Dr. Trani is also my advisor in my Master’s program in air trans-portation . Trani encouraged me to continue my studies at the Ph.D. level and prepared meexactly to work at that level. I would like to express my heartful appreciation to Dr. are extended to Dr. Hanif D. Sherali, who offered advice and guidance as my committee mem-bers in this research. I appreciate Dr. Gerardo W. Flintsch to be my committee member for supportingthis research and review this dissertation. I also wish to express thanks to Dr. Dusan Teodorovic for hisadvice and guidance. Thanks very much also extended to Dr. Hojong Baik, Dr. Baik provide me re-search advice and give me encouragement and helpful discussions.I greatly appreciate my father, my brothers and sisters, my family, and my parent-in-law. I am thankfulto Mr. Gu, Mr. Zhang, and other colleagues at Virginia Tech. My lovely daughter, Tiffany, always mademe smile and kept me busy through my doctoral studies. This work is dedicated to my wife, Jingli Qu,who gave me encouragement, love, patience, and y, I would like to dedicate this dissertation to my mother, who passed away during this research,but she is always with me in all the sadness and joy in my
Table of ContentsPreface
Abstract
iiAcknowledgements
Table of Contents
List of Figures
xiList of Tables
1 Introduction
1.1 Background
1.2 Problem Statement
1.2.1 Aviation Problems
1.2.1.1 Aviation System Congestion and Delay
1.2.1.2 Flight Accidents and Incidents
1.2.2 Cause Factors
1.2.2.1 Aviation Weather
1.2.2.2 Communication
1.3 Research Motivation
1.4 Objectives
1.5 Organization of the Dissertation
2 Literature Review
2.1 Air Transportation Industry
2.2 National Airspace System
2.2.1 Overall National Airspace System
2.2.2 Airspace Classification
2.3 Air Traffic Management
2.3.1 Air Traffic
2.3.2 Existing Air Traffic Flow Models
2.3.2.1 SIMMOD
2.3.2.2 TAAM
2.3.2.3 RAMS
2.3.2.4 NASPAC
2.3.2.5 AOM
2.3.2.6 Severe Weather-Modeling Paradigm
vivvxvi1223566
78192020
2
5
1
12 12
14 16
17
2.4 Aviation Weather
2.4.1 Review FAA Weather Requirement Regulation
2.4.2 Aviation Weather Support Systems and Products
2.4.2.1 FAA’s Support Systems
2.4.2.2 NOAA’s Support Systems
2.4.2.3 Weather Products
2.4.3 Aviation Weather Products Deficiencies
2.4.4 Aviation Weather Information and Requirements Model
2.5 Aviation Weather Communication Systems
2.5.1 Terminal Region
2.5.2 En-route Region
2.6 Aviation Weather Economic Impact
3 System Approach and Methodology
3.1 Introduction to Modeling and Simulation
3.1.1 Modeling
3.1.2 Simulation
3.2 Tools and Software Package
3.2.1 Systems Dynamics
3.2.2 Software Packages
3.2.2.1 MATLAB
3.2.2.2 ITHINK
4 Air Traffic Flow Analysis
4.1 Description National Airspace System
4.1.1 National Airspace System Structure
4.1.1.1 Uncontrolled Airspace
4.1.1.2 Controlled Airspace
4.1.2 Meteorology Flight Conditions in NAS
4.1.2.1 Uncontrolled Airspace – IFR Flight
4.1.2.2 Uncontrolled Airspace – VFR Flight
4.1.2.3 Controlled Airspace – IFR Flight
4.1.2.4 Controlled Airspace – VFR Flight
4.1.3 Air Traffic Control Support Centers
4.1.3.1 Air Traffic Control System Command Center
4.1.3.2 Air Route Traffic Control Center
4.1.3.3 Terminal Radar Approach Control Facility
4.1.3.4 Air Traffic Control Tower
4.1.3.5 Flight Service Station
vi 21 21 24 24 25 26 26 28 29 29 29 30
32 33 33 34 36 36 37 37 38
41 41 42 42 42 43 44 45 46 46 48 49 49 51 52 53
4.2 Flight Operations Analysis 53 4.2.1 Departure Segment 55 4.2.2 En-route Segment 56 4.2.3 Arrival Segment 57 4.3 Air Traffic Flow Model 57 4.3.1 Causal Diagram and Model Equation
4.3.1.1 Causal Diagram
4.3.1.2 Model Equation
4.3.2 Air Traffic Flow Model Interface
5 Aviation Weather Information, Products, and Requirements Analysis 5.1 Aviation Weather Phenomena
5.1.1 Fundamental of Weather Phenomena
5.1.1.1 The Atmosphere
5.1.1.2 Moisture
5.1.1.3 Air Masses
5.1.1.4 Thunderstorm
5.1.1.5 Gust Fronts
5.1.1.6 Downbursts
5.1.1.7 Wind
5.1.1.8 Icing
5.1.2 Categories of Weather Systems
5.1.2.1 Weather Systems
5.1.2.2 Air Motion
5.1.2.3 Precipitations
5.1.2.4 Icing
5.1.2.5 Visibility and Ceilings
5.1.2.6 Other Categories
5.2 Aviation Weather Domain Analysis
5.2.1 Tactical Decisions
5.2.2 Strategic Decisions
5.2.2.1 Far-term Strategic
5.2.2.2 Near-term Strategic
5.3 Aviation Weather Information Requirements
5.3.1 Preflight Planning and Flight Plan Filing
5.3.2 Preflight Operations
5.3.3 Taxi Out and Take Off Operations
5.3.4 Departure, Initial Climb, and Initial Cruise
5.3.5 Cruise
5.3.6 Approach
vii 58 58 60 79 83 84 84 84 86 87 88 89 89 90 91 91 92 93 94 94 95 96 97 97 98 99100 101 103 106 107 107 108 108
5.3.7 Landing
5.3.8 Taxi In and Parking Operations
5.3.9 Alternative
5.4 Aviation Weather Product
5.4.1 Existing Aviation Weather Product Characteristics
5.4.1.1 Aviation Weather Products for Tactical Decision
5.4.1.2 Aviation Weather Products for Strategic Decision
5.4.2 Potential Improvements of Aviation Weather Product
5.4.2.1 New Graphical Weather Products
5.4.2.2 Weather Product Improvement
5.5 Aviation Weather Sensors -Aircraft
5.5.1 On-Board Sensors
5.5.2 Electronic Pilot Reports
5.6 Aviation Weather Information and Bandwidth Requirements Model
5.6.1 AWINBRM Organization
5.6.2 AWINBRM Causal Diagram and Equation
5.6.2.1 Causal Diagram
5.6.2.2 Model Equation
5.6.3 AWINBRM Interface
5.6.3.1 Tactical Aviation Weather Interface
5.6.3.2 Strategic Aviation Weather Interface
5.6.3.3 Aircraft as Aviation Weather Sensor Interface
6 Aviation Weather Communication Systems Analysis
6.1 General Aviation Communication Considerations
6.2 Current and Planned Aviation Weather Communication Systems
6.2.1 Aviation Datalink Communication Systems
6.2.1.1 VHF Datalink
6.2.1.2 Inmarsat Satellite Data ACARS
6.2.1.3 HF Datalink
6.2.1.4 UHF Datalink
6.2.1.5 ADS-B Datalink
6.2.2 Voice Communication Systems
6.2.2.1 VHF Voice
6.2.2.2 UHF Voice
6.2.2.3 HF Voice
6.2.2.4 Other Voice
6.2.3 Summary
viii 111 111 113 113 113 113 124 129 131 133 134 134 135 138 138 139 139 142 146 146 147 149 151 152 154 155 155 159 159 160 160 162 162 164 164 164 165
6.3 Potential Solution from Non-Aviation Communication 165 6.3.1 Cellular / PCS Telephone Technology 166 6.3.1.1 Cellular or PCS 168 6.3.1.2 Cellular Phone Systems 168 6.3.1.3 Personal Communication Systems 168 6.3.1.4 LEO/MEO Satellite Extension to Cellular 169 6.3.1.5 Future Cell Phone System - UMTS 169 6.3.1.6 Aviation Weather Applications for Cell/PCS Phone Technology 170 6.3.1.7 Cell Phones in the Cockpit 171 6.3.2 Microwave Distribution Systems 171 6.3.2.1 Multi-channel, Multi-point Distribution System 171 6.3.2.2 Local Multi-point Distribution System 171 6.3.2.3 Potential for Using MMDS/LMDS for Aviation Weather Distribution 6.3.3 Satellite – Digital Audio Radio Service 172 6.3.3.1 XMTM Satellite Radio 173 6.3.3.2 Sirius Satellite Radio 173 6.3.3.3 Potential Aviation Weather Application of S-DARS 173 6.3.4 Airborne Internet 174 6.3.4.1 Teledesic: Internet-in-the-Sky 174 6.3.4.2 DirectPCTM Internet-in-the-Sky 175 6.3.4.3 Potential Aviation Weather Application 175 6.3.5 Software Defined Radios 176 6.3.5.1 Potential Aviation Weather Applications of SDR 176 6.3.6 Summary of Solutions Available from Non-Aviation Communication Systems 177 6.3.6.1 Voice Weather Products 177 6.3.6.2 Text Weather Products 177 6.3.6.3 Graphics / Gridded Data 177
7 Model Application and Economic Impact of Aviation weather 178 7.1 Air Traffic Flow Model Application
7.1.1 Model Data 1807.1.1.1 Data Sources 1807.1.1.2 Aircraft and Flight Data 1817.1.1.3 Aircraft Dwell Time 182 7.1.2 Model Result and Analysis 186 7.1.2.1 Base Year in 2005 186
7.1.2.2 Future Year in 2025 1927.2 Aviation Weather Information and Bandwidth Requirement Model Application
7.2.1 Model Result and Analysis in Base Year 2007.2.1.1 Tactical Aviation Weather Requirements and Analysis in 2005 200
ix178199 172
7.2.1.2 Strategic Aviation Weather Requirements and Analysis in 2005 2047.2.1.3 Aircraft as Sensor Results and Analysis in 2005 208 7.2.2 Model Result and Analysis in Future Year 2097.2.2.1 Tactical Aviation Weather Requirements and Analysis in 2025 2107.2.2.2 Strategic Aviation Weather Requirements and Analysis in 2025 2137.2.2.3 Aircraft as Sensor Results and Analysis in 2025 2177.2.3 AWINBRM Sensitivity Analyses
7.2.3.1 Doubling the Existing Sampling Rate of Aviation Products
7.2.3.2 Quadrupling Existing Sampling Rate of Aviation Products
7.2.4 AWINBRM Summary
7.3 Aviation Weather Economic Impact
7.3.1 Modified Airspace Occupancy Model
7.3.1.1 MAOM Overview
7.3.1.2 MAOM Assumption and Input
7.3.1.3 MAOM Process
7.3.2 Aircraft Impacted and Detour Model
7.3.2.1 AIDM Flowchart
7.3.2.2 Input Data
7.3.2.3 AIDM Process
7.3.3 Model Results and Analysis
7.3.3.1 Original and Detour Trajectory Analysis
7.3.3.2 Impacted Flight Analysis
7.3.3.3 Cost Effectiveness Analysis
8 Conclusions and Recommendations 245
8.1 Conclusions
8.2 Recommendations
Appendices
248
Appendix A. Acronyms
Appendix B. ITHINK Source Code
Appendix C. MATLAB Source Code
Reference
288I. Documents and Articles
II. World Wide Web
Vita
300
x2252348254271288295 218 219 222 224
225 225 226 229
231 233 233
237 240 241
List of FiguresFigure 1.1
Figure 1.2
Figure 2.1
Figure 2.2
Figure 3.1
Figure 3.2
Figure 4.1
Figure 4.2
Figure 4.3
Figure 4.4
Figure 4.5
Figure 5.1
Figure 5.2
Figure 5.3
Figure 5.4
Figure 5.5
Figure 5.6
Figure 5.7
Figure 5.8
Figure 5.9
Projected Air Traffic Growth and Number of Accidents
Cause of Flight Delay
Air Route Traffic Control Centers 13Over 5,000 Aircraft Operating in the NAS 14Modeling and Simulation Study Schematic 35Basic Building Blocks in ITHINK 7.0 39Air Traffic Control Centers in the USA 48Twelve Phases of Flight 54General Causal Diagram of Aircraft States inside ARTCC Region 59Air Carrier Traffic Flow Model Interface 80Air Carrier Traffic Flow Model Diagram 81Atmosphere Systems 85Three Weather-Related Decision Arenas 99Flight Phases and Weather Domain 102Significant Weather Forecast Chart 131EPIREP Dissemination Structure 136Spatial Retrieval Information for Aircraft as a Weather Sensor 137AWINBRM Model Flowchart 140AWINBRM Causal Diagram 141AWINBRM Causal Diagram – AC METAR/SPECI1 145xi 4 5
Figure 5.10 AC Tactical Aviation Weather Product Model Interface
Figure 5.11 AC Strategic Aviation Weather Product Model Interface
147 148Figure 5.12
Figure 6.1
Figure 6.2
Figure 6.3
Figure 6.4
Figure 6.5
Figure 7.1
Figure 7.2
Figure 7.3
Figure 7.4
Figure 7.5
Figure 7.6
Figure 7.7
Figure 7.8
Figure 7.9
Figure 7.10
Figure 7.11
Aircraft as Weather Sensor Model Interface 149Decision Arenas and Phases of Flight
Datalink Areas of Concern 153Existing Aviation Communication Systems Architecture
Aviation Weather Datalink and Voice Communication Systems 156Potential Aviation Weather Information Communication Systems 167Atlanta ARTCC and Sectorization
Number of Air Carrier Aircraft over 24 Hours in 2005 189Number of Air Taxi/Commuter Aircraft over 24 Hours in 2005 190Number of General Aviation Aircraft over 24 Hours in 2005 191Number of Military Aircraft over 24 Hours in 2005 192Number of Air Carrier Aircraft over 24 Hours in 2025 195Number of Air Taxi/Commuter Aircraft over 24 Hours in 2025 196Number of General Aviation Aircraft over 24 Hours in 2025 197Number of Military Aircraft over 24 Hours in 2025 198Number of Air carrier Aircraft at Approach Operation and
Initial Climb Segment Phases over 24 Hours in 2015
Tactical Aviation Weather Information Requirement Size
for Air Carrier in 2005
xii 152 154 179 199 201
Figure 7.12
Figure 7.13
Figure 7.14
Figure 7.15
Figure 7.16
Figure 7.17
Figure 7.18
Figure 7.19
Figure 7.20
Figure 7.21
Figure 7.22
Figure 7.23
Tactical Aviation Weather Information Requirement Size
for Air Taxi/Commuter in 2005
Tactical Aviation Weather Information Requirement Size
for General Aviation in 2005
Tactical Aviation Weather Information Requirement Size
for Military in 2005
Strategic Aviation Weather Information Requirement Size
for Air Carrier in 2005
Strategic Aviation Weather Information Requirement Size
for Air Taxi/Commuter in 2005
Strategic Aviation Weather Information Requirement Size
for General Aviation in 2005
Strategic Aviation Weather Information Requirement Size
for Military in 2005
Aircraft as Sensor in 2005
Tactical Aviation Weather Information Requirement Size
for Air Carrier in 2025
Tactical Aviation Weather Information Requirement Size
for Air Taxi/Commuter in 2025
Tactical Aviation Weather Information Requirement Size
for Genera Aviation in 2025
Tactical Aviation Weather Information Requirement Size
for Military in 2025
xiii 202 203 204 205 206 207 208 209 210 211 212 213
Figure 7.24 Strategic Aviation Weather Information Requirement Size
for Air Carrier in 2025 214Figure 7.25
Figure 7.26
Figure 7.27
Figure 7.28
Figure 7.29
Figure 7.30
Figure 7.31
Figure 7.32
Figure 7.33
Figure 7.34
Figure 7.35
Figure 7.36
Figure 7.37
Strategic Aviation Weather Information Requirement Size
for Air Taxi/Commuter in 2025 215Strategic Aviation Weather Information Requirement Size
for General Aviation in 2025 216Strategic Aviation Weather Information Requirement Size
for Military in 2025 217Aircraft as Sensor in 2025 218Tactical Aviation Weather Information Requirement Size
at Double of Existing Sampling Rate for Air Carrier in 2025 219Strategic Aviation Weather Information Requirement Size
at Double of Existing Sampling Rate for Air Taxi/Commuter in 2025
Aircraft as Sensor at Double of Existing Sampling Rate in 2025 221Tactical Aviation Weather Information Requirement Size
at Four Times of Existing Sampling Rate for Air Carrier in 2025 222Strategic Aviation Weather Information Requirement Size
at Four Times of Existing Sampling Rate for Air Taxi/Commuter in 2025
Aircraft as Sensor at Four Times of Existing Sampling Rate in 2025 224Modified Airspace Occupancy Model Flowchart
Aircraft Impacted and Detour Model Flowchart 232Impacted Flight and Re-route Flight Path 235xiv 223 220 227
Figure 7.38 Impacted Flight and Re-route Flight Path Special Case
Figure 7.39 Original Flight Trajectories
236 238 239Figure 7.40 Surrogate Flight Trajectories for Impacted Flights
Figure 7.41
Figure 7.42
N Surrogate Flight Paths for One Impacted Flight 240Flights Impacted over Time in 2015 241xv
List of TablesTable 2.1
Table 3.1
Aviation Weather Products
27Systems Dynamics Variables and Symbols 37Table 4.1
Table 4.2
Table 4.3
Table 5.1
Table 5.2
Table 5.3
Table 5.4
Table 5.5
Table 5.6
Table 5.7
Table 5.8
Table 5.9
Table 5.10
Table 5.11
Table 5.12
Decision Heights and RVR Requirements for IFR Flight
Weather Conditions under VFR in Uncontrolled Airspace 45Weather Conditions under VFR in Controlled Airspace
Minimum and Maximum Cruise Altitudes for Some Basic
Types of Aircraft
Weather Systems 92Air Motion Phenomena
Precipitation Types 94Phenomena Contributing to the Ice on Aircraft Structures
Phenomena Contributing to Visibility/Ceiling Conditions
Additional Weather Phenomena Impacting Aviation Safety 96Aviation Weather Information Requirements 104Weather Information Required During the Planning, Preflight,
and Taxi and Take-Off Phases of Flights
Flight Plan Components that May be Impacted by Weather 106Weather Information Required During the Departure, Initial Climb,
and Initial Cruise Phases of Flights 109Weather Information Required During the Cruise, Approach,
and landing Phases of Flights 110
xvi 44 47 86 93 95 95 105
Table 5.13
Table 5.14
Table 5.15
Table 5.16
Table 5.17
Table 5.18
Table 5.19
Table 7.1
Table 7.2
Table 7.3
Table 7.4
Table 7.5
Table 7.6
Table 7.7
Table 7.8
Table 7.9
Table 7.10
Table 7.11
Table 7.12
Table 7.13
Table 7.14
Weather Information Required During the Taxi-In, Post,
and Alternative Phases of Flights
PIREP Information and Codes
Aviation Weather Products Using for Tactical Decision Making
Aviation Weather Products Using in Strategic Decision Making
Possible Sensors On-board Aircraft 135Aircraft as a Weather Sensor Communication Information Data Sets 138Aircraft as a Sensor Data Size with Low Sampling Rate
Base Aircraft in Atlanta ARTCC 181Air Carrier and Military Aircraft Mean Dwell Time and Variance 182Air Taxi and Commuter Aircraft Mean Dwell Time and Variance 183General Aviation Aircraft Mean Dwell Time and Variance 184Idle Aircraft Dwell Time at Airport 185Air Traffic Volumes at the Airport in 2005 186Air Traffic Volume in the Terminal in 2005
Air Traffic Volume in the Airspace in 2005
Air Traffic Volume at the Airport in 2025 193Air Traffic Volume in the Terminal in 2025
Air Traffic Volume in the Airspace in 2025
Values of Passenger Time per Hour 242Aircraft Operating Costs per Hour
Cost Comparison between Detour Flights and Delayed
Flights at Airports
xvii 112 123 124 129 138 187 188 194 194 242 243
CHAPTER 1
Introduction1.1 BackgroundIn just 100 years since the Wright brothers’ first successful flight, air transportation has grown into avery large industry, essential to modern society. There are fifty thousands commercial flights every dayover the U.S. alone. Commercial air transportation is safe and affordable. Aircraft are extremely reli-able. The U.S. commercial air transportation operations have steadily increased for decades, a trendwhich is likely to continue in the forseeable future. Passenger enplanements, for example, have histor-ically grown at about 7% per year [Air Transport Association (ATA), 1999] before 2000. In 2000,U.S. airlines enplaned a record 670 million passengers [ATA, 2000]. Although the events of September11, 2001, shocked the U.S. and hurt the air transportation industry when the average seating capacityof the U.S. carriers declined 15 percent. However, due to lower fares and a solid economy recovery, itis reported that airlines in 2004 have flown 685 million passengers. On a typical day in the UnitedStates, over 1.8 million people fly safely aboard some 50,000 flights [Federal Aviation Administra-tion (FAA), 2005]. The United States maintains an excellent aviation safety record. In economic termsthe U.S. civil aviation industry contributes about 6 percent of the annual U.S. gross domestic product,so there are also economic incentives to maintain a safe and healthy civil aviation industry [FAA,1
2000].The National Airspace System (NAS) constitutes a network of airspace links/nodes, airports, naviga-tion aids, air traffic control equipment across the United States. The NAS operates non-stop - 24 hoursa day, every day of the year - providing safe air transportation for millions of passengers. The NASincludes more than 20,000 airports, 21 air route traffic control centers, over 460 air traffic control tow-ers and 75 flight service stations, and approximately 4,500 air navigation facilities. Over 34,000 piecesof maintainable equipment including radars, communications switches, ground-based navigation aids,computer displays, and radios are used in NAS operations [NAS 5.0, 2004].1.2 Problem StatementIf the claim that “all roads lead to Rome” was the key indicator of that city's economic greatness inancient times, a modern city's equivalent claim would have to be “all airlines land here.” Just as in thepast shipping, railway and then highway systems have played vital roles in determining a city's eco-nomic power. Today global air transportation systems play a substantial role in the regional and nation-al economies. Undoubtedly, air transportation is an “engine” of the economy. However, economicgrowth and record air travel demand during the late 1990s and early in the twenty first century havecreated problems in the air transportation industry. These include capacity and throughput issues whichoften lead congestion and delays. The congestion and delays can also increase controller and pilotworkloads, threatening aviation safety.1.2.1 Aviation Problems1.2.1.1 Aviation System Congestion and DelayThe year 2000 was a memorable one for U.S. air travelers. This superlative, however, was not a posi-tive one. Delays, Cancellations, and Congestion! It seemed as though this
spared no airport throughoutthe nation’s large hub-and-spoke air traffic system. Historically, the FAA has spent billions of dollarsmodernizing the NAS through the development, acquisition, and implementation of new technologies.2
Many of these capabilities entrenched in the FAA programs have made claims that delays will be re-duced significantly as air traffic demand grows. However, some recent developments indicate that airtransportation delays are increasing at a faster pace than justified by the demand for air transportationservice. In 2000, one in every four flights was delayed, canceled or diverted according to FAA statis-tics. The equivalent of 163 million fliers were delayed according to data compiled by the Transporta-tion Department’s inspector general [, 2001]. Departure and arrival delaysincreased 126% between 1997 and 2000 [, 2001]. For travelers, this meansa simple trip from A to B now feels more like A to Z. Based on work done by Russ Chew at ATA, ifthe air traffic control system is not fixed and if the events of September 11, 2001 would not have oc-curred, ATA estimates that delays would have increase by some 250% by 2005 [ATA, 2000]. Althoughthis situation would not occur due to the impact of September 11 terrorist attacks, the flight delays havestarted to creed up after the spring 2004 as air traffic reaches or exceeds the record levels experiencedin the year 2000. Based on current statistical data from the Bureau of Transportation Statistics [BTS,2006] 23 percent of flights were delayed, canceled or diverted in the first five-month in 2006, whichis close to the situation in 2000. Before September 11, 2001, air traffic delays were costing airlines andtheir passengers an estimated $6 billion a year [, 2001]. Today, individualairlines say delay costs are mounting on them.1.2.1.2 Flight Accidents and IncidentsCongestion and delays can also increase controller and pilot workloads, ultimately affecting aviationsafety. The National Transportation Safety Board (NTSB) statistics show that the U.S. airlines' safetyrecord has improved steadily through the years, most notably including the years since commercial aviation major accident rate (as judged by hull losses per million departures) hasbeen nearly constant over the past two decades. Although the rate is very low, increasing traffic overthe years has resulted in the absolute number of accidents to increase. The worldwide demand for airtravel is expected to increase even further over the coming two decades—doubling by 2025 with therequirement for $1 trillion in new aircraft deliveries [Boeing, 2001]. If these predictions materializethe congestion and delays in air transportation system will hit record level. Without an improvement3
in the accident rate, such a traffic volume would lead to 50 or more major accidents a year—a nearlyweekly occurrence (Figure 1.1). Given the very visible, damaging, and tragic effects of even a singlemajor accident, this number of accidents would clearly have an unacceptable impact upon the public’sconfidence in the aviation system and impede the anticipated growth of commercial air-travel.
The safety of the general aviation (GA) system is also critically important. The current GA accidentrate is 20 times greater than that of scheduled commercial transport operations. Eighty-five percent ofaviation accidents occurring from 1990-1996 involved small GA aircraft. With the GA market alsopoised to grow significantly in future years, safety considerations must be removed as a barrier if thisgrowth is to be realized.50Millions ofdeparturesper yearHull lossaccidentsper yearHull lossaccident rateper milliondepartures454980Year19902000Accident rate2010ProjectedtrafficNumber ofaccidentsFigure 1.1 Projected Air Traffic Growth and Number of Accidents
(Data obtained from the Boeing Company (2000)128 and the FAA83).4
1.2.2 Causal Factors1.2.2.1 Aviation WeatherAviation safety and efficiency are affected by a number of factors, weather system is one of r is a major contributor to aviation delays, congestion, accidents, and incidents. In the past fiveyears weather has accounted for 68% of all delays in the NAS and forty percent of the GA accidentsare attributed to weather according to statistics compiled and published by the FAA. Atmosphericweather varies in size and in shape from few of square miles to thousands of square miles. The con-nection between air traffic and weather is that both sometimes occupy the same 1.2 indicates the cause of flight delays. Except when the delay is caused by weather, the nextlargest category of delay is due to traffic volume but it just represents eight percent of the total delaysin the system.
Equipment2%Closed
Runways/Taxiways5%Center Volume4%Other13%Termial Volume8%Weather68%Figure 1.2 Cause of Flight Delay (Data obtained from the FAA85).5
1.2.2.2 CommunicationThe capacity of the NAS is a complex combination of the collective capacities of airports, airspace,airlines asset, and air traffic control. It is obvious that such systems will not work in isolation. The com-munication among pilots, air traffic controllers, and weather providers plays an important role in theoperational capabilities of the NAS. Unfortunately, the frequencies used to obtain aviation weather in-formation often become saturated, limiting access to the information at times when it is needed tune radios to receive automated weather services such as Hazardous In-flight Weather AdvisoryService (HIWAS) and Automated Terminal Information Service (ATIS) to obtain a broadcast overlarge areas or specific reporting stations. The information from these aural sources is limited and maybe relevant only for a very localized area.1.3 Research Motivation
In 1997, the United States set a national goal to reduce the fatal accident rate for aviation by 80% withinten years based on the recommendations by the Presidential Commission on Aviation Safety and Se-curity. Achieving this goal would require the combined efforts of government, industry, and academiain the areas of technology research and development, implementation, and operations. To respond tothe national goal, the National Aeronautics and Space Administration (NASA) has developed a pro-gram that will focus resources on performing research and developing technologies that will enableimprovements in many areas of aviation safety. The NASA Aviation Safety Program (AvSP) is orga-nized into six research areas: Aviation System Modeling and Monitoring, System Wide Accident Pre-vention, Single Aircraft Accident Prevention, Weather Accident Prevention, Accident Mitigation, andSynthetic Vision. Specific project areas include Turbulence Detection and Mitigation, Aviation Weath-er Information, Weather Information Communications, Propulsion Systems Health Management, Con-trol Upset Management, Human Error Modeling, Maintenance Human Factors, Fire Prevention, andSynthetic Vision Systems for Commercial, Business, and General Aviation aircraft. Research is beenperformed at all four NASA aeronautics centers and closely coordinated with the FAA and other gov-ernment agencies, industry, academia, as well as the aviation user community. Many research projects6
to achieve the program goals are related to weather on the national aviation to improve air traffic management goal and two projects - “Integrationof Reusable Launch Vehicle (RLV) into Air Traffic Management” and “Use of Next-generation Satel-lite Systems for Aeronautical Communications” performed by the National Center of Excellence forAviation Operation Research (NEXTOR) at Virginia Tech we developed a research topic on an “Inte-grated of Modeling of Air Traffic, Aviation Weather, and Communication Systems”.1.4 ObjectivesThe purpose of this research effort is to study air traffic flow and aviation weather information andbandwidth requirements through modeling and simulation. The ultimate goal of the models describedhere is to serve as a living laboratory where policies can be tried before implementing them into thereal system. Moreover, these computer models can evolve dynamically through time allowing decisionmakers to exercise policies at various points in time to quantify results with areas of research have been analyzed in this project: 1) Air Traffic Flow Analysis, 2) AviationWeather Information, Products, and Requirements Analysis, and 3) Aviation Weather CommunicationSystems Analysis. Three computer models have been developed to study these areas of research usingMATLAB 6.1, a general engineering software package developed by the Mathworks [Mathworks,1997] and ITHINK 7.0, a Systems Dynamics software package used to develop conceptual frame-works for underlying construction and subsequent simulation of mental models [High Performance,2001]. These models are: 1) the Air Traffic Flow Model (ATFM), 2) the Aviation Weather Informationand Bandwidth Requirement Model (AWINBRM) and 3) the Aircraft Impacted and Detour Model(AIDM). All models can be executed on any Windows 98/2000/XP/NT compatible PC. Macintosh, orLunix Workstation without ATFM model is used for quantifying the volume of air traffic at each phase of flight including en-route, terminal, and on the ground traffic regions. The results of the ATFM model are used as inputsfor the AWINBRM model. The AWINBRM model is an aviation weather information and bandwidth7
requirement model. This model is used to define required aviation weather information and their sizesat each phase of flight in three flight regions. This provides detailed information for planning aviationweather communication systems in the future. For example, if weather in the cockpit requirements areconceptualized, AWINBRM could determine the bandwidth necessary to satisfy. The AIDM model isused to detect the impacted flights by an aviation weather system and to generate detoured flight pathsaround the aviation weather system in a case study. The aviation weather communication system anal-ysis is focus on the examination of aviation weather information communication requirement, currentand planned aviation weather communication systems, and potential solutions from non-aviation com-munication systems.
1.5 Organization of the DissertationThis dissertation is composed of eight chapters organized according to the following sequence:Chapter 1 presents an introduction to the problem and a brief description of the air transportation sys-tem. This chapter also presents the motivation, objectives, and scope of this r 2 reviews pertinent literature about the air transportation industry, the National Airsapce Sys-tem, air traffic management, aviation weather information and products, aviation weather communi-cation system, and aviation weather economic impacts. Several air traffic flow models and weathermodels are reviewed in this r 3 outlines the research requirements and the corresponding methodology adopted in this re-search. A review of the Systems Approach and Systems Dynamics is r 4 examines the current state of the National Airspace System and the features of each phaseof flight pertinent to this research. Phases of flight examined are: at the airport, in the terminal, and en-route airspace. In order to quantify the air traffic flows in one Air Route Traffic Control Center(ARTCC), the Air Traffic Flow Model (ATFM) is developed.
Chapter 5 describes Aviation Weather Information, Products, Requirements Analysis. In this chapter,the fundamentals of weather phenomena and aviation weather systems are discussed. Based on air-8
borne weather-related decision-making activities, two aviation weather domains - tactical and strategicare defined. Aviation weather information requirements at each phase of flight are also defined. In thisanalysis, the aircraft is considered both a source and a user of aviation weather information, aircraft asaviation weather sensor is analyzed. Finally, the Aviation Weather Information and Bandwidth Re-quirements Model (AWINBRM) is developed to quantify aviation weather information at each phaseof r 6 describes communication systems. This chapter focuses on the exploration of current andplanned aviation weather communication systems and potential communication solutions from non-aviation communication r 7 conducts model applications and economic impact analysis of aviation weather. Atlanta airroute traffic control center is used to run the ATFM and AWINBRM models. The analyses of the mod-els’ results are provided in this chapter. For the further research - a cost effectiveness analysis for theflights impacted by weather system is conducted. The Modified Airspace Occupancy Model (MAOM)and Aircraft Impacted and Detour Model (AIDM) are explained and developed in this Chapter 8, the conclusions and recommendations for this research are discussed.9
CHAPTER 2
Literature Review2.1 Air Transportation IndustryAir transportation industry has three major components which are: 1) airlines, 2) airports, and 3) air-space and air traffic control systems. The U.S. scheduled airlines, as air transportation operators, areclassified by the government on the basis of the amount of revenue generated from operations. Theseclassifications are air carrier, air taxi/commuter, general aviation, cargo carrier, and military. Air car-riers generally provide nationwide, and in some cases, worldwide service and operate mostly medium-and large-sized jets. As their name implies, air taxi/commuter carriers are airlines whose service, forthe most part, is limited to a single region of the country, transporting travelers between the major citiesof their region and smaller, surrounding communities. They usually use regional jets and small sizeturboprops. This has been one of the fastest growing and most profitable segments of the industry sincederegulation, especially after September 11. General aviation (GA) encompasses all aviation otherthan scheduled airline flights and military flights. It includes everything from privately-owned lightsingle-engine aircraft to business jets, news gathering, police, pipeline patrol, emergency medicalflights, crop-dusting, rotorcraft, gliding, sport ballooning and many other aerial activities. Aircraft inuse by principally all cargo carriers, called freighters, carry nothing but freight. Military is specialcategory which is operated by military including air force, national guard etc. Military flight are con-10
trolled by military controllers but they require coordination with the FAA’s air traffic control discussed above, aircraft is a major asset in various airlines categories. Similar to airlines classifi-cations, aircraft are also divided into four categories in this research: 1) air carrier aircraft, 2) air taxi/commuter aircraft, 3) GA aircraft, and 4) military aircraft. Large cargo aircraft are considered in theair carrier aircraft category and small cargo aircraft such as turboprop engine aircraft belong to GA cat-egory. Since Orville and Wilbur Wright made the first powered flight in a heavier-than-air machine onDecember 17, 1903; aircraft have developed rapidly in its size and speed. In the early year of air trans-portation most airplanes were relatively small with single or twin piston or turboprop engines and flewat low speeds. In 1952, a 36-seat British-made jet, the Comet I, flew from London to Johannesburg,South Africa, at speeds of up to 500 miles per hour. In 1958, the first U.S. passenger jet, the Boeing707 could carry up to 181 passengers and travel at speeds of 550 miles per hour. The year 1969 markedthe debut of another revolutionary aircraft, the Boeing 747. It was the first widebody jet, with twoaisles, a distinctive upper deck over the front section of the fuselage, and four large engines. With seat-ing for as many as 450 passengers, it was twice as big as any other Boeing jet of the time.
During the same period, efforts were underway in both the United States and Europe to build a super-sonic commercial aircraft. The former Soviet Union was the first to succeed, testing the Tupolev 144in December of 1968. A consortium of West European aircraft manufacturers first flew the Concordetwo months later and eventually produced fourteen fast, but small, jets for commercial service. Recent-ly, aviation industry is moving forward a new generation aircraft, such as, Airbus’s A380 and the Boe-ing 787 Dreamliner. In 2007, air travelers will step onto a double-deck jetliner A380 capable ofcarrying up to 650 passengers over 7000 miles at a cruise speed of 560 MPH. The Boeing 787 Dream-liner would fly 300 passengers at 550 MPH with 15 percent in saving per seat-mile compared to exist-ing twin engine aircraft United States has the largest, most extensive aviation system in the world with more than 20,000airports [NAS 5.0, 2004], ranging from large commercial transportation centers enplaning more than40 million passengers annually, to small grass strips serving only a few aircraft each year. Of these,3,304 are designated as part of the national plan for an integrated airport system (NPIAS). The air-11
space and air traffic control systems will described in the following paragraphs.2.2 National Airspace System
2.2.1 Overall National Airspace SystemThe national airspace system (NAS) spans all U.S. territories and extends beyond the continental NAS includes all air traffic control (ATC) and air traffic management facilities and personnel aswell as equipment used for communication, navigation, and surveillance such as VHF/UHF voicetransmitters and receivers, navigation beacons, weather and wind-shear radars, and instrument landingequipment. The FAA procures, operates, and maintains this equipment.
The overall airspace above the continental United States is divided into 20 areas which are shown inFigure 2.1, with the control of each area assigned to a facility known as an air route traffic control cen-ter (ARTCC). The airspace of each center is further divided into numerous sectors which are generallysmall enough to be managed by one, two or three controllers. Most large airports have an air trafficcontrol tower (ATCT) and/or a terminal radar approach control (TRACON), which may assume re-sponsibility for the separation of aircraft in the vicinity of the airport.2.2.2 Airspace ClassificationTo organize air traffic and facilitate Air Traffic Control (ATC), the U.S. airspace is divided into sixclasses: A, B, C, D, E, and G. In addition to these classes of normal airspace, there are also several typesof Special Use Airspace. Since September 16, 1993, airspace classifications have been divided as fol-lows [Aviation Communication, 1997]:• Class A Airspace is the region from 18,000 to 60,000 feet above mean sea level (MSL).
• Class B Airspace is often specified around the busiest airports, generally from 0 to about
10,000 feet, and may consist of layers stacked like an inverted wedding cake.12
Figure 2.1 Air Route Traffic Control Centers (Modified from the FAA98)• Class C Airspace may be specified around an airport that is serviced by a control tower andradar approach control, and has a certain amount of IFR traffic. Class C airspace usuallyconsists of a circular region of radius 5 nm from 0 to 1,200 feet, beneath a larger region ofradius 10 nm, from 1,200 to 4,000 feet.
• Class D Airspace surrounds all airports that have control towers but are not associated withClass B or C airspace. Class D airspace surrounds the airport area from 0 to 2,500 feet (lat-eral dimensions vary).
• Class E Airspace - also called Controlled Airspace - applies, in short, to all controlled air-space not designated as Class A - D.
• Class G Airspace - also called Uncontrolled Airspace - applies to all uncontrolled airspace.
• Special Use Airspace is designed to restrict aircraft operations, or in some cases to prohibitflights entirely, within certain areas. Among the categories of SUA are prohibited areas,13
restricted areas, military operations areas, alert areas, warning areas, controlled firingzones, and areas under temporary flight restrictions. SUA areas can also be used to estab-lish a safety buffer around all space operations, such as Space Shuttle launches and land-ings, to keep air traffic that is not involved in the operation at a safe distance.2.3 Air Traffic Management2.3.1 Air Traffic
There are up to 5,500 aircraft operating in the NAS during peak periods today. This equates toapproximately 50,000 aircraft operations per day [FAA, 2005]. Figure 2.2 shows over 5,000 aircraftoperating in the system at one time.
Figure 2.2 Over 5,000 Aircraft Operating in the NAS ( Photo obtained from the FAA102)14
There are many varieties of air traffic in the NAS. One way to categorize traffic is by aircraft example, the basic types of air vehicles are helicopters, piston engine aircraft, turboprops, tiltro-tors, subsonic jets, and supersonic jets. The types of aircraft are important in Air Traffic Management(ATM), because different types of aircraft can have a wide range of operating performance character-istics. These include: climb, descent rate, cruise speed and altitude. Some of these vehicles operate inspecific areas, for example, helicopters operate from small confined metropolitan areas (called heli-ports), others fly in overlapping traffic can also be grouped by purpose or affiliation. The FAA is responsible for all commercial,military, and general aviation in the NAS. Commercial aviation includes all air carriers providingscheduled, public air transportation. Military aviation describes the peacetime activities of militaryaircraft, such as training. GA refers to all other U.S. civil aviation activities, including training, recre-ational flight, business travel by private aircraft, agricultural crop dusting, etc. These categories ofaviation represent a range of activities, involving different types of aircraft and placing various loadson the ATM system.
Not only are there at least six types of vehicles and three categories of aviation, there are also two dif-ferent systems under which pilots can operate: Visual Flight Rules (VFR) and Instrument Flight Rules(IFR). VFR is a mode in which aircraft are responsible for self-separation (“see-and-avoid”) fromother aircraft. As long as they remain clear of clouds by at least 1000 feet and maintain horizontal vis-ibility of at least 3 nautical miles (NM), they are free to fly anywhere in the airspace. VFR aircraft donot receive separation services from controllers, and VFR is only an option in clear weather. Mostgeneral aviation (GA) traffic operate under VFR. IFR aircraft, on the other hand, actively participatein the ATC system. IFR traffic is continuously monitored by radar, and IFR pilots must maintain radiocontact with controllers, whose clearance must be obtained before changing course or altitude. IFRaircraft may fly under adverse weather conditions. large and high-performance aircraft always oper-ate under IFR, as do nearly all commercial aircraft. In general, the VFR system operates in the lowerairspace below 18,000 feet, while the IFR system operates in the upper airspace and around airport.15
2.3.2 Existing Air Traffic Flow ModelsIn air traffic flow management field, a considerable number of models have been developed over theyears to study traffic flow phenomena. Indeed, this is the oldest area of model development, with thefirst significant models dating back to the late 1950s. It is also the area where the most advanced mod-eling capabilities currently exist. There well-known air traffic flow models are reviewed in the follow-ing section.
2.3.2.1 SIMMODSIMMOD, the FAA’s current airport and airspace simulation model, depicts the dynamic interactionof aircraft movements. This model programmed in the language SIMSCRIPT II.5, simultaneouslystudies and evaluates en-route traffic, terminal area traffic, and ground operations at one or more air-ports. SIMMOD produces measures of airport capacity, aircraft travel time, aircraft delay, and aircraftfuel consumption. After a standard scenario has been established with data from existing or proposedoperations, the input data may be changed to develop and evaluate different scenarios. This allows the“what-if” questions to be analyzed. The model may be implemented for projects as large as a majorroute network and as limited as individual terminal gate provides highly detailed statistics on each aircraft simulated. Outputs can be obtained on:aircraft travel times; traffic flows past specified points; throughput capacity per unit of time; delays bytime of day and location on the airfield or in airspace, along with the immediate reason for each delay;and fuel of the main drawbacks of the model is that traffic must move on a pre-specified network of nodesand links according to pre-specified operating strategies or “rules of the road”. In terms of conflictsbetween aircraft paths, SIMMOD is essentially a one-dimensional model, checking for conflicts alongthe aircraft's longitudinal path only, with no possibility to check for lateral or vertical separation the hands of a skilled user, SIMMOD is possibly the most powerful existing tool for “fine granular-ity” simulation of airport surface operations, allowing for arbitrarily high levels of detail (e.g., simula-16
tion of push-back operations, gate occupancies, de-icing procedures, etc.). Several airport studiesconducted with SIMMOD to date illustrate this principal perceived weakness of SIMMOD is that it is a “labor intensive” model whose users mustundergo a significant amount of training. Moreover, to avoid several potential pitfalls, SIMMOD usersmust have a very good understanding of ATM and airport operations. For example, because SIMMODis essentially a one-dimensional model (i.e., it can check for conflicts between aircraft only along thepaths traced by the elements of a network) care must be taken so that the network structure on whichthe traffic moves is based on sets of nodes and links with sufficient lateral and vertical separations toavoid the presence of undetected conflicts during the simulation. Another difficulty in SIMMOD is themodeling of dynamic rerouting of aircraft to simulate the ATM system's responses to local or regionalcongestion problems [SIMMOD User Manual, ATAC, 2000].2.3.2.2 TAAMThe Total Airspace & Airport Modeller (TAAM) developed by Preston Group is an application for thesimulation of airspace and airport operations like SIMMOD. TAAM model is a gate-to-gate systemthat models the entire airside and airspace environment in detail, including pushback, runways, termi-nals, en-route and oceanic airspace. TAAM can be used as a planning tool or to conduct analysis andfeasibility studies of ATM concepts. TAAM can simulate most ATM functions in detail and can pro-vide scenario generation for real-time ATC simulators. The simulations cover the entire gate to gateATM process, generally in more detail than competing models.
These are in general aggregated metrics and can be reported on system or sector wide basis.• System delays• Conflicts: counts by degree of severity, whether successfully resolved or not• Airport movements, delays, operations on taxiways and runways, runway occupancy• Airspace operation metrics such as usage of routes, sectors, fixes and coordination• Noise contours• Total fuel burnt17
• Costs: aggregate, fuel, non-fuel• Controller workloads• Individual Aircraft flight profiles• Scenario for real-time ATC simulators or other playback• “Show Logic” diagnostics which gives the operator an insight into TAAM's decision mak-ing process• Text messages (extent and content user selectable) which contain further details of TAAMevents• ErrorsA 2D or 3D graphical visualization of the simulation can also be generated. The graphical output canbe viewed in several windows simultaneously, each window having an independent 2D or 3D viewwith the scale ranging from 30 m to 40,000 km. Hazardous weather, or special use airspace cannot yetbe modeled dynamically. Weather modeling was limited to winds aloft in sectors. Also TAAM is amore expensive software package [TAAM User Manual, Preston, 1998].2.3.2.3 RAMSThe Reorganized ATC Mathematical Simulator (RAMS) is a fast-time simulation tool developed bythe Eurocontrol Experimental Center (EEC) at Bretigny (France). RAMS is a major upgrade of EAM(Eurocontrol Airspace Model), which for the past 15 years has been Eurocontrol's principal simulationtool for evaluating proposed changes to airspace structure and sector configuration in the EEC memberstates. RAMS deals with all segments of flights starting from take-off until just before landing. How-ever, runway interactions with airborne operations may be modeled, such as for parallel or intersectingrunways [RAMS User Manual, , 2004].RAMS provides a flexible airspace simulation environment where a broad variety of new conceptsmay be tested at the desired level of detail. Due to the flexible design of RAMS, the system is capableof carrying out planning, organizational, high-level, or in-depth studies of a wide range of ATC con-cepts. This design includes 4-dimensional flight profiles, conflict detection and conflict resolution18
mechanisms, workload models, modern user interfaces and a data preparation carrying out comparative analyses between different simulated scenarios, the effects of proposedchanges can be expressed in terms of:• Distribution of workload over centers, sectors, and individual control positions;• Traffic loads within each sector/center overall and per route, level band, point, classified
according to cruise, climb and descent;• Penalties imposed upon traffic resulting from imposing ATM measures, flight level
changes, en-route/ground delays, and arrival holding.• Frequency distribution based on many iterations of a given scenario (Monte-Carlo simula-tions).2.3.2.4 NASPACThe National Airspace System Performance Capability (NASPAC) is a fast-time simulation model thatmay encompass large regions of airspace and a large number of airports. The simulation “flies” indi-vidual aircraft through daily itineraries (that may include landings and take-offs at a sequence of air-ports) and provides statistical reports on delays and flow rates observed. The model includes simplifiedrepresentations of en-route sectors, as well as of airports. Some graphical outputs by airport, sector orregion can be provided. NASPAC was originally conceived as a macroscopic-level model that wouldsupport studies dealing with issues related to strategies for national airport investments and to policyfor national and international ATM. However, much detail has been added to it over the years and itmay actually be better suited today to answer questions of a more tactical nature, such as the effects ondelays of alternative flow management main outputs of NASPAC consist of estimates of delay and of flows past given points (“through-put”) in the system modeled. Delay is reported in the form of “technical delay” (defined as the localdelay incurred at any specific point in the system) and of “effective delay” (defined as the differencebetween scheduled and actual times of events, such as the arrival or departure from a gate).Use of the model requires considerable training and significant resources in terms of both costs and19
personnel. Arrangements must be made with one of the organizations that operate the model. Extensivedata are also needed [, 2005].2.3.2.5 AOMIn 1997 - 1999, Virginia Tech carried out research on the “Integration of Reusable Launch Vehicle(RLV) into Air Traffic Management”. The main focus of this project was the evaluation of traffic im-pacts due to closures of airspace during rocket launches, an economic impact model was developedand also an optimal routing model to detour flights around Special Use Airspace (SUA) [Sherali, etal., 1998]. In 1999, another project on titled “Use of Next-generation Satellite Systems for Aeronauti-cal Communications” sponsored by NASA was carried out by a joint effect between the University ofMaryland and Virginia Tech [Ball, et al., 2001]. The primary objective of this research is to furtherdevelop these two projects and employ the technologies developed in the projects into NASA AviationSafety Program.
Aircraft Occupancy Model (AOM) was developed for the project - “Integration of Reusable LaunchVehicle (RLV) into Air Traffic Management” at Virginia Tech. AOM can read ETMS flight data andSector data and output air traffic workload in each sector or center. In this research, AOM will be mod-ified to use for the case study in Chapter 7.2.3.2.6 Severe Weather-Modeling ParadigmMcCrea et al. developed a severe weather-modeling paradigm and a new concept of “Probability-nets”in aviation industry. These are used to generate new flight paths around convective weather systemswith specified operability threshold levels. This research also developed probabilistic delay assess-ment methodology for estimating planned paths that might encounter potentially disruptive weatheralong its trajectory. Finally, an economic benefit analysis for new flight paths is conducted [McCreaet al. 2006].Weather data is a major component and many current weather forecasts are examined in this Model Output Statistics (MOS) is chosen to use for this research. MOS is developed by the Na-20
tional Weather Service’s Meteorological Development Lab (MDL), it produces the necessary informa-tion in three-hour or six-hour time intervals using a statistical modeling method. The pertinent aviationMOS text forecasts are available in short-range GFS (6-84 hours), Eta (6-72 hours), and extended-range GFS (12-192 hours) formats. MOS provides specific probability for various weather , convective, ceiling, temperature, etc.) at over 1,500 reporting sites throughout the United Statesand Puerto Rico [McCrea et al. 2006].
The probabilities at each reporting site are used to build a probability-nets for one region or entirecountry. After constructing the probability-nets, a flight plan that enters only one probability-net willbe assigned an exit probability. The strand intersection probability value is introduced. It means thatthe discrete representation of the probability data lends itself to a subjective assignment of probabilityvalues at the point of intersection between the flight plan and strand of interest. New flight paths thatskirts the weather systems are controlled by specified probability threshold. This research also can de-termine a time-dependent shortest path probability-nets is a very new and innovative concept for developing new flight paths aroundweather system. However, most flights are short activity and usually they stay from 1 to 3 hours in theair in the United States. MOS forecasts should provide (1-6 hours) and (2-12 hours) forecasts with in-terval 1 hour.2.4 Aviation Weather
2.4.1 Review FAA Weather Requirement RegulationsAll pilots need the same basic weather information for safe operation. Aircraft performs in adverseconditions is a function of the type of aircraft, the equipment, and the pilot’s training/certification. FAAweather information requirements vary depending upon the category of operation. Similar weather in-formation is needed for each type of operator. There are various civilian categories of aircraft operatorsidentified by the FAA. Each category has its own set of requirements under the Federal Aviation Reg-ulations. The largest segment of operators falls under the following three categories:21
• Part 91 – General Operating and Flight Rules• Part 135 – Air Taxi Operators and Commercial Operators• Part 121 – Domestic Commercial OperatorsThe following paragraphs provide a review of FAR requirements for weather information by categoryof 91 - General Operating and Flight RulesPart 91 flight operations include personal flights, business and corporate flights, training flights andspecial operations, (e.g., flight-tests, glider towing, parachuting, etc.). Weather information require-ments are relatively lenient under Part 91. “Each pilot in command shall, before beginning a flight, be-come familiar with all available information concerning that flight. This information must include fora flight under IFR or a flight not in the vicinity of an airport, weather reports and forecasts, fuel re-quirements, alternatives available if the planned flight cannot be completed, and any known traffic de-lays of which the pilot in command has been advised by air traffic control …other reliable informationappropriate to the aircraft, relating to aircraft performance under expected values of airport elevationand runway slope, aircraft gross weight, and wind and temperature” [FAR 91.103, DOT].However, the FAR does not state what types of weather reports or forecasts are required or informationabout their timeliness. Since the FARs are not specific on how weather information is to be obtained,many Part 91 pilots obtain weather information from TV, radio, and the 135 – Air Taxi Operators and Commercial OperatorsGenerally, Part 135 operations include:• Commuter (scheduled passenger-carrying operations in airplanes that have passenger-seat-ing configurations of less than 10) or on-demand (charter) operations, and• Nonstop sightseeing flights for compensation or hire that begin and end at the same airport,and are conducted within a 25 statute mile radius of that airport [/_landings/pages/].Weather requirements under Part 135 are more stringent than Part 91. FAR 135.213 states: “Whenever22
a person operating an aircraft under this part is required to use a weather report or forecast, that personshall use that of the U.S. National Weather Service (NWS), a source approved by the U.S. NationalWeather Service, or a source approved by the Administrator. However, for operations under VFR, thepilot in command may, if such a report is not available, use weather information based on that pilot'sown observations or on those of other persons competent to supply appropriate observations…weatherobservations made and furnished to pilots to conduct IFR operations at an airport must be taken at theairport where those IFR operations are conducted, unless the Administrator issues operations specifi-cations allowing the use of weather observations taken at a location not at the airport where the IFRoperations are conducted” [[FAR 135.213, DOT]].Part 121 – Domestic Commercial OperatorsPart 121 operations include:• Passenger and cargo domestic, flag (international), and supplemental operations (e.g., oper-ating aircraft with 10 or more seats or more than 7,500 pounds payload capacity), and• Nonstop sightseeing flights conducted with airplanes having a passenger-seat configurationof 30 seats or fewer and a maximum payload capacity of 7,500 pounds or less that beginand end at the same airport, and are conducted within a 25 statute mile radius of that airport[/_landings/pages/].Part 121 operators conducting domestic or flag operations must have sufficient dispatch centers locat-ed at points necessary to ensure proper operational control of each flight. Weather service requirementsunder Part 121 are extensive. FAR 121.101 states in part: “domestic or flag operations must show thatenough weather reporting services are available along each route to ensure weather reports and fore-casts necessary for the operation. Except as provided in paragraph of this section, no certificate holderconducting domestic or flag operations may use any weather report to control flight [FAR 121.101,DOT].23
2.4.2 Aviation Weather Support Systems and Products2.4.2.1 FAA’s Support SystemsGenerally, The current system which provides weather information to the aviation community is a part-nership between the FAA and the National Oceanic and Atmospheric Administration (NOAA). Asmentioned before, an aircraft’s flight can be grouped into three regions: en-route, in the terminal area,and on the ground. The national air traffic control system has been designed to support the specificneeds of these regions of flight.
En-routeThe Air Route Traffic Control Centers (ARTCCs) provide airspace management to aircraft operatingunder IFR flight plans. A Center Weather Service Unit (CWSU), composed of both National WeatherService meteorologists and FAA support personnel, is associated with each of the ARTCCs. Theweather service units provide up-to-date weather information based on analysis of weather productsobtained from a number of different the Terminal Area and on the GroundThe terminal area and ground are managed by the Airport Traffic Control Tower (ATCT). Weather in-formation is provided to the tower from a number of sources. In turn, the tower serves as one potentialsource of weather information for arriving and departing aircraft. At some airports, an automated sys-tem is in place to provide up-to-date weather information to arriving and departing pilots. This auto-mated system is termed the automatic terminal information service.
OthersAnother component of the FAA weather information support system is the FAA Flight Service Stations(FSSs) and the Automated Flight Service Stations (AFSSs). FSSs and AFSSs provide pilots with pre-flight weather briefings, flight planning assistance, weather and en-route flight information, and airportterminal advisory services.24
2.4.2.2 NOAA’s Support SystemsSupport CentersThe NWS, under the NOAA, measures, analyzes, forecasts, and distributes weather information to thedifferent FAA centers and to pilots as official FAA approved weather products. The NWS is organizedinto a number of offices and centers which serve the meteorological and hydrological needs of the na-tion. Four centers of the NWS that provide direct information to the aviation community. They are Na-tional Center Operations, Storm Prediction Center, Aviation Weather Center, and Tropical PredictionCenter [NOAA, 2000].
Another agency under NOAA that provides weather information to the aviationcommunity is the National Environmental Satellite, Data, and Information Service (NESDIS). NES-DIS provides satellite images of the atmosphere, which are used in modeling and r Forecast Models
The National Centers for Environmental Prediction (NCEP) supports several mesoscale models. A fewof the current and future models are described here. The Eta-32 model produces 48 hour forecast twicea day at 0000 and 1200 UTC, a 33 hour forecast at 0300 UTC, and a 30 hour forecast at 1800 UTC[/nwplessons/etalesson2/]. In support of shorter range forecast, theNCEP supports the Rapid Update Cycle (version 2) (RUC-2) model. The RUC forecasts are unique inthat they are initialized with very recent data. The RUC-2 produces updated forecast every hour [/]. A third mesoscale model that has found acceptance in the mod-eling community is the fifth-generation National Center for Atmospheric Research (NCAR)/PennState Mesoscale Model (MM5). This mesoscale model is a limited-area, nonhydrostatic or hydrostaticterrain-following sigma-coordinate model designed to simulate or predict mesoscale and regional-scale atmospheric circulation [/mm5/]. The NCEP is alsocurrently overseeing the development of the next generation in mesoscale modeling termed the Weath-er Research and Forecast (WRF) model. This collaborative effort is scheduled to produce a product bythe end of 2003. The model will provide a common tool for both research and operations [/mmb/wrf//m].The NWS also has Weather Forecast Offices (WFO) located in each state. The NWS WFO provides25
up-to-date information on weather in its assigned region and route forecast and terminal area forecast.
2.4.2.3 Weather productsWeather products are defined as information (measured data, processed data, forecasts) that have beenpackaged for interpretation by the recipient to aid in making both strategic and tactical decisions af-fecting aviation safety. Table 2-1 contains a listing and brief description of 23 weather products.
For the en-route phases of flight, weather products may provide information on atmospheric eventsthat are affecting a very large area or the weather product may address events on a much smaller scaleor along a specific route. For example, the Aviation Routine Weather Report
(AIRMETs) and
Signifi-cant Meteorological Information (SIGMETs) are in-flight advisories provided by the Aviation WeatherCenter which warn
pilots of hazardous conditions that are affecting or will be affecting an area of atleast 3,000 square miles at any one instant in time. Route Forecasts (RF), issued by the NWS WeatherForecast Offices (WFO), provide pilots forecast information for more than 200 specific routes over thecontiguous United States. Weather products also are designed to provide pilots with information thatis very location specific. For example, the pilot reports (PIREPS) are issued by pilots who have expe-rienced adverse weather conditions in flight. This information provides other pilots with a snap shot ofpotential adverse conditions that may lie along his route2.4.3 Aviation Weather Product DeficienciesThere are four key areas that contain components that are deficient in some qualitative way. The keyareas are data format, support systems, sensors, and forecasting and FormatThe utility of a weather product, in many cases, depends on the delivery system’s ability to provide theinformation in a timely manner and in a format that can be easily interpreted. With the amount of in-formation and the format of some of the information (e.g., radar products) currently available to thepilot, a graphical display is needed to reduce the pilot’s workload and to aid in the interpretive , a coordinate overlay with hazard areas defined).26
Table 2.1 Aviation Weather ProductsNumber223Aviation Routine Weather Report (METAR)Aviation Selected Special Weather Report (SPECI)
Terminal Area Forecast (or Aerodrome Forecast) (TAF)
Area Forecasts (AF)Airman’s Meteorological Advisory (AIRMET)
Domestic Significant Meteorological Information (Domestic SIGMET)
Convective Significant Meteorological Information (Convective SIGMET)
International Significant Meteorological Information (International SIGMET)Low Level Significant Weather Charts (LLSWC)
High Level Significant Weather Charts (HLSWC)
Winds and Temperatures Aloft (WA and TA)
Route Forecast (RF)Meteorological Impact Statement (MIS)
Center Weather Advisory (CWA)
Severe Weather Watch (SWW)
Pilot Reports (PIREPS)
Satellite Imagery (SI)
Radiosonde Additional Data (RAD)
Convective Outlook (CO)Next Generation Weather Surveillance Radar (NEXRAD)
Terminal Doppler Weather Radar (TDWR)
Low Level Wind Shear Alert System (LLWAS)
Weather Systems Processor (WSP)
Names27
Support SystemThe FAA depends on the NWS to provide weather information that can be tailored to the needs of theaviation community. However, the NWS often provides weather information on a much coarser gridthan that required for aviation. The aviation community would like to continue to see weather productsthat are designed for aviation.
SensorsSensors were identified as having deficiencies in a number of areas. The deficiencies have beengrouped into five categories: lack of availability, lack of confidence, loss of capability, lack of capabil-ity, and required tuning.
Forecasting and ModelingThe fourth area where deficiencies have been identified is the area of forecasted weather products. Me-soscale modeling is required to forecast winds and temperatures aloft. However, the model’s forecastproducts are a function of the model’s fidelity and the sensor data input to the model.
2.4.4 Aviation Weather Information and Bandwidth Requirement ModelThere are many existing weather forecast models which can produce many aviation weather productsas described earlier in this dissertation and some research projects related to the analysis of aviationweather information. However, there is no existing model to examine aviation weather information andbandwidth requirements combining the volume of air traffic at each phase of flight in three flight re-gions. It is necessary for aviation industry to determine the quantity of aviation weather informationtransmitted between pilots and the ground service centers so that aviation industry could build a effi-cient and timely communication system with minimum budget in the future. This is very new areaneeded to be explored and developed.2.5 Aviation Weather Communication SystemsCommunication systems carry information such as weather information between ground stations and28
aircraft, and among aircraft themselves. They constitute a very important element in the navigation,ATC and safety aspects of aviation.
2.5.1 Terminal RegionPilots may receive weather and forecast information from a number of different sources. The Automat-ed Weather Observing System (AWOS) and Automated Surface Observation System (ASOS) broad-cast local weather information directly to pilots via discrete very high frequency (VHF) transmissionsor as the voice portion of a local navigational aid (NAVAID). The Automatic Terminal InformationService (ATIS) is a continuous broadcast of recorded weather and runway conditions of importance toarriving and departing aircraft. ATIS is also broadcast over discrete VHF radio channels or the voiceportion of a local NAVAID. The Aircraft Communications Addressing and Reporting System (AC-ARS) is a VHF air/ground datalink that relays weather information to the cockpit in a digital Terminal Weather Information for Pilots (TWIP) and the Digital Automated Terminal Informa-tion Service (D-ATIS) are available through ACARS.
2.5.2 En-route RegionPilots have direct access to weather information and flight planning assistance via the FSSs and AF-SSs. If available, an En-route Flight Advisory Service (EFAS) (Flight Watch) provides weather up-dates and advisories by providing pilots direct access to weather specialists. FSSs, AFSSs and EFASsall transmit data directly over VHF radio. For short or local flights, pilots can use the TranscribedWeather Broadcast (TWEB), which provides continuous, up-to-date, recorded weather can also receive or request weather information directly from their operation centers over VHFradio through ACARS. The ARTCCs are capable of direct communications with IFR air traffic on spe-cific frequencies. If hazardous weather conditions develop, pilots will be advised to tune into the Haz-ardous In-Flight Weather Advisory Service (HIWAS) for a continuous broadcast of recorded in-flightweather advisories. For oceanic flights, pilots can receive updated weather information via Lockheed Martin report [Ball, J. W., et al.,
1999] provides additional information into the current29
set of delivery systems.A number of systems have been developed to provide pilots with the latest weather information. How-ever, the majority of these systems require the pilot to manually request information. In some cases,the pilot may not know what information to request since conditions may have changed considerablysince initiating flight. For all of the delivery systems, except ACARS, voice is the only means of re-ceiving information during flight. For the high-end aircraft, ACARS provides the capability to supportboth text and ly, the FAA seems to be moving in a direction that will support information presentation to thepilot in a graphical format, making it easier to interpret and making possible additional information toaid the pilot in making both strategic and tactical decisions.2.6 Aviation Weather Economic Impact
All the deleterious effects of weather ultimately affect the operating economy of aviation-based enter-prises, especially that of commercial air carriers. The most visible item of financial loss in an air disas-ter is due to the loss of aircraft and the subsequent cost of replacement which may run into hundredsof millions of dollars in single instances in the case of modern airliners (as also transport aircraft andhigh-end military aircraft). Other important items of cost associated with airline accidents arise frompossible damage to ground facilities and other public and private property, increased cost of insurance,accident investigation, litigation, and compensation to crew and passengers. In addition to these directand/or closely connected costs, accidents also involve consequential or social costs which may bemany times higher. Loss of life in accidents results in social and commercial dislocation, and loss ofimportant cargo can have severe consequential implications. This effect is even more severe in rela-tively poor economies where the privilege of air travel and transportation is reserved essentially for themost important people and cargo. Passenger discomfort and poor schedule-keeping also result in highlevels of direct and consequential costs. Bumpy flights lead to the erosion of passenger confidence andpreference for specific airlines or air routes, or for air travel in general. In extreme cases, bumpy flightscan cause injury to passengers and damage to their belongings even if the aircraft as a whole may not30
be economic implications of poor schedule-keeping are even more severe for airlines. Significant de-lays in takeoffs and landings lead to revenue loss due to the reduced number of operations. They alsoresult in low aircraft utilization factors, necessitating larger capital and recurring expenditures formaintaining a given level of airline operation. Further, unscheduled delays on the part of passengerslead to individual schedule disruption and loss of productivity. In the modern hub-and-spoke model ofairline operations, where given pairs of points are often connected through multiple flights, delays inone leg usually get compounded by more missed flights, which further amplifies consequent ATA estimates that the loss of productivity caused by delayed flights at 6 billion dollars in 2000alone. As mentioned before, a majority of flight delays are usually caused by costs incurred due to loss of aviation system efficiency are equally serious. The most significantways in which weather affects aviation efficiency are related to aircraft route modification to avoidhazardous weather zones and partial or total shutdown of airports for landing and takeoff ion of flight paths to skirt hazardous weather entails consumption of additional fuel and loss oftime. Airport or runway closure often necessitates in-flight holding of aircraft for considerable periods,again leading to wastage of fuel and time. The loss is much higher when the closure of airports or run-ways forces flights to be diverted to different airports , the most significant bottleneck in improving the traffic handling capacity of air traffic controlsystems is due to the reduction in capacity of airports occurring under instrument flight rule (IFR) con-ditions. It has been estimated that benefits of 3.5 billion dollars can be obtained through a modest in-crease of 16% in the IFR terminal capacity in the US [Evans, 1991]. A large part of this gain is throughsavings in petroleum products, which is a nonrenewable resource. A major contribution to these gainscan come from proper weather information made available in a timely manner.31
CHAPTER 3
Systems Approach and
Methodology“The system approach is the modus operandi of dealing with complex system. It is holistic in scope,creative in manner and rational in execution. Thus, it is based on looking at a total activity, project,design or system, rather than considering the efficiency of the component tasks independently. It is in-novative, in that rather than seeking modifications of older solutions to similar problems, new problemdefinitions are sought, new alternative solutions generated and new measures of evaluation are em-ployed if necessary” [Drew, 1995].A methodology is a system of rules which guides scientific inquiry. A methodology is usually com-prised of procedures (orders of action for defining problems in terms of variables), tools, or elementsof communication in the form of verbal, graphical and mathematical constructs, that aid in the execu-tion to “models” representing the problems. A model is an idealized representation of reality developedwith the aid of a methodology. Three components of a methodology for creating and utilizing a modelare: (1) a substantive component which specifies how the model’s variables and relations are selected(2) a set of criteria that can be used to determine whether the results generated by the model are accept-able; and (3) a scheme for structuring and manipulating the model for performing policy analysis[Drew, 1995].32
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