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16.72 Air Traffic Control Overview

Prof. R. John Hansman

MIT Department of Aeronautics and Astronautics

US Capacity Issue

Prior to 9/11 the US Air Transportation system is approaching a criticalsaturation threshold where nominal interruptions (e.g. weather) resulted in anonlinear amplification of delay

US and Regional Economies highly dependant on Air Transportation Business travel (stimulated by info technology)

Air Freight

Personal travel

System is highly complex and interdependent Need better understanding of system dynamics and real constraints to guide

and justify efforts to upgrade NAS Current efforts will not provide capacity to meet demand which will re-emerge

when the economy cycles up

Impact of upcoming capacity crisis is not well understood Operational Impact

Economic Impact

Similar Issues in Europe Different Issues in Emerging Regions (eg China, India)

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Passenger Traffic by Region

Scheduled Revenue Passenger-Kilometers by Region

1400

1200

1000

800

600

400

200

0

1970 1975 1980 1985 1990 1995 2000 2005

RP

K (b

illio

n)

North America

Europe

Asia and Pacific

Latin America & Caribbean

Middle East

Africa

Source: ICAO, scheduled services of commercial air carriers

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Trends in Aircraft Size A

vera

ge

seat

s p

er d

epar

ture

150

140

130

120

110

100

90

80

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

Source: DOT Form 41 data (including Regional Jets and Turboprops)

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US FlightUS DelaysFlight Delaysfrom 1995 tofrom 20061995 to 2006

Data source: FAA Operational Network (OPSNET)

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Flight Cancellations

Cancellations

Thousands 250

200

150

100

50

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

Source: BTS, Airline On Time Performance data

0

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US FlightUS DelaysFlight Delaysfrom 2000 tofrom 20062000 to 2006

Source: FAA OPSNET data

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Delays at Chicago OHarePressure for Demand Managment

ORD: Total Delays

0

2000

4000

6000

8000

10000

12000

14000

16000

To

tal D

elay

s 2004

2003

2002

2001

2000

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month

Source: FAA OPSNET data

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1980 198

2 198

4 198

6 198

8 199

0 199

2 199

4 199

6 199

8 200

0

2000

2002

20

04

Consumer complaints

0

5

10

15

20

25

Com

plai

nts

to t

he D

OT

(00

0) Southwest

USAirways United TWA Northwest America West Delta Continental Alaska American

Note: Year 2005 consumer complaints is an extrapolation using data from Jan-Mar 2005

Data source: DOT Aviation Consumer Protection Division, available at: http://airconsumer.ost.dot.gov/

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Air Traffic Control Functions

Aircraft Separation Assurance

Traffic Congestion Management

Flight Information

Search and Rescue

Example of a Command, Control and Information System

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COMPONENTS OF AIR TRANSPORTATION INFRASTRUCTURE

Airports Runways Terminals Ground transport interface Servicing Maintenance

Air traffic management Communications

Navigation

Surveillance

Control

Weather Observation

Forecasting

Dissemination

Skilled personnel

Cost recovery mechanism

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Current Control Structure

Surface Control Ground

Local Control Tower

Terminal Area Control (TRACON) Approach and Departure

Enroute Control (ARTCC) Center

Oceanic Control (FIR) Oceanic

Flow Control (ATCSCC) Central Flow

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US Air Route Traffic Control Center (ATRCC) Airspace - 20 Centers

ZSE ZMP

ZLC ZAU ZBW

ZOB ZDV ZNY

ZOA ZKC ZID ZDC

ZLA ZME ZAB ZFW

ZTL

ZJX

ZHU ZMA

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High Level Sectors257

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Low Level Sectors 378

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TRACONSMIT ICAT MIT

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Overall StructureMIT ICAT MIT

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ATM System CurrentFunctional Structure

Planning - Strategic Level

Sector Traffic

Planning

Aircraft StateAircraft Guidance and

Navigation

Sector Traffic Control

Traffic Sensor

Vectors

ClearancesPlanning

Approved Handoffs

Desired Sector Loads

Clearance Requests

Flight Planning

Weather

Filed

Negotiate < 5 min

Execution - Tactical Level

Pilot

Planned Flow Rates

Clearance Requests

AOC Schedule of Capacities

Approved Flight

National PlansFlow

Facility Flow

Planning

Flight

Plans

Flight

Schedule

Airline

hrs - day hrs 5-20 min 5 min Handoffs

CFMU TMU D-side R-side

Measurement

Real State Plan/Intent

Requests

AC State Sensor Other Aircraft

States

Efficiency Throughput Safety

Increasing Criticality Level

Source: A. Haraldsdottir Boeing

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ATC Control LooRadar Surveillance Limits

Vectors

Aircraft F light

M anagementC omp ute r

S tate

Flight PlanAmendments

Autop ilo tAuto thrust

MCP Controls

ATCF lightS trip s

Surveillance: Enroute: 12.0 s Terminal: 4.2 s

S tate C ommands

Tra jecto rC ommands

Initial Clearances

CDU

ADS : 1 sDisplays

AOC: Airline Operations Center

Pilot

DisplaysManual Control

Voice

ACARS (Datalink)

Decision Aids

N av igation

Emerging Approaches: ADS-B and Multi-Lateration

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Radar Display Example

CO 123 350C B757 310

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ATM is a Human Centered Process

Contract process Negotiation Execution Monitoring Re-negotiation/amendment

Agents Controllers

Strategic Tactical

Pilots

Airlines

Dispatchers ATC coordinators

Airports

Resources Airspace

Runway

Airport surfaces

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Flight Progress StripMIT ICAT MIT

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Human Factors and

Adaptation

ATM is a human centered contract process for the allocation ofairspace and airport surface resources.

Current NAS has evolved over 60 years

The system has significant local adaptations resulting innonhomogeneity Airspace design

Local procedures

Letters of agreement

Noise restrictions

Site specific training (FPL = 3-5 years)

Major operational changes were event driven, enabled btechnical capability Positive radar control - Grand Canyon 1956

TCAS - Los Cerritos 1982

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New York Arrival and Departure Tracks

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ATC Workload as a System Constraint

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Blocking

Air traffic controller

Blocking action

Controlled resource

Block the flow to maintain number of aircraft within the acceptable level (ex. Set by AAR or OALT)

Finite capacity buffer

AAR is Airport Acceptance Rate OALT is sector Operationally Acceptable Level of Traffic

Saturated resource

Number of aircraft threshold corresponding For example,

to, for example, AAR or rate set by

OALT, (varies depending AAR or OALT

on current conditions)

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Downstream Flow Constraints

Flow Management Capacity Constraint ex. Airport

Capacity Acceptance Constraint Rate (AAR)

Departure flow

Gates Ramp Taxiways Runways Terminal area and exit fixes

En route sector airspace

Destination airports

Gate Restrictions

ex. Sector Operationally Acceptable Level of Traffic (OALT)

Ramp Restrictions

Runway Restrictions

Taxi Restrictions Capacity

Constraint ex. Miles In Trail through exit fix

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12:19 p.m. 153 Aircraft In-bound

Dallas Fort-Worth

Aircraft are condensed into distinct flows feeding 4 arrival fixes.

June 20, 2001

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116 Aircraft In-bound

Atlanta

Condensation and merges have reduced 116 trajectories at airport to 4

ARTCC

Boundaries

Route

Flown

11:15 a.m. June 14, 2001

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78 Aircraft In-bound

San Francisco

Special use airspace provides additional constraints

Special Use

Airspace

Route

Flown

Flight Plan

June 11, 2001 4:13 p.m.

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Projected % DevelopmentalControllers

From: ATCS Workforce Plan Briefing

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Capacity Limit Factors

Demand Peak Demand

Hub & Spoke Networks

Airspace Capacity Airspace Design

Controller Workload

Balkanization

Airport Capacity Runways Gates Landside Limits (including Security) Weather

Environmental Limits Noise (relates to Airport) Emissions (local, Ozone, NOX, CO2)

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Airport SysteCapacity Limit Factors

Runways

Weather Capacity Variability

Convective Weather

Landside Limits Gates

Terminals & Security

Road Access

Downstream Constraints

Controller Workload Environmental

Community Noise

Emissions

Safety

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Arr

ival

s p

er H

ou

rA

rriv

als

per

Ho

ur

MITMIT Airport Capacity EnvelopeICATICAT Boston (BOS)

100

80

90

68,50VFR ASPM - Apr 2000 - Visual Approaches ASPM - Jul/Aug 2000 - Visual

ApproachesCalculated VMC Capacity

70 Optimum Rate (BOS)

60

50

40

30

20

10

0

0 10 20 30 40 50 60 70 80 90 100

Departures per Hour

100

IFR ASPM - Apr 2000 - Instrument Approaches 90 ASPM - Jul/Aug 2000 - Instrument Approaches Calculated IMC Capacity 80 Reduced Rate (BOS)

70

60

50 44,44

40

30

20

10

0

0 10 20 30 40 50 60 70 80 90 100

Departures per Hour Source: FAA Benchmark Data

Separation Requirements for

Arrival (Same Runway)

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Wake Turbulence Requirement Radar Separation requirements

Trailing Aircraft

Leading

Aircraft

Heavy Large Small Heavy 4 5 5 B757 4 4 5 Large 3(2.5) 3(2.5) 4 Small 3(2.5) 3(2.5) 3(2.5)

Visual Separation requirements Pilots Discretion

Preceding arrival must be clear of runway at touchdown Runway Occupancy time

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Variable Capacity Effects1995 Delays vs Operations

Data from FAA Capacity Office, CY95

0 200000 400000 600000 800000 1000000

Total Operations (CY95)

0

10

20

30

40

50

60

Dela

yed

Flig

hts

(per

100

0)

SFO

LGA EWR STL

LAX

ORD

DFW

ATL BOS

JFK

PHX

LAS

SJU

HNL PIT DEN

CLT

IAH

MEM

From John Andrews, MIT Lincoln Lab

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Safety vs CapacityMIT ICAT MIT ICAT

The current airborne system is extremely safe but conservative

Increased capacity with current infrastructure implies Reduced OperationalSeparation Airborne Separation Standards

Runway Occupancy Times

Wake Vortex

Controller Personal Buffers

...

How do you dependably predict the safety impact of changes in a complexinterdependent system? Statistics of small numbers

Differential analysis limited to small or isolated changes

Models??

Safety Veto Effect

Runway Incursions are an area of concern

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EN ROUTE MINIMA HAVE NOT

CHANGED DESPITE 5 x IMRPOVEMENT

IN RADAR PERFORMANCE

ARSR-1 ARSR-4 ASR-6 ASR-9 Mode A Mode S 0

20

40

60

80

100

120

Azim

uth

reso

lutio

n at

max

imum

rang

e as

% o

f en

rout

e m

inim

a 5 nm en route separation minima

1950

2000 1960

2000 1960

2000

1950 2000

Long range Medium range Medium range

primary radars primary radars secondary radars

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SEPARATION ASSURANCE CONSIDERATIONS

PERSONAL SURVEILLANCE SAFETY BUFFER UNCERTAINTY

MINIMUM

SEPARATION

STANDARD

PROCEDURAL HAZARD ZONESAFETY

BUFFER

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IMPROVED SURVEILLANCE HAS NOT LED TO REDUCED EN ROUTE MINIMA

WHEN STANDARDS IMPROVED SURVEILLANCE WERE DEVELOPED ENVIRONMENT

(e.g. 1950s for en route radar) (e.g. today for en route radar) Minimum

Separation

Standard

Surveillance has improved, but separation minima have not changed:procedural safety buffer has implicitly increased

Schedule FactorsMIT ICAT MIT ICAT

Peak Demand/Capacity issue driven (in part) by airline Hub and Spokescheduling behavior Peak demand often exceeds airport IFR capacity (VFR/IFR Limits) Depend on bank spreading and lulls to recover Hub and Spoke amplifies delay

Hub and spoke is an efficient network Supports weak demand markets

Schedules driven by competitive/market factors Operations respond to marketing

Trend to more frequent services, smaller aircraft

Ratchet behavior

Impact of regional jets

Ultimately, airlines will schedule rationally To delay tolerance of the market (delay homeostasis)

Limited federal or local mechanisms to regulate schedule

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MIT ICAT Hub and Spoke Network

Completely Connected Network = 2(N-1) Flights

(eg., 50 Airports, 98 Flights)

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MIT ICAT Fully Connected Network

Completely Connected Network = N(N-1)

(eg., 50 Airports, 2450 Flights)

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Capacity Exampl(50 Flights/hr)

70

60

50

40

30

20

10

0

Time

0

50

100

150

200

250

T ime

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Capacity Exampl(40 Flights/hr)

0

10

20

30

40

50

60

70

Time

250

200

150

100

50

0

T ime

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Capacity Exampl(30 Flights/hr)

0

50

100

150

200

250

T ime

0

10

20

30

40

50

60

70

Time

Classic Delay vs Demand

Curve

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DELAY

CapacityLimit

Linear Region

Non-Linear Region

DEMAND

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MIT ICAT LGA Air 21 Impact

LaGuardia Airport

0

20 40

60

80

100 120

140

160 180

200

06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Time of Day

Historic Movements AIR-21 Induced Svc.

Maximum Hourly Operations Based on Current Airspace & ATC Design

Source: William DeCota, Port Authority of New York

DELA

Y

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DEMAND

Capa

city

Lim

it

Source: William DeCota, Port Authority of New York

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Flight Delays at LGAFlight Delays at LGAfrom 2000 to 2006from 2000 to 2006

Source: FAA OPSNET data

Suggested Political

Solutions to Capacity Shortfall

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Full or Partial Privatization (eg AIR-21) May improve modernization,costs and strategic management

Limited impact on capacity

Re-regulation Increased Costs to Consumer

Demand Management (eg Peak Demand Pricing) Reduced service to weak markets

Need to insure that revenues go to improved capacity

Run System Tighter Requires improved CNS

Safety vs Capacity Trade

Build more capacity Local community resistance

Multi-modal transportation networks

ConclusionMIT ICAT MIT ICAT

Technology in Pipeline will have limited impact on peak Capacity atCurrently Stressed Airports 20% to 40% Optimistically

System will become (is) Capacity Restricted Airlines will Schedule in Response to Market Demand

Delay Homeostasis (at Hubs)

Increased Traffic at Secondary Airports

High Frequency Service

Changing Value for Reliability

Overall system response is not clear

Need Protection of Airport and Spectrum Resources

More runways in critical locations

New ATM paradigms

Need for leadership

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Multi-Stakeholder Considerations & Role of System Transition Plans

Demand Performance

Stakeholder Decisions

Transformative Actions

Change Process

Implementation

SystemCapability

Selected Actions

AggregateInefficiencyMetrics

Corrective Actions

Monitoring & Forecasting

Stakeholder Awareness or Perception Ai

Research and Development

Capabilities

Research Needs System Concepts

Road Map

Stakeholder Values Vi

Stakeholder Objectives Oi Stakeholder

Decisions Stakeholder Decisions

Stakeholder i Optimization

FAA>OEP JPDO > NGATS EU > CESARE

Focus is the OEP 35 airportsMIT ICAT MIT ICAT

More? Oakland Burbank Long Beach John Wayne-Orange County Tucson Albuquerque San Antonio Houston Hobby Palm Beach

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