The Modernized NASPAC Simulation Environment

Presented to: NAS-Wide Simulation & NextGen workshop

By: Kimberly Noonan, Joseph Post

Date: December 10th, 2008

Federal AviationAdministrationThe Modernized

NASPAC Simulation Environment

Federal AviationAdministration

2The Modernized NASPAC Simulation Environment10 December 2008

Your Father’s NASPAC

• The FAA’s standard system-wide model

• Originally developed in late 1980s

• Represents NAS as network of interconnected queues– Airports– TRACONs– En route sectors

• Discrete-event– SIMSCRIPT II.5– Fortran, C, Pascal pre-processors

• Sun Solaris platform

• Used mainly for investment analysis (i.e., cost-benefit analysis)

National Airspace System Performance Analysis Capability



Legacy NASPAC Environment

TAF = Terminal Area Forecast OAG = Official Airline GuideETMS = Enhanced Traffic Management System

OAG

TAF

TrajectoryBuilder

FixInserter

4DTrajectories

SectorCrossings

SectorEntry/Exit

Times CoreQueuingModel

OutputTraceFiles

SectorCapacities

Airport Capacities

SectorGeometries

FutureDemand

Generator

ETMS Routes

Flow Restrictions

ItineraryPurgeETMS



Objectives of Modernized NASPAC

Make available to more analysts and projects Maintain fast run time Incorporate traditional trajectory module

with fuel burn computation Automate airport weather scheduler Obtain modern, configuration-controlled, documented

source code Produce standard, analyst-friendly, repeatable output Validate• Develop GUI and output visualization tools• Facilitate Monte Carlo simulation



Modernized NASPAC Environment

Wx = weather

TAF = Terminal Area Forecast

MAP = Monitor Alert Parameter

ETMS = Enhanced Traffic Management System

Pareto Curves

MAP Values

Wx

ETMS

Flight Table

Airport Table

Sector Table

TAF

Fleet Evolution

UnconstrainedTraj.-Based

Forecast (2D)

ConstrainedTraj.-Based

Forecast (2D)

JavaTrajectory

Module

4DTrajectories

SectorCrossings

Sector Entry/ExitTimes

CoreQueuingModel

Delay Wx

SectorCapacities

Airport Capacities

UnsatisfiedDemand

CapacityScheduler

Legacy NASPAC

FutureScheduleGenerato

r

Flow Restrictions

OutputParser

ItineraryGeneration

Industry/RegulatoryResponse

WindField

SectorGeometries

Fuel Burn Rate

Δ Fuel Burn

FlightDelays

FleetForecast



Future Traffic Generation

Airport A Airport B

Airport C

Airport D2007ETMS

TAF

Airport A Airport B

Airport C

Airport D2010

Forecast

• FAA airport forecasts are unconstrained– Yield excessive and unrealistic future delays at some airports

• Estimated airport capacities used to constrain traffic growth– Mimic operator and FAA response to large demand and capacity

imbalances– Apply both schedule smoothing and trimming at 110 airports



Itinerary Generation

• Constrained schedule consists of ETMS flight legs– No tail numbers

• Create aircraft itineraries – Link flight legs with same airline and aircraft type– Minimize total fleet size, i.e. number of itineraries – Respect schedule turn time constraints

Min schedule turn time

Flight Leg arriving ATL

ATL

Flight Leg Departing ATL

Flight Leg Departing ATL

A

C

B



Fleet Evolution• Retire and replace aircraft with newer types

– minimize changes across seat-class/engine-type categories

• Consistent with APO and Mitre Fleet Forecast• Domestic passenger and cargo airlines only

Forecast by category (2008)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

% o

f T

ota

l Fle

et

T<20

T020-049

T050-099

T100-150

J020-049

J050-099

J100-150

J151-210

J211-300

J301-400

J401-500

J500-601

J



Java Trajectory Module

• Aircraft performance – BADA 3.6 tables

• Waypoints / cruise alt. – ETMS flight plan

• Arrival/departure fixes– Assigned to flight path

• Wind data – NCEP/NCAR

Global Reanalysis Model

• 4D track points computed at 1 min. intervals



Airspace Modeled939 airspace elements



OEP AirportsOther Airports

Airports Modeled• All IFR flights touching U.S. airspace are modeled

• Arrival/departure capacities for 110 airports included– All other airports assumed to have infinite capacity

• VFR flights at 73 airports included

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120

Departures (/hr)

Arr

lival

s (/

hr)

VMC

MMC

IMC

Washington Dulles InternationalAirport Capacities



Output Files

Airport Capacity File (airportc)

ATO-P Input Schedule

pre-configuration File

Sector Capacity File (sector_sim)

sim-configuration File

Arrival Trace File(t_arr)

Arrivals-Departures at Sink Trace File(t_snk)

At-Gate Trace File(t_agt)

Change Parameter File (change_apt)

Cross Arrival Fix-Departure Fix-Restriction Trace File(t_cnd)

Departure Trace File(t_dep)

Enter-Exit Sector Trace File(t_sec)

IFR Trajectories(traject)

JTM Bad Flights File

JTM Flight Map File

JTM Fuel Usage File

JTM Generate Itineraries Schedule

Pushback Trace File(t_pbk)

Flight

File

Airport

File

Sector

File

Oracle

Database

Perl

Scripts

Input Files

Output Files



Metrics• Flights accommodated

– Flight trimming process

• Delay– Gate push-back– Departure runway/fix queuing– Sector queuing– Arrival fix/runway queuing

• Fuel Burn– Origin to Destination– US airspace

• CO2– Jet A savings converted to CO2 using multiplier of 21.095 lb/gal



NASPAC Project Wiki



Validation Process

• Run simulation for eight historical days– Demand variation

• Two days per season (1 weekend, 1 weekday)– Weather variation

• Actual weather used for each day• Distribution of surface and en route weather

• Compute flight time, delay, fuel burn metrics

• Compare validation metrics to observed system response– Ground Truth ≡ ASPM, ASQP, BTS databases– Mean, variance– Pooled, pair-wise statistics

Every new software release validated!



Airborne Delay, Daily Observations

v5d

Airborne Delay, v5d

y = 8E-10x2.0557

y = 4E-09x1.8972

0.0

0.5

1.0

1.5

2.0

2.5

0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000

Flight Count

Av

g.

Air

bo

rne

De

lay

(m

in) ASPM

NASPAC

Power (NASPAC)

Power (ASPM)



OEP 35 Airports, v5d

y = 0.8636x + 0.6282

R2 = 0.3575

-6

-4

-2

0

2

4

6

8

10

0 2 4 6 8 10

NASPAC Airborne Delay (min)

AS

PM

Air

bo

rne

Del

ay (

min

)

Airborne Delay, OEP Airports

19 Oct. 2006 v5d

ORD

FLL



Taxi-Out Delay, Daily Observations

v5d

Taxi-Out Delay, v5d

0

1

2

3

4

5

6

7

8

9

0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000

Flight Count

Av

g.

Ta

xi-

Ou

t D

ela

y (

min

)

ASPM

NASPAC



Push-Back Delay

v5d

Push-Back Delay, v5d

y = 3.1782x + 4.1314

R2 = 0.0429

0

5

10

15

20

25

0 0.5 1 1.5 2 2.5 3 3.5

NASPAC Avg. Push-Back Delay (min)

AS

PM

Avg

. Pu

sh-B

ack

Del

ay (

min

)



ETE Distributions, 19 Oct. 2006

v5d

ETE Distribution, v5d

0

5

10

15

20

25

30

25 50 75 100

125

150

175

200

225

250

275

300

325

350

375

400

425

450

475

500

Estimated Time En Route (min)

Fre

qu

en

cy

(%)

NASPAC/JTM

ASPM



Airport Arrival Rate, 19 Oct. 2006

Charlotte-Douglas International Airport v5d

CLT Arrival Rates, 10/19/06, v5d

0

2

4

6

8

10

12

14

16

18

20

7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Local Hour (EDT)

Arr

iva

ls (

pe

r 1

5 m

in.

ep

oc

h)

NASPAC

ASPM



Fuel BurnDomestic Commercial Flights 1 10,843,220 Domestic Commercial Flights 3 10,563,035

Fuel 4

Nominal Taxi Out (gal) 310,763,808 2.3%

Excess Taxi Out (gal) 50,646,405 0.4%

Nominal Airborne (gal) 12,742,782,169 93.6%

Excess Airborne (gal) 315,232,694 2.3%

Nominal Taxi In (gal) 116,787,683 0.9%

Excess Descent (gal) 82,043,414 0.6%

Actual Fuel: Total 2 13,594,891,330 Model Fuel: Total 13,618,256,172 100.0%

Fuel per Flight

Nominal Taxi Out (gal / flt) 29 2.3%

Excess Taxi Out (gal / flt) 5 0.4%

Nominal Airborne (gal / flt) 1,206 93.6%

Excess Airborne (gal / flt) 30 2.3%

Nominal Taxi In (gal / flt) 11 0.9%

Excess Descent (gal / flt) 5 7.8 0.6%

Actual Fuel: per Flight 1,254 Model Fuel: per Flight 1,289.2 100.0%

Notes:

1. Sum total of revenue departures in domestic service, reported by U.S. carriers filing DOT Form 41, Table T-1

2. Gallons of fuel used in domestic service, reported by U.S. carriers filing DOT Form 41, Table P-12a

3. Domestic flights, excluding the categories of "Fractional / Business", "GA", and "Military"

4. Nominal fuel use taken from ATO's JTM trajectory modeler.

Excess fuel used on taxi and enroute derived by multiplying minutes of NASPAC delays times BADA or ICAO fuel burn

Excess fuel used on descent taken from estimates of below-cruise vertical holding on domestic flights arriving at the OEP 35 airports

5. Excess minutes per flight on descent is the ratio of the excess time at the OEP airports to the number of total domestic flights.

FY 2007 Actual Fuel Usage FY 2007 Modeled Fuel Usage

2.8% diff.



Conclusions

• Modernized model runs much faster, accessible to more users, and easier to use

• Deterministic trajectory model provides easy means of specifying flight trajectories– Uses standard Eurocontrol BADA data– Fuel burn computation integrated into trajectory model– Accommodates wind field– Achieves good accuracy in nominal flight time and fuel burn

• Airborne delays close to observed values

• Surface delays appear underestimated



Next Steps

• Evolve International carrier fleet

• Enhance airport capacity model– Incorporate additional airport pareto curves based on

alternative configurations and/or wind conditions

• Improve taxi-out delay– Update departure fix en trail constraints

• Incorporate Traffic Flow Management (TFM)– Ground Delay Programs

• Include Monte Carlo simulation capability

• Validation, validation, validation



Questions?

The Modernized NASPAC Simulation Environment

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