Continuous Descent Approach (CDA) Modeling...

Federal AviationAdministrationAviation Environmental

Design Tool (AEDT)

Continuous Descent Approach

(CDA) Modeling Demonstration

Presented to: TRB AEDT/APMT Workshop #4

By: Eric Dinges

Date: 6-8 December 2006

2 2Federal AviationAdministration

CDA Modeling DemonstrationDecember 6-8, 2006

What is a CDA?• Continuous Descent Approach (CDA):

– An optimized approach procedure where the aircraft descends continually at idle thrust from cruise to landing.

– Actual procedures and trajectories dependent upon aircraft performance, aircraft equipage, and local airspace considerations

NonNon--CDACDA

CDACDA



Motivation• FAA/PARTNER Center of Excellence sponsors research in

Continuous Descent Approach (CDA) Operational Studies:

– Quantified Environment Effects in 2002 Flight Test

– Air Traffic Control Operational Proofing in 2004 Flight Test

– Demonstrations Identified Reduced Noise, Fuel Burn, Engine Emission and Time savings (Louisville CDA study: Report No. PARTNER-COE-2005-002, January 2006)

• Modeling CDA offers an alternative aircraft operational flight procedure for targeted environmental mitigation.

• Establishing this capability in AEDT allows for: – modeling real-world, wide-scale environmental benefits– projecting cost/benefits of future CDA implementation



Typically Modeled vs. Actual Approach Profiles

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Approach Routes

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nautical miles

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CDA Demonstration Development

Define Initial Methodology

Develop Initial Analysis Capability

for One Airport

Acquire Data for One Airport

Analyze Trajectory Output and

Refine Method

Perform Coordinated

Noise/Emissions Analysis

Analyze Applicability at

Multiple Airports

• Capability Demonstration is still underway:



Assumptions

• Limited initial airport study :– Operations and trajectories derived from 3 days of radar data

– Only one operating configuration modeled

– Only Approach operations modeled

– Hypothetical CDA trajectory assumed

– Assumed CDAs can be implemented across all approach routes

– Assumed CDA implementation levels determined by traffic levels

• Ongoing/future rounds of analyses will include expanded scope



Baseline Approach Profiles

• Radar is the best widely available data source for current baseline approach trajectories

• Requires derivation of thrust levels in order to be used for environmental modeling– No standardized method exists

– Requires aircraft performance data that is missing from available databases for several important aircraft

• Society of Automotive Engineers (SAE) A21 committee has recently formed a Project Working Team to address the issue– Current CDA Demonstration methodology to serve as the basis

for guidance document development



CDA Approach Profiles• CDAs assumed to follow constant 3-deg glide slope with

aircraft type-specific speed schedules observed from Straight-In approaches

• Future analyses will use actual observed CDA profiles

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Scenario Percentage

of Operations Flying CDAs

Baseline 0.0

Threshold 1 5.9

Threshold 2 21.0

Threshold 3 42.9

Threshold 4 67.3

All-CDA 100.0

CDA Implementation Levels

• Realistic CDA implementation levels are currently undefined for most airports

• Six scenarios ranging from current baseline to all-CDA operations were modeled using traffic flow thresholds

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1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 9615-Minute Time Interval (1 = Midnight Local Time)

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Flight Path Dispersion

• Goal is to make CDA modeling capability available for Local Legacy analyses

• Requiring every actual radar trajectory to define baseline conditions can be impractical– Computationally prohibitive for Local analyses– Historical radar data does not allow for projecting

flight paths and operational levels into the future– Large amounts of high-resolution radar data may not

always be available

• Horizontal and vertical dispersion simplify modeled trajectories and allow profile trends to be projected into the future



Horizontal Dispersion

• Common practice in INM studies

• Recommended practice included in ECAC-Doc 29

• Automated for AEDT

10 Nautical Miles

Runway

Radar track

Dispersed trackCluster boundary



Vertical Dispersion

• More challenging than horizontal dispersion as vertical position trends more heavily impact aircraft thrust, noise, fuel burn and emissions

• Difficulty is in simplifying vertical profiles without washing-out key characteristics like level segments

• Various automated methods are being created and evaluated for use in baseline modeling



Vertical Dispersion 1

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-- 1.56%

-- 9.38%

-- 23.44%

-- 31.24%

-- 23.44%

-- 9.38%

-- 1.56%

• Average altitude vs. distance per population group

• Smoothes over level segments




-- 6.50%

-- 24.00%

-- 39.00%

-- 24.00%

-- 6.50%

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• One level altitude per weight class and route

• Unique level distance per population group

• Total level distance retained but altitude of level segments changed




-- % varies by weight class/ route

• Binned level altitudes, average level distance

•Total level distance retained, altitude of level segments remains consistent

• Length distribution of level segments lost0

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Day-Night Average Noise Level (DNL) Contour Impacts

Radar Baseline All CDA

DNL = 45 dB 50

55

60



A-Weighted Sound Exposure Level (SEL) Grid Points• Grid points can help determine noise impacts of

both vertical profile and horizontal track differences per approach type

0 5NM

CDA Tracks

Grid Point

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CDA Tracks

Grid Point



SEL Comparisons

-10-9-8-7-6-5-4-3-2-10123456789

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Track Distance (nmi)

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ta d

B (

SE

L, d

B -

CD

A m

inu

s B

asel

ine

) Straight-In CenterlineStraight-In 4 nmi OffsetDownwind CenterlineDownwind 4 nmi OffsetSouthern CenterlineSouthern 4 nmi Offset



Fuel Burn and Emissions

% Change Relative to Baseline Emiss Straight-

In Downwind Southern

CO -8.7 -13.8 -26.7

THC -8.8 -11.0 -23.9 NMHC -8.8 -11.0 -23.9

VOC -8.8 -11.0 -23.9

NOx -18.1 -32.3 -51.8

SOx -14.7 -26.9 -46.1

CO2 -14.7 -26.9 -46.1

H2O -14.7 -26.9 -46.1

Fuel -14.7 -26.9 -46.1

10,000 ft AFE to Touchdown



Verification and Validation

• Modeling simplifications such as vertical dispersion need to be validated against results using all data at several airports

• Methods for calculating thrust from RADAR data can be enhanced and validated using Flight Data Recorder (FDR) information, preliminary efforts have already been completed– Comprehensive FDR data sets are being obtained

– SAE A-21 PWT efforts will directly support this



Current Limitations• Lack of CDA profile definitions

– Round 2 analysis currently underway using data observed from actual CDAs at the modeled airport to define flight paths

• Unknown CDA implementation issues– Changes to the airspace required for CDAs not accounted for

• Limited operations data set– Round 2 analysis currently underway using a larger radar data

set from throughout the year• Limited aircraft performance data

– EUROCONTROL currently working with Airbus to supply necessary data for entire Airbus fleet, FAA working on additional Boeing data

• Limited use of wind data– Need to balance accuracy requirements vs. publicly available

wind data sources



Context for AEDT

• Baseline and CDA operations definitions and trajectories developed for the CDA Demonstration are usable across AEDT and legacy models

• Methodology applicable to modeling other alternative flight procedures

• Radar analysis capabilities developed for the CDA Demonstration can support PARTNER efforts related to CDA implementation, JPDO efforts, and other AEDT efforts related to operations mitigation

• Automated aircraft identification and horizontal/vertical dispersion methods available for legacy analyses to improve standardization across modelers



Summary• New modeling methods being developed and applied

– Methods still being refined and require validation

– Working in conjunction with technical groups such as SAE A21

• Limited scope analysis completed– Limited radar data set

– Only one operating configuration

– Only approach operations

• CDA benefits vary greatly across approach routes

• Analysis scope will be increased and repeated at multiple airports



Next Steps

• Obtain and incorporate additional aircraft performance data

• Support development of and incorporate standardized methodology for deriving thrust from aircraft position data

• Develop guidance on appropriate vertical dispersion techniques

• Evaluate CDA Demonstration methodology at a number of airports

• Develop method for concurrent display of noise and emissions results

• Perform significant validation work on any new computational methods developed



??? Questions ???

FAA Environmental Tools web site:

http://www.faa.gov/about/office_org/headquarters_offices/aep/models/

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