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COMMISSIONING THE WIDE AREA AUGMENTATION SYSTEM. Jimmy R. Snow. OVERVIEW. WAAS System/Procedures WAAS Commissioning Considerations Ohio University Study MITRE Computer Modeling MITRE/Flight Inspection Validation WAAS Receiver WAAS Limitations Future Challenges.

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COMMISSIONING THE WIDE AREA AUGMENTATION SYSTEM

Jimmy R. Snow


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OVERVIEW

  • WAAS System/Procedures

  • WAAS Commissioning Considerations

  • Ohio University Study

  • MITRE Computer Modeling

  • MITRE/Flight Inspection Validation

  • WAAS Receiver

  • WAAS Limitations

  • Future Challenges


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GNSS RNAV PROCEDURES

LPVTakes Advantage of WAAS Capability

Equivalent to Localizer Lateral With Vertical Between ILS and LNAV/VNAV, HAT 250 ft & Up

LNAV/VNAVVertically Guided Approach With Decreasing Vertical Obstruction Clearance, HAT 350 ftand Up

LNAVNon-Precision Approach With 250 ft ROC, Smaller Protected Area Than VOR, No Vertical Guidance

CIRCLING Approach Procedure to a runway and then

Maneuver to Land on Another Runway


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Status Of FAA

GPS Procedures (9/22/03)

Year97 98 99 00 01 0203

GPS Proc Published 573 516 531 504 447 618 510

TOTAL

LPV 7

LNAV/VNAV Published 613

LNAV Published3,237

Military/Specials 237

GPS Proc Published 4,094


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WAAS COMMISSIONINGCONSIDERATIONS

  • WAAS Commissioning Date Established Approximately Two Years in Advance

  • Scheduled on Procedures Publication Date, July 10, 2003

  • Estimated Over 600 LNAV/VNAV Approaches Published for FMS Baro VNAV Operations

  • Over 3,000 LNAV Approaches Published for TSO C-129 Receivers

  • Very Limited WAAS Flight Inspection Capability (Prototype MMR Receiver in Lear 60)

  • Technical Center WAAS Coverage Chart and Outage Records Used to Restrict Certain LNAV/VNAV Approaches

  • Numerous Discussions With Certification and Flight Standards


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WAAS COMMISSIONING OPTIONS

  • No Flight Inspection or Evaluation of Procedures

  • Evaluate Each Procedure on Next Periodic (One and Half Years or Longer to Evaluate All)

  • Surge Effort After WAAS IOC (up to 1,000 Flight Hours)

  • Non-Traditional Evaluation of Existing Procedures


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OHIO UNIVERSITY SUPPORT

  • Initiated Discussions With Ohio University, Avionics Engineering Center May 2001

  • Established Procedure Parameters With FAA Working Group

  • Held Discussions With Ohio University to Evaluate WAAS Requirements

  • Established a Technical Task Directive With Ohio University July 2001 to Evaluate WAAS Commissioning Requirements

  • Study Delivery Not Later Than Nine Months After Task Signed


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FLIGHT INSPECTION COMPARISON

  • GPS/Baro VNAV

    • Obstacle Evaluation

    • Standard Instrument Approach Procedure (Section 214)

    • Procedure Design (Database, Waypoints, Accuracy)

    • Electromagnetic Spectrum (RFI)

  • WAAS LNAV/VNAV

    • Obstacle Evaluation

    • Standard Instrument Approach Procedure

    • Procedure Design

    • Electromagnetic Spectrum

    • Geosynchronous Satellite Signal


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OHIO UNIVERSITY CONCLUSIONS

  • Result

    • Inspection of GPS/Baro VNAV Procedures Should Accomplish All Anticipated WAAS LNAV/VNAV Requirements

    • EXCEPT Ensuring Adequate GEOSAT Signal Coverage

  • GEOSAT

    • Provides Integrity Information, and Differential Corrections

    • Without, WAAS Receiver Reverts to LNAV Only Capability

    • Thus, LNAV/VNAV Procedures Can Not Be Conducted


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OHIO UNIVERSITY STUDY ASSUMPTIONS

  • Assumptions

    • The inherent WAAS monitoring is capable of detecting system faults within the required time-to-alarm

    • The WAAS receiver reverts to a GPS-only capability in the absence of a GEOSAT signal

    • The FAA has authorized WAAS for supporting LNAV/VNAV approach procedures

    • The SIAP procedure has been previously commissioned for GPS/Baro VNAV

    • The availability of GPS/Baro VNAV and WAAS LNAV/VNAV is at least 95 percent

    • The descent altitude is the same for the WAAS LNAV/VNAV and GPS/Baro VNAV procedures

    • There is a high-correlation between predicted (monitoring) and actual WAAS system performance


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STUDY CONCLUSIONS

  • ~ 600 GPS/Baro VNAV Procedures Expected to be Commissioned Before WAAS IOC

  • Inspection of GPS/Baro VNAV Procedures Should Accomplish All Anticipated WAAS LNAV/VNAV Requirements EXCEPT Ensuring Adequate GEOSAT Signal Coverage

  • Computer-based GEOSAT Coverage Screening Models May be Used to Streamline Flight Inspection Process (To determine if GEOSAT is shadowed on final approach segment)


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STUDY RECOMMENDATIONS (1)

  • The Comparison of GPS/Baro VNAV and WAAS LNAV/VNAV Flight Inspection Requirements Should Be Repeated Once Formal Criteria Are Available in FAA Order 8200

  • The Feasibility and Benefit of Developing a Screening Model for Assessing GEOSAT Signal Coverage Should Be Assessed Further

  • Low Confidence Cases, the WAAS LNAV/VNAV Procedure Should Be Flight Inspected Before Being Authorized for Use,Low Priority


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STUDY RECOMMENDATIONS (2)

  • Marginal Confidence Cases, the WAAS LNAV/VNAV Procedure Should Be Flight Inspected Before Being Authorized for Use, High Priority

  • High Confidence Cases, WAAS LNAV/VNAV Operations Authorized and Inspection Performed During Next Periodic Inspection of GPS/Baro VNAV Procedure

  • For WAAS Procedures Authorized Prior to Formal Flight Inspection, Authorization Should Be Withdrawn if a “Problem Report” Is Received


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SECOND PHASECOMPUTER MODELING

  • FAA Contacted MITRE, Center for Advanced Aviation System Development For Assistance (CAASD)

  • MITRE Advised They Could Modify an Existing Software Program to Do What Ohio University Recommended

  • Meetings Were Scheduled to Discuss:

    • Establishing an Agreement Between FAA and MITRE

    • Delivery Schedules

    • Evaluation Requirements

    • Data Requirements


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FAA-MITRE AGREEMENT

  • AVN Would Provide MITRE the Following:

    • Airport Identifier

    • Airport Reference Point (latitude/Longitude)

    • Airport Elevation

    • Airport Priority for Screening

    • If Available Airport Name and Location

  • MITRE Will Evaluate Each Airport Using the Following Criteria:

    • Evaluate a point 250 ft Above the ARP From 090 to 270 Degrees

      • At Least One WAAS GEO is More Than 10 Degrees Above the Horizon

      • No Terrain Within 40 nm of the ARP More Than 5-deg Elevation Angle Viewed From 250 ft Above the ARP

    • MITRE Would Use Worst-case WAAS GEO Positions

    • MITRE Would Validate the Computer Model and Peer Review Results


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Elevation Angles in USA and Canada(POR and AOR-W)


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TERRAIN MASKING:Forty Nautical Miles

Geo

Mount

Ranier

(14,400 ft)

10° (minimum)

ARP (Sea Level)

FAF (Sea Level)

4.5°

10 nm

30 nm


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TERRAIN MASKING:Results

  • An Airport Passing the Screening Test Will Not Have Geo Masking Due to Terrain and Should Not Require Re-flight Check For Terrain

    • A detailed look at the airport is not required

  • Failure of the Screening Does Not Necessarily Imply That GEO Masking Will Occur During an Approach to that Airport

    • Failure implies that a closer look at the airport is warranted

  • Availability of LNAV/VNAV Approaches Was Not Addressed


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VALIDATION EFFORTS

  • AVN Airport Database Entries Were Compared With

    Jeppesen and Other Databases

  • GEO Angles Were Computed by Several Methods With No

    Significant Differences Between Methods

  • Terrain Masking Code Was Checked Independently

  • Terrain Results Were Spot Checked With Sectional Charts

  • AVN Will Spot Check Some Airports During a Later

    Validation Check


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AIRPORT GROUP ONESummary

  • 223 Total Airports With RNAV (LNAV/VNAV) Approaches Developed by AVN

  • 215 Airports Passed Screening

    • GEO > 10 Degrees Elevation and

    • Terrain to South < 5 Degrees Elevation

  • 8 Airports Failed Screening

    • 3 Failed for Terrain

    • 5 Failed for GEO Elevation

      • 3 in Northern Alaska


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AIRPORT GROUP TWOSummary

  • 155 Total Airports With RNAV (LNAV/VNAV) Approaches Planned by AVN

  • 142 Airports Passed Screening

    • GEO > 10 Degrees Elevation and

    • Terrain to South < 5 Degrees Elevation

  • 13 Airports Failed Screening

    • 12 Failed for Terrain

    • 1 Failed for GEO Elevation


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AVN VALIDATION

  • MITRE Evaluated 378 Airports/AVN Flight Inspected 65 Airports To Validate MITRE results

    • 11 of the 21 Identified by MITRE Did Not Have GEO Coverage

    • 2 Additional Airports of the 65 Would Not Support VNAV For Geo Coverage

  • AVN Accepted the Results As Satisfactory


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WAAS MMR RECEIVER

  • Have Six Collins MMR Receivers With WAAS and LAAS

  • Two Lear 60s Have WAAS Capability

  • Due to No TSO Receiver and No STC, Aircraft in Experimental Status

  • Currently in a MOPS “Beta” Configuration

  • With the FMS We Must Change the MMR Into “Delta” Configuration, Estimate 2 Years

  • LPV and LAAS Have FAS Datablock That the AFIS Reads

  • Aircraft Flying LNAV/VNAV While AFIS Evaluates LPV

  • New Contract Let to Complete VFR STC (estimate completion January 05)


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LPV

FLIGHT INSPECTION RESULTS


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ILS vs WAAS LPV

Flight Inspection Comparison

ILS Glideslope

WAAS Approach


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WAAS LIMITATIONS

  • Inverse W on RNAV Approach Charts/Limitations

    • Indicates WAAS Outages May Occur Daily (32 airports)

    • WAAS NOTAMS Are Not Provided For the Procedure

    • Use LNAV Minima For Flight Planning (Destination or

    • Alternate)

    • If Receiver Indicates LNAV/VNAV or LPV Available

    • Guidance May Be Used

    • If WAAS Is Lost Revert to LNAV Minima If Receiver

    • Allows or LNAV Data Is Available

  • WAAS VNAV NA on RNAV Charts That Did Not Pass

    MITRE Modeling and Flight Inspection


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INMARSAT 3

POR

178°E

INMARSAT 3

AOR/W

54°W

INMARSAT III COVERAGE


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Jimmy Snow

NAVIGATION CONSULTANT

405-249-4329

[email protected]


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