jimmy r. snow commissioning the wide area augmentation system
TRANSCRIPT
Jimmy R. Snow
COMMISSIONING THE WIDE AREA AUGMENTATION
SYSTEM
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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
LPV Takes Advantage of WAAS Capability
Equivalent to Localizer Lateral With Vertical Between ILS and LNAV/VNAV, HAT 250 ft & Up
LNAV/VNAV Vertically Guided Approach With Decreasing Vertical Obstruction Clearance, HAT 350 ftand Up
LNAV Non-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 FAAGPS Procedures (9/22/03)
Year 97 98 99 00 01 02 03
GPS Proc Published 573 516 531 504 447 618 510
TOTAL
LPV 7
LNAV/VNAV Published 613
LNAV Published 3,237
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 VNAVo Obstacle Evaluationo Standard Instrument Approach Procedure (Section 214)o Procedure Design (Database, Waypoints, Accuracy)o Electromagnetic Spectrum (RFI)
WAAS LNAV/VNAVo Obstacle Evaluationo Standard Instrument Approach Procedureo Procedure Designo Electromagnetic Spectrum o 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
o At Least One WAAS GEO is More Than 10 Degrees Above the Horizono 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
10 nm 30 nm
MountRanier
(14,400 ft)
4.5°ARP (Sea Level) FAF (Sea Level)
Geo
10° (minimum)
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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
TERRAIN MASKING:Results
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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
VALIDATION EFFORTS
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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
o 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
Site HPL
Meters
VPL
Meters
XTK
Error
Feet
ATK
Error
Feet
SNR Below Path SNR
Worst
SNR
KFDR 23 16.7 22.4 -3 -8 41 42 39KCHK 16L 14.2 23.2 -4 -3 42 42 40KTYO 17 14.5 19.9 3 -7 41 42 40KGAI 14 16.5 21.1 6 0 41 41 41KOKC 17R 12 21.5 -3 7 40 41 40KOKC 35R 10.5 19 1 -6 40 40 40KOSH 36 12.6 18.6 4 -17 40 41 38
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WAAS Approach
ILS Glideslope
ILS vs WAAS LPVFlight Inspection Comparison
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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 3AOR/W
54W
INMARSAT 3POR178E
INMARSAT III COVERAGE
