WAAS OVERVIEW-Honeywell.pdf

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approach capability: Space-based (SBAS), Ground-based (GBAS), and Aircraft-Based (ABAS) Augmentation

Systems. The FAAs WAAS program is an example of a SBAS architecture, and the FAAs LAAS program is an

example of a GBAS architecture. ABAS refers to augmentation methods that rely upon multiple aircraft sensors

that provide additional ranging sources that aid in the position estimate of the aircraft. An FMS augmented withGPS and INS would be an example of this type of system.

The performance of GPS navigation equipment is specified with respect to accuracy, integrity, continuity, andavailability. Accuracy specifies the precision of the position estimate of the GPS receiver with respect to the true

location of the aircraft, and is expressed as a requirement for a given phase of flight. Integrity is the assurance that

the GPS solution is not corrupted and providing potentially hazardously misleading navigation information to the

pilot. Todays aviation GPS receivers provide integrity monitoring by use of Receiver Autonomous Integrity

Monitoring (RAIM) algorithms that alert the pilot to integrity issues with the GPS receiver solution. Moresophisticated receivers can detect and exclude satellites with errors in their ranging signals from the overall position

estimate through the use of Fault Detection and Exclusion (FDE) algorithms. Availability requirements assure that

the navigation function can support a particular phase of flight or operation. Continuity requirements provideassurance that the pilot will not lose the navigation capability, once available, during a particular phase of flight or

operation. To accommodate the desire for increased airspace capacity, efficiency, and safety, the ability to operate

in the oceanic, en route, terminal and non-precision and precision approach airspace environments are requiringincreasingly demanding levels of the four basic performance metrics. An overview of the various performance

requirements with respect to each of the operational phases of flight are included for reference in Table 4 and Table

1 at the end of this paper.

What is the WAAS? Why is it necessary and how is it di fferent from the GPS systems usedtoday?

A SBAS, or WAAS, is a satellite-based system that provides regional augmentation of GPS signals unliketraditional ground-based navigation aids. In traditional navigation systems, ground-based transmitters produce

navigation information relative to the terrestrial location and direction from the aircraft. The complementary

airborne equipment consists of receivers that determine the relative direction and/or distance from the ground

stations. In contrast, basic GPS airborne navigation equipment requires no terrestrial based infrastructure, but

instead determines absolute latitude and longitude of the aircraft by triangulation of ranging information fromnumerous GPS satellites orbiting the earth. To achieve higher levels of performance however, terrestrial based GPS

equipment is necessary to provide fixed references for use in assessing real-time errors in the satellite-only position

estimates. The calculated errors in turn are used to produce differential corrections and additional integrityinformation for broadcast to the airborne equipment. WAAS airborne navigation sensors (WAAS/GPS receivers)

are currently certified by the FAA under TSO-C145a, and airborne navigation equipment (WAAS/GPS navigators)

are certified under TSO-C146a.

The WAAS ground infrastructure consists of many Wide-Area Reference Station (WRS) sites located throughout

the continental US (CONUS) and Alaska. These WRS locations are precisely surveyed so that their location with

respect to the GPS coordinate system is absolutely known. Each of the WRS sites process the ranging information

from the GPS constellation and calculate a position estimate. The WRS position estimates are then forwarded to theWAAS Master Station (WMS) via a ground-based communications network. At the WMS, the estimates from each

reference station are compared to the actual WRS survey positions, the differences calculated, and the WAAS

augmentation messages generated. In addition to position correction messages, the WMS also calculates andprovides integrity information regarding the GPS constellation. In general, the messages contain error and

performance information that allow WAAS capable GPS receivers to remove errors in the GPS signal and flagspecific satellites in the GPS constallation that are providing degraded or misleading information, allowing for a

significant increase in location accuracy and integrity.

Once processed by the WMS, the augmentation messages are sent to uplink stations to be transmitted to

geostationary communications satellites (currently INMARSAT). There are currently two satellites in orbit that are

transmitting the WAAS signal-in-space, with plans for a third to provide a level of redundancy for the system. Thenavigation payloads provide bi-directional communications to the WMS and convert and re-broadcast the

augmentation messages to aircraft on GPS L1 spectrum in a WAAS message format. WAAS capable GPS receivers

on aircraft then process both ranging information from the raw GPS constellation and the augmentation message to


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provide corrected position estimates for the current position, and integrity information for the GPS constellation.

The GPS-like signal from the WAAS geostationary transponder can also be used by an airborne receiver as an

additional ranging source for calculation of the position estimate, i.e. the WAAS geostationary satellite doubles for

another GPS satellite. Integrity information provided in the WAAS augmentation message allows the airbornenavigator to isolate malfunctioning satellites and exclude them from the overall navigation solution. With this

information included in the WAAS messages, the RAIM and FDE algorithms of the raw GPS navigator are non-

essential, but can be used to augment the integrity and fault isolation capabilities of the airborne receiver. Figure 1provides a pictoral overview of the WAAS operation.

In comparison to Space-based augmentation, Ground based GPS augmentation systems like the FAAs LAAS

provide local augmentation by collecting information from the GPS constellation with a locally surveyed ground

station, typically located at an airport. GPS correction, integrity, and approach information is then transmitted via aterrestrial VHF datalink to the aircraft operating within range of the transmitter, typically 20 to 30 nautical miles.

Airborne GPS solutions must have the capability to receive and interpret these VHF transmissions and apply the

correction information to the overall navigation solution. The principle and implementation of differentialaugmentation is the same, but the operational performance achievable with the LAAS is greater than that of the

WAAS since the augmentation service is confined to a smaller region of coverage.

Figure 1: WAAS Architecture and Operation (Ref. Performance Specification FAA-E-2963, WAAS GeostationaryCommunication and Control Segment, Draft, June 2002)

Accuracy and Integri ty How much is better? What s the di fference?

The accuracy achievable with raw GPS navigation is incredible when compared to traditional navigation aids, andthe capability to navigate directly between to arbitrary points on the earth has changed the way we look at operations

in the future airspace environment. Differentially corrected GPS positions provide nearly another order of

magnitude better accuracy. Table 1provides a comparison of the accuracy achievable with raw GPS and the WAAS

and LAAS. Accuracy however, is only part of the equation when assessing performance of GPS-based navigationsystems.


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Table 1: GPS Position Accuracy Performance

95%

Horizontal (Meters)

95%

Vertical (Meters)GPS Position Accuracy

PerformanceGoal Observed Goal Observed

Raw GPS with S/A Active* 100 45 100 156 156

Raw GPS with S/A Off 100 6 156 16

GPS with SBAS (WAAS) 7.6 2 7.6 3

GPS with GBAS (LAAS CAT I) 1.0 0.4 2.0 0.6

*Selective Availability (S/A) dithering removed from GPS Signal on May 1, 2000

The basic design of GPS makes accuracy an intrinsic capability of the performance equation and is therefore theeasiest element to achieve. The remaining performance elements, i.e. Integrity, Continuity, and Availability also

need to be addressed when assessing the overall navigation capability. The real challenge and limiting factor to

WAAS performance, and GPS navigation in general, is the systems ability to the meet the integrity requirementsfor precision vertical navigation operations.

As GPS satellites change their orbital positions and ionospheric conditions fluctuate, the WAAS coverage and

performance levels experience slight fluctuations. If the performance degrades below the minimum requirements,

the WAAS must provide notification to airborne receivers within several seconds to alert the pilot of a potential lossof service. Although the WAAS accuracy performance typically exceeds the specifications as shown in Table 1,the

integrity performance can only protect to 40m horizontal and 50m vertical.

Continued improvements are planned for WAAS to further expand the benefits it provides. The first set of

improvements will focus on the expansion of the WAAS. Current FAA plans include the addition of 10 WAAS

reference stations and 3 geostationary satellite communication links to replace the INMARSAT satellites used today.

This continued development would increase the availability of the WAAS signal to pilots, and expand the broadcastcoverage area to include 100% of the continental U.S. and most of Alaska. Other improvements may be made to

incorporate changes associated with GPS modernization, but the FAAs commitment and schedule for all of the

upgrades is uncertain.

What types of WAAS receivers are available?

An overview of functional and operational classes and capabilities for WAAS equipment is given in Figure 2. MostGPS sensors in service today do not have WAAS capability, but many designs are being updated to accommodate

the WAAS signal-in-space. Several current receiver designs can be upgraded with software modifications but are

limited to Class 2 operations, and only two commercially available receivers can support Class 3 operations. It is

fully expected that within the next several years, most GPS sensors in new and retrofit products will have Class 3capability.


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Class 1 Class 2 Class 3 Class 4

Class(Sensor)

TSO-C145a

Oceanic, En route,

Terminal, NPA

Oceanic, En route,

Terminal, NPA,

LNAV/VNAV

Oceanic, En route,

Terminal, NPA,

LNAV/VNAV, APV, LPV

N/A

Class (Equipment)

TSO-C146a

Oceanic, En route,

Terminal, NPA

Oceanic, En route,

Terminal, NPA,

LNAV/VNAV

Oceanic, En route,

Terminal, NPA,

LNAV/VNAV, APV, LPV

N/A

Class(Equipment)

N/A N/A N/APrecision Approach

(APV, LPV)

Operational Class

FunctionalClass

WAAS Equipment Classes

TSO-C145a/C146a

Figure 2: WAAS Receiver Types

What is the status of the WAAS program?

The WAAS program reached a milestone in July 2003 by receiving commissioning for operational use in the USnational airspace (NAS). Although the initial operational capability (IOC) does not meet the original design goal of

Category I minimums, the current performance will provide some operational benefit to light general aviation users

and potential for others when reduced minimums using WAAS are introduced as modifications to the current RNAV

approach procedures. Some of the high-level milestones for past and future capability for the WAAS developmentinclude:

WAAS Initial Operational Capability IOC (LNAV/VNAV) - July 2003- 95% of Continental U.S. (CONUS), portions of Alaska- Equivalent capability to Baro-VNAV operations with Class 2/3 receiver- 350-ft minimumsThis provides aircraft equipped with Class 2 or 3 WAAS capability to fly RNAV approaches with vertical

guidance and LNAV/VNAV. This is equivalent to flying an LNAV/VNAV approach today with an aircraft

equipped with Baro-VNAV capability.

WAAS Operational (Initial LPV) September/October 2003- 7 procedures drafted to publish in Sept./Oct. database cycle- Remaining LPV procedures TBD (2003 through 2006)- 250-ft minimumsSeven LPV procedures will be published in the Sept./Oct. 2003 database update cycle. Of those seven,

several have come very close to reaching the desired 250-ft minimums, and all have resulted in lower

minimums than LNAV/VNAV. These seven approaches however provide a narrow sampling of LPV

minimums to ascertain the exact improvement over LNAV/VNAV operations today. Therefore the

cost/benefit of the airspace design and aircraft investment for LPV approaches is impossible to quantify at

this time. Aircraft equipped with Baro-VNAV and WAAS augmentation capability will provide equivalent

vertical guided approach capability on all RNAV (GPS) approaches to LNAV/VNAV minimums.

WAAS Full Operational Capability FOC (LPV) - 2006- Full Continental U.S.- Most of Alaska-


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LPV TERPS criteria. For those airports with ILS approach capability to some runway end, much of the

obstacle survey data is available, but adding WAAS LPV at those airports has limited utility to operators.

Airports without ILS approaches will have the largest benefit by the addition of precision vertical

guidance, but unfortunately do not have the appropriate obstacle data to support the procedure design.

The FAA is currently investigating methods that can expedite this process, however 2006 may be an

optimistic estimate for completion of the entire process.

WAAS FOC+ (GLS L5) 2013- WAAS 200 Minimums- Interference Mitigation- Addition of a 3rdGeostationary satellite

Long-term WAAS improvements require an additional GPS frequency (L5 in addition to L1, L2) and

modified equipment capable of receiving the new signals. This is required for SBAS to reach Category I

landing capability without other forms of augmentation.

The addition of a third geostationary satellite and/or replacement of the current INMARSAT payloads are

also much-needed improvements to the system. With the two-satellite system currently in operation, the loss

of one satellite would in effect result in the loss of half of the WAAS augmentation signal coverage. A third

satellite is necessary to mitigate this failure mode. Procurement of the third satellite is under way, and will

probably occur well before 2013.

What approach procedures are available today that make use of WAAS capability? Are therereally over 500 approaches available for WAAS capability?

There indeed are over 500 RNAV (GPS) instrument approach procedures defined and published by the FAA today.

These approaches have been previously designed for aircraft equipped with raw GPS navigators, or a FlightManagement System (FMS) that may or may not have barometric VNAV (baro-VNAV) capability. Each of the

procedures has published minimums for non-precision (Circling and LNAV) approaches, and for vertical navigation

operations (LNAV/VNAV). Aircraft equipped with GPS equipment certified to TSO-C129a IFR capability may

perform these RNAV approaches to non-precision minimums, and those equipped with baro-VNAV capability may

perform the approaches to any of the non-precision or vertical navigation minimums.

With the introduction of WAAS, the RNAV (GPS) approaches will be modified to contain minimums for another

type called LPV. LPV is an acronym that has evolved into one with no true meaning, but loosely refers to Lateralguidance with Precision Vertical, or Localizer Performance with Vertical guidance. Currently, there are seven

(7) approaches that have been designed for LPV minimums that are to be published in the September or October

2003 database update cycle. Table 2 lists the locations and details for each of these approaches. The intent is toprovide a set of approach minimums specifically for use by WAAS equipment that result in lower minimums than

that of the baro-VNAV approaches. Of the seven approaches, all LPV types have resulted in lower minimums than

LNAV/VNAV, and some have come very close to achieving 250 minimums. The true extent of this improvement

to the broader scope of RNAV (GPS) approaches however is unknown at this time.

It is of interest to note that several of the seven LPV amended RNAV approaches have resulted in LNAV minimums

that have increased when compared to the currently published procedures. This is true for cases where the approach

geometry required modification to accommodate the obstacle clearance requirements of LNAV/VNAV and LPV.Others that did not require geometric modification are unaffected. The extent to which this will occur in the overall

RNAV approach redesign process is not known.


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Table 2: Proposed Amendments to RNAV IAP(s) with LPV Minimums (Sept./Oct. 2003)

A B C D

LPV (DA)

LNAV/VNAV (DA) 1020 - 2 1/2 724

LNAV (MDA) 1 000 - 2 7 04 1000 - 2 1/4 704

Circling 1080 - 2 1/2 777

LPV (DA)

LNAV/VNAV (DA)

LNAV (MDA) 1 200 - 2 6 77 1200 - 2 1/4 677

Circling 1 200 - 2 6 61 1200 - 2 1/4 661

LPV (DA)

LNAV/VNAV (DA)

LNAV (MDA) 1 080 - 2 6 98 1080 - 2 1/4 698

Circling 1 080 - 2 6 91 1080 - 2 1/4 691

LPV (DA)

LNAV/VNAV (DA)

LNAV (MDA) 640 - 3/4 448 640 - 1 448

Circling 720 - 1 3/4 528 760 - 2 568

LPV (DA)

LNAV/VNAV (DA)1600/40

318 (400-3/4)

LNAV (MDA)1840/50

558 (600-3/4)

1840/60

558 (600-1 1/4)

Circling1840 - 1 1/2

545 (600-1 1/2)

1860 - 2

565 (600-2)

LPV (DA)

LNAV/VNAV (DA)

LNAV (MDA)

Circling1740 - 1

445 (500-1)

1760 - 1

465 (500-1)

1760 - 1 1/2

465 (500-1 1/2)

1860 - 2

565 (600-2)

LPV (DA)

LNAV/VNAV (DA)

LNAV (MDA) 1240/40 432 1240/50 432

Circling 1260 - 1 1/2 451 13 60 - 2 5 51

8+ ...TBD

1020 - 2 1/2 724

1110/24 302

1160/40 352

1240/24 432

1260 - 1 451

1840 - 1 545 (600-1)

1530/50 253

1580/50 303 (300-1)

1580/50 303 (300-1)

700 - 1 3/4 508

1540/24 258

1600/24 318 (400-1/2)

1840/24 558 (600-1/2)

6

7

Type

640 - 1 257

740 - 1 1/4 358

1080 - 1 698

1080 - 1 1/4 691

480 - 1/2 287

720 - 1 1/4 528

640 - 1/2 448

2

3

4

5

Oshkosh, W I W ittman Regional

(ILS)

KOSH RNAV (GPS) RWY 36

Oklahoma City, OK Will Rogers World(ILS)

KOKC RNAV (GPS) RWY 35L

Oklahoma City, OK Will Rogers World(ILS)

KOKC RNAV (GPS) RWY 17R

Manassas , VA Manassas Reg iona l /

Harry P. Davis Field(ILS)

KHEF RNAV (GPS) RWY 16L

Leesburg , VA Leesburg Executive(ILS)

KJYO RNAV (GPS) RWY 17

Gaithersburg, MD Montgomery County

Airpark

KGAI RNAV (GPS) RW Y 14

1200 - 1 6771200 - 1 1/2 661

Frederick Municipal(ILS)

KFDK RNAV (GPS) RWY 23

1000 - 3/4 704

1020 - 2 1/2 717

780 - 1 257

920 - 1 1/2 397

#Aircraft Performance Category

690 - 1 1/2 394Frederick, MD1

City Airport Identifier RNAV Approach

Is the WAAS service available worldwide?

No, the WAAS provides regional augmentation and at this time is intended to provide coverage only within the

continental US and Alaska. There are however, several SBAS systems similar to the FAAs WAAS that areplanning to provide basic interoperability with avionics that are designed for WAAS operation. These include the

European Geostationary Navigation Overlay Service (EGNOS) and Japans Multi-Transport Satellite (MT-SAT)

based Augmentation System (MSAS). India has also begun some preliminary work on its own SBAS, the GPS andGEO Augmented Navigation (GAGAN) system.

In terms of WAAS capability for the CONUS and Alaska, Figure 3 and Figure 4 show snapshots of the VerticalNavigation Service for the WAAS coverage area for a typical morning and afternoon on July 23, 2003. The

snapshots provide information regarding the Vertical Protection Level (VPL) provided by WAAS augmentation as

colored contours, and outlined service contours for LNAV/VNAV (dashed) and LPV (red) vertical navigation

service levels. Figure 3 represents a near best case scenario, whereas Figure 4 is representative of the lower limit of

capability. As shown in each of the figures, availability of the WAAS augmentation necessary for precision vertical

navigation is not assured to the extents of the intended coverage areas and varies dramatically throughout the day.The continental U.S. has fairly good coverage, however coastal areas and many border fringes of the country have

periods where vertical navigation service will be limited to LNAV/VNAV (Baro-VNAV) or LNAV (NPA)

minimums. Alaska on the other hand has periods where the vertical navigation service will not support anyLNAV/VNAV capability and will be limited to LNAV only operations. Note that aircraft equipped with Baro-

VNAV capability will still be able to operate in these situations to LNAV/VNAV minimums regardless of the

WAAS VPL performance at the time of the approach.


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Figure 3: WAAS VPL on July 23, 2003, 10:58am Figure 4: WAAS VPL on July 23, 2003, 4:17pm

Reference: http://www.nstb.tc.faa.gov/vpl.html

In general, what benefit does the WAAS provide for me as an operator? What changes to myaircraft are necessary?

The actual benefits and the changes required to provide those benefits will vary depending on whether operations

utilize Air Transport, Regional, Business, and/or Light GA aircraft, and where the bulk of the operations occur. The

following table attempts to address the affects of WAAS upgrades to current equipage for the various aircraft types.

Table 3: Notional Operational Benefits and Upgrades to WAAS or Equivalent Capability

Aircraft TypeTypical Operational

EnvironmentDescription of WAAS or Equivalent Capabilities and Upgrade

With Baro-VNAV capability:

All air transport aircraft are suitably equipped with ILS precision approach and many willhave Baro-VNAV capability provide by FMS.

- Upgrade to WAAS capability will most likely require new Class 3 receiver design forMulti-Mode Receiver type LRU. This would also require integration with otheraircraft navigation systems such as an FMS.

- Upgrade provides extremely limited benefit over Baro-VNAV capability currentlyavailable since reduction of minimums will not have much impact at majority of

airports served. ILS is already available, and LPV minima provide questionableimprovements that justify investment in modification.

- Most operators will likely continue to use existing ILS service until GBAS (LAAS)capability is available, and mitigate ILS outages with Baro-VNAV capability.

- Investment in RNP and RNP-RNAV capability will continue to improve the RNAVapproach capabilities.

Air Transport High-Altitude En route

Terminal AreaApproach

Surface Movement

Upper Tier airports with ILS

(CAT I/II and some CAT III)

approach capability.

Without Baro-VNAV capability:

All air transport aircraft will be suitably equipped with ILS precision approach and some

will NOT have Baro-VNAV capability provide by FMS.

-

Upgrade of FMS to provide Baro-VNAV capability. This typically requires softwaremodification and would be lowest cost alternative to provide vertical guidance in

addition to ILS. This upgrade also provides worldwide vertical navigation coverage

due to autonomy of the capability in the airborne equipment.- Upgrade to WAAS capability will most likely require new Class 3 receiver design for

Multi-Mode Receiver type LRU.

- WAAS upgrade provides marginal benefit when compared to Baro-VNAV upgrade.ILS is already available for the majority of airports served and absence of publishedLPV approaches

- Most operators will likely continue to use existing ILS service until GBAS (LAAS)capability is available.
http://www.nstb.tc.faa.gov/vpl.htmlhttp://www.nstb.tc.faa.gov/vpl.html


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Aircraft with Inertial Reference Systems (IRS):Many air transport aircraft will be equipped with Inertial Reference Systems (IRS) that may

be integrated with FMS/GPS to provide enhanced approach capability as part of an Aircraft

Based Augmentation System (ABAS).

- WAAS/SBAS upgrade to these systems would provide potential benefit depending onthe level of integration with other navigation systems.- Most operators will likely continue to use existing ILS services until GBAS (LAAS)capability is available. LAAS upgrades alone will most likely achieve Performance

Type I (Category I service levels), but tightly integrated IRS augmentation may be

one method of achieving requirements for LAAS Performance Type II and III

approaches (Category II and IIIa,b,c service levels).

Aircraft without GPS capability:Many air transport aircraft will not be equipped with raw GPS capability.

- Upgrade to future GPS capability will most likely include WAAS and potential LAAScapability.

- Investment in RNP and RNP-RNAV capability without GPS sensors will continue toprovide and improve RNAV approach capabilities.

With Baro-VNAV capability:

All regional aircraft are suitably equipped with ILS precision approach and some will haveBaro-VNAV capability provide by FMS.

- Upgrade to WAAS capability will most likely require new Class 3 receiver design forfederated navigation radio package or integrated avionics system. This would alsorequire integration with other aircraft navigation systems such as an FMS.

- Upgrade provides extremely limited benefit over Baro-VNAV capability currentlyavailable since reduction of minimums will not have much impact at majority ofairports served. ILS is already available, and LPV minima provide questionable

improvements that justify investment in modification.

- Most operators will likely continue to use existing ILS service until GBAS (LAAS)capability is available and mitigate ILS outages with Baro-VNAV capability.

- Continued investment by operators in RNP and RNP-RNAV capability will erodebenefit of WAAS equipment upgrades.


All regional aircraft are suitably equipped with ILS precision approach and many will NOThave Baro-VNAV capability provide by FMS.

- Upgrade of FMS to provide Baro-VNAV capability. Typically requires softwaremodification and would be lowest cost alternative to provide vertical guidance in

addition to ILS.- Upgrade to WAAS capability will most likely require new Class 3 receiver design for

federated navigation radio package or integrated avionics system.

- Upgrade may provide some questionable benefit in l ieu of Baro-VNAV within thecontinental U.S.

- For the majority of airports served, the WAAS capability may provide mitigation ofILS outage situations. In these cases however, LNAV approaches are typically

available, and LPV minimums provide marginal benefit to justify investment in an

upgrade.


Regional Mid/High-Altitude En route


Surface Movement

Mid to upper-tier airports with

ILS, VNAV and NPA

approach capability.

Aircraft with Inertial Reference Systems (IRS):

Most regional aircraft will most likely NOT be equipped with Inertial Reference Systems(IRS). Some regional aircraft WILL be equipped with Inertial Reference Systems (IRS)

that may be integrated with FMS/GPS to provide enhanced approach capability as part of

an Aircraft Based Augmentation System (ABAS).

- WAAS/SBAS upgrade to these systems would provide potential benefit depending onthe level of integration with other navigation systems.

- Most operators will likely continue to use existing ILS services until GBAS (LAAS)capability is available. LAAS upgrades alone will most likely achieve PerformanceType I (Category I service levels), but tightly integrated IRS augmentation may be

one method of achieving requirements for LAAS Performance Type II and III



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With Baro-VNAV capability:Most business aircraft will be suitably equipped with ILS precision approach and many will

have Baro-VNAV capability provide by FMS.

- Upgrade to WAAS capability will most likely require new Class 3 receiver designupgrade and/or replacement of federated navigation radio package or integrated

avionics system.- Upgrade to WAAS provides extremely limited benefit over Baro-VNAV capabilitycurrently available. Reduction of minimums will not have much impact at majority of

airports served. ILS is already available, and LPV minima provide questionable

improvements that justify investment in modification.- Most operators will likely continue to use existing ILS service until GBAS (LAAS)

capability is available.

- Potential but limited benefit at airports that currently do not have ILS services due toBaro-VNAV capability.


Most business aircraft will be suitably equipped with ILS precision approach and some may

NOT have Baro-VNAV capability provide by FMS.- Upgrade of FMS to provide Baro-VNAV capability. Typically requires software

modification and would be lowest cost alternative to provide vertical guidance in

addition to ILS.

- Upgrade to WAAS capability will most likely require new Class 3 receiver designupgrade and/or replacement of federated navigation radio package or integrated

avionics system.- Upgrade to WAAS provides questionable benefit in lieu of Baro-VNAV within the

continental U.S.

- For the majority of airports served, the WAAS capability may provide mitigation ofILS outages. Baro-VNAV capability would provide similar mitigation and would belower cost solution to current equipage.


Corporate/

Business

Mid/High-Altitude En route


Surface Movement

Potentially all airport types,

but typically mid to upper-

tier, most with ILS and manywith a minimum VNAV and

NPA approach capability.

Aircraft with Inertial Reference Systems (IRS):Many business aircraft will be equipped with Inertial Reference Systems (IRS) that may be

integrated with FMS/GPS to provide enhanced approach capability as part of an Aircraft

Based Augmentation System (ABAS).

- WAAS/SBAS upgrade to these systems would provide potential benefit depending onthe level of integration with other navigation systems.

- Most operators will likely continue to use existing ILS services until GBAS (LAAS)capability is available. LAAS upgrades alone will most likely achieve Performance

Type I (Category I service levels), but tightly integrated IRS augmentation may beone method of achieving requirements for LAAS Performance Type II and III


Without TSO-C129a GPS Navigator Capability:

Many Light GA aircraft within the U.S. do not have GPS navigation capabili ty today.- Upgrade to TSO-C129a IFR navigation equipment would provide en route, terminal

area, and non-precision (NPA) RNAV approach capability to LNAV minimums.

- Upgrade to TSO-C146a, Class 2 WAAS/GPS navigation equipment would provide enroute, terminal area, NPA, and RNAV/VNAV capability to LNAV/VNAV minimumsequivalent to Baro-VNAV. These approaches are available today.

- A Class 3 WAAS/GPS navigator would provide additional RNAV/VNAV capabilityto LPV minimums. Only 7 of these approaches have been designed with others to be

determined over the next 2 to 3 years.

General

Aviation

Low/Mid-Altitude En route


All airport types, but typically

lower to mid-tier, some with,and some without ILS

capability. Many with RNAV(GPS) approaches, and most

with at least NPA approaches.

With TSO-C129a GPS Navigator Capability:Many Light GA aircraft within the U.S. have been equipped with TSO-C129a VFR/IFR

GPS navigation capability.

- Units without approach capability would require replacement if vertical guidance isdesired and/or required.

- Upgrade of existing IFR approved equipment may require replacement of unit sinceGPS engines may not be WAAS capable. Some receivers may have provisions to be

upgraded to WAAS Class 2, which would provide approach capability to

LNAV/VNAV minimums.

- If LPV approach performance is desired, replacement or addition of a TSO-C146aClass 3 navigator is required.

Assumptions:

- Regional, and Business is aircraft with Flight Management Systems (FMS) include raw-GPS (TSO-C129a) capability


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REFERENCEMATERIAL

Table 4: Navigation Performance Requirements

Integrity

OperationalPhase-of-Flight Accuracy(95%) Time-to-Alert Alert Limit Probability ofHMI

Availability(Range) Continuity(Loss of Nav.)

Associated

RNP Type(H/V)

Oceanic,

En route

& Remote

12.4 nm2 min 12.4 nm 10-7/ hr

0.99 0.99999

1 x 10-5/ hr 5 20(No Vertical)

Domestic

En route

2.0 nm

(3.7 km)1 min 2.0 nm 10-7/ hr

0.99

0.999991 x 10-6/ hr 2 10

(No Vertical)

Terminal0.4 nm

(0.74 km)30 sec 1.0 nm 10-7/ hr

0.99

0.999991 x 10-6/ hr 1

(No Vertical)

Non-Precision

(LNAV)

220 m

(720 ft)10 sec 0.3 nm 10-7/ hr

0.99

0.999991 x 10-5/ hr 0.5 0.3

(No Vertical)

APV-1(LNAV/VNAV)

100m 8 sec 556m (H)50m (V)

10-7/ hr 0.99 0.99999

1-5 x 10-5

Approach0.3/125

LPV

(WAAS)

7.6 (16) m (H)

7.6 (20) m (V)6 sec

40m (H)

50m (V)

1-2 x 10-7/

Approach

0.99

0.99999

1-5.5 x 10-5/

Approach0.03/125

APV-2 (TBD)

(Notional)

XXm (H)

XXm (V)5.2 sec

40m (H)

20m (V)

6 x 10-8/

Approach

0.99

0.99999Y x 10-Z/ hr 0.03/50

Precision (PT-1)

Category I

16 m (H)

4.0 m (V)6 sec

40 m (H)

10 m (V)

2 x 10-7/

Approach

0.99

0.99999

8.0 x 10-6/

Approach0.02/40

Precision (PT-2)

Category II

6.9 m (H)2.0 m (V)

2 sec17.3 m (H)5.3 m (V)

2 x 10-9/Approach

0.99 0.99999

4 x 10-6/ 15s 0.01/15

Precision (PT-3)Category III

6.2 m (H)2.0 m (V)

2 sec1 sec (goal)

15.5 m (H)5.3 m (V)

2 x 10-9/Approach

0.99 0.99999

2 x 10

-6

/ last 15s1 x 10-7/ last 15s

(vertical)

0.003/z


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Page 12 of 13

Table 5: Existing and Proposed RNP Operational Types

Required Accuracy(95% Containment)

RNP

TypeHorizontal Vertical

Description

20(No Vertical) 20.0 NM N/A The minimum capability considered acceptable to support ATS routeoperations.

12.6(No Vertical)

12.6 NM N/ASupports limited optimized routing in areas with a reduced level of

navigation facilities.

10(No Vertical)

10.0 NM N/ASupports reduced lateral and longitudinal separation minima and

enhanced operational efficiency in oceanic and remote areas where

the availability of navigation aids is limited.

5(No Vertical)

5.0 NM N/AAn interim type implemented in ECAC airspace to permit the

continued operation of existing navigation equipment. Equates to B-

RNAV in ECAC airspace.

4(No Vertical)

4.0 NM N/ASupports ATS routes and airspace based upon limited distances

between navaids. Normally associated with continental airspace but

may be used as part of some terminal procedures.

2(No Vertical)

2.0 NM N/A Domestic Enroute.

1(No Vertical)

1.0 NM N/ASupports Arrival, Initial/Intermediate Approach andDeparture; also envisaged as supporting the most efficient ATS route

operations. Equates to P-RNAV in ECAC airspace.

0.5(No Vertical)

0.5 NM N/ASupports Initial/Intermediate Approach and Departure. Only

expected to be used where RNP 0.3 cannot be achieved (poor navaid

infrastructure) and RNP 1 is unacceptable (obstacle rich environment)

0.3(No Vertical)

0.3 NM N/ASupports Initial/Intermediate Approach, 2D RNAV Approach, and

Departure. Expected to be the most common application.

0.3/125 0.3 NM 125 ftRNAV/VNAV Approaches using Barometric inputs or SBAS inputs.

(APV-1)

0.xx/xxx 0.03 NM 125 ft LPV

0.03/50 0.03 NM 50 ft RNAV/VNAV Approaches using SBAS or GBAS. (APV-II)

0.02/40 0.02 NM 40 ftProposed for CAT I Precision Approach to 200 ft DH

(ILS, MLS, GBAS and SBAS)

0.01/15 0.01 NM 15 ftProposed for CAT II Precision Approach to 100 ft DH

(ILS, MLS and GBAS)

0.003/z 0.003 NM z ftProposed for CAT III Precision Approach and Landing including

touchdown, landing roll and take-off roll requirements.(ILS, MLS and GBAS). No vertical requirement specified to date.

Reference:

Eurocontrol Document , Guidance Material for the Design of Terminal Procedures for Area Navigation (DME/DME, B-GNSS,

Baro-VNAV & RNP-RNAV, Version 3.0.

ICAO Annex 10, Aeronautical Telecommunications, Volume 1, 5 thEdition, Radionavigation Aids, July 1996.


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Table 6: Navigation System Performance metrics and their relationship to Operational Considerations

SAFETY ECONOMY

Integrity

Accuracy

ContinuityAvailabi li ty

Integrity

The integrity of a system is a quality that indicates the trust that can be placed in the correctness of the information supplied by the total

system. Integrity risk is the probability of an undetected (latent) failure of the specified accuracy. Integrity includes the ability of the

system to provide timely warnings to the user when the system should not be used for the intended operation.

Integrity is uniquely related to safety since misleading information without warning is a safety of flight situation. Integrity is the glue

for the remaining performance metrics of Accuracy, Continuity, and Availability for operational capability.

Accuracy

The degree of conformance between the estimated or measured value and the true value at the time of the measurement.

Accuracy is more closely related to safety since the lack of conformance could result in a potential safety of flight situation. Accuracy

is a trade-off favoring the required performance for safe operations and economic cost to provide that operational performance.

ContinuityThe ability of the total system (comprising all elements necessary to maintain aircraft position within the defined airspace) to perform

its function without interruption during the intended operation. More specifically, continuity is the probability that the specified systemperformance will be maintained for the duration of a phase of operation, presuming that the system was available at the beginning of

that phase of operation.

Continuity is more closely related to economic considerations since loss of function once committed to an operation does not

necessarily result in an unsafe condition. With integrity, loss of function during an operation does not necessarily result in a safety of

flight situation. Continuity is a trade-off favoring the economic cost to provide continuity of function and the required performance for

safe operations.

Availability

The ability of the navigation system to provide the required function and performance at the initiation of the intended operation. Short-term system availability is the probability that the aircraft can conduct the approach at the destination given that the service at the

destination was predicted to be available at dispatch. Long-term service availability is the probability that the signal in space from the

service provider will be available for any aircraft intending to conduct the approach.

Availability is more closely related to economic considerations since loss of function prior to an operation does not necessarily result in

an unsafe condition. With integrity, loss of function prior to an operation does not result in a safety of flight situation. Availability is

uniquely related to the economic considerations of the design, i.e. a system that exhibits low availability provides little utility and

operational benefit, but is not a safety issue.

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