U.S.
Department of Transportation Federal Aviation Administration Advisory Circular Subject: Guidance for Localizer Performance with Vertical Guidance and Localizer Performance without Vertical Guidance Approach Operations in the U.S. National Airspace System Date: 2/11/11 AC No: 90-107 Initiated by: AFS-400 Change:
This advisory circular (AC) provides guidance for operators to conduct Title 14 of the Code of Federal Regulations (14 CFR) part 97 instrument flight rules (IFR) Area Navigation (RNAV) Global Positioning System (GPS) instrument approach procedures (IAP) with localizer performance with vertical guidance (LPV) and localizer performance without vertical guidance (LP) lines of minima using the wide area augmentation system (WAAS). This AC applies to all operators conducting RNAV (GPS) approach procedures to LPV or LP lines of minima using WAAS navigation avionics under 14 CFR parts 91, 91 subpart K (part 91K), 121, 125, 129, 133, 135 and 137 within the U.S. National Airspace System (NAS). This AC provides operational approval information for operators flying parts 91K, 121, 125, 133, 135 and 137. For additional airworthiness guidance, refer to AC 20-138, Airworthiness Approval of Positioning and Navigation Systems.
ORIGINAL SIGNED by /s/ Raymond Towles for John M. Allen Director, Flight Standards Service
Page 1 (and 2)
CONTENTS Paragraph Page
1. PURPOSE1
2. A PPLICABILITY1
3. RELATED 14 CFR PARTS1
4. DEFINITIONS1
5. RELATED READING MATERIAL (current editions)4
6. BACKGROUND5
7. AIRCRAFT AND SYSTEM REQUIREMENTS7
8. OPERATIONAL CONSIDERATIONS8
9. TRAINING10
10. OPERATIONAL APPROVAL12
11. AC FEEDBACK FORM13
APPENDIX 1. ADDITIONAL GUIDANCE FOR HELICOPTER APPROACHES
(2 pages)1
APPENDIX 2. EXAMPLE RNAV (GPS) APPROACH CHART (LPV LINE OF MIN
IMA) (2 pages)1
APPENDIX 3. EXAMPLE RNAV (GPS) APPROACH CHART (LP LINE OF MIN
IMA) (2 pages)1
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1. PURPOSE. This advisory circular (AC) provides guidance for operators to conduct Title 14 of the Code of Federal Regulations (14 CFR) part 97 instrument flight rules (IFR) Area Navigation (RNAV) Global Positioning System (GPS) instrument approach procedures (IAP) with localizer performance with vertical guidance (LPV) and localizer performance without vertical guidance (LP) lines of minima using the wide area augmentation system (WAAS). The contents of this document do not have the force and effect of law and are not meant to bind the public in any way. This document is intended only to provide clarity to the public regarding existing requirements under the law or agency policies.
NOTE: For additional airworthiness guidance, refer to AC 20-138, Airworthiness Approval of Positioning and Navigation Systems.
2. APPLICABILITY. This AC applies to all operators conducting RNAV (GPS) approach procedures to LPV or LP lines of minima using WAAS navigation avionics under 14 CFR parts 91, 91 subpart K (part 91K), 121, 125, 129, 133, 135 and 137 within the U.S. National Airspace System (NAS). This AC provides operational approval information for operators flying parts 91K, 121, 125, 133, 135 and 137. This AC is not mandatory, and it does not change, add, or delete regulatory requirements or authorize deviations from regulatory requirements. In lieu of following the guidance in this AC without deviation, operators may elect to follow an alternative method, provided the alternative method is found to be acceptable by the Federal Aviation Administration (FAA).
3. RELATED 14 CFR PARTS.
• Part 61;
• Part 91 and 91K;
• Part 95;
• Part 97;
• Part 121, § 121.567;
• Part 125, §§ 125.203, 125.287, and 125.325;
• Part 129;
• Part 133;
• Part 135; and
• Part 137.
4. DEFINITIONS.
a. Advisory Vertical Guidance. Vertical path deviation guidance indication that is generated by any means, but is only an aid provided by some manufacturers to help pilots meet altitude restrictions. Advisory vertical guidance is an optional capability implemented at the manufacturer’s discretion; not a requirement for positioning and navigation equipment.
NOTE: It is the pilot’s responsibility to use the barometric altimeter to ensure compliance with altitude restrictions, particularly during approach operations. Advisory vertical guidance is not approved vertical guidance like that found on approaches with lateral navigation (LNAV)/vertical
Page 2 Par 4 navigation (VNAV), LPV, or instrument landing system (ILS) lines of minima.
b. Approved Vertical Guidance. Actual vertical path deviation guidance indications generated by certified means for charted approach procedures that contain a U.S. Standard for Terminal Instrument Procedures (TERPS)-protected glidepath (e.g., approaches with LNAV/VNAV, LPV, or ILS lines of minima).
c. Area Navigation (RNAV). A method of navigation which permits aircraft operation on any desired flightpath within the coverage of ground or space-based Navigational Aids (NAVAID) or within the limits of the capability of self-contained aids, or a combination of these.
d. RNAV System. A navigation system which permits aircraft operation on any desired flightpath within the coverage of ground or space-based NAVAIDs or within the limits of the capability of self-contained aids, or a combination of these. An RNAV system may be included as part of a flight management system (FMS).
e. Barometric Aiding (Baro-Aiding). A method of augmenting the GPS integrity solution in receiver autonomous integrity monitoring (RAIM) by using a barometric altitude input source.
Baro-aiding requires four satellites and a barometric altimeter to detect an integrity anomaly (the current altimeter setting may need to be entered into the receiver as described in the operating manual). Baro-aiding satisfies the RAIM requirement in lieu of a fifth satellite.
f. Barometric Vertical Navigation (Baro-VNAV). An RNAV system function which uses barometric altitude information from the aircraft’s altimeter to compute and present a vertical guidance path to the pilot. The specified vertical path is computed as a geometric path, typically computed between two waypoints or an angle based computation from a single waypoint.
g. Decision Altitude (DA). In an approach with approved vertical guidance, DA is a specified altitude expressed in feet above mean sea level (MSL) at which a missed approach must be initiated if the required visual references to continue the approach have not been established.
h. Fault Detection and Exclusion (FDE). A RAIM algorithm that can automatically detect and exclude a faulty satellite from the position solution when measurements from six or more satellites are available. WAAS equipment uses FDE for integrity whenever a WAAS signal is not available to permit continued operation from en route through approach operations.
i. Flight Technical Error (FTE). FTE is the accuracy with which an aircraft is controlled, as measured by the indicated aircraft position with respect to the indicated command or desired position. It does not account for procedural blunder errors.
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j. Glo bal Navigation Satellite System (GNSS). GNSS refers collectively to the worldwide positioning, navigation, and timing determination capability available from one or more satellite constellations in conjunction with a network of ground stations.
k. Global Positioning System (GPS). GPS refers to the worldwide positioning, navigation and timing determination capability available from the U.S. satellite constellation. The service provided by GPS for civil use is defined in the GPS Standard Positioning System Performance Standard. GPS is composed of space, control, and user elements.
l. Integrity. Integrity is a measure of the trust that can be placed in the correctness of the information supplied by the total system. Integrity includes the ability of a system to provide timely and valid warnings to the user (alerts).
m. Lateral Navigation (LNAV). An RNAV function that computes, displays, and provides horizontal approach navigation without approved vertical guidance.
n. Lateral Navigation/Vertical Navigation (LNAV/VNAV). An RNAV function that computes, displays, and provides both horizontal and approved vertical approach navigation.
Both WAAS vertical guidance and baro-VNAV support approaches to LNAV/VNAV lines of minima.
o. Localizer Performance with Vertical Guidance (LPV). An RNAV function requiring WAAS, using a Final Approach Segment (FAS) data block, which computes, displays and provides both horizontal and approved vertical approach navigation to minimums as low as 200 foot ceiling and ½ mile visibility.
p. Localizer Performance without Vertical Guidance (LP). An RNAV function requiring WAAS, using an FAS data block that computes, displays, and provides horizontal approach navigation using the horizontal accuracy and integrity of LPV without the approved vertical guidance. The LP line of minima is provided at locations where issues prevent the use of LPV vertical guidance, and provides a higher probability of achieving the lowest minimum at these locations.
q. Minimum Descent Altitude (MDA). In an approach without approved vertical guidance, MDA is a specified minimum altitude expressed in feet above MSL.
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r. Receiver Autonomous Integrity Monitoring (RAIM). An algorithm that verifies the integrity of the position output using measurements from five or more GPS satellites, or four or more GPS satellites and baro-aiding.
s. Required Navigation Performance (RNP). RNP is a statement of the 95 percent navigation accuracy performance that meets a specified value for a particular phase of flight or flight segment and incorporates associated on-board performance monitoring and alerting features to notify the pilot when the RNP for a particular phase or segment of a flight is not being met.
t. Required Navigation Performance Approach (RNP APCH). RNP APCH is a navigation specification based on area navigation that includes the requirement for on-board performance monitoring and alerting features to notify the pilot when the RNP for the approach phase of flight is not being met. (LPV and LP operations are found in the RNP APCH navigation specifications of the International Civil Aviation Organization (ICAO) Performance-based Navigation (PBN) Manual.)
u. Satellite-Based Augmentation System (SBAS). SBAS is a wide area coverage augmentation system. The user receives GPS constellation augmentation information from a geostationary satellite-based transmitter. SBAS complements the core GPS satellite constellation by increasing navigation accuracy, integrity, continuity and availability provided within a service area. The U.S. SBAS is WAAS.
5. RELATED READING MATERIAL (current editions). The following documents are related to this AC.
a. Where You Can Find ACs/Orders/Notices. You can find these ACs at http://www.faa.gov/regulations_policies/advisory_circulars and orders/notices at https://employees.faa.gov/tools_resources/orders_notices. Inspectors can also access these ACs through the Flight Standards Information Management System (FSIMS) at http://fsims.avs.faa.gov (see the link to http://rgl.faa.gov). Operators and the public may find this information at http://fsims.faa.gov (see the link to http://rgl.faa.gov).
(1) AC 20-138, Airworthiness Approval of Positioning and Navigation Systems.
(2) AC 20-153, Acceptance of Aeronautical Data Processes and Associated Databases.
(3) AC 29-2, Certification of Normal Category Rotorcraft.
(4) AC 90-105, Approval Guidance for RNP Operations and Barometric Vertical Navigation in the U.S. National Airspace System and in Oceanic and Remote Continental Airspace.
(5) FAA Order 8260.42, United States Standard for Helicopter Area Navigation (RNAV).
(6) FAA Order 8900.1.
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b. FAA Technical Standard Orders (TSO).
(1) TSO-C115, Required Navigation Performance (RNP) Equipment Using Multi-Sensor Inputs.
(2) TSO-C145, Airborne Navigation Sensors Using the Global Positioning System Augmented by the Satellite-Based Augmentation System (SBAS).
(3) TSO-C146, Stand-Alone Airborne Navigation Equipment Using the Global Positioning System Augmented by the Satellite Based Augmentation System (SBAS).
c. RTCA Documents. Copies of the following RTCA documents may be obtained from RTCA, Inc., 1150 18th Street NW, Suite 910, Washington, DC 20036, or purchased online at http://www.rtca.org/.
(1) RTCA DO-187, Minimum Operational Performance Standards for Airborne Area Navigation Equipment Using Multi-Sensor Inputs.
(2) RTCA DO-229, Minimum Operational Performance Standards for Global Positioning System/Satellite Based Augmentation System Airborne Equipment.
(3) RTCA DO-236, Minimum Aviation System Performance Standards: Required Navigation Performance for Area Navigation.
d. Additional Documents.
(1) FAA Instrument Flying Handbook (FAA-H-8083-15).
(2) FAA Instrument Procedures Handbook (FAA-H-8083-16).
(3) FAA Aeronautical Information Manual (AIM).
(4) ICAO Doc 9613, Performance-based Navigation (PBN) Manual.
6. BACKGROUND.
a. GNSS Overview. GNSS includes global constellations, augmentations and regional systems. Examples of global constellations are GPS of the United States, Russia’s Global Orbiting Navigation Satellite System (GLONASS) and in the future Europe’s European Satellite Navigation System (GALILEO). Examples of augmentations include the WAAS of the United States, the Multi-Functional Transport Satellites (MTSAT) Satellite-based Augmentation System (MSAS) of Japan, the European Geostationary Navigation Overlay Service (EGNOS) of Europe, and the GPS and Geostationary Augmented Navigation System (GAGAN) of India.
Additionally, both the Russian Federation and China have announced plans for ICAO Standards and Recommended Practices (SARP) compliant SBAS systems. Finally, there are plans for regional constellations including Japan’s Quasi-Zenith Satellite System (QZSS) and India’s Indian Regional Navigation Satellite System (IRNSS).
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b. WAAS Overview. WAAS improves the accuracy, integrity, availability and continuity of GPS signals. Additionally, the WAAS geostationary satellites provide ranging sources to supplement the GPS signals. If there are no airworthiness limitations on other installed navigation equipment, WAAS avionics enable aircraft navigation during all phases of flight from takeoff through vertically guided approaches and guided missed approaches. WAAS avionics with an appropriate airworthiness approval can enable aircraft to fly to the LPV, LP, LNAV/VNAV and LNAV lines of minima on RNAV (GPS) approaches. One of the major improvements WAAS provides is the ability to generate glidepath guidance independent of ground equipment. Temperature and pressure extremes do not affect WAAS vertical guidance unlike when baro-VNAV is used to fly to LNAV/VNAV line of minima. However, like most other navigation services, the WAAS network has service volume limits, and some airports on the fringe of WAAS coverage may experience reduced availability of WAAS vertical guidance.
When a pilot selects an approach procedure, WAAS avionics display the best level of service supported by the combination of the WAAS signal-in-space, the aircraft avionics, and the selected RNAV (GPS) instrument approach.
NOTE: This AC does not preclude the use of WAAS receivers to fly to LNAV and LNAV/VNAV lines of minima.
c. SBAS Interoperability. The primary purpose of WAAS is to augment GPS and support RNAV (GPS) approach operations to LPV and LP lines of minima. The design of the WAAS and associated avionics is interoperable with similar systems from other service providers.
However, each State in conjunction with the service provider will determine the levels of service its SBAS implementation supports.
NOTE: This document addresses only U.S. WAAS-based operations. It does not cover other States’ SBAS and accompanying instrument procedures, which are interoperable with TSO-C145/C146 (all revisions) avionics. There may be differences in the operational capabilities and qualifications to use these systems.
NOTE: RNAV (GPS) approach operations to LNAV, LNAV/VNAV, LPV and LP lines of minima are classified as an RNP APCH in the ICAO PBN Manual.
d. LPV Lines of Minima. RNAV (GPS) approaches to LPV lines of minima take advantage of the improved accuracy of WAAS lateral and vertical guidance to provide an approach that is very similar to a Category I (CAT I) ILS. Just as with an ILS, LPV has vertical guidance and is flown to a DA. The design of the LPV approach incorporates angular guidance with increasing sensitivity as an aircraft gets closer to the runway (or point in space (PinS) type approaches for helicopters). The sensitivities are nearly identical to those of the ILS at similar distances. This was done intentionally to allow the skills required to proficiently fly an ILS to readily transfer to flying RNAV (GPS) approaches to the LPV line of minima.
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e. LP Lines of Minima.
(1) LP lines of minima take advantage of the improved accuracy of WAAS to provide approaches with lateral guidance. Lateral sensitivity increases as an aircraft gets closer to the runway (or PinS type approaches for helicopters), similar to localizer approaches. Unlike LPV, the LP line of minima is an MDA rather than a DA. Procedures with LP lines of minima will not be published with lines of minima that contain approved vertical guidance (LNAV/VNAV or LPV). Publishing an LP line of minima will only occur if terrain, obstructions, or some other reason prevent publishing a vertically guided procedure. It is possible to have LP and LNAV published on the same approach chart, but LP will only be published if it provides lower minima than the associated LNAV line of minima.
(2) LP is not a fail-down mode for LPV. The avionics integration may include advisory vertical guidance during an LP approach to an LP line of minima. (See subparagraph 8b below for further information on advisory vertical guidance.) Barometric altimeter information remains the primary altitude reference for complying with any altitude restrictions.
7. AIRCRAFT AND SYSTEM REQUIREMENTS.
a. Equipment Requirements. TSO-C145c/C146c operational class 3 (and the earlier revision “b”) define the avionics performance standards for WAAS equipment approved for LPV and LP lines of minima. (See subparagraph 7c(2) for information on revision “a” equipment.) An aircraft equipped with WAAS can operate within the coverage of the GPS constellation and WAAS service volume without the need for other radio navigation equipment. In the event of a WAAS failure, WAAS avionics revert to GPS-only operation which is equivalent in function to unaugmented GPS avionics and satisfies the requirements for IFR use of GPS. Though not required, operators may consider retaining backup navigation equipment in their aircraft to guard against potential outages or interference.
b. Aircraft Flight Manual (AFM) and Rotorcraft Flight Manual (RFM) Requirements.
Operators must conduct WAAS instrument operations in accordance with the FAA-approved AFM, RFM, and Aircraft Flight Manual Supplements (AFMS), as well as manufacturers’ operating guides for their avionics. The AFMS and operating guides will state the type of IAPs the avionics support. IFR-approved WAAS receivers can support any approach procedure that has “GPS” in the title. The AFM, RFM, or AFMS, along with the manufacturer’s operating guide, will specifically state any WAAS avionics limitations. Operators should be thoroughly familiar with the capabilities and limitations of their WAAS avionics.
c. Limitations. Not all WAAS avionics are capable of supporting all lines of minima on an approach chart. For example:
(1) Operational class 1 and 2 WAAS avionics do not support LPV or LP.
(2) Equipment compliant with TSO-C145a/C146a operational class 3 and class 4 provides LPV capability, but is not required to provide LP capability. In some cases manufacturers may choose to modify their equipment to provide LP capability.
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(3) An FMS with WAAS integration might only provide position, velocity and time output to support RNAV or RNP operations without supporting LPV or LP.
(4) See also subparagraph 8d, RNP Considerations.
8. OPERATIONAL CONSIDERATIONS.
a. Alternate Weather Minima. IFR-approved WAAS installations allow operators to select an alternate airport during their flight planning using an RNAV (GPS) approach to LNAV minimums rather than an approach supported by ground-based NAVAIDs. Operators must use part 91, IFR alternate airport weather minima guidance for nonprecision approach procedures (refer to part 91, § 91.169) or Operations Specification (OpSpec)/Management Specification (MSpec)/Letter of Authorization (LOA) C055, Alternate Airport IFR Weather Minimums, or OpSpec/MSpec H105, Alternate Airport IFR Weather Minimums, as applicable. Upon arrival at the alternate airport, if the WAAS navigation system indicates availability of LNAV/VNAV, LP, or LPV service, the pilot may use that level of service to complete the instrument approach.
b. Advisory Vertical Guidance. An RNAV (GPS) instrument approach may contain both the LNAV and the LP lines of minima, and a pilot may use advisory vertical guidance when flying to either the LNAV or LP lines of minima. The vertical guidance is advisory only and pilots must use the barometric altimeter as the primary altitude reference to ensure compliance with any and all altitude restrictions during instrument approach operations. (See Table 1’s “Advisory guidance” column.)
NOTE: Some aircraft integrations may use GPS to provide lateral path deviation indications and baro-VNAV to provide vertical path deviation indications for charted LNAV/VNAV lines of minima. This integration constitutes approved vertical guidance for charted LNAV/VNAV lines of minima. Do not confuse this integration with advisory vertical guidance.
(Refer to AC 20-138 for LNAV and LNAV/VNAV based on baro-VNAV.)
TABLE 1. LINE OF MINIMA AND GUIDANCE Line of minima Approved guidance Advisory guidance LPV X LP X
LNAV/VNAV X LNAV X* *LPV-capable equipment requires special considerations when using advisory vertical guidance; see the manufacturers’ operating guides or limitations section in the AFM, RFM, or AFMS.
c. Notices to Airmen (NOTAM). The FAA NOTAM system permits operators to determine WAAS operational availability in any geographic region of the United States. Prior to WAAS IFR operation, the operator must review appropriate Aeronautical Information Services (AIS) and NOTAMs for WAAS service outages. On RNAV (GPS) instrument approach charts, the inverse W symbol (a white W on a black background, see figure in Appendix 2), indicates
Par 8 Page 9 that the FAA provides no NOTAMs or air traffic advisories for outages of WAAS LNAV/VNAV or LPV vertical guidance and that WAAS vertical guidance service outages may occur frequently for short periods of time due to system coverage limitations. Operators must use LNAV minima for flight planning to these airports. If the WAAS avionics indicate availability of LNAV/VNAV or LPV vertical guidance, then pilots may use the displayed level of service to complete the approach.
d. RNP Considerations. Pilots of aircraft with a recognized RNP airworthiness capability must not fly to LPV/LP lines of minima based solely upon their RNP capability. Only operators of aircraft with an airworthiness approval for WAAS LPV/LP capability may fly RNAV (GPS) procedures using the LPV/LP line of minima. The aircraft must use WAAS to fly to the LPV/LP line of minima on an RNAV (GPS) approach.
e. Contingency Procedures. Pilots must be familiar with the fail-down capability of their WAAS integration. The operator should develop contingency procedures to react safely following the loss of GPS and/or WAAS capability (see subparagraphs (1), (2), and (3) below).
Pilots must notify air traffic control (ATC) of any loss of GPS and/or WAAS capability, together with their proposed course of action.
(1) Example: LPV or LP lines of minima approach not available due to reduced WAAS service.
(a) Prior to the final approach fix (FAF):
• The LNAV or LNAV/VNAV line of minima may still be available to pilots depending on the nature of the reduced service.
• Pilots may elect to continue the approach to the LNAV or LNAV/VNAV line of minima.
• Alternatively, pilots may select a different approach using a ground-based NAVAID or fly to an alternate airport.
(b) After the aircraft passes the FAF an alert may result in a fail-down to LNAV-only operations.
• Pilots can continue to the LNAV minimums if the aircraft is above the MDA or the next step-down fix altitude for the LNAV approach.
• Pilots must initiate a missed approach if below a required altitude on the approach and cannot transition visually to land.
NOTE: TSO-C146a minimum performance requirements do not require avionics equipment to offer LNAV fail-down capability although some manufacturers have chosen to include it. If TSO-C146a equipment does not include LNAV fail down capability, the pilot must perform a missed approach when the vertical guidance is flagged or another integrity alert is indicated. The pilot must perform a missed approach for any TSO-C146 equipment if both lateral and vertical guidance is flagged or another integrity alert is indicated.
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(2) Example: No WAAS service—this situation is comparable to unaugmented GPS equipment (e.g., TSO-C196 equipment).
(a) Prior to the aircraft passing the FAF:
• The avionics will provide integrity using FDE.
• If there is no lateral flag or other integrity alert, a pilot may complete the RNAV (GPS) approach using the LNAV line of minima.
• If a pilot sees a lateral flag or integrity alert, the pilot should do one of the following:
1. Request clearance from ATC to enter and remain in a holding pattern (fuel permitting) until the lateral flag or integrity alert disappears,
2. Request a clearance from ATC for a different approach using ground-based NAVAIDs (if available), or
3. Request a clearance from ATC to fly to an alternate airport.
(b) After the aircraft passes the FAF, if the avionics provide a lateral flag or integrity alert, the pilot must perform a missed approach if unable to continue visually.
(3) Example: Complete GPS service outage or avionics malfunction. When a GPS service outage occurs all RNAV (GPS) approaches will be out of service. In either instance, the pilot must choose an instrument approach based on ground-based NAVAIDs such as very high frequency omni-directional range (VOR), Non-Directional Beacons (NDB), or ILS.
9. TRAINING.
a. Training Program. Training for RNAV (GPS) instrument approach operations including use of the LPV and/or LP lines of minima should include the following items (see list below).
Operators must be familiar with how to use their avionics in compliance with the aircraft and/or avionics manufacturer’s operations manuals and should take advantage of applicable training tutorials. Parts 91K, 121, 125, 133, 135, and 137 operators should address the following specific training elements:
NOTE: No special crew qualifications, other than those necessary for RNAV and ILS instrument approaches, are currently specified for WAAS operations. If RNAV approaches are already integrated into a current training program, operators are not required to have a separate program to incorporate LPV and LP specific training elements from this AC. In the absence of a training program, operators should use this guidance to develop their training curriculum and document the training as outlined in subparagraph 9b.
(1) The information in this AC.
(2) The meaning and proper use of aircraft equipment/navigation suffixes.