Localizer Performance with Vertical Guidance (LPV)

• An LPV (Localizer Performance with Vertical guidance) approach is an RNAV (GPS) approach with minimums that are typically lower than LNAV or LNAV/VNAV approaches. An LPV approach is an approach procedure designed specifically for SBAS environments. WAAS/LPV procedures are RNAV approaches defined by the FAA as one of four possible lines of approach minimums found on an RNAV approach chart. WAAS avionics equipment approved for LPV approaches is required for this type of approach.
• The terms SBAS Approach or SBAS approach operations are used interchangeably with WAAS/LPV approach, or simply, LPV approach. [G-450 OM 2B-08-120, Section 27.B]

Source: G450 Aircraft Operating Manual, §2B-08-120 ¶27.B

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 glide path 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.

Source: AC 90-107, ¶6.b.

• 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.
• The Space-Based Augmentation System (SBAS) is the implementation of a ground sensor-generated correction signal transmitted to an SBAS-equipped GPS receiver by way of a geosynchronous satellite. Several countries and/or groups of countries are developing their own SBAS system with their own respective names. The SBAS systems in development at this time are as follows:
• Wide Area Augmentation Systems (WAAS) for the United States and Canada
• European Geostationary Navigation Overlay System (EGNOS) for Europe
• Multifunction transportation Satellite-based Augmentation System (MSAS) for Japan

Source: AC 90-107, ¶4.u.

Although several SBAS systems are currently under development, they are all expected to be compatible and interoperable.

Source: G450 Aircraft Operating Manual, §2B-08-120 ¶27.A.

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 glide path (e.g., approaches with LNAV/VNAV, LPV or ILS lines of minima).

Source: AC 90-107, ¶4.b.

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.

Source: AC 90-107, ¶4.g.

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.

Source: AC 90-107, ¶4.o.

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.

Source: AC 90-107, ¶6.e.

RNAV-SBAS: ASC 059B (or later approved revision) required to fly an RNAV (GPS) or an RNAV (GNSS) approach to LPV minima

Source: G450 Airplane Flight Manual, §1-03-10 ¶10.E.

Guidance for Localizer Performance with Vertical Guidance and Localizer Performance without Vertical Guidance Approach Operations in the U.S. National Airspace System, 2/11/11, U.S. Department of Transportation

Source: Advisory Circular 90-107

Part 91 Operator/Aircraft Approval. Part 91 operators should review their AFM, RFM or AFMS to establish that their aircraft meets navigation system eligibility as detailed in paragraph 7. Once the operator has established system eligibility, the operator should review the operational and training considerations as detailed in paragraphs 8 and 9. After completing these actions, the operator may conduct LPV and LP approach operations to a published DA and MDA, respectively. An LOA is not required when eligibility is based on the AFM, RFM or AFMS and provisions of this AC.

Source: AC 90-107, ¶10.a

Parts 91K, 121, 125, 133, 135 and 137 operators receive approval to fly RNAV (GPS) instrument approaches via OpSpec/MSpec/LOA, paragraph C052, OpSpec/MSpec paragraph H102 or OpSpec/MSpec paragraph H122, Special Non CFR Part 97 Instrument Approach or Departure Procedures for Rotorcraft Operations, as applicable. If the operator has already been approved to fly IAP with vertical guidance using RNAV (GPS) or RNAV (GNSS), such as baro-VNAV, then no further authorization is required. If the operator is not already approved to fly IAP with vertical guidance using RNAV (GPS) or RNAV (GNSS), the Principal Operations Inspector will authorize LPV and/or LP operations for the operator via OpSpec/MSpec/LOA, paragraph C052, OpSpec/MSpec paragraph H102 or OpSpec/MSpec paragraph H122.

Source: AC 90-107, ¶10.c.

An optional LOA template is provided to satisfy a request from foreign regulatory authorities for evidence of training and approval to fly GNSS-based approaches. Unlike the other C052 templates, the inspector only has the option of GLS or RNAV (GNSS) approaches to LNAV, LNAV/VNAV, LPV or Localizer Performance (LP) lines of minima. As a result, this LOA is not a comprehensive list of authorized approaches for the operator, but only a subset to address foreign GNSS-based approaches.

Source: FAA Order 8900, Vol 3, Ch. 18, Part C, C052

• Honeywell Flight Technical Services has received several questions regarding the use of an LPV approach as a backup to a visual approach. Many pilots are familiar with using a localizer and glideslope as a backup when flying a visual approach, but does loading an LPV approach work just as well?
• Having course guidance and a vertical path helps to maintain a stabilized approach. However, using an LPV to backup a visual approach does have its limitations. For example, if a turn onto final occurs inside the FAF, or a side step to another runway is required, the excessive deviation monitor may remove information from the display.
• Pilots are aware that the ILS transmitter is located physically on the field and projects a signal that is then directly received by the aircraft. With an LPV approach, the FMS navigation database contains the final approach segment (FAS) data block associated with the LPV minimums for the RNAV procedure. The FAS data block consists of the lateral and vertical definition for the final approach path to be flown during the approach. The FAS data block is transmitted from the FMS to the Global Navigation System Sensor Unit (GNSSU) and is used to compute the aircraft lateral and vertical deviations for the final approach segment.
• As mentioned previously, there is a monitoring system in the GNSSU for excessive deviations. This monitor is set to trip when either lateral or vertical deviation exceeds two dots of deviation when inside the FAF. The system supplies the pilot with an annunciator in the event of an excessive deviation from the defined LPV final approach segment. This annunciator may be displayed as a flashing lateral or vertical deviation scale in aircraft equipped with an integrated LPV PFD solution, or for aircraft with an external annunciator, an LPV UNAVAIL annunciator is lit and the lateral and vertical deviations are flagged invalid. The annunciator for excessive deviation occurs when the aircraft position has exceeded a set deviation limit (one or two dots of lateral or vertical deviation, depending on the aircraft) while the aircraft is inbound to the runway. The excessive deviation detection initiates 2 NM prior to the FAF and is active until reaching the MAP.
• If an RNAV approach with LPV minimums is selected as a backup to a visual approach, be familiar with the excessive deviation logic found in the AFM. If expected to fly direct to, turn final inside the FAF, or possibly side step and exceed two dots lateral deviation, it is recommended that LNAV or LNAV/VNAV minimums is selected from the approach page on the CDU. This will eliminate the possibility of a loss of any advisory information.

Source: Honeywell Direct To Newsletter, Nov 2013, "LPV Approach as a Visual Approach Backup"