LPV Approach

James Albright (a former G450 driver)

Updated: 2013-10-03

The LPV approach has become the first choice approach for many airports. Refer to  Localizer Performance with Vertical Guidance Approach for background information about: regulatory requirements, equipment requirements, advantages and disadvantages, and limitations.

We often think of the LPV as a precision approach but it actually exists in a third category: Approach with Vertical Guidance.

Everything here is from the references shown below, with a few comments in an alternate color.

Approach Category

If you have ASC 007 you are a Category C airplane unless you have a maintenance logbook entry raising your maximum landing weight. If you do not have ASC 007, you are a Category D airplane, end of discussion. See G450 Approach Category for an explanation.

Approach Selection

Approach selection is made either through the MCDU (NAV > ARRIVAL) or the NAV display.

There is an advantage to making this selection on the NAV display: if the appropriate chart is selected in green from the CHARTS page, future changes to the approach on the NAV display will automatically change the selected chart.

G450 Operational Approval

[G450 Aircraft Operating Manual §1-34-30 ¶3.] Approaches:

a. Approved Procedures

• RNAV (GPS) or RNAV (GNSS)

• RNAV (RNP)

• GPS

• VOR/DME RNAV

• VOR*

• VOR/DME*

• TACAN

• NDB*

*Approaches above, suffixed with an asterisk, may be flown with FMS guidance provided the appropriate civil aviation authority has approved such operations. See that country’s Aeronautical Information Publication, or AIP, to confirm approval. In the US, AC 90-108 advises that RNAV systems cannot be used as a substitute for the navaid lateral guidance during the final approach segment.

Can you fly an RNAV (GNSS) approach?

Probably: see RNAV (GNSS) Example.

b. Limitations and Exceptions:

1. The final segment of the approach must be flown with the FMS in the Approach Mode. DR or DEGRADE annunciators cancel the Approach Mode.

2. For airplanes having ASC 059B (or later approved revision), RNAV (GPS) or RNAV (GNSS) approaches can be executed to LPV minima. When loading an approach with LPV minima into the FMS, either graphically or using the MCDU, the FMS will default to the LPV criteria. Removing the LPV criteria from the FMS in order to perform the approach using LNAV or LNAV / VNAV minima can be done only using the MCDU. With the LPV mode captured, it is recommended that transition to LNAV minima or a go-around be performed if the LPV Unavailable caution CAS message displays.

   NOTE: EGPWS Mode 6 must be operable and the associated audio call outs not inhibited, when performing RNAV (GPS) approaches to LPV minima.

3. Prior to conducting RNAV (RNP) approaches with Authorization Required (AR), appropriate operational approval (i.e., Operations Specifications (OpsSpecs), Letter of Authorization (LOA), or Management Specifications (Mspecs)) must be obtained. Requirements and operational guidance are found in AC 90-101, and in the Gulfstream RNP AR Operations Manual, GAC-OIS-02 or GAC-OIS-07 (basic issue or later approved revision).

c. For airplanes having ASC 059B (or later approved revision), RNAV (GPS) approaches can be executed to LPV minima. When loading a RNAV (GPS) approach with LPV minima into the FMS, either graphically or via the MCDU, the FMS will default to the LPV criteria. Removing the LPV criteria from the FMS in order to perform the approach using LNAV or LNAV/VNAV minima can be done only on the MCDU. With the LPV mode captured, it is recommended that transition to LNAV minima or a go-around be performed if the amber LPV Unavailable caution CAS message appears.

d. For airplanes having ASC 059B or (later approved revision) with SBAS receivers), SBAS-enabled GPS navigators are in compliance with TSO-145c/146c.

[G450 Aircraft Operating Manual §1-34-30 ¶3.] Non-WGS-84 Airspace / Countries Partially Compliant with WGS-84: When operating in non-WGS-84 airspace or in countries where the airspace is partially compliant with WGS- 84, the FMS with GPS position updating meets the required navigation accuracy and may be used for SIDS, STARS and en route navigation. When flying ILS, VOR or ADF approaches and missed approach procedures in these two situations, the GPS updating does not need to be inhibited or deselected provided the appropriate raw data is used throughout the approach and missed approach as the primary navigation reference. For countries that are partially WGS-84 compliant, when RNAV (GNSS) approaches are offered, these approaches may be flown using the FMS with GPS position updating provided the approach chart is annotated with “PANS OPS”.

This bit of advice has changed over the years. For a G450 you can generally navigate en route, fly departures and arrivals on GPS any place in the world. You can fly approaches using GPS in countries that are WGS-84 compliant. For countries that are not compliant, or partially compliant, look for "PANS OPS" on the chart. RNAV (GNSS) approaches will require a bit more research on your part. See:

• G450 WGS-84

• WGS-84

• RNAV (GNSS) Example

Loading the Approach

[G450 Airplane Flight Manual §1-34-30] When loading a RNAV(GPS) approach with LPV minima into the FMS, either graphically or via the MCDU, the FMS will default to the LPV criteria. Removing the LPV criteria from the FMS in order to perform the approach using LNAV or LNAV/VNAV minima can be done only on the MCDU.

[G450 Aircraft Operating Manual §2B-08-120, §28.B] When an RNAV approach with LPV minimums is selected on the FMS ARRIVAL page, a prompt labeled RNAV MIN is displayed in line 2R. 

[G450 Aircraft Operating Manual §28.D-G] The FMS will display "PREDICT LPV UNAVAIL" in the scratchpad if a predictive check of LPV availability fails. It will display "FMS/LPV Miscompare" if the FMS Channel ID does not match the GPS ID Channel for the approach. It will display "LPV APPR LOAD FAIL" if the final approach segment does not load successfully. "LPV" is displayed in white on the PFD when it is armed.

Identification of Approach

[G450 Aircraft Operating Manual §2B-08-120, §28.I]

To assure the proper approach is loaded into the GPS, the reference path identifier (sometimes called the Approach ID) is displayed in white in the FMS Annunciator box on the PFD:

The reference path identifier field is displayed when the following conditions are true:

• FMS navigation information is valid

• GPS navigation information is valid

• Navigation source is FMS

• GPS Airport ID is valid

• GPS Approach ID is valid

• FMS NAV mode is not Dead Reckoning

The GPS-derived airport ICAO identifier is also displayed next to the reference path identifier. The flight crew must visually match this data with the information on the approach chart to verify that the proper FAS data block is loaded into the GPS. If the LPV status transitions to unavailable, the airport identifier and reference path identifier flash amber inverse video for 5 seconds, and then are displayed in steady amber.

The reference path identifier and the airport identifier are displayed in the same place on the PFD and are mutually exclusive with the DR (dead reckoning) annunciator.

Navigation Source During LPV Approach

[G450 Aircraft Operating Manual §28.J] The navigation source during LPV approaches is FMS. The navigation source is annunciated as FMS1, FMS2 or FMS3. The navigation source indicated on the display controller is the same as the navigation source indicated on the PFD (FMS1, FMS2, or FMS3). The LNAV and VGP flight director modes are normally used to fly the final segment of an LPV approach.

Lateral and Vertical Deviations During LPV Approaches

[G450 Aircraft Operating Manual §28.K] During an LPV approach, the lateral and vertical deviations on the PFD are driven by the GPS receiver. When LPV status is active, the lateral and vertical deviations are angular in nature. Lateral deviation is indicated by a blue FMS lateral deviation indicator on the HSI. Vertical deviation is indicated by a blue FMS (VGP) deviation indicator displayed on the vertical deviation scale located to the left of the altitude readout. The deviations are driven directly by the GPS receiver, however, the FMS still acts as the source of the database data and the manager of the approach.

Vertical Deviations with LPV Armed

[G450 Aircraft Operating Manual §28.L] The VGP pointer is used to indicate vertical path deviations during an LPV approach. The VGP scale is displayed as a preview when the FAF becomes the active leg during an LPV approach. When the VGP mode is armed and the VGP pointer moves toward the center and the capture criteria is satisfied, the FMS captures the VGP mode and the VGP (active) pointer is displayed.

LPV Armed

[G450 Aircraft Operating Manual §2B-08-120, §28.Q] The LPV armed annunciator is displayed once the aircraft is inside the terminal area of the airport, the NAV source is FMS and the FMS is producing a channel ID (Approach ID is displayed).

The LPV icon on the PFD will display in white text, indicating an armed status, when the approach has been loaded into the FMS and the airplane is within 30 nm of the destination airport. [G450 Quick Reference Handbook §NG-48]

VGP Armed

[G450 AOM, §2B-08-120, §28.Q] The VGP mode is armed once the FMS determines that the VGP mode arm criteria have been met and the APR button on the guidance panel is pushed.

VGP Captured

[G450 AOM, §2B-08-120, §28.Q] Once the VGP mode is armed and the VGP pointer moves toward the center of the scale and enters the FMS capture criteria, the FMS captures the VGP mode.

LPV Captured

[G450 Aircraft Operating Manual §2B-08-120, §28.Q] Shortly after the APPROACH ID is displayed, and the LPV capture criteria are met, the LPV captured annunciator is displayed. This indicates that the FMS is now using angular deviations directly from the SBAS-capable GPS to guide the vertical path of the aircraft.

[G450 Quick Reference Handbook §NG-48] When within approximately two miles of the FAF, the LPV icon will transition to green text, indicating captured status, and the approach may be continued to LPV minima.

PFD and CAS Alerts

[G450 Aircraft Operating Manual §28.Q] If the "LPV" on the PFD is displayed in amber, the LPV is unavailable and the approach should not be continued to LPV minimums. Descend to LNAV minimums, select another approach, or execute a missed approach.

[G450 Quick Reference Handbook §MB-39]The SBAS signal is unavailable on one or both GPS receivers, reconfigure for an alternate approach.

Limitations (G450)

[G450 Airplane Flight Manual §1-34-30.B.] Approved procedures: RNAV (GPS) or RNAV (GNSS)

1. The final segment of the approach must be flown with the FMS in the Approach Mode. DR or DEGRADE annunciators cancel the Approach Mode.

2. For airplanes having ASC 059B (or later approved revision), RNAV (GPS) or RNAV (GNSS) approaches can be executed to LPV minima. When loading an approach with LPV minima into the FMS, either graphically or using the MCDU, the FMS will default to the LPV criteria. Removing the LPV criteria from the FMS in order to perform the approach using LNAV or LNAV / VNAV minima can be done only using the MCDU. With the LPV mode captured, it is recommended that transition to LNAV minima or a go-around be performed if the LPV Unavailable caution CAS message displays.

NOTE: EGPWS Mode 6 must be operable and the associated audio call outs not inhibited, when performing RNAV (GPS) approaches to LPV minima. 

If the amber "LPV Unavailable" caution CAS message displays, either transition to LNAV minima or perform a go-around.

 References:

Advisory Circular 90-107, 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

Advisory Circular 90-108, Use of Suitable Area Navigation (RNAV) Systems on Conventional Routes and Procedures, 3/3/11, U.S. Department of Transportation

Gulfstream G450 Aircraft Operating Manual, Revision 35, April 30, 2013.

Gulfstream G450 Aircraft Service Change 007C, Maximum Landing Gross Weight, 58,500 pounds, Category C, Provisions, October 26, 2011

Gulfstream G450 Aircraft Service Change Number 059B, Enhanced Navigation, December 22, 2011

Gulfstream GV Airplane Flight Manual, Revision 30, 13 May 2008

Gulfstream G450 Quick Reference Handbook, GAC-AC-G450-OPS-0003, Revision 34, 18 April 2013