RNAV/GPS approach procedures require GPS and can be selected for use. When the display shows ‘gps’ after a NAVAID prefix (such as `VORGPS 17L’), this indicates the procedure is an Overlay Approach. The procedure may be flown either as a conventional, ground-based approach procedure or may be flown using GPS.

Just as the system supports navigating an airway using GPS, and using GPS instead of DME, the system also supports using GPS as an alternate means of navigation for NAVAID exclusive approaches (not including localizer based approaches). The pilot has the option to fly a NAVAID exclusive approach with either GPS/FMS or the NAVAID as the selected CDI source. Refer to the current, pertinent flight manual and regulations for information on alternatively using GPS navigation for NAVAID exclusive approaches.

When the display shows an approach with ‘+V’, this indicates the system will provide advisory vertical guidance when using GPS to fly the approach. Procedure briefing and execution of the approach must be made in accordance with the published approach and applicable landing minimums for this aircraft; +V does not circumvent step down fix restrictions or descent beyond the Minimum Descent Altitude (MDA) without establishing the necessary visual references.

The system will allow the applicable level of service for the chosen approach using GPS navigation; selection of ‘+V’ means advisory vertical guidance will be displayed for that particular level of service. See the following table for levels of service allowed by the system, and the accompanying approach mode indication on the HSI:

Table 27: Approach Level of Service

Level of Service	Selected Approach Mode	Description	Example on HSI
LNAV	LNAV or LNAV+V	Approach to the published MDA Advisory vertical guidance to the MDA available when ‘LNAV+V’ or ‘LP+V’ is selected
LP	LP or LP+V
L/VNAV	L/VNAV	Approach with approved vertical guidance to the published DA
LPV	LPV

The system GPS receivers will use Satellite Based Augmentation (SBAS) when available. Some approach modes require the use of SBAS for lateral and/or vertical GPS navigation. For information on how lateral and vertical guidance is depicted on the PFD, see the Flight Instruments Section.