.  
at least one GPS or one DME is operational

.  
any additional GPS or DME requirements specified by Operations
Specification or by the selected terminal area procedure must be satisfied

.  
when operating with the following RNP values, or smaller:

Approach Type  RNP 
NDB, NDB/DME  0.6 NM 
VOR, VOR/DME  0.5 NM 
RNAV  0.5 NM 
GPS  0.3 NM 

.  no UNABLE REQD NAV PERF - RNP alert is displayed during the
approach.

Use of LNAV
To use LNAV for approaches and missed approaches, a proper series of legs/waypoints that describe the approach route (and missed approach) must appear on the LEGS page. There are two methods of loading these waypoints:
.  Database Selection This method is required for RNAV and GPS approaches. An approach procedure selected through the FMC ARRIVALS page provides the simplest method of selecting proper waypoints. Procedures in the
database comply with obstruction clearance criteria for non-ILS approaches. No waypoints may be added or deleted between the FAF and the MAP. If
the approach to be flown is not in the database, another approach having the same plan view may be selected. For example, an ILS procedure might be selected if the plan view (route) is identical to an NDB approach. In this case, waypoint altitudes must be checked and modified as required. When an approach is flown by this "overlay" method, raw data should be monitored throughout the approach to assure obstacle clearance.
Note: If an NDB approach for the desired runway is in the database, an
overlay approach should not be used. If a waypoint is added to or deleted from a database procedure, FMC “on approach” logic (as described in the FCOM) is partially or completely disabled and the VNAV obstacle clearance integrity of the procedure may be adversely affected. If an additional waypoint reference is desired, use the FIX page and do not modify waypoints on the LEGS page.
.  Manual Waypoint Entry Due to potentially inadequate terrain clearance, manual waypoint entry
should not be accomplished for RNAV or GPS approaches, nor should this method be used with VNAV after the FAF. When no procedure is available from the FMC ARRIVALS page, manual
entry of a series of waypoints may be accomplished to define the approach routing. The waypoints may be conveniently defined by using names of waypoints or navaids in the database, bearing/distance from such fixes, intersections of radials or latitude/longitude information.
Copyright . The Boeing Company. See title page for details.
5.38  FCT 737 (TM) October 31, 2006
Procedure turns and DME arcs cannot usually be manually entered
(unless they can be defined by a series of waypoints). Deviation from the
defined route may require use of “DIRECT TO” or “INTERCEPT
COURSE TO” when intercepting the inbound course. Constant
monitoring of raw data during the approach is required.
Note:  Procedure turns and DME arcs may require use of HDG SEL.
LNAV cannot be used to track fix or radial data displayed on the map that is not part of the active route. A navaid/waypoint and the appropriate radial may be inserted on the FIX page to create a “course” line on the map that helps to improve situational awareness. A similar display may be created by manually tuning an appropriate VOR and selecting the desired course. These methods provide reference information on the map display only. They are not reflected on the LEGS page and cannot be tracked with LNAV. These methods should only be used when there is no opportunity to use an approach selected from the navigation database and should therefore be considered only when normal means of displaying approaches are not available. Pilots should be aware that the displayed course is an FMC calculated course and is not raw data information.
Note:  HDG SEL should be used to fly the approach ground track.
Note:  VNAV PTH operation using speed intervention (as installed) is not available with manually entered waypoints.
If the approach is not available in the NAV database, select the landing runway from the FMC ARRIVALS page. The runway and associated extended centerline then displays on the map to aid in maintaining position awareness.
Pilots should not become involved in excessive “heads down” FMC manipulation to build map displays while at low altitude. Raw data VOR, ILS, and ADF displays should be used to avoid distractions during higher workload phases of flight. Map building should be avoided below 10,000 feet AGL.
Use of VNAV
Approaches using VNAV may be accomplished using any of the recommended roll modes provided in the FCOM procedure.
　
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