background image



which are presently authorized to conduct GPS 



GPS receivers approved for approach operations in 
accordance with: AC 20

138, Airworthiness Approval of 

Positioning and Navigation Systems, qualify for this 
minima. WAAS navigation equipment must be approved in 
accordance with the requirements specified in 

C145() or TSO

C146() and installed in accordance 

with Advisory Circular AC 20



Other systems may be authorized to utilize 

these approaches. See the description in Section A of 
the U.S. Terminal Procedures books for details. 
Operational approval must also be obtained for 

VNAV systems to operate to the LNAV/VNAV 

minimums. Baro

VNAV may not be authorized on 

some approaches due to other factors, such as no local 
altimeter source being available. Baro

VNAV is not 

authorized on LPV procedures. Pilots are directed to 
their local Flight Standards District Office (FSDO) 
for additional information. 



RNAV and Baro

VNAV systems must have a manufacturer 

supplied electronic database which must include the 
waypoints, altitudes, and vertical data for the procedure to 
be flown. The system must be able to retrieve the procedure 
by name from the aircraft navigation database, not just as 
a manually entered series of waypoints. 

3.  ILS or RNAV (GPS) charts. 


Some RNAV (GPS) charts will also 

contain an ILS line of minima to make use of the ILS 
precision final in conjunction with the RNAV GPS 
capabilities for the portions of the procedure prior to 
the final approach segment and for the missed 
approach. Obstacle clearance for the portions of the 
procedure other than the final approach segment is 
still based on GPS criteria. 



Some GPS receiver installations inhibit GPS navigation 


ILS frequency is tuned. Pilots flying 

aircraft with receivers installed in this manner must wait 
until they are on the intermediate segment of the procedure 
prior to the PFAF (PFAF is the active waypoint) to tune the 
ILS frequency and must tune the ILS back to a VOR 
frequency in order to fly the GPS based missed approach. 

(b)  Charting

.  There are charting differences 

between ILS, RNAV (GPS), and GLS approaches. 


The LAAS procedure is titled “GLS 

RWY XX” on the approach chart. 


The VDB provides information to the 

airborne receiver where the guidance is synthesized. 


The LAAS procedure is identified by a 

four alpha

numeric character field referred to as the 

RPI or approach ID and is similar to the IDENT 
feature of the ILS. 


The RPI is charted. 


Most RNAV(GPS) approach charts 

have had the GLS (NA) minima line replaced by an 
LPV line of minima. 


Since the concepts for LAAS and 

WAAS procedure publication have evolved, GLS 
will now be used only for LAAS minima, which will 
be on a separate approach chart. 

4.  Required Navigation Performance (RNP). 


Pilots are advised to refer to the 

tion A) of the U.S. Government Terminal Procedures 
books for aircraft approach eligibility requirements 
by specific RNP level requirements. 


Some aircraft have RNP approval in their 

AFM without a GPS sensor. The lowest level of 
sensors that the FAA will support for RNP service is 
DME/DME. However, necessary DME signal may 
not be available at the airport of intended operations. 
For those locations having an RNAV chart published 
with LNAV/VNAV minimums, a procedure note may 
be provided such as “DME/DME RNP

0.3 NA.” 

This means that RNP aircraft dependent on 
DME/DME to achieve RNP

0.3 are not authorized to 

conduct this approach. Where DME facility 
availability is a factor, the note may read “DME/DME 

0.3 Authorized; ABC and XYZ Required.” 

This means that ABC and XYZ facilities have been 
determined by flight inspection to be required in the 
navigation solution to assure RNP

0.3. VOR/DME 

updating must not be used for approach procedures. 

5.  Chart Terminology. 


Decision Altitude (DA) replaces the 

familiar term Decision Height (DH). DA conforms to 
the international convention where altitudes relate to 
MSL and heights relate to AGL. DA will eventually 
be published for other types of instrument approach 
procedures with vertical guidance, as well. DA 
indicates to the pilot that the published descent profile 
is flown to the DA (MSL), where a missed approach 
will be initiated if visual references for landing are not 

Arrival Procedures