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AIM

10/12/17

1

−1−22

Navigation Aids

(5)

GPS instrument approach/departure

operations outside the U.S. must be authorized  by
the appropriate sovereign authority.

4. Departures and Instrument Departure

Procedures (DPs)

The GPS receiver must be set to terminal (±1 NM)
CDI sensitivity and the navigation routes contained in
the database in order to fly published IFR charted
departures and DPs. Terminal RAIM should be
automatically provided by the receiver. (Terminal
RAIM for departure may not be available unless the
waypoints are part of the active flight plan rather than
proceeding direct to the first destination.) Certain
segments of a DP may require some manual
intervention by the pilot, especially when radar
vectored to a course or required to intercept a specific
course to a waypoint. The database may not contain
all of the transitions or departures from all runways
and some GPS receivers do not contain DPs in the
database.  It is necessary that helicopter procedures be
flown at 70 knots or less since helicopter departure
procedures and missed approaches use a 20:1
obstacle clearance surface (OCS), which is double
the fixed

−wing OCS, and turning areas are based on

this speed as well.

5. GPS Instrument Approach Procedures

(a)

GPS overlay approaches are designated

non

−precision instrument approach procedures that

pilots are authorized to fly using GPS avionics.
Localizer (LOC), localizer type directional aid
(LDA), and simplified directional facility (SDF)
procedures are not authorized. Overlay procedures
are identified by the “name of the procedure” and “or
GPS” (e.g., VOR/DME or GPS RWY 15) in the title.
Authorized procedures must be retrievable from a
current onboard navigation database. The naviga-
tion database may also enhance position orientation
by displaying a map containing information on
conventional NAVAID approaches. This approach
information should not be confused with a GPS
overlay approach (see the receiver operating
manual, AFM, or AFM Supplement for details on
how to identify these approaches in the navigation
database).

NOTE

Overlay approaches do not adhere to the design criteria
described in Paragraph 5

−4−5m, Area Navigation (RNAV)

Instrument Approach Charts, for stand

−alone GPS

approaches. Overlay approach criteria is based on the
design criteria used for ground

−based NAVAID ap-

proaches.

(b)

Stand

−alone approach procedures spe-

cifically designed for GPS systems have replaced
many of the original overlay approaches. All
approaches that contain “GPS” in the title (e.g.,
“VOR or GPS RWY 24,” “ G PS RWY 2 4 ,” or
“RNAV (GPS) RWY 24”) can be flown using GPS.
GPS

−equipped aircraft do not need underlying

ground

−based NAVAIDs or associated aircraft

avionics to fly the approach. Monitoring the
underlying approach with ground

−based NAVAIDs is

suggested when able. Existing overlay approaches
may be requested using the GPS title; for example,
the VOR or GPS RWY 24 may be requested as “GPS
RWY 24.” Some GPS procedures have a Terminal
Arrival Area (TAA) with an underlining RNAV
approach.

(c)

For flight planning purposes,

TSO-C129() and TSO-C196()

−equipped users

(GPS users) whose navigation systems have fault
detection and exclusion (FDE) capability, who
perform a preflight RAIM prediction for the
approach integrity at the airport where the RNAV
(GPS) approach will be flown, and have proper
knowledge and any required training and/or
approval to conduct a GPS-based IAP, may file
based on a GPS

−based IAP at either the destination

or the alternate airport, but not at both locations. At
the alternate airport, pilots may plan for:

(1)

Lateral navigation (LNAV) or circling

minimum descent altitude (MDA);

(2)

LNAV/vertical navigation (LNAV/

VNAV) DA, if equipped with and using approved
barometric vertical navigation (baro-VNAV) equip-
ment;

(3)

RNP 0.3 DA on an RNAV (RNP) IAP,

if they are specifically authorized users using
approved baro-VNAV equipment and the pilot has
verified required navigation performance (RNP)
availability through an approved prediction program.

(d)

If the above conditions cannot be met, any

required alternate airport must have an approved
instrument approach procedure other than GPS

based that is anticipated to be operational and
available at the estimated time of arrival, and which
the aircraft is equipped to fly.