AIM

4/3/14

5−4−25

Arrival Procedures

provide a stabilized descent to the LNAV MDA;

however, extra caution should be used in the visual

segment to ensure a vertical correction is not

required. If the VGSI is aligned with the published

glidepath, and the aircraft instruments indicate on

glidepath, an above or below glidepath indication on

the VGSI may indicate that temperature error is

causing deviations to the glidepath. These deviations

should be considered if the approach is continued

below the MDA.

NOTE

−

Many systems which apply Baro

−VNAV temperature

compensation only correct for cold temperature. In this
case, the high temperature limitation still applies. Also,
temperature compensation may require activation by
maintenance personnel during installation in order to be
functional, even though the system has the feature. Some
systems may have a temperature correction capability, but
correct the Baro

−altimeter all the time, rather than just on

the final, which would create conflicts with other aircraft
if the feature were activated. Pilots should be aware of
compensation capabilities of the system prior to
disregarding the temperature limitations.

NOTE

−

Temperature limitations do not apply to flying the LNAV/
VNAV line of minima using approach certified WAAS
receivers when LPV or LNAV/VNAV are annunciated to be
available.

(g) WAAS Channel Number/Approach ID.

The WAAS Channel Number is an optional

equipment capability that allows the use of a 5−digit

number to select a specific final approach segment

without using the menu method. The Approach ID is

an airport unique 4−character combination for

verifying the selection and extraction of the correct

final approach segment information from the aircraft

database. It is similar to the ILS ident, but displayed

visually rather than aurally. The Approach ID

consists of the letter W for WAAS, the runway

number, and a letter other than L, C or R, which could

be confused with Left, Center and Right, e.g., W35A.

Approach IDs are assigned in the order that WAAS

approaches are built to that runway number at that

airport. The WAAS Channel Number and Approach

ID are displayed in the upper left corner of the

approach procedure pilot briefing.

(h)

At locations where outages of WAAS

vertical guidance may occur daily due to initial
system limitations, a negative W symbol ( ) will be
placed on RNAV (GPS) approach charts. Many of

these outages will be very short in duration, but may

result in the disruption of the vertical portion of the
approach. The   symbol indicates that NOTAMs or
Air Traffic advisories are not provided for outages

which occur in the WAAS LNAV/VNAV or LPV

vertical service. Use LNAV or circling minima for

flight planning at these locations, whether as a

destination or alternate. For flight operations at these

locations, when the WAAS avionics indicate that

LNAV/VNAV or LPV service is available, then

vertical guidance may be used to complete the

approach using the displayed level of service. Should

an outage occur during the procedure, reversion to

LNAV minima may be required. As the WAAS
coverage is expanded, the   will be removed.

NOTE

−

Properly trained and approved, as required, TSO-C145()
and TSO-C146() equipped users (WAAS users) with and
using approved baro-VNAV equipment  may plan for
LNAV/VNAV DA at an alternate airport. Specifically au-
thorized WAAS users with and using approved baro-VNAV
equipment may also plan for RNP 0.3 DA at the alternate
airport as long as the pilot has verified RNP availability
through an approved prediction program.

5

−

4

−

6. Approach Clearance

a.

An aircraft which has been cleared to a holding

fix and subsequently “cleared . . . approach” has not

received new routing. Even though clearance for the

approach may have been issued prior to the aircraft

reaching the holding fix, ATC would expect the pilot

to proceed via the holding fix (his/her last assigned

route), and the feeder route associated with that fix (if

a feeder route is published on the approach chart) to

the initial approach fix (IAF) to commence the

approach.  WHEN CLEARED FOR THE
APPROACH, THE PUBLISHED OFF AIRWAY
(FEEDER) ROUTES THAT LEAD FROM THE
EN ROUTE STRUCTURE TO THE IAF ARE PART
OF THE APPROACH CLEARANCE.

b.

If a feeder route to an IAF begins at a fix located

along the route of flight prior to reaching the holding

fix, and clearance for an approach is issued, a pilot

should commence the approach via the published

feeder route; i.e., the aircraft would not be expected

to overfly the feeder route and return to it. The pilot

is expected to commence the approach in a similar

manner at the IAF, if the IAF for the procedure is

located along the route of flight to the holding fix.