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12.3 Minimum Safe/Sector Altitudes (MSA) are
published for emergency use on IAP charts. For
conventional navigation systems, the MSA is
normally based on the primary omnidirectional
facility on which the IAP is predicated. The MSA
depiction on the approach chart contains the facility
identifier of the NAVAID used to determine the MSA
altitudes. For RNAV approaches, the MSA is based
on the runway waypoint (RWY WP) for straight−in
approaches, or the airport waypoint (APT WP) for
circling approaches. For GPS approaches, the MSA
center will be the missed approach waypoint
(MAWP). MSAs are expressed in feet above mean
sea level and normally have a 25 NM radius;
however, this radius may be expanded to 30 NM if
necessary to encompass the airport landing surfaces.
Ideally, a single sector altitude is established and
depicted on the plan view of approach charts;
however, when necessary to obtain relief from
obstructions, the area may be further sectored and as
many as four MSAs established. When established,
sectors may be no less than 90 in spread. MSAs
provide 1,000 feet clearance over all obstructions but
do not necessarily assure acceptable navigation
signal coverage.
31 JULY 08
AIP ENR 1.5−21
United States of America 15 MAR 07
Federal Aviation Administration Nineteenth Edition
12.4 Terminal Arrival Area (TAA)
12.4.1 The objective of the TAA is to provide a
seamless transition from the en route structure to the
terminal environment for arriving aircraft equipped
with Flight Management System (FMS) and/or
Global Positioning System (GPS) navigational
equipment. The underlying instrument approach
procedure is an area navigation (RNAV) procedure
described in this section. The TAA provides the pilot
and air traffic controller with a very efficient method
for routing traffic into the terminal environment with
little required air traffic control interface, and with
minimum altitudes depicted that provide standard
obstacle clearance compatible with the instrument
procedure associated with it. The TAA will not be
found on all RNAV procedures, particularly in areas
of heavy concentration of air traffic. When the TAA
is published, it replaces the MSA for that approach
procedure. See FIG ENR 1.5−20 for a depiction of a
RNAV approach chart with a TAA.
12.4.2 The RNAV procedure underlying the TAA
will be the “T” design (also called the “Basic T”), or
a modification of the “T.” The “T” design
incorporates from one to three IAFs; an intermediate
fix (IF) that serves as a dual purpose IF (IAF); a final
approach fix (FAF), and a missed approach point
(MAP) usually located at the runway threshold. The
three IAFs are normally aligned in a straight line
perpendicular to the intermediate course, which is an
extension of the final course leading to the runway,
forming a “T.” The initial segment is normally from
3−6 NM in length; the intermediate 5−7 NM, and the
final segment 5 NM. Specific segment length may be
varied to accommodate specific aircraft categories
for which the procedure is designed. However, the
published segment lengths will reflect the highest
category of aircraft normally expected to use the
procedure.
12.4.2.1 A standard racetrack holding pattern may
be provided at the center IAF, and if present may be
necessary for course reversal and for altitude
adjustment for entry into the procedure. In the latter
case, the pattern provides an extended distance for the
descent required by the procedure. Depiction of this
pattern in U.S. Government publications will utilize
the “hold−in−lieu−of−PT” holding pattern symbol.
12.4.2.2 The published procedure will be annotated
to indicate when the course reversal is not necessary
when flying within a particular TAA area; e.g.,
“NoPT.” Otherwise, the pilot is expected to execute
the course reversal under the provisions of 14 CFR
Section 91.175. The pilot may elect to use the course
reversal pattern when it is not required by the
procedure, but must inform air traffic control and
receive clearance to do so. (See FIG ENR 1.5−12,
FIG ENR 1.5−13, FIG ENR 1.5−20, and paragraph
8, Procedure Turn and Hold−in−lieu of
Procedure Turn.)
31 JULY 08
ENR 1.5−22 AIP
15 MAR 07 United States of America
Nineteenth Edition Federal Aviation Administration
FIG ENR 1.5−12
Basic “T” Design
AIP ENR 1.5−23
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