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The maximum authorized altitude (MAA) is the highest
altitude at which the airway can be flown with assurance
of receiving adequate navigation signals. Chart depictions
appear as “MAA-15000.”
When an MEA, MOCA, and/or MAA change on a segment
other than at a NAVAID, a sideways “T” is depicted
on the chart. If there is an airway break without the symbol,
one can assume the altitudes have not changed (see the upper
left area of Figure 8-2). When a change of MEA to a higher
MEA is required, the climb may commence at the break,
ensuring obstacle clearance. [Figure 8-4]
Navigation Features
Types of NAVAIDs
Very high frequency omnidirectional ranges (VORs) are the
principal NAVAIDs that support the Victor and Jet airways.
Many other navigation tools are also available to the pilot.
For example, nondirectional beacons (NDBs) can broadcast
signals accurate enough to provide stand-alone approaches,
and DME allows the pilot to pinpoint a reporting point on the
airway. Though primarily navigation tools, these NAVAIDs
can also transmit voice broadcasts.
Tactical air navigation (TACAN) channels are represented
as the two- or three-digit numbers following the three-letter
identifier in the NAVAID boxes. The NACG terminal
procedures provide a frequency-pairing table for the
TACAN-only sites. On NACG charts, very-high frequencies
and ultra-high frequencies (VHF/UHF) NAVAIDs (e.g.,
VORs) are depicted in black, while low frequencies and
medium frequencies (LF/MF) are depicted as brown.
[Figure 8-5]
Identifying Intersections
Intersections along the airway route are established by a
variety of NAVAIDs. An open triangle indicates the
location of an ATC reporting point at an intersection. If the
triangle is solid, a report is compulsory. [Figure 8-4]
8-8
Figure 8-4. Legend From En Route Low Attitude Chart, Air Traffic Services and Airspace Information Section.
8-9
Figure 8-5. Legend From En Route Low Attitude Chart.
8-10
necessary to enable traffic flow. When a holding pattern is
charted, the controller may provide the holding direction and
the statement “as published.” [Figure 8-4]
Boundaries separating the jurisdiction of Air Route Traffic
Control Centers (ARTCC) are depicted on charts with blue
serrations. The name
of the controlling facility is printed on the
corresponding side of the division line.
ARTCC remote sites are depicted as blue serrated boxes
and contain the center name, sector name, and the sector
frequency. [Figure 8-4]
Weather Information and Communication Features
En route NAVAIDs also provide weather information and
serve communication functions.
When a NAVAID is shown as a
shadowed box, an automated flight
service station (AFSS) of the same
name is directly associated with the facility. If an AFSS is
located without an associated NAVAID, the shadowed box is
smaller and contains only the name and identifier. The AFSS
frequencies are provided above the
box. (Frequencies 122.2 and 255.4,
and emergency frequencies 121.5 and
243.0 are not listed.)
A Remote Communications Outlet (RCO) associated with
a NAVAID is designated by a thinlined
box with the controlling AFSS
frequency above the box, and the
name under the box. Without an
associated facility, the thin-lined
RCO box contains the AFSS name
and remote frequency.
Automated Surface Observing Station (ASOS), Automated
Weather Observing Station (AWOS), Hazardous Inflight
We a the r Advi sory Se rvi c e
(HIWAS) and Tr ans c r ibe d
Weather Broadcast (TWEB) are
continuously transmitted over
selected NAVAIDs and depicted in the NAVAID box. ASOS/
AWOS are depicted by a white “A”, HIWAS by a “H” and
TWEB broadcasts by a “T” in a solid black circle in the upper
right or left corner.
New Technologies
Technological advances have made multifunction displays
and moving maps more common in newer aircraft. Even older
aircraft are being retrofitted to include “glass” in the flight
deck. [Figure 8-6] Moving maps improve pilot situational
awareness by providing a picture of aircraft location in
NDBs, localizers, and off-route VORs are used to establish
intersections. NDBs are sometimes collocated with
intersections, in which case passage of the NDB would mark
the intersection. A bearing to an off-route NDB also can
provide intersection identification. A localizer course used to
identify an intersection is depicted by a feathered arrowhead
symbol on the en route chart.
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