2/14/08 AIM
En Route Procedures 5-3-1
Section 3. En Route Procedures
5-3-1. ARTCC Communications
a. Direct Communications, Controllers and
Pilots.
1. ARTCCs are capable of direct communications
with IFR air traffic on certain frequencies.
Maximum communications coverage is possible
through the use of Remote Center Air/Ground
(RCAG) sites comprised of both VHF and UHF
transmitters and receivers. These sites are located
throughout the U.S. Although they may be several
hundred miles away from the ARTCC, they are
remoted to the various ARTCCs by land lines or
microwave links. Since IFR operations are expedited
through the use of direct communications, pilots are
requested to use these frequencies strictly for
communications pertinent to the control of IFR
aircraft. Flight plan filing, en route weather, weather
forecasts, and similar data should be requested
through FSSs, company radio, or appropriate military
facilities capable of performing these services.
2. An ARTCC is divided into sectors. Each
sector is handled by one or a team of controllers and
has its own sector discrete frequency. As a flight
progresses from one sector to another, the pilot is
requested to change to the appropriate sector discrete
frequency.
3. Controller Pilot Data Link Communications
(CPDLC) is a system that supplements air/ground
voice communications. As a result, it expands
two-way air traffic control air/ground communications
capabilities. Consequently, the air traffic
system's operational capacity is increased and any
associated air traffic delays become minimized. A
related safety benefit is that pilot/controller readback
and hear-back errors will be significantly
reduced. The CPDLC's principal operating criteria
are:
(a) Voice remains the primary and controlling
air/ground communications means.
(b) Participating aircraft will need to have the
appropriate CPDLC avionics equipment in order to
receive uplink or transmit downlink messages.
(c) CPDLC Build 1 offers four ATC data link
services. These are altimeter setting (AS), transfer of
communications (TC), initial contact (IC), and menu
text messages (MT).
(1) Altimeter settings are usually transmitted
automatically when a CPDLC session and
eligibility has been established with an aircraft. A
controller may also manually send an altimeter
setting message.
NOTEWhen
conducting instrument approach procedures, pilots
are responsible to obtain and use the appropriate altimeter
setting in accordance with 14 CFR Section 97.20. CPDLC
issued altimeter settings are excluded for this purpose.
(2) Initial contact is a safety validation
transaction that compares a pilot's initiated altitude
downlink message with an aircraft's ATC host
computer stored altitude. If an altitude mismatch is
detected, the controller will verbally provide
corrective action.
(3) Transfer of communications automatically
establishes data link contact with a succeeding
sector.
(4) Menu text transmissions are scripted
nontrajectory altering uplink messages.
NOTEInitial
use of CPDLC will be at the Miami Air Route Traffic
Control Center (ARTCC). Air carriers will be the first
users. Subsequently, CPDLC will be made available to all
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