Air Traffic Management Concept Baseline Definition - The Boeing ...

geostationary, they orbit over the equator at an altitude such that they appear stationary to
a ground observer. Therefore, the satellite appears near the horizon to an aircraft flying at
a high latitude. There are four Inmarsat locations (Atlantic Ocean East, Atlantic Ocean
West, Indian Ocean, and Pacific Ocean), so coverage extends nearest the poles directly
north (or south) of each satellite location.
Voice broadcast is provided in the VHF communications band for ATIS, ASOS, and
AWOS. TWEB is available on some VOR and NDB stations. Some countries also
provide ATIS on a VOR frequency instead of a VHF communications frequency.
5.2.1.2 ACARS
Voice communication can provide direct communication from a person’s brain, through
his voice, to the brain of another person. Data communication, on the other hand, has the
capability to communicate from a computer to another computer. This allows
communication of important data without human intervention. On the other hand, text
messages can be presented by the computer to the pilot and controller, which can
communicate some information more efficiently and accurately than voice. The
advantages are improved communication accuracy and a potential reduction in workload.
ARINC Communications Addressing and Reporting System (ACARS) was developed by
the airline industry nearly 20 years ago to support their AOC needs. Most of the
communication requirements of the federal regulations are met by ACARS. The
Out/Off/On/In reports, which were the first messages of ACARS, have been supplemented
by a wide variety of messages, conveying information both to and from the airplane. For
instance, some airlines regularly send flight plans to their airplanes for direct loading into
the FMC. Onboard maintenance computers can automatically send reports to the ground
at a specific point in the flight, in case of a detected fault, or in response to a ground
request. The airlines are continuing to expand the functionality of ACARS with additional
message formats.
As seen in Figure 5.3, ACARS is also used for air traffic services communication. The
FAA provides pre-departure clearances for about 40 of the major airports. This is not a
direct ATC-to-airplane service, but rather has used some existing capabilities to provide
this service. ARINC receives the departure clearances from the FAA for contracting
airlines and delivers them to the airline. The airline in turn forwards the clearance to the
designated airplane. Although this is generally considered an ACARS service, the airline
can use any appropriate means, such as delivering a printout to the cockpit, to get the
clearance to the airplane. The FAA is in the process of installing digital ATIS in a number
of towers at major airports, which will allow the flight crew to request and receive the
current ATIS information by ACARS. Like pre-departure clearances, the FAA version of
ATIS is unique to the FAA.
68