Avionics News April 2014 - 15

to create a compliant "system." While this isn't used in light general
aviation applications, it made sense in the early days of developing
the ADS-B solutions. Today, the FAA is on a fast track to develop a
new TSO specific for self-contained ADS-B solutions better geared
for light general aviation applications.
There have been promises of limited field approvals if the aircraft
and system have been previously approved via an STC. Most of
the new entrants into the ADS-B approvals have been approved via
AML (approved model list) STC. For the need to add that "one-off"
aircraft, you should work with your local FAA FSDO (flight standards district office) and the FAA headquarters office responsible
for ADS-B to promote and allow a follow-on field approval.
Communications
According to the FAA, "datalink services are added to the NAS
to reduce frequency congestion, aircrew workload, controller workload, enhance safety and reduce confusion."
Datalink applications are being implemented in flight operations
utilizing FANS (future air navigation system) 1/A, which includes
CPDLC and ADS-C (automatic dependent surveillance-contract).
The FANS 1/A system used in oceanic and remote airspace is a datalink system that communicates over ACARS (aircraft communications addressing and reporting system), which uses a variety of subnetworks like satellite, VDL Mode 0/A, VDL Mode 2 and HFDL.
For the light general aviation community, there aren't any changes in the communication arena on the radar. Most of the domestic
discussions have been focused on the terminal datalink services in
the national airspace system. Every conversation with the FAA has
led to a commitment that rulemaking is not imminent; however,
it will be working from a "best equipped - best served" scenario.
Should an aircraft choose to operate from an airport that is utilizing
terminal datalink services, then likely the lone aircraft with voiceonly capabilities will receive clearances last.
Pre-departure clearance is a subscriber-based service used at
the larger airports in the NAS to provide an effective and efficient
means of delivering departure clearances before aircraft pushback.
Datalink technologies are utilized within the NAS to provide a
PDC message to a subscriber's airline operations computer. Once
the PDC message has been deposited on the subscriber's AOC, it is
then retrieved and printed by the subscriber through one of several
means:
1. Internet access.
2. Airline gate terminal.
3. Airline operations area terminal.
4. FBO terminal.
5. Cockpit avionics via A/G or other datalink.
According to the FAA, it is not necessary for an aircraft to be
equipped with datalink avionics for a flight to participate in the PDC
service; it is only necessary for the flight crew to be able to obtain
a printed copy of the PDC message prior to pushback through one
of these means.
This is not to say there aren't international mandates, again
airspace specific, for datalink communications. The International

Civil Aviation Organization has some transoceanic mandates for
the North Atlantic as well as certain Asia-Pacific routes. Refer to the
ICAO Global Operational Datalink Document for the latest description of the intended datalink operations.
Navigation
In the future, there will be an increased dependence on the use
of RNAV in lieu of routes defined by ground-based navigation aids.
Area Navigation, or RNAV, is the chosen method of navigation that
permits aircraft operation on any desired flight path within the coverage of ground- or space-based navigation aids or within the limits
of the capability of self-contained aids, or a combination of these.
Required navigation performance, or RNP, refers to both aircraft
capability as well as the air traffic statement of the criticality of air
routes. On the aircraft side, RNP is RNAV with onboard navigation
monitoring and alerting. On the ATC side, RNP also is a statement
of navigation performance necessary for operation within a defined
airspace.
A critical component of aircraft RNP is the ability of the aircraft
navigation system to monitor its achieved navigation performance,
and to identify for the pilot whether the operational requirement is,
or is not being met during an operation. Aircraft meeting RNP criteria will have an appropriate entry, including special conditions and
limitations in its aircraft flight manual or supplement. Operators of
aircraft not having specific AFM-RNP certification may be issued
operational approval, including special conditions and limitations
for specific RNP levels.
Situational Awareness
Situational awareness is commonly referred to as ADS-B In.
Without causing an argument from our manufacturing family, the
surveillance folks at the FAA routinely remind us that the information systems being delivered to the aircraft are not surveillance.
Having said this, the operating community, the avionics industry, as
well as the manufacturers, refers to this functionality and the associated products as ADS-B In.
ADS-B In includes the technologies of FIS-B (flight information
services - broadcast) and TIS (traffic information service). I suspect
as technologies advance, we may likely see more situational awareness information being broadcast into the cockpit.
The one note here on the situational awareness information is
that it is "for reference only." It is not intended for making active
operational decisions like the more advanced "approved" traffic or
weather products used on larger transport category aircraft.
Among the first FAA-provided data services, TIS is intended to
improve the safety and efficiency of "see-and-avoid" flight through
an automatic display that informs the pilot of nearby traffic and
potential conflict situations.
The TIS provides information to the cockpit via datalink, which
is similar to VFR radar traffic advisories normally received over
voice radio.
Continued on page 49
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