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necessary levels of accuracy and availability.
The CAASD is helping the navigation system of the
U.S. to evolve toward a satellite-based system. The
CAASD analysts are providing the modeling necessary
to understand the effects of atmospheric phenomena on
the GPS signal from space, while the CAASD is providing the architecture of the future navigation system and
writing the requirements (and computer algorithms) to
ensure the navigation system’s integrity. Moving toward
a satellite-based navigation system allows aircraft to
divorce themselves from the constraints of ground-based
NAVAIDs and formulate and fly those routes that aircraft route planners deem most in line with their own
cost objectives.
With the advent of SATNAV, there are a number of
applications that can be piggybacked to increase capacity in the NAS. Enhanced navigation systems will be
capable of “random navigation,” that is, capable of
Figure 1-15. FMS Control Display Unit. This depicts an aircraft
established on the Atlantic City, NJ, RNAV (GPS) Rwy 13
instrument approach procedure at the Atlantic City
International Airport, KACY. The aircraft is positioned at the
intermediate fix UNAYY inbound on the 128 degree magnetic
course, 5.5 nautical miles from PVIGY, the final approach fix.
treating any latitude-longitude point as a radio navigation fix, and being able to fly toward it with the
accuracy we see today, or better. New routes into and
out of the terminal areas are being implemented that
are navigable by on-board systems. Properly
equipped aircraft are being segregated from other aircraft streams with the potential to increase volume at
the nation’s busy airports by keeping the arrival and
departure queues full and fully operating.
The CAASD is working with the FAA to define the
nation’s future navigation system architecture. By itself,
the GPS satellite constellation is inadequate to serve all
the system’s needs. Augmentation of the GPS signal via
WAAS and LAAS is a necessary part of that new architecture. The CAASD is developing the requirements
based on the results of sophisticated models to ensure the
system’s integrity, security, and availability.
SURVEILLANCE SYSTEMS
Surveillance systems are set up to enable the ATC system to know the location of an aircraft and where it is
heading. Position information from the surveillance
system supports many different ATC functions. Aircraft
positions are displayed for controllers as they watch
over the traffic to ensure that aircraft do not violate separation criteria. In the current NAS, surveillance is
achieved through the use of long-range and terminal
radars. Scanning the skies, these radars return azimuth
and slant range for each aircraft that, when combined
with the altitude of the aircraft broadcast to the ground
via a transceiver, is transformed mathematically into a
position. The system maintains a list of these positions
for each aircraft over time, and this time history is used
to establish short-term intent and short-term conflict
detection. Radars are expensive to maintain, and position information interpolated from radars is not as good
as what the aircraft can obtain with SATNAV. ADS-B
technology may provide the way to reduce the costs of
surveillance for air traffic management purposes and to
get the better position information to the ground.
New aircraft systems dependent on ADS-B could be
used to enhance the capacity and throughput of the
nation’s airports. Electronic flight following is one
example: An aircraft equipped with ADS-B could be
instructed to follow another aircraft in the landing pattern, and the pilot could use the on-board displays or
computer applications to do exactly that. This means
that visual rules for landing at airports might be used in
periods where today the airport must shift to instrument
rules due to diminishing visibility. Visual capacities at
airports are usually higher than instrument ones, and if
the airport can operate longer under visual rules (and
separation distances), then the capacity of the airport is
maintained at a higher level longer. The CAASD is
working with the Cargo Airline Association and the
Figure 1-16. Airline Flight Deck Instrument Displays
Primary Flight Displays (PFD) Navigation Displays (ND)
Engine Indicating and Crew
Alerting System (EICAS)
Multifunction Display (MFD)
Flight Management Control
Display Units (CDU)
Photo and graphic courtesy of Boeing
Commercial Airplane Group
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FAA to investigate these and other applications of the
ADS-B technology.
　
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