System Improvement Plans
6-1In the next ten years, exciting new technologies will be
implemented to help ease air traffic congestion, add to
system capacity, and enhance safety. Some of these
changes will be invisible to pilots and will be made
seamlessly. Others will entail changing some old habits
and learning new procedures. New aircraft equipment
will bring powerful new capabilities, but will require
training and practice to master.
FLEET IMPROVEMENT
Airlines and other operators will continue trying to find
more efficient ways to use the National Airspace System
(NAS). More and more users are working with federal
agencies to write new policies and develop exchanges of
real-time flight information, all in the interest of improving their service as well as their bottom lines. As new
business strategies emerge, there also will be changes in
the aircraft fleet. For example, as regional jets continue to
increase in popularity, they have significant potential to
reduce traffic at major airports as well as on the most
crowded airways. Providing service along underused area
navigation (RNAV) routes directly between smaller city
pairs, they can bypass congested hubs and avoid airborne
choke points. The number of regional jets is forecast to
increase by more than 80 percent in the next decade.
Compared to the turboprop airplanes they will replace,
RJs fly at similar speeds and altitudes as larger jets, so
they mix into traffic
streams more smoothly,
making en route traffic
management easier for
controllers.
At the other end of
the spectrum, larger
airplanes capable of
carrying over 500
passengers are now
flying. These “superjumbos” have the
potential to reduce
airway and terminal
congestion by transporting more people
in fewer airplanes.
This ability is especially valuable at major hubs, where the
number of flight operations exceeds capacity at certain
times of day. On the other hand, some of these airplanes
have a double-deck configuration that might require
extensive changes to terminals so that large numbers of
passengers can board and deplane quickly and safely.
Their size may require increased separation of taxiways
and hold lines from runways due to increased wingspans
and tail heights. Their weight also may require stronger
runways and taxiways, as well as increased separation
requirements for wake turbulence.
Other innovative airplanes include the turbofan-powered
very light jets (VLJs), which are relatively small turbo-
Figure 6-1. Regional Jets.
Figure 6-2. Superjumbo Airplanes.
6-2
fan-powered aircraft with 6 to 8 seats, with cruising
speeds between 300 and 500 knots, and with a range of
around 1,000 nautical miles (NMs). If initial orders are an accurate indicator of their popularity,
they will soon form a significant segment of the general
aviation fleet. The FAA predicts that the business jet
fleet will nearly double over the next ten years,
approaching 16,000 airplanes by 2016. At least eight
manufacturers are planning VLJs, several prototypes
are flying, and the first new airplanes are being delivered to customers. Most are intended for single-pilot
operation, and most will be certified for flight up to
FL410. All will be technically advanced aircraft, with
advanced glass cockpit avionics, digital engine controls, and sophisticated autopilots. These new airplanes
will be capable of RNAV, required navigation performance (RNP), and reduced vertical separation minimum
(RVSM) operations, and will operate mostly point-topoint, either on Q-Routes or random off-airways routes.
With prices well below other business jets and competitive with turboprop singles, VLJs will appeal to many
customers who could not otherwise justify the cost of a
jet aircraft. VLJs have the potential of providing air
taxi/air limousine services at costs comparable to commercial airlines, but with greater schedule flexibility,
relatively luxurious accommodations, faster travel
times, and the ability to fly into thousands more airports.
ELECTRONIC FLIGHT BAG
As part of an ongoing effort to use the best technology
available, industry has improved the timeliness and accuracy of information available to the pilot by converting it
from a paper to a digital medium. An electronic flight bag
(EFB) is an electronic display system intended primarily
for cockpit/flightdeck or cabin use. EFBs can display a
variety of aviation data or perform basic calculations,
such as determining performance data or computing fuel
requirements. In the past, paper references or an airline’s
flight dispatch department provided these functions. The
EFB system may also include various other hosted databases and applications. These devices are sometimes
referred to as auxiliary performance computers or laptop
auxiliary performance computers.
The EFB is designed to improve efficiency and safety
by providing real-time and stored data to pilots electronically. Use of an EFB can reduce some of a pilot’s
time-consuming communications with ground controllers while eliminating considerable weight in paper.
EFBs can electronically store and retrieve many
required documents, such as the General Operations
Manual (GOM), Operations Specifications (OpSpecs),
company procedures, Airplane Flight Manual (AFM),
maintenance manuals and records, and dozens of other
documents.
In addition, advanced EFBs can also provide interactive
features and perform automatic calculations, including
performance calculations, power settings, weight and
balance computations, and flight plans. They can also
display images from cabin-mounted video and aircraft
exterior surveillance cameras.
An EFB may store airport maps that can help a pilot
avoid making a wrong turn on a confusing path of runways and taxiways, particularly in poor visibility or at
an unfamiliar airport. Many runway incursions are due
to confusion about taxi routes or pilots not being quite
sure where they are on the airport.
The FAA neither accepts or approves Class 1 or 2 EFBs
which contain Types A, B, or C application software.
Those who operate under 14 CFR parts 91K, 121, 125,
129, or 135 must obtain authorization for use. Advisory
Circular 120-76, Guidelines for the Certification,
Airworthiness, and Operational Approval of Electronic
Flight Bag Computing Devices, sets forth the acceptable
means for obtaining both certification and approval for
operational use of Class 3 EFBs. It also outlines the
capabilities and limitations of each of the three classes
of EFBs, which are grouped according to purpose and
function. Depending on the features of the specific unit,
these devices are able to display a wide range of flightrelated information. The most capable EFBs are able to
display checklists, flight operations manuals (FOMs),
CFRs, minimum equipment lists, en route navigation
and approach charts, airport diagrams, flight plans, logbooks, and operating procedures. Besides serving as a
cockpit library, they can also make performance calculations and perform many of the tasks traditionally handled by a dispatch department. Some units can also
accept satellite weather data or input from global positioning system (GPS) receivers, combining the aircraft
position and graphic weather information on a moving
map display.
Figure 6-3. Very Light Jets are expected to become a sizeable
segment of the high-altitude fleet.
Courtesy Eclipse Aviation.
6-3
Figure 6-4. Electronic Flight Bag. The EFB has the potential to replace many paper charts and manuals in the cockpit.
Figure 6-5. Moving Map Taxi Diagram on EFB.
6-4
Class 1 EFBs are portable. They can be used both on
the ground and during flight, but must be stowed for
takeoff and landing. They are limited to providing supplemental information only and cannot replace any
required system or equipment. It may be connected to
aircraft power through a certified power source, to
operate the EFB and recharge its batteries. They are
allowed to read data from other aircraft systems, and
may receive and transmit data through a data link.
Class 1 EFBs can display many different kinds of tabular data, such as performance tables, checklists, the
FOM, AFM, and pilot’s operating handbook (POH).
While a Class 2 EFB is also removable from the aircraft,
it is installed in a structural-mounting bracket. This
ensures that the EFB will not interfere with other aircraft systems. While Class 1 and 2 EFBs are both considered portable electronic devices, a logbook entry is
required to remove the Class 2 EFB from the aircraft. It
can be connected to aircraft power and to the aircraft’s
datalink port. The EFB can exchange data with aircraft
systems, enabling it to make interactive performance
calculations. It can be used to compute weight and balance information as well as takeoff and landing Vspeeds, and to display flight critical pre-composed data,
such as navigation charts. Since it is not necessarily
stowed for takeoff and landing, pilots can use it to display departure, arrival, and approach charts.
The most capable EFBs are Class 3. These are built into
the panel and require a Supplemental Type Certification
(STC) or certification design approval with the aircraft
as part of its equipment. Paper charts may not be
required. Depending on the model, it may be connected
to the GPS or Flight Management System (FMS), and it
may be able to combine GPS position with the locations
and speed vectors of other aircraft and graphic weather
information into a single, detailed moving map display.
Its detailed database can also provide obstacle and terrain warnings. It is important to remember that an EFB
does not replace any system or equipment required by
the regulations.
INCREASING CAPACITY AND SAFETY
Safety is, and will remain, the highest priority in all
plans to increase capacity for the future. As demand for
air travel continues to rise, it is clear that the NAS capacity must grow. Both the number of airport operations and
en route capacity must increase simultaneously to
accommodate the expanding needs. Neither can realistically be treated separately from the other, but for the
sake of convenience, this chapter first discusses increasing the arrival/departure rate, then en route issues.
The number of aircraft operations is expected to increase
by about 30 percent over the next decade. Although most
parts of the NAS are able to handle current traffic,
increasing operations will strain system capabilities
unless capacity grows to match demand. The FAA has
identified and corrected several existing “choke points”
in the NAS. While relatively few airports and airways
experience large numbers of delays, the effects snowball
into disruptions throughout the rest of the system, especially in adverse weather. Capacity must be increased to
manage future growth. The FAA is implementing a
number of programs to increase the capacity and efficiency of the NAS. Industry itself is also taking specific
actions to address some of the problems.
INCREASING THE
DEPARTURE/ARRIVAL RATE
Relatively few routes and airports experience the majority of congestion and delays. In the case of airports, peak
demand occurs for only a few, isolated hours each day,
so even the busiest hubs are able to handle their traffic
load most of the time. Adjusting the number of arrivals
and departures to get rid of those peak demand times
would ease congestion throughout the system.
MORE RUNWAYS
At some major hubs, adding new runways or improving
existing runways can increase capacity by as much as 50
percent, but the process is complex and time-consuming. During the planning phase, the appropriate FAA
offices must review the new runway’s impact on airspace, air traffic control (ATC) procedures, navigational
aids (NAVAIDs), and obstructions. New instrument procedures must be developed, and economic feasibility
and risk analysis may be required.
The next phase includes land acquisition and environmental assessment. Often, the airports that most need
new runways are “landlocked” by surrounding developed areas, so obtaining land can be difficult. On top of
that, residents and businesses in the area sometimes
resist the idea of building a new runway. Concerns range
from increased noise to safety and environmental
impact. While environmental assessments and impact
statements are essential, they take time. The FAA is
working with other federal authorities to streamline
the process of obtaining permits. Good community
relations are extremely important, and working with
airport neighbors can often address many of the questions and concerns.
The next phase of development involves obtaining the
funding. A new runway typically costs between 100 million and one billion dollars. Money comes from airport
cash flow, revenue and general obligation bonds, airport
improvement program grants, passenger facility
charges, and state and local funding programs.
The last phase includes the actual construction of the
new runway, which may take as many as three years to
complete. In all, over 350 activities are necessary to
commission one new runway. The FAA has created the
6-5
Runway Template Action Plan to help airport authorities
coordinate the process.
SURFACE TRAFFIC MANAGEMENT
In cooperation with the FAA, the National Aeronautics
and Space Administration (NASA) is studying
automation for aiding surface traffic management at
major airport facilities. The surface management
system is an enhanced decision support tool that will
help controllers and airlines manage aircraft surface
traffic at busy airports, thus improving safety, efficiency,
and flexibility. The surface management system provides tower controllers and air carriers with accurate
predictions of the future departure demand and how the
situation on the airport surface, such as takeoff queues
and delays at each runway, will evolve in response to
that demand. To make these predictions, the surface
management system will use real-time surface surveillance, air carrier predictions of when each flight will
want to push back, and computer software that accurately predicts how aircraft will be directed to their
departure runways.
In addition to predictions, the surface management system also provides advisories to help manage surface
movements and departure operations. For example, the
surface management system advises a departure
sequence to the ground and local controllers that efficiently satisfies various departure restrictions such as
miles-in-trail and expected departure clearance times
(EDCTs). Information from the surface management
system is displayed in ATC towers and airline ramp towers, using either dedicated surface management system
displays or by adding information to the displays of
other systems.
Parts of the system were tested in 2003 and 2004, and
are now ready for deployment. Other capabilities are
accepted in concept, but are still under development.
Depending on the outcome of the research, the surface
management system might also provide information to
the terminal radar approach control (TRACON) and
center traffic management units (TMUs), airline operations centers (AOCs), and ATC system command
centers (ATCSCCs). In the future, additional developments may enable the surface management system to
work with arrival and departure traffic management
decision support tools.
The surface movement advisor (SMA) is another program now being tested in some locations. This project
facilitates the sharing of information with airlines to
augment decision-making regarding the surface movement of aircraft, but is concerned with arrivals rather
than departures. The airlines are given automated radar
terminal system (ARTS) data to help them predict an air-
craft’s estimated touchdown time. This enhances airline
gate and ramp operations, resulting in more efficient
movement of aircraft while they are on the ground.
Airline customers reported reduced gate delays and
diversions at the six locations where SMA is in use.
TERMINAL AIRSPACE REDESIGN
The FAA is implementing several changes to improve
efficiency within terminal airspace. While some methods increase capacity without changing existing routes
and procedures, others involve redesigning portions of
the airspace system. One way of increasing capacity
without major procedural changes is to fill the gaps in
arrival and departure streams. Traffic management advisor (TMA) is ATC software that helps controllers by
automatically sequencing arriving traffic. Based on
flight plans, radar data, and other information, the software computes very accurate aircraft trajectories as
much as an hour before the aircraft arrives at the TRA-
CON. It can potentially increase operational capacity by
up to ten percent, and has improved capacity by 3 to 5
percent for traffic into the Dallas/Ft. Worth, Los
Angeles, Minneapolis, Denver, and Atlanta airports.
One limitation of TMA is that it uses information on
incoming flights from a single Air Route Traffic Control
Center (ARTCC). Another version is under development
that will integrate information from more than one
ARTCC. It is called multi-center traffic management
advisor (McTMA). This system is being tested in the
busy Northeastern area, and the results are promising.
Another software-based solution is the passive final
approach spacing tool (pFAST). This software analyzes
the arriving traffic at a TRACON and suggests appropriate runway assignment and landing sequence numbers
to the controller. Controllers can accept or reject the
advisories using their keyboards. The early version carries the “passive” designation because it provides only
runway and sequence number advisories. A more
advanced version, called active FAST (aFAST), is currently under development at NASA Ames Research
Center. In addition to the information provided by
pFAST, aFAST will display heading and speed, and it is
expected to improve capacity by an additional 10 percent over pFAST.
Airlines can help ease congestion on shorter routes by
filing for lower altitudes. Although the airplane uses
more fuel at a lower cruising altitude, the flight may
prove faster and more economical if weather or high
traffic volume is delaying flights at higher levels. The
tactical altitude assignment program consists of published routes from hubs to airports 200 to 400 NM away.
Based on results of evaluation, it is not expected to be
implemented nationally, although it may remain available in local areas.
6-6
Beyond using existing facilities and procedures more
effectively, capacity can often be increased by making
relatively minor changes in air traffic procedures. For
example, in some instances, departure and arrival patterns have remained unchanged from when there was
very little air traffic, and congestion results when today’s
traffic tries to use them. Likewise, arrival and departure
procedures may overlap, either because they were based
on lower volumes and staffing or because they are based
on ground-based navigation. The interdependence of
arrival and departure routes tends to limit throughput in
both directions.
Separating departures from incoming traffic can simplify
the work of controllers, reduce vectoring, and make more
efficient use of terminal airspace. In the four corner post
configuration, four NAVAIDs form the four corners of
the TRACON area, roughly 60 NM from the primary airport. All arrivals to the area fly over one of these “corner
posts” (also called arrival meters or feeder fixes). The
outbound departure streams are spaced between the
arrival streams.
As more and more aircraft are equipped for RNAV,
new arrival and departure routes are being created that
do not depend on very high frequency omni-directional range (VOR) airways or ground-based
NAVAIDs. Shifting traffic to new RNAV routes eases
congestion on existing airways. There are already several new RNAV routes in use and many more are being
developed.
SEPARATION STANDARDS
Current regulations permit a 3 NM separation within 40
NM of a single radar sensor. The FAA is looking at
ways to increase the use of the 3 NM separation standard to improve efficiency and maximize the volume
of traffic that can be safely moved into busy terminal
areas. The methods involve increasing the size of terminal areas to include more en route airspace,
redesigning airspace to encompass multiple airports
within a single ATC facility, and consolidating certain
TRACON facilities. This will involve major changes
on the ground for ATC facilities, and changes in
charts and procedures for pilots.
Figure 6-6. Four Corner Post Configuration.
6-7
As gaps are filled in arrival and departure streams and the
3 NM separation standard is applied more extensively,
traffic advisories from the traffic alert and collision avoidance system (TCAS) are bound to increase. While newer
software enhances functionality, provides more timely
resolution advisories, and eliminates many nuisance
alerts, data link technology based on GPS position information may offer even better results.
MAINTAINING RUNWAY USE
IN REDUCED VISIBILITY
Although traffic in congested airspace typically operates
under instrument flight rules (IFR), adverse weather and
actual instrument meteorological conditions (IMC) can
drastically reduce system capacity. Many parallel runways cannot be used simultaneously in IMC because of
the time delay and limited accuracy of terminal area
radar, and the runways are spaced closer than the minimum allowable distance for wake vortex separation.
LAAS AND WAAS IMPLEMENTATION
The wide area augmentation system (WAAS) became
available at most locations in 2003. Additional ground
reference stations are expected to become operational
in Canada, Mexico, and Alaska by 2008, providing
more complete WAAS coverage for the continental
United States. The local area augmentation system
(LAAS) provides even greater accuracy and may be
certified for use in precision approaches at some locations beginning in 2007.
Another benefit of LAAS and WAAS is that better
position information can be sent to controllers and
other aircraft. Automatic dependant surveillancebroadcast (ADS-B) uses GPS to provide much more
accurate location information than radar and
transponder systems. This position information is
broadcast to other ADS-equipped aircraft (as well as
ground facilities), providing pilots and controllers
with a more accurate real-time picture of traffic.
For full safety and effectiveness, every aircraft under
the control of ATC will need ADS-B. Until that occurs,
controllers must deal with a mix of ADS-B and
transponder-equipped aircraft. Equipment is already
available that can fuse the information from both
sources and show it on the same display. Traffic information service-broadcast (TIS-B) does just that.
Although TIS-B is primarily intended for use on the
ground by controllers, the information can be transmitted to suitably equipped aircraft and displayed to pilots
in the cockpit. The cockpit display of traffic information (CDTI) provides information for both ADS-B and
non-ADS-B aircraft on a single cockpit display.
Since this information is shown even
while the aircraft is on the ground, it also improves situational awareness during surface movement, and can
help prevent or resolve taxiing conflicts.
090
HGD MAG
GS 215 TAS 229
105/15
12 6
114.3
CRS 055
DME 27.9
VOR R
FROM
RW23
9
+04
DAL117
-09
UPS350
-09
Radar
Target
ADS-B Target
UPS Flight 350
900 ft below
and descending
Flight Track
ADS-B Target
DAL Flight 117
900 ft below
and climbing
Figure 6-7. Cockpit Display of Traffic Information. This
display shows both ADS-B and other aircraft radar targets.
6-8
REDUCING EN ROUTE CONGESTION
In addition to the congestion experienced at major hubs
and terminal areas, certain parts of the en route structure have reached capacity. Easing the burden on
high-volume airways and eliminating airborne choke
points are some of the challenges addressed by new
airspace plans.
MATCHING AIRSPACE
DESIGN TO DEMANDS
More new RNAV routes are being created, which are
essentially airways that use RNAV for guidance instead
of VORs. They are straighter than the old VOR airways,
so they save flight time and fuel costs. By creating additional routes, they reduce traffic on existing airways,
adding en route capacity. As new routes are created near
existing airways, chart clutter will become more of an
issue. Electronic chart presentations are being developed
that will allow pilots to suppress information that is irrelevant to their flight, while ensuring that all information
necessary for safety is displayed. The high degree of
accuracy and reliability of RNP procedures offers
another means of increasing capacity along popular
RNAV routes. Instead of having all the aircraft that are
using the route fly along the same ground track, RNP
allows several closely spaced parallel tracks to be created for the same route. In essence, this changes a
one-lane road into a multi-lane highway.
REDUCING VOICE COMMUNICATION
Many runway incursions and airborne clearance mistakes are due to misunderstood voice communications.
During busy periods, the necessity of exchanging
dozens of detailed instructions and reports leads pilots
and controllers to shorten and abbreviate standard
phraseology, often leading to errors. It stands to reason
that better ways to transfer information could reduce
voice communications, and thus reduce the incidence of
communication errors. One such innovation is similar to
the display screen at fast-food drive-up windows. As the
cashier punches in the order, it is displayed on the monitor so the customer can verify the order. This kind of
feedback reduces the common problem of hearing what
is expected to be heard, which is particularly problematic in ATC clearances and read backs. Not only does
reducing voice communications reduce frequency
congestion, it also eliminates certain opportunities for
misunderstanding.
Controller pilot data link communication (CPDLC) augments voice communications by providing a second
communication channel for use by the pilot and controller, using data messages that are displayed in the
cockpit. This reduces delays resulting from congestion
on voice channels. The initial version of CPDLC will
display a limited number of air traffic messages, but
future versions will have expanded message capabilities
and permit pilot-initiated requests.
Point A
Point B
Figure 6-8. RNP allows parallel tracks along the same route, multiplying capacity along that route.
6-9
AIRCRAFT COMMUNICATIONS
ADDRESSING AND REPORTING SYSTEM
Of course, pilot-controller communication is compromised when the crew is listening to other frequencies or
engaged in other communications, such as talking to
their company. If these communications could be
accomplished silently and digitally, voice communications with ATC would improve. The Aircraft
Communications Addressing and Reporting System
(ACARS) is a commercial system that enables the crew
to communicate with company personnel on the ground.
It is often used to exchange routine flight status messages, weather information, and can serve as a non-voice
communication channel in the event of an emergency.
Many of the messages are sent and received automatically, such as the time the flight leaves the gate
(triggered by the release of the parking brake), takeoff and touchdown times (triggered by landing gear
switches), and arrival time (triggered when a cabin
door is opened). Other information may include
flight plans, significant meteorological information
(SIGMETs), crew lists, cargo manifests, automatic
terminal information service (ATIS) reports, en
route and destination weather, clearances, and fuel
reports. Some ACARS units can interface with
onboard engine and performance-monitoring systems
to inform company ground personnel of maintenance
or operations related issues.
Significant valuable meteorological data can be obtained
by collecting data from aircraft fitted with appropriate
software packages. To date, the predominant sources of
automated aviation data have been from aircraft
equipped with aircraft to satellite data relay (ASDAR)
and ACARS, which routes data back via general purpose
information processing and transmitting systems now
fitted to many commercial aircraft. These systems offer
the potential for a vast increase in the provision of aircraft observations of wind and temperature. Making an
increasingly important contribution to the observational
database, it is envisioned that ACARS data will
inevitably supersede manual pilot reports (PIREPS).
Another use of ACARS is in conjunction with Digital
ATIS (D-ATIS), which provides an automated process
for the assembly and transmission of ATIS messages.
ACARS enables audio messages to be displayed in text
form in the flight decks of aircraft equipped with
ACARS. A printout is also provided if the aircraft is
equipped with an on-board printer. D-ATIS is operational at over 57 airports that now have pre-departure
clearance (PDC) capability.
AUTOMATIC DEPENDENT
SURVEILLANCE-BROADCAST
Unlike TCAS and terrain awareness and warning systems
(TAWS), which have been used in airline and military air-
craft for at least a decade, ADS-B is a relatively new air
traffic technology. It is an onboard system that uses Mode
S transponder technology to periodically broadcast an aircraft’s position, along with some supporting information
like aircraft identification and short-term intent. By picking up broadcast position information on the ground
instead of using ground radar stations, ADS-B represents
a significant advancement over the existing ATC system
by providing increased accuracy and safety. This is possible because ADS-B addresses the major deficiency of
TCAS - accuracy. In the TCAS system, aircraft positions
are only accurate to a few degrees; thus, the accuracy of
TCAS decreases with distance. Moreover, the reliance on
transmission timing for range data in TCAS is errorprone. The method used by ADS-B avoids this problem.
In addition to the broadcast of position to the ground,
ADS-B can be used to enable a new collection of aircraft-based applications. Unlike conventional radar,
ADS-B works at low altitudes and on the ground. It is
effective in remote areas or in mountainous terrain
where there is no radar coverage, or where radar coverage is limited. One of the greatest benefits of ADS-B is
Figure 6-9. ACARS Communications Display.
6-10
its ability to provide the same real-time information to
pilots in the aircraft cockpit and to ground controllers,
so that for the first time, both can view the same data.
ADS-B will also enable aircraft to send messages to
each other to provide surveillance and collision avoidance through data link. Other aircraft in the immediate
vicinity can pick up position information broadcasts
from equipped aircraft. This enables equipped aircraft to
formulate a display of nearby aircraft for the pilot; the
pilot’s awareness of the current situation is enhanced.
Combined with databases of current maps and charts,
the onboard displays can show terrain as well as proximate aircraft. This is a powerful inducement for change.
The heightened situational awareness offered by satellite navigation in conjunction with modern database
applications and map displays, combined with the position of proximate aircraft, builds a picture in the cockpit
equivalent to that on the ground used by the controller.
This is particularly important in places like Alaska
where aviation is vital, NAS infrastructure is minimal
(because of the harsh conditions), and weather changes
quickly and in unpredictable fashions.
Eventually, as the fleets equip, it may be possible to save
money by retiring expensive long-range radars.
Identified by the FAA as the future model for ATC,
ADS-B is a major step in the direction of free flight.
While ADS-B shows great promise for both air-to-air
and air-to-ground surveillance, current aircraft transponders will continue to support surveillance operations in
the NAS for the foreseeable future. If enough users
equip with ADS-B avionics, the FAA will install a
compatible ADS ground system to provide more accurate surveillance information to ATC compared to
radar-based surveillance.
In the United States, two different data links have been
adopted for use with ADS-B: 1090 MHz Extended
Squitter (1090 ES) and the Universal Access Transceiver
(UAT). The 1090 ES link is intended for aircraft that primarily operate at FL180 and above, whereas the UAT
link is intended for use by aircraft that primarily operate
at 18,000 feet and below. From a pilot's standpoint, the
two links operate similarly and both support ADS-B and
TIS-B. The UAT link additionally supports Flight
Information Service-Broadcast (FIS-B) at any altitude
when within ground based transmitter (GBT) coverage.
FIS-B is the weather information component, and
provides displays of graphical and textual weather
information. Areas of approved use for the UAT
include the United States (including oceanic airspace
where air traffic services are provided), Guam, Puerto
Rico, American Samoa, and the U.S. Virgin Islands.
The UAT is approved for both air and airport surface
use. ADS-B broadcast over the 1090 MHz data link
has been approved for global use.
REDUCING VERTICAL SEPARATION
Current vertical separation minima (2,000 feet) were
created more than 40 years ago when altimeters were
not very accurate above FL 290. With better flight and
navigation instruments, vertical separation has been
safely reduced to 1,000 feet in most parts of the world,
except Africa and China.
RVSM airspace has already been implemented over the
Atlantic and Pacific Oceans, South China Sea, Australia,
Europe, the Middle East and Asia south of the
Himalayas. Domestic RVSM (DRVSM) in the United
States was implemented in January 2005 when FL 300,
320, 340, 360, 380, and 400 were added to the existing
structure. To fly at any of the flight levels from FL 290
to FL 410, aircraft and operator must be RVSMapproved.
REDUCING HORIZONTAL SEPARATION
The current oceanic air traffic control system uses filed
flight plans and position reports to track an aircraft’s
progress and ensure separation. Pilots send position
reports by high frequency (HF) radio through a private
radio service that then relays the messages to the air traffic control system. Position reports are made at intervals
of approximately one hour. HF radio communication is
subject to interference and disruption. Further delay is
added as radio operators relay messages between pilots
and controllers. These deficiencies in communications
and surveillance have necessitated larger horizontal separation minimums when flying over the ocean out of
radar range.
As a result of improved navigational capabilities made
possible by technologies such as GPS and CPDLC, both
lateral and longitudinal oceanic horizontal separation
standards are being reduced. Oceanic lateral separation
standards were reduced from 100 to 50 NM in the
Northern and Central Pacific regions in 1998 and in the
Central East Pacific in 2000. The FAA plans to extend
the 50 NM separation standard to the South Pacific.
Because flight times along the South Pacific routes often
exceed 15 hours, the fuel and time savings resulting
from more airplanes flying closer to the ideal wind route
in this region are expected to be substantial. Separation
standards of 30 NM are already undergoing operational
trials in parts of South Pacific airspace for properly
authorized airplanes and operators.
DIRECT ROUTING
Based on preliminary evaluations, FAA research has evidenced tremendous potential for the airlines to benefit
from expected routing initiatives. Specifically, direct
routing or “Free Flight” is the most promising for reducing total flight time and distance as well as minimizing
congestion on heavily traveled airways. Traditionally,
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pilots fly fixed routes that often are less direct due to
their dependence on ground-based NAVAIDs. Through
Free Flight, the FAA hopes to increase the capacity, efficiency, and safety of the NAS to meet growing demand
as well as enhance the controller’s productivity. The aviation industry, particularly the airlines, is seeking to
shorten flight times and reduce fuel consumption.
According to the FAA’s preliminary estimates, the benefits to the flying public and the aviation industry could
reach into the billions of dollars once the program is
fully operational.
Free Flight Phase 1 began in October 1998 and launched
five software tools over the next four years. These were
Collaborative Decision Making (CDM), the User
Request Evaluation Tool (URET), and the previously
discussed SMA, TMA, and pFAST.
CDM allows airspace users and the FAA to share information, enabling the best use of available resources. It
provides detailed, real-time information about weather,
delays, cancellations, and equipment to airlines and
major FAA air traffic control facilities. This shared data
helps to manage the airspace system more efficiently,
thereby reducing delays.
CDM consists of three components. The first component allows airlines and the FAA’s System Command
Center in Herndon, Virginia, to share the latest information on schedules, airport demand, and capacity at times
(usually during bad weather) when airport capacity is
reduced. This shared information is critical to getting
the maximum number of takeoffs and landings at airports. The second component creates and assesses
possible rerouting around bad weather. This tool
enables the Command Center and busy major ATC
facilities to share real-time information on high-altitude traffic flows with airline operations centers, thus
developing the most efficient ways to avoid bad
weather. The third component provides data on the
operational status of the national airspace system.
Examples include runway visibility at major airports
and the current availability of Special Use Airspace.
URET allows controllers to plot changes in the projected
flight paths of specific airplanes to see if they will get
too close to other aircraft within the next 20 minutes.
URET means that controllers can safely and quickly
respond to pilots’ requests for changes in altitude or
direction, which leads to smoother, safer flights and
more direct routings. During trials in the Memphis and
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Figure 6-10. DRVSM High Altitude Routes.
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Indianapolis en route centers, the use of more direct
routes made possible by URET was found to save airlines about $1.5 million per month.
ACCOMMODATING USER
PREFERRED ROUTING
Free Flight Phase 2 builds on the successes of Free
Flight Phase 1 to improve safety and efficiency within
the NAS. Implementation of Phase 2 will include the
expansion of Phase 1 elements to additional FAA facilities. This program will deploy a number of additional
capabilities, such as CDM with collaborative routing
coordination tool (CRCT) enhancements and CPDLC.
The National Airspace System status information
(NASSI) tool is the most recent CDM element to be
introduced. NASSI enables the real-time sharing of a
wide variety of information about the operational status
of the NAS. Much of this information has previously
been unavailable to most airspace users. NASSI currently includes information on maintenance status and
runway visual range at over 30 airports.
The CRCT is a set of automation capabilities that can
evaluate the impact of traffic flow management rerouting strategies. The major focus of this tool is
management of en route congestion.
IMPROVING ACCESS TO
SPECIAL USE AIRSPACE
Special use airspace (SUA) includes prohibited,
restricted, warning, and alert areas, as well as military
operations areas (MOAs), controlled firing areas, and
national security areas. The FAA and the Department of
Defense are working together to make maximum use of
SUA by opening these areas to civilian traffic when they
are not being used by the military. The military airspace management system (MAMS) keeps an
extensive database of information on the historical
use of SUA, as well as schedules describing when
each area is expected to be active. MAMS transmits
this data to the special use airspace management
system (SAMS), an FAA program that provides current and scheduled status information on SUA to
civilian users. This information is available at the following link http://sua.faa.gov/. The two systems
work together to ensure that the FAA and system
users have current information on a daily basis.
A prototype system called SUA in-flight service
enhancement (SUA/ISE) provides graphic, near-realtime depictions of SUA to automated flight service
station (AFSS) specialists who can use the information to help pilots during flight planning as well as
during flight. Pronounced “Suzy,” this tool can display individual aircraft on visual flight rule (VFR)
flight plans (with data blocks), plot routes of flight,
identify active SUA and display weather radar echoes.
Using information from the enhanced traffic management
system, AFSS specialists will see this information on a
combined graphic display. This data may also be transmitted and shown on cockpit displays in general and
commercial aviation aircraft.
The central altitude reservation function (CARF) coordinates military, war plans, and national security use of
the NAS. While SAMS handles the schedule information regarding fixed or charted SUA, CARF handles
unscheduled time and altitude reservations. Both subsystems deal with planning and tracking the military’s
use of the NAS.
The FAA and the U.S. Navy have been working together
to allow civilian use of offshore warning areas. When
adverse weather prevents the use of normal air routes
along the eastern seaboard, congestion and delays can
result as flights are diverted to the remaining airways.
When offshore warning areas are not in use by the
Navy, the airspace could be used to ease the demand
on inland airways. To facilitate the use of this airspace,
the FAA established waypoints in offshore airspace
along four routes for conducting point-to-point navigation when the Navy has released that airspace to the
FAA. The waypoints take advantage of RNAV capabilities and provide better demarcation of airspace
boundaries, resulting in more flexible release of airspace in response to changing weather. These new
offshore routes, which stretch from northern Florida
to Maine, are an excellent example of how close coordination between military and civil authorities can
maximize the utility of limited airspace.
HANDLING EN ROUTE SEVERE WEATHER
Interpreting written or spoken weather information is
not difficult, nor is visualizing the relationship of the
weather to the aircraft’s route, although verbal or textual
descriptions of weather have inevitable limitations.
Color graphics can show more detail and convey more
information, but obtaining them in flight has been
impractical, until recently. The graphical weather service (GWS) provides a nationwide precipitation mosaic,
updated frequently, and transmitted to the aircraft and
displayed in the cockpit. Whether the display is used to
strategize navigation, to avoid weather en route, or for
departures and approaches, consideration must always
be given to the timeliness of the graphic update. Pilots
can select any portion of the nationwide mosaic with
range options of 25, 50, 100, and 200 NM. In addition to
providing information on precipitation, this service can
be expanded to include other graphical data. Some systems will place the detailed weather graphics directly on
a moving map display, removing another step of interpretation and enabling pilots to see the weather in relation to their flight path.
NATIONAL ROUTE
PROGRAM
In the U.S., the national route program (NRP), also
known as “Free Flight,” is an example of applying
RNAV techniques. The NRP is a set of rules and procedures that are designed to increase the flexibility of user
flight planning within published guidelines. The Free
Flight program allows dispatchers and pilots to choose
the most efficient and economical route for flights operating at or above FL 290 between city pairs, without
being constrained to airways and preferred routes.
Free Flight is a concept that allows you the same type of
freedom you have during a VFR flight. Instead of a NAS
that is rigid in design, pilots are allowed to choose their
own routes, or even change routes and altitudes at will
to avoid icing, turbulence, or to take advantage of
winds aloft. Complicated clearances become unnecessary, although flight plans are required for traffic planning purposes and as a fallback in
the event of lost communication.
Free Flight is made possible with
the use of advanced avionics, such
as GPS navigation and datalinks
between your aircraft, other aircraft, and controllers. Separation is
maintained by establishing two airspace zones around each aircraft, as
shown in Figure 6-12. The protected zone, which is the one closest to the aircraft, never meets the
protected zone of another aircraft.
The alert zone extends well beyond
the protected zone, and aircraft can
maneuver freely until alert zones
touch. If alert zones do touch, a
controller may provide the pilots
with course suggestions, or
onboard traffic displays may be
used to resolve the conflict. The size of the zones is
based on the aircraft’s speed, performance, and equipment. Free Flight is operational in Alaska, Hawaii, and
part of the Pacific Ocean, using about 2,000 aircraft. Full
implementation is projected to take about 20 years.
As the FAA and industry work together, the technology
to help Free Flight become a reality is being placed into
position, especially through the use of the GPS satellite
system. Equipment such as ADS-B allows pilots in their
cockpits and air traffic controllers on the ground to “see”
aircraft traffic with more precision than has previously
been possible. The FAA has identified more than 20
ways that ADS-B can make flying safer. It can provide a
more efficient use of the airspace and improve your situational awareness.
DEVELOPING TECHNOLOGY
Head-up displays (HUDs) grew out of the reflector
gun sights used in fighter airplanes before World War
II. The early devices functioned by projecting light
onto a slanted piece of glass above the instrument
panel, between the pilot and the windscreen. At first,
the display was simply a dot showing where bullets
would go, surrounded by circles or dots to help the
pilot determine the range to the target. By the 1970s,
the gun sight had become a complete display of flight
information. By showing airspeed, altitude, heading,
and aircraft attitude on the HUD glass, pilots were
able to keep their eyes outside the cockpit more of the
time. Collimators make the image on the glass appear
to be far out in front of the aircraft, so that the pilot
need not change eye focus to view the relatively
nearby HUD. Today’s head-up guidance systems
(HGS) use holographic displays. Everything from
weapons status to approach information can be shown
on current military HGS displays. This technology has
Figure 6-11. Prototype Data Link Equipment. This display
shows a radar image of weather within 50 NM of the Seattle-
Tacoma International Airport (KSEA).
Figure 6-12. Free Flight.
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obvious value for civilian aviation, but until 1993 no
civilian HGS systems were available. This is changing, and application of HGS technology in airline and
corporate aircraft is becoming widespread.
A large fraction of aircraft accidents are due to poor
visibility. While conventional flight and navigation
instruments generally provide pilots with accurate
flight attitude and geographic position information,
their use and interpretation requires skill, experience,
and constant training. NASA is working with other
members of the aerospace community to make flight
in low visibility conditions more like flight in visual
meteorological conditions (VMC). Synthetic vision
is the name for systems that create a visual picture
similar to what the pilot would see out the window in
good weather, essentially allowing a flight crew to see
through atmospheric obscurations like haze, clouds,
fog, rain, snow, dust, or smoke.
The principle is relatively simple. GPS position information gives an accurate three-dimensional location,
onboard databases provide detailed information on terrain, obstructions, runways, and other surface features,
and virtual reality software combines the information to
generate a visual representation of what would be visible
from that particular position in space. The dynamic image
can be displayed on a head-down display (HDD) on the
instrument panel, or projected onto a HGS in such a way
that it exactly matches what the pilot would see in clear
weather. Even items that are normally invisible, such as
the boundaries of special use airspace or airport traffic
patterns, could be incorporated into such a display. While
the main elements of such a system already exist, work is
continuing to combine them into a reliable, safe, and practical system. Some of the challenges include choosing the
most effective graphics and symbology, as well as making
the synthetic vision visible enough to be useful, but not so
bright that it overwhelms the real view as actual terrain
becomes visible. Integrating ADS-B information may
make it possible for synthetic vision systems to show
other aircraft.
A natural extension of the synthetic vision concept is the
highway in the sky (HITS) program. This technology
adds an easy-to-interpret flight path depiction to an electronic flight instrument system (EFIS) type of cockpit
display, which may be located on the instrument panel
or projected on a HUD. The intended flight path is
shown as a series of virtual rectangles that appear to
stand like a series of window frames in front of the aircraft. The pilot maneuvers the aircraft so that it flies
“through” each rectangle, essentially following a visible
path through the sky. When installed as part of a general
aviation “glass cockpit,” this simple graphic computer
display replaces many of the conventional cockpit
instruments, including the attitude indicator, horizontal
situation indicator, turn coordinator, airspeed indicator,
altimeter, vertical speed indicator, and navigation indicators. Engine and aircraft systems information may
also be incorporated.
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Figure 6-14. Synthetic Vision.This system uses projected images
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Figure 6-13. Head-up Guidance System.
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Figure 6-15. Highway in the Sky. The HITS display conveys flight
path and attitude information using an intuitive graphic interface.
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