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Background
Efficient and safe flight
operations within the international air transportation
system continue to challenge the technological
capabilities of the aerospace community. The dramatic
increase in demand for air travel by the public
and business sectors in the 1990s led to increased
airport congestion, and the unacceptable nature
of commercial and private aircraft accidents demanded
even more options for improved safety, especially
with most of the accidents attributed to human
error. The scope of these challenges includes many
of the operating problems issues discussed in previous
sections, such as wind shear and runway operations
during inclement weather conditions. Technological
solutions to these issues require a careful integration
of advanced concepts for aircraft flight systems
including advanced cockpit displays, flight management
concepts, avionics architecture and integration,
and system health monitoring concepts.
The Langley Research Center
is widely recognized for its international leadership
and research contributions to advanced flight systems
for commercial and general aviation aircraft. By
utilizing carefully coordinated efforts including
ground-based activities (such as piloted simulators
and avionics laboratories) and sophisticated flight-test
assessments of new technology using unique research
aircraft, the Center has maintained its leading-edge
perspective in this area.
In recognition of the special
challenges to the relevance and implementation
of new flight system technologies, Langley maintained
a close partnership and working relationship with
regulatory agencies such as the FAA and with industry.
Emphasis in the Langley program was placed on cooperative
studies with the FAA and industry partners so that
the transfer of technology into aerospace applications
was facilitated and encouraged. A key strategy
in this process was the use of aircraft flight
demonstrations of the potential improvements provided
by new concepts to prove the technology in the
actual environment and to increase significantly
the probability that it would be introduced into
production aircraft. One major outcome of this
NASA, FAA, and industry relationship is the installation
of an awareness and sensitivity by the Langley
researcher to factors—such as cost, certification
issues, and integrated system effectiveness—that
might limit the extent of applications of emerging
concepts. With this approach, Langley has successfully
contributed critical technology that has been implemented
into civil aircraft of the 1980s and 1990s.
Langley Research and Development
Activities
The most significant impetus
to the establishment of a formal flight systems
expertise at the Langley Research Center was a
national awareness of the challenges facing the
rapidly growing U.S. air transportation system
in the late 1960s. During that time, signs of the
emerging congestion of airports, the impact of
adverse weather, and the potential benefits of
advanced technologies to improve the efficiency
and reliability of flight operations were already
apparent to leaders in Congress and to the research
community. Under the leadership of John P. Reeder,
George B. Graves, Jr., and others in the early
1970s, Langley researchers formulated the plans
for a research program whose objectives were directed
toward the improvement of air operation efficiencies
around and at the Nation’s airports. The
research project, known as the Terminal Configured
Vehicle (TCV) Program, included research on advanced,
nonstandard approach paths for noise abatement
and increased runway acceptance rates, displays
of traffic information in the cockpit, use of optimal
fuel-efficient flight paths, data links with air
traffic controllers, high-speed runway turnoffs,
and optimization of air operations using the Microwave
Landing System (MLS).
Reeder’s vast experience
and expertise gathered in years of extensive piloting
experience with a multitude of different military
and civil aircraft, together with his role as Chief
of Flight Research at Langley, enabled him to provide
the strong technical management, advocacy, and
critical outside contacts required for the initiation
and success of the TCV Program. The highly successful
initiation of the program, its early accomplishments,
and the impact on the aeronautics community were
directly related to his leadership, international
recognition, and personal dedication. In 1982,
the scope of the TCV Program was expanded to focus
on the larger perspective of air transportation
system problems, rather than individual aircraft
technologies. The newly formulated program was
named the Advanced Transport Operating Systems
(ATOPS) Program under the management of Jeremiah
F. Creedon. Over a 20-year life span, various projects
sponsored by the TCV and ATOPS Program offices
brought leading-edge technologies into the spotlight
as potential breakthroughs and critical problem-solving
mechanisms for some of the most critical issues
facing the U.S. air transportation system. As a
result of outstanding and sustained technical expertise,
dedication, and professionalism, the highly successful
efforts of Langley researchers and their technical
partners provided critical contributions to U.S.
civil aircraft of the 1980s and 1990s.
John Reeder, principal
advocate and leader of Terminal Configured Vehicle
(TCV) Program.
The technical contributions
and ultimate applications of concepts and results
of the TCV and ATOPS Programs were primarily directed
at commercial transports. However, along with these
highly acclaimed contributions, other Langley researchers
contributed advanced flight system technologies
that significantly advanced the state of the art
for general aviation aircraft. One of the major
stimuli for these contributions was the NASA Advanced
General Aviation Technology Experiments (AGATE)
Program, under the leadership of Bruce J. Holmes.
As discussed earlier in the introduction, the extraordinary
visionary perspective of Holmes on the impact of
advanced technology and its ability to revitalize
the faltering general aviation industry in the
United States is considered one of the critical
ingredients to the current health of the industry.
The coalition of industry partners formed under
the auspices of this remarkable program provided
significant leaps in technology levels and potential
applications for flight systems of advanced general
aviation and business aircraft in the late 1990s.
As the new millennium began, flight systems technology
was being rapidly incorporated into emerging new
general aviation aircraft.
Langley Boeing 737 Research
Aircraft
Because the focus of the
TCV Program involved tightly integrated interactions
between aircraft, aircrews, and air traffic controllers,
it was relatively obvious to Langley researchers
that a representative transport aircraft would
greatly facilitate the technology assessments,
technology transfer, and acceptability of their
research efforts. At the time of the inception
of the program, Langley did not have an appropriate
research aircraft, and after considering several
candidate aircraft, the Center acquired the original
prototype Boeing 737-100 aircraft for its research
vehicle. The aircraft, which had first flown on
April 9, 1967, had been equipped with special instrumentation
for FAA certification testing, which added to its
research value. After the aircraft was purchased
by NASA from The Boeing Company for $2.2 million
on July 26, 1973, the aircraft was modified by
Boeing to NASA requirements and delivered to Langley
on May 17, 1974, where its aircraft designation
was NASA 515 and its initial name was the Research
Support Flight System (RSFS). The first flight
of the Langley RSFS occurred on June 7, 1974. Later,
the name of the aircraft became the Terminal Configured
Vehicle (TCV) aircraft, then the Transport Systems
Research Vehicle (TSRV). Over the next 20 years,
this remarkable aircraft would be involved in some
of the most important leading-edge civil research
ever conducted by the Langley Research Center.
During initial discussions
with Boeing regarding TCV-related research, Reeder
had pointed out that most of NASA’s display
studies had been accomplished with only one side
of the cockpit reconfigured for research; however,
in commercial operations, the entire crew must
work together for flight deck management. As a
small team of NASA and Boeing engineers thought
through this issue, they explored the requirements
and approaches that might be used for both crew
members to share the workload. Boeing engineers
suggested that safely integrating a second cockpit
into the aircraft might be feasible, and with the
participation of Langley engineers led by Eugene
L. Kelsey, an innovative approach was adopted.
The new research aircraft was modified from its
original 737 configuration to incorporate a second
cockpit in the forward part of the main cabin for
studies of advanced flight deck technology. The
aft-flight deck was essentially a computer-controlled,
auxiliary cockpit that could be used to study new
concepts in a realistic, two-crew environment.
The pilot and copilot stations were provided with
primary flight displays and a navigation display.
Initially, the aft cockpit was equipped with four
monochrome cathode ray tube (CRT) displays, but
the sophistication of the cockpit display technologies
rapidly advanced as the aircraft contributed to
research programs conducted by Langley, FAA, and
industry. As a result of the versatility provided
by the aft cockpit, research pilots could evaluate
the effectiveness of advanced displays and controls
from the aft cockpit while safety pilots monitored
flight operations from the conventional forward
cockpit. Many research projects conducted with
the aircraft emphasized operations in instrument
flight rules (IFR) conditions; therefore, the lack
of visibility to the outside world did not adversely
impact the research objectives. The computers that
ran the experimental systems and the data instrumentation
equipment were located behind the aft cockpit in
the cabin area. Research stations were also provided
for observers and other project participants.
The scope of research conducted
by Langley with its TSRV aircraft is legendary
within the accomplishments of aeronautical research
at the Center. Details of the history of the aircraft,
as well as the objectives and accomplishments of
numerous cooperative studies conducted with the
U.S. aerospace industry, the FAA, and the military
are discussed in Lane Wallace’s outstanding
publication, NASA SP-4216, Airborne Trailblazer.
Wallace’s book covers research efforts that
used the aircraft during such diverse studies as
demonstrations of the U.S. MLS, effect of weather
conditions on runway friction, aerodynamic flight
tests of drag reduction and high-lift technology,
advanced cockpit displays, wind-shear research,
data link for air traffic control communications,
flight management concepts, and the satellite-based
global positioning system (GPS). Throughout its
operational life, the primary pilots for the TSRV
aircraft were Lee H. Person, Jr., and Kenneth R.
Yenni. From 1974 until 1995, Person and Yenni flew
the aircraft in over 20 different research projects.
Cutaway view of model of
TSRV
aircraft showing aft cockpit layout.
NASA Boeing 737 TSRV research
aircraft became operational at Langley in 1974.
In the mid-1990s, Langley
decided to finally retire its Boeing 737 and to
replace it with a more modern Boeing 757 aircraft.
The Boeing 737 was formally retired from NASA service
at a ceremony held in the Langley aircraft hangar
on September 19, 1997, with representatives from
Boeing, the FAA, and other organizations in attendance.
Later that same afternoon, Langley pilots Harry
A. Verstynen and Philip W. Brown flew the veteran
research aircraft to Seattle, Washington, where
it has been retired to the Boeing Museum of Flight.
Langley dedicated its new
Boeing 757 Airborne Research Integrated Experiments
System (AIRES) on November 23, 1998. NASA bought
the Boeing 757-200 for $24 million in 1994 from
the Eastern Airlines bankruptcy sale. The aircraft
is continuing the work begun by its predecessor
in state-of-the-art technologies such as electronic
cockpit displays, flight management systems, and
flight safety devices. The aircraft is being used
to conduct research to increase aircraft safety,
operating efficiency, and compatibility with future
air traffic control systems. It is a vital research
tool in support of the Agency’s Aviation
Safety and Aviation Systems Capacity Programs.
Cockpit Displays for Commercial
Transports
One of the most critical
contributions of the Langley Research Center to
civil aircraft has been the conception and development
of advanced cockpit displays, especially the development
and acceptance of flat-panel displays and the “glass
cockpit.” Langley researchers conducted pioneering
research that led to worldwide applications of
advanced displays in vehicles ranging from large
commercial transports to personal-owner general
aviation aircraft.
When Congress terminated
the national Supersonic Transport (SST) Program
in 1971, it authorized Boeing to continue research
on technology related to electronic cockpit displays
and digital flight controls. When NASA approached
Boeing to acquire the prototype Boeing 737, it
was apparent that common interests existed in advanced
electronic display technology. In the early 1970s,
typical commercial aircraft had more than 100 cockpit
instruments, and together with ever-increasing
numbers of indicators, crossbars, and symbols they
competed for cockpit space and pilot attention.
From Langley’s perspective, advanced electronic
displays that could process raw aircraft system
and flight data into an integrated, easily understood
picture of the aircraft situation, position, and
progress offered the potential to significantly
reduce the pilot workload and enhance guidance
capabilities. A formal request to NASA from the
Department of Transportation to support Boeing’s
follow-on development was accepted by Langley,
and agreements with the FAA were formalized to
permit testing of FAA-owned display equipment.
Following the acquisition of the 737 for the TCV
Program, the research flight deck (aft cockpit)
was designed to accommodate advanced flight displays.
Using advanced CRT displays, Langley researchers
first developed promising display concepts in the
ground-based TSRV simulator, then proceeded to
assess the more promising concepts using the actual
TSRV aircraft.
Led by Reeder, a team of
Langley researchers defined a program that would
lead to pioneering efforts in new flight systems
technologies. Initial key team members included
Robert T. Taylor, Thomas M. Walsh, Samuel A. Morello,
George G. Steinmetz, Charles E. Knox, and Roland
L. Bowles.
TSRV forward cockpit display
in original layout. Note electromechanical gauges
and dials; control and
command panel added on glare shield to engage and
transfer control to and from aft research flight
deck.
Research deck (aft cockpit)
of TSRV configured with CRT displays.
Under the leadership of Morello,
initial studies of advanced displays during the
1970s centered on the impact of electronic displays
on the pilot’s ability to fly complex, curved
approaches to airports. During that same period,
Boeing began design of its new Boeing 757 and 767
transports, including extensive cost-benefit studies
of advanced technologies for potential applications
to these new aircraft. In recognition of the potential
benefits of advanced technologies being researched
at Langley within the TCV Program, Boeing sent
a contingent of its engineers to Langley, from
1974 to 1979, to work with the TCV Office and to
maintain awareness of emerging technology. When
the leaders of this group with “hands-on”
Langley experience in the area of advanced cockpit
displays returned to Boeing, they were subsequently
assigned leadership positions in the emerging transport
programs and were extremely influential in the
decision-making processes for Boeing’s selection
of advanced cockpit displays.
As Boeing and its airline
customers considered the cost of ownership for
CRT displays versus conventional electromechanical
instruments, Langley’s TSRV aircraft provided
opportunities for a significant number of airline
pilots and operators to become familiar with the
benefits of the advanced CRT display technology.
As a result of the advocacy of certain Boeing personnel
that had participated in the Langley program and
the management pilots for the customer airlines
that had flown in the TSRV, Boeing decided to incorporate
advanced CRT technology into the cockpit of its
new aircraft in 1978, and United Airlines and Eastern
Airlines were among the first airlines ordering
the Boeing 757 and 767 with advanced electronic
flight displays. Newer Boeing versions of existing
aircraft, including the Boeing 747 and 737, were
also upgraded to electronic displays. The technology
has also been applied to the Boeing 777. The widespread
implementation of electronic displays and flight
management computers in virtually all new commercial
transports and business jets is indicative of the
value and benefits provided by the new cockpit
technology.
Langley’s unique role
in the conception and transfer of advanced cockpit
displays, from 1974 to 1978, is often overlooked
by the aviation community; however, the intense
cooperative studies undertaken by the Boeing and
Langley team provided the key technical demonstrations
and industrial advocacy to simulate a major advance
in U.S. aviation technology.
Flight Management Systems
Associated with the fundamental
and applied research conducted at Langley on glass
cockpit concepts, extensive studies were also initiated
on innovative new Flight Management Systems (FMSs).
The objectives of these broad research studies
were directed at improving the efficiency and safety
of aircraft operations. The scope of research studies
included takeoff and performance monitors, cockpit
displays of traffic information, and efficient
flight profiles.
Langley researchers Charles
E. Knox, Dan D. Vicroy, and David H. Williams led
an aggressive study of the potential impact of
more efficient flight profiles on fuel efficiency.
Emphasis during the studies was on more efficient
profile descent paths because commercial jet engines
operated most efficiently at high altitudes but
consumed excessive fuel during the descent and
approach phases prior to landing. Although the
FAA had recognized and tried to improve air traffic
control methods and regulations to allow pilots
to descend at their discretion, the application
of manual calculations and air traffic metering
resulted in operations that could be further optimized.
In the late 1970s, the Langley researchers teamed
with Boeing to study a new four-dimensional (4-D)
FMS concept. In addition to the normal three-dimensional
parameters of vertical and horizontal flight paths,
the 4-D concept added time as a critical parameter.
The pilots of aircraft equipped with a 4-D FMS
had the ability to adhere to specific guidance
for vertical flight paths as well as the ability
to accelerate or decelerate for a specific arrival
time. In principle, the air traffic controller
would specify an altitude, speed, and time to cross
the metering point, and the pilot would enter these
parameters into the 4-D FMS, which would then calculate
the most fuel-efficient flight path to the specified
metering point at the specified time.
After initial conceptual
studies using the Langley TSRV piloted simulator,
the concept was evaluated in the actual TSRV Boeing
737 aircraft at the Denver Stapleton Airport, Denver,
Colorado. With two NASA pilots and four airline
pilots providing their critiques, the research
flights took place in June 1979. The results of
the study showed that pilots who flew without the
4-D FMS tended to descend from cruise altitude
earlier to ensure arrival at the metering point
at the correct altitude airspeed; thus, flight
was prolonged at the inefficient lower altitudes.
The arrival times between flights with and without
the FMS differed only slightly; however, when the
FMS was used, the profile descent used 28-percent
less fuel. Unfortunately, numerous real-world issues
needed to be faced, such as the potential impact
of the mixing of different aircraft using different
descent paths and speed profiles. Although the
4-D FMS concept offered considerable promise, the
air traffic control infrastructure was not equipped
to incorporate it while maintaining safe separation
of air traffic.
Despite these and other issues,
continued development of less complex three-dimensional
(3-D) FMS systems by Boeing and its contractors
led to the Boeing 767 being the first U.S. commercial
aircraft to include an FMS as standard equipment
(3 years after the Langley Denver profile flight
test program). Continued development of Boeing’s
interest in 4-D FMS concepts led to a system modified
by Smith Industries being incorporated in the advanced
models of the Boeing 737, 767, and 747 aircraft.
Although the pioneering efforts of Langley’s
researchers in airborne 4-D FMS systems were not
directly applied to aircraft of the 1990s, the
TSRV assessments and demonstrations stimulated
industry interest in pursuing more efficient flight
profiles. Ultimately, a concept, originally developed
by Heinz Erzberger of the NASA Ames Research Center,
using a ground-based Center Tracon Automation System
(CTAS) was selected by the FAA for installation
at major airports across the United States. The
CTAS system incorporated the basic principles and
objectives of the 4-D FMS, but it required no airborne
equipment and took other air traffic into account.
Microwave Landing System and
Global Positioning System Demonstrations
Beginning in 1937, the Instrument
Landing System (ILS) was implemented to provide
pilots with a radio signal giving precise lateral
and vertical guidance for approach and landing.
The ILS broadcasted a straight, narrow signal beam
that provided a glide slope angle of 3∞ for
approach. The pilot’s task was to fly down
the ILS beam, which was laterally centered on the
runway. This system significantly improved the
safety and reliability of air operations, especially
in low visibility conditions. By 1949, the ILS
system was the world standard for landing guidance
systems. During the 1960s, however, the pressures
of airport congestion and reduced noise requirements
demanded that new concepts be explored to provide
more operational versatility than the ILS. One
of several limitations of the ILS was its lack
of ability to accommodate multiple approaches to
a runway, especially curved or segmented approaches
that might be very desirable from a noise reduction
perspective.
In 1972, the International
Civil Aviation Organization (ICAO), an agency of
the United Nations that oversees international
civil aviation procedures and standards, began
a formal selection process for a new standard for
international precision and approach and landing
guidance systems. ICAO solicited proposals for
the new system from all its member countries. In
1973, the FAA awarded contracts to U.S. industry
to evaluate two different concepts that employed
a microwave frequency-based, scanning-beam principle
to permit more flexible approach paths. In early
1975, a concept known as the Time Reference Scanning
Beam was chosen by the FAA as the U.S. candidate
for international standards. Other nations submitted
different standards, including the United Kingdom,
the Federal Republic of Germany, and France.
As competition for the international
standards intensified, the FAA managers sought
out capabilities that might make favorable impressions
and impact the final ICAO selection process. Meanwhile,
researchers at Langley had already begun to gather
data with prototype MLS systems at the NASA Wallops
Flight Facility. Langley’s objective was
not to demonstrate the U.S. microwave candidate,
but rather to utilize MLS signals for curved and
variable approach paths as part of TCV research.
Langley researchers built MLS airborne receivers
for use in the Center’s de Havilland Twin
Otter aircraft, and they were able to use the equipment
for flight operations research. Langley researchers
had also begun research on the most efficient locations
for MLS antennas on aircraft using Langley anechoic
chambers; as a result of these activities, Langley
was positioned to contribute directly to the FAA
interests.
In July 1975, Langley agreed
to an FAA request that Langley demonstrate curved-path
approaches and automatic landings to the ICAO decision-making
group during 1976. An immense number of design
and fabrication challenges faced the Langley team
in preparing TCV Boeing 737 aircraft for the demonstration.
By accepting the aggressive flight schedule, the
Center came under a national and international
spotlight. Extensive laboratory development efforts,
sophisticated simulations, and flight test assessments
(in early 1976) were conducted to ensure that the
equipment was ready for the demonstrations.
The demonstration of the
capabilities of the MLS system to the ICAO group
occurred at the FAA’s National Aviation Facilities
Experimental Center (NAFEC). The demonstrations
consisted of two basic curved MLS approaches followed
by automatic landings. The flight included observers
during the demonstration process, and the dramatic
capabilities and the potential beneficial impact
on international air operations impressed ICAO.
However, following the demonstration, intense competition
from the British-sponsored MLS competitor rose
to new heights; the situation became critical when
a close vote by the ICAO group selected the U.S.
MLS system in 1977 for an international standard.
Intense lobbying by the British resulted in an
international controversy that culminated in the
review by the FAA Administrator agreeing to a series
of international demonstrations with the aid of
the TSRV Boeing 737 aircraft.
The first international demonstration
of the U.S. MLS system occurred in late 1977 at
Buenos Aires, Argentina, with the Langley researchers
designing two descending, curved-path approaches
to the airport that minimize the noise impact on
the heavily populated areas under the conventional
ILS approach. Fifty-six automatic approaches and
landings were made, and the ICAO representatives
from the Organization of American States were extremely
impressed. In December 1977, the second series
of demonstrations occurred at the John F. Kennedy
(JFK) Airport in New York City, pitting the U.S.
MLS system against the British MLS system. The
TSRV flew a total of 38 automatic approaches, emphasizing
curved-path approaches that could make a tremendous
difference in airport safety and capacity at a
congested area such as JFK. The British demonstrator
aircraft, on the other hand, was not as impressive,
because it did not have an autoland system or the
capability to fly curved-path approaches. The last
MLS demonstration flown by the TSRV was for the
ICAO final-decision panel in Montreal, Canada,
in April 1978, with both the British and the U.S.
systems to be demonstrated on separate aircraft.
Again, the TSRV demonstrated curved-path approaches
and an increase in glide slope angle to over 4∞.
On April 19, 1978, the decision-making
ICAO organization voted in favor of the U.S. MLS
standard. Unfortunately, 20 years later, only a
handful of MLS installations have now been completed.
The FAA’s adoption and implementation of
the MLS system took so long that new emerging technology
capability provided by the GPS overtook it.
In 1983, the Reagan Administration
made the U.S. satellite navigation network, which
was originally developed by the DOD, available
for international civil use. The system, which
is based on an array of satellites, offers more
capability and flexibility than any other preceding
aircraft navigation system. However, to ensure
the superiority of U.S. military capability, the
DOD permitted “selective availability”
and intentionally degraded the accuracy of the
satellites for civil use. The resulting degraded
accuracy was only within 100 meters (without selective
availability, the GPS accuracy is normally 15 meters),
which would not be precise enough for a landing
system. These position errors could theoretically
be corrected, but significant questions remained
in the aviation community regarding the accuracy
of the system for precision approaches.
In an act of serendipity,
Langley researchers and the TSRV aircraft engaged
in a cooperative project with industry in 1990
that had an extremely significant impact on the
outlook of GPS for aircraft navigation and landing.
Led by Cary R. Spitzer, the ATOPS Office aggressively
pursued the emerging technology. Honeywell, Inc.,
proposed a cooperative evaluation of a GPS concept
it had developed as a potential landing aid for
returning space vehicles such as the space shuttle.
Langley suggested that the cooperative effort include
integrating the GPS equipment with the existing
TSRV autoland system. In late 1990, the ATOPS Program
demonstrated, for the first time, that a GPS-guided
autoland was possible for commercial aircraft.
The results of these flight tests directly answered
the question of whether GPS could be used for landings.
From this, the new question that then emerged was
what degree of accuracy could be achieved. In 1993,
Langley conducted a cooperative effort with Ashtech,
Inc., and Ohio University with a more accurate
Differential GPS (DGPS) receiver, which provided
3- to 5-meter accuracy. The demonstration showed
that it was possible to use GPS for a precision
approach, flare, and rollout.
As the Nation continued to
contend with a rapidly expanding and congested
national air transportation system in the 1990s,
the role of Langley demonstrations of the potential
benefits of MLS technology and the relative accuracies
of the emerging GPS navigational system played
key roles in the formulation and outlook for future
systems. Currently, the FAA is developing the Wide
Area Augmentation System (WAAS) Program for use
in precision flight approaches. WAAS corrects for
GPS signal errors caused by ionospheric disturbances,
timing, and satellite orbit errors and provides
vital integrity information regarding the health
of each GPS satellite. Accuracy of the new system
is projected to be within 3 meters.
Data Link
Because of increasing congestion
in the terminal area, it became difficult to break
into the growing numbers of radio transmissions
between pilots and controllers. Because of the
necessary rapidity of control or instructions,
errors were sometimes introduced that required
repetitive commands and increased pilot workload.
Langley researchers led by Charles E. Knox, Charles
H. Scanlon, Marvin C. Waller, David H. Williams,
and David A. Hinton conducted simulator studies
and flight tests to develop and assess the impact
of a two-way data link system between ground controllers
and pilots. In the data link concept, messages
would be exchanged and displayed on CRT screens
in the cockpit and at the controller station. With
the aid of a satellite network, the concept could
also allow pilots to communicate with controllers
from remote locations. Weather information and
charts in the cockpit would also be accommodated.
After Hinton and others conducted
a highly successful evaluation of a two-way data
link system in the early 1980s with a light twin-engine
aircraft and flight and simulator studies of single-pilot
IFR flight operations, Langley researchers became
encouraged to apply the concept to commercial transports.
At the time, a form of a data link system was already
in use by the airlines to provide airline dispatchers
with the capability to relay company messages,
weather, and flight plan information to pilots.
However, using a two-way data link as the primary
communication mode for air traffic control information
would be much more of a challenge. In 1990, the
researchers continued development of their concept
by using a combination of CRT message screen concepts
together with digitized voices for more effective
transmissions. Using a touch-sensitive panel that
allows for rapid pilot inputs, ground-based simulator
studies were conducted to mature the concept, and
flight tests with the TSRV aircraft using NASA
and commercial airline pilot evaluations were conducted.
The results of the demonstration were impressive.
Several instances of confusion occurred with conventional
voice communications between the controller and
pilots, and messages had to be repeated many times.
The Langley experiments were the first flight tests
using data link as the primary source for air traffic
control communications. After the research flights
were completed in May 1990, over 60 airline representatives
showed up at Langley to witness the operation of
the data link system. Interest in the FAA on the
use of data link as a method to reduce radio frequency
congestion and control workload began to peak,
and it was recognized that, if the data link were
combined with a GPS, the position of airplanes
could be automatically sent to the controllers
so that they could view all the aircraft in their
control area on an oceanic scale.
Stimulated by emerging air
traffic control technologies and the demonstrated
value of the Langley concept, the FAA in 1993 made
plans for a traffic control data link system for
transoceanic flights. The airlines were especially
enthusiastic about the data link capability, and
Boeing included such systems in new versions of
the Boeing 747 and 767, as well as the Boeing 777.
Langley’s contribution of demonstrating the
value of integrating information in a data-linked
air traffic scenario was a critical factor in influencing
the community and accomplishing the fundamental
research required for the implementation of the
FAA’s GPS-based Future Air Navigation Services
Phase 1 (FANS-1). Boeing equipped most of its long-range
aircraft in the late 1990s with FANS-1, including
the Boeing 747-400 and the 777.
Landing Flare Control Laws
One of the most critical
aspects of commercial aircraft operations is the
efficient and timely interspersing of aircraft
landings. A key factor in these operations is the
ability of aircraft to land, slow down, and taxi
off runways. The challenges to efficient operations
increase significantly in low visibility conditions,
and autoland systems face precision requirements
that are extremely difficult to meet. An important
element involved in autoland systems is the provision
of an automatic landing flare capability, which
would theoretically provide more precision and
allow aircraft to turn off active runways more
rapidly. Early versions of flare control laws used
in transport aircraft were based on the aircraft’s
altitude above the runway for initiation of the
flare. Unfortunately, the effect of head winds
and tail winds severely impacted the precision
of the aircraft landing on the intended touchdown
point.
In 1978, Boeing and Langley
cooperated in a joint assessment of advanced flare
control laws using the TSRV Boeing 737 aircraft.
Led by Jeremiah F. Creedon (who later became the
Director of Langley Research Center), Langley studies
included two approaches: one based on the aircraft
ground speed as measured by an inertial navigation
system (INS) and the other, a flare trajectory
law known as “path in space,” which
aimed the aircraft toward a specific point on the
runway. Flight tests of the new flare control laws
indicated that touchdown dispersions were much
less than those required by the FAA; this offered
the potential for significant improvements in airport
capacity. Some industry observers doubted that
the specific approach used in the Langley studies
would work—the TSRV aircraft demonstrations
quickly eliminated those concerns. Boeing subsequently
incorporated autoland refinements similar to the
path-in-space control laws for versions of the
Boeing 757, 767, 747, and 737 aircraft.
Engine Monitoring and Control
System
In its continuing development
of new cockpit display concepts, Langley also directed
efforts toward technical approaches that might
provide more efficient and effective information
on the status and health of engine systems on advanced
transports. Taking advantage of the research display
versatility provided by emerging advanced electronic
displays, Terence S. Abbott of Langley initiated
research in 1987 on new concepts for engine information
known as the Engine Monitoring and Control System
(E-MACS).
The E-MACS was a computer-based
display concept that processed and displayed engine
information such as engine pressure ratio (EPR),
low-pressure engine compressor speed (N1), and
high-pressure engine compressor speed (N2) in an
efficient manner that permitted rapid evaluation
and alerts to the pilot. Abbott’s innovative
approach to the integration of this information
for rapid decision making included a unique arrangement
of electronic vertical bar graphics to provide
clear indications of the actual and commanded engine
thrust levels, as well as the relative health and
levels of the individual engine parameters. The
E-MACS display provided an intuitive, rapid assessment
of engine operations; this resulted in a dramatic
increase in the number of parameters that could
be monitored and absorbed by pilots in a given
period of time.
Extensive ground-based simulator
studies of the E-MACS concept were conducted by
Abbott using NASA, airline, and Air Force pilots
in 1988. Results of the evaluation were extremely
impressive and demonstrated that the display concept
would provide a vastly improved capability to minimize
potentially dangerous pilot misinterpretations,
or lack of recognition of engine faults. The pilots
stated an overwhelming preference for the capabilities
provided by the E-MACS format compared with standard
instruments.
Flight assessments of the
E-MACS concept on the TSRV Boeing 737 were conducted
in 1991 with positive results. The first applications
of the principles and approach used by Abbott’s
concept were by ARNAV Systems, Inc., a general
aviation avionics manufacturer. ARNAV built on
Abbott’s pioneering efforts and made several
improvements to the concept in developing its MFD
5000 Cockpit Management System in 1992.
Digital Autonomous Terminal
Access Communication
In 1983, Langley researchers
responsible for the development and operations
of the advanced experimental research systems employed
by the TSRV aircraft became aware of an innovative
new approach to data system integration being developed
at Boeing. Rather than using separate, dedicated
connections between individual computers and data
system components, the Boeing approach utilized
an innovative, magnetic coupling principle in which
components shared information on a single “data
bus.” In this approach, a far greater number
of components could be integrated into aircraft
systems. If this new concept was successful, the
NASA TSRV research system could be upgraded with
significantly more research potential. However,
the Boeing concept required much more development
and a demonstration of its potential benefits.
Langley’s David C.
E. Holmes obtained approval to pursue a joint effort
with Boeing to demonstrate the effectiveness of
the Digital Autonomous Terminal Access Communication
(DATAC) concept on Langley’s Boeing 737 aircraft.
During 1984, Holmes and his coworkers designed
the required hardware and software interfaces to
permit flight assessments of a prototype DATAC
system that was designed and fabricated by Boeing.
The integration process included an intensive laboratory
integration and checkout effort by a cooperative
Boeing-Langley team at Langley. The DATAC system
was installed in the TSRV aircraft in August 1984,
and flight tests of the system demonstrated problem-free
operations and reliability.
Subsequent interactions between
Langley researchers and advanced design engineers
from Boeing regarding potential new technologies
for future Boeing aircraft included discussions
of the benefits of the new DATAC system. In 1985,
briefings by William E. Howell, Chief of the Langley
ATOPS Program, to Boeing representatives regarding
the highly successful integration of the DATAC
concept provided the stimulus for Boeing’s
consideration to apply the concept to new aircraft.
Ultimately, the fundamental DATAC architecture
was incorporated into the Boeing 777. In addition,
the nonprofit standards-setting organization Aeronautical
Radio, Inc. (ARINC), adopted the DATAC as the basis
of a new industry data bus standard for all future
aircraft. The specification, ARINC 629, was instituted
in 1989.
The DATAC experience is an
example of numerous successful cooperative projects
that utilized Langley’s unique research facilities,
aircraft, and technical expertise in providing
significant contributions to advanced aircraft
of the 1990s. Common technical interests, the availability
of a unique research aircraft, and a highly dedicated
and professional effort by Langley researchers
provided critical links for this significant contribution
for future aircraft.
Visit of Boeing 777 to Langley
Research Center
In 1996, the new Boeing 777
was honored as the greatest achievement in aerospace
in America during the previous year, and The Boeing
Company received the prestigious Collier Trophy.
As a gesture of thanks for NASA’s technology
contributions to its creation, Boeing flew the
first 777 to Langley for a “thank you”
visit on May 10, 1996. The aircraft and company
officials participated in a formal ceremony that
included speeches by officials of Boeing and NASA
and a walk-through inspection by Langley employees.
Langley’s staff touring
first Boeing 777 aircraft during a “thank
you” visit to Langley in 1996.
Basic research performed
at NASA’s four research centers contributed
significantly to the precedent-setting jet’s
design and commercial success. The Boeing 777 was
designed for medium- to long-range passenger flights
and was the largest twin-engine jet manufactured
in the 1990s. Its first passenger-carrying flights
were conducted by United Airlines in May 1995.
Langley-developed analytical
technologies and facilities used by Boeing in the
Boeing 777 development work included fundamental
mathematical procedures for computer-generated
airflow images, which enabled advanced computer-based
aerodynamic analysis; wind-tunnel testing for flutter;
knowledge of how to reduce engine and other noise
for passengers and terminal-area residents; radial
tire strength and durability testing at the Langley
Aircraft Landing Dynamics Facility; increased use
of lightweight aerospace composite structures for
increased fuel efficiency and range; a digital
data bus system; and a modern glass cockpit that
uses computer technology to integrate information
and display it on monitors in easy-to-use formats.
Cockpit Displays for General
Aviation Aircraft
Since World War II, Langley
has directed considerable research toward concepts
that might provide general aviation pilots with
improved cockpit displays for enhanced operating
efficiency and increased safety. For example, extensive
fundamental research has been contributed by Langley
researchers on the problem of loss of orientation
during flight in marginal weather conditions. Simulator
and flight studies of the basic phenomena and critical
parameters that cause loss of control and accidents
in such scenarios were conducted in a program known
as Single-Pilot IFR led by John D. Shaughnessy
and Hugh P. Bergeron. Langley researchers also
pioneered new and innovative approaches to displaying
primary flight information for inexperienced pilots;
thereby the time and cost of pilot training were
reduced. An ultimate objective of this research
thrust was to make flying a general aviation aircraft
as simple as driving an automobile. Under the descriptive
title of “Highway in the Sky,” researchers
developed advanced electronic displays that literally
projected a highway-type display for the pilot.
An emerging vision of Langley
researchers in the early 1990s was an airspace
system that would provide a point-to-point, on-demand,
personal air transportation system that was competitive
in cost and safety with alternative travel modes.
A safe and affordable small aircraft transportation
system infrastructure brings the mainstream of
business, commerce, trade, tourism, health care,
and education opportunities to the Nation’s
small communities and rural areas. These areas
will benefit from the highway-in-the-sky concept
as America benefited from the Interstate Highway
System. Under the sponsorship of the NASA Advanced
General Aviation Transport Experiment (AGATE) Program,
a national assessment of the technology was planned.
The 1996 Olympic Summer Games
in Atlanta provided the backdrop for an early success
story for Highway in the Sky. In partnership with
the Atlanta Vertical Flight Association, Helicopter
Association International, Georgia Tech Research
Institute, NASA, and eight AGATE member companies
developed the world’s first free-flight system
for use in Atlanta. Working together under the
FAA-led Operation Helistar, the team created a
highway-in-the-sky capability. This system was
installed in 50 aircraft, and an additional 60
units were produced at the request of the White
House to meet requirements for special security
forces. The system provided public and private
sector aircraft with free-flight access to the
restricted airspace during the Olympics. Satellite-based
navigation, digital radio data link communications,
and advanced flat panel display technologies were
integrated to produce a communication, navigation,
and surveillance system providing pilots and controllers
with graphical traffic, weather, moving maps, and
Olympic venue status information in real time.
The effort was accomplished in less than 7 months
with a joint government-industry investment of
less than $2 million. The commercial cargo operators
using the system in Atlanta estimated that over
$20 million was generated in revenues that would
have been lost without the Helistar technologies.
The Atlanta Olympics project set the stage and
accelerated the pace for modernization of the Nation’s
emerging air traffic management free-flight system.
Weather Displays
In 1998, as part of a new
NASA aviation safety initiative, Langley personnel
studied the compelling need to provide real-time
graphical weather information in the cockpit. Weather-related
accidents typically comprise 33 percent of the
commercial air carrier accidents and 27 percent
of the general aviation accidents, and more detailed
data for the pilot would significantly reduce such
accidents. A concept known as the Aviation Weather
Information (AWIN) system for commercial airliners
and general aviation aircraft was formulated to
provide weather information in the cockpit. Langley
solicited U.S. companies to submit proposals for
research, development, prototyping, and implementation
of AWIN systems and components. Industry teams
submitted more than 40 proposals in three weather
information categories: a national and worldwide
system, a general aviation system, and topical
areas or specific components.
Langley initiated nine cooperative
efforts with industry teams in which NASA and the
industry participants shared in funding the proposed
research. Collectively, these teams included over
40 different industry, university, and government
organizations. At the beginning of the new millennium,
a team led by Honeywell was developing a national
and worldwide Weather Information Network (WINN)
including strategic and tactical airborne displays,
airborne and ground-based servers, and multiple
providers of weather products and data link services.
A prototype of this system was installed on a business
jet and demonstrated to airlines during the summer
of 1999. The Boeing Company is leading an “Aviation
Weather Information (AWIN)” implementation
team that is using both a Federal Express Boeing
MD-11 and an Air Force C-135C transport to evaluate
a complete weather information system with weather
sources, terrestrial networks, and ground-to-air
satellite communications. The graphic display of
current and advanced weather products to the flight
crew is being evaluated during normal transport
operations.
Weather information systems
for general aviation are being developed by teams
led by ARNAV Systems and AlliedSignal (now Honeywell).
During 1999, the ARNAV team conducted in-flight
evaluations of four advanced weather products being
developed by the National Center for Atmospheric
Research (NCAR). Additionally, the ARNAV team initiated
evaluation of electronic reporting of humidity,
temperature, and icing conditions from short haul
aircraft being operated by Federal Express. The
AlliedSignal team is developing an affordable,
open architecture Flight Information Services (FIS)
system for general aviation. Another team led by
AlliedSignal has developed a prototype low-cost
sensor package for in-flight measurement and transmission
of automated weather observations from small airplanes
that must fly “down in the weather.”
In July 1999, both ARNAV and AlliedSignal were
selected by the FAA to implement nationwide weather-in-the-cockpit
information systems. Both systems utilize technologies
that were developed with support from the NASA
AGATE Program and the AWIN Project.
During 1999, Rockwell Science
Center completed a prototype of a web-based system
to improve general aviation preflight weather briefing
and enroute situation awareness. Text and graphical
weather information sources are integrated, and
information is filtered, to display to the user
only that which is route or time relevant (based
on mission, equipment, flight rules, and pilot
risk threshold). Rockwell Science Center is also
developing a system that will integrate onboard,
in situ, radar information with up-linked ground
radar information. Honeywell Technology Center
has developed a prototype route optimization tool
that integrates both weather data and perception
of weather hazards. The NCAR leads a team undertaking
the development and phased evaluation of an operational
weather hazard dissemination system for aviation
operations in oceanic and remote areas. The intent
is to provide a timely summary of potential weather
hazards to airline dispatch centers, air traffic
control centers, and flight crews of en route aircraft.
Information transmission systems are currently
being verified prior to initiation of tests on
transports flying across the South Pacific.
Results of these cooperative
efforts will be commercialized by industry and
will be used by NASA as the basis for development
of enhancements to improve the coverage, affordability,
and ease of use of weather information systems.
Widespread applications of this technology are
expected to occur in the early twenty-first century.
General Aviation Cockpit Technologies
Since early 1998, a Beech
Bonanza F33C owned and modified by Raytheon Aircraft
has been serving as an “integration platform”
test bed for validation experiments of new technologies
being developed by the AGATE Team. The experiments
have resulted in the first successful combination
of a number of breakthrough technologies on a single
aircraft. Flight systems technology developments
have included graphical, integrated, intuitive
pilot displays and advanced avionics system architecture
for revolutionizing general aviation cockpit information
retrieval, processing, and display. Flight-path
guidance information displayed through flat panel
displays in the cockpit provides a highway-in-the-sky
presentation developed from a NASA concept that
gives an intuitive three-dimensional (3-D) presentation
of the flight path and replaces the conventional
cockpit displays. Integrated graphical weather,
terrain, and traffic data provide simplified situational
awareness. The information rich environment created
by these technologies allows the pilot to focus
on critical decision-making information rather
than on reducing data, which results in a significant
impact on safety, reliability, and ease of use.
Cirrus SR20 and Lancair
Columbia 300 advanced general
aviation aircraft on display at Langley during
a visit in 1999.
The first two advanced general
aviation aircraft to make extensive use of the
new Langley-inspired technology paid a courtesy
visit to the Center on February 11, 1999. The Cirrus
SR20, built by Cirrus Design Corporation, Duluth,
Minnesota, and the Lancair Columbia 300, built
by Lancair International, Inc., Redmond Bend, Oregon,
both received flight certification in the fall
of 1998. These pioneering four-to-six-seat airplanes
incorporate technologies that contribute to ease
of operation through single-lever power control—a
concept that greatly simplifies the integrated
control of the engine and propeller—and multifunction
display of satellite navigation and airport information.
The display technology also handles graphical display
of real-time weather, terrain, and digital air-to-ground
communications.
Applications
The flight systems area has
proven to be one of the most difficult to penetrate
with new technology. The obstacles to the implementation
of new concepts are precipitated by the fact that
any new concepts must not only be cost-effective
but also seamlessly integrated into a complex air
transportation system that demands acceptance and
enthusiastic endorsement from pilots, air traffic
controllers, airport operators, and the general
public. For example, innovative approaches to improve
en route and approach and landing flight operations
must be compatible with existing and near-term
infrastructure, and there must be agreement between
pilots and air traffic controllers over roles and
responsibilities for decision-making options. Because
of these critical interactions, and factors that
transcend technology, many of the promising results
of Langley research in-flight systems have been
slow to be implemented in current civil aircraft.
Nonetheless, the national air transportation system
has benefited tremendously from Langley’s
contributions to airborne wind-shear detection
systems, advanced cockpit displays, avionics standards,
and demonstrations of the potential improvements
provided by new technologies.
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