9th AIAA Aviation Technology, Integration, and Operations Conference (ATIO) <br>and<br>Air
21 - 23 September 2009, Hilton Head, South Carolina
AIAA 2009-7121
Advanced Vehicle Concepts in the Next Generation Air
Transportation System
Matthew Blake1, Ray Young2, James A. Smith3, Ken Wright4,Ricky Mediavilla5, and Fred Wieland6
Sensis Corporation, Reston Technology Center, Reston, VA
This paper discusses the impact of new vehicle technologies on the Next Generation Air
Transportation System (NextGen). Four specific new vehicles are analyzed. The four
vehicles, the analysis method, and some sample results are presented. The main thesis of this
paper is that new vehicle technologies can help bridge the gap between anticipated air traffic
demand twenty to thirty years from now and the air traffic demand that can be efficiently
processed by implementing NextGen technologies with only conventional vehicles.
I. Introduction
This paper discusses the highlights of a project involving the interaction of advanced aircraft concepts with the Next
Generation Air Transportation System (NextGen). It sets the context of the study, discusses the research plan, and
highlights some key results. It also serves as an overview and introduction to nine additional papers at this
conference that each present in detail some aspect of the analysis.
NextGen represents a transformation of the air traffic control system from its present highly manual state into one in
which digital technology, information sharing, and automation is ubiquitous. This transformation has implications
across the gamut of aviation activity, from airline business models through airspace rulemaking. The Joint Planning
and Development Office (JPDO) is responsible for coordinating this transformation among multiple government
organizations with collaboration from industry.
In addition to the transformation occurring in air traffic management, a technology and business driven
transformation is occurring in aircraft design, production, and manufacture. Advances in materials science, such as
the development of carbon composites for use in airplane fuselages and wings, promise lighter, stronger, and more
fuel efficient vehicles. Engine design technology is expected to improve, resulting in quieter engines for next
generation aircraft. Engine manufacturers have also recently begun building small, lightweight, and energy-efficient
turbofan engines,i which spurred the manufacture of very light jets and the opening of an on-demand air taxi
market.ii Unmanned aircraft systems (UASs), widely used by the military, are expected to enter civilian service
once a reliable and cost-effective sense-and-avoid capability is developed.iii Tiltrotor aircraft for civilian use are
currently being developed by the Bell/Agusta Aerospace Company. Their model BA609, a nine-passenger vertical
takeoff vehicle with a cruise speed of 275 knots and a range of 1,000 nautical miles, expects to receive certification
in 2010.iv
Given that both the air traffic management system and aircraft design are currently undergoing significant
transformations, an interesting research question arises. To what extent does the NextGen transformation either
constrain or promote new vehicle designs? Conversely, to what extent should the design of new vehicles influence
the NextGen specification? Closely related to these questions are issues concerning the aspects of NextGen that are
critical to realize the full performance capability of these new aircraft, as well as the overall throughput, capacity,
delay, environmental, and safety impacts of the combination of these new vehicles with the NextGen
transformations.
1
Principal Investigator, 11111 Sunset Hills Road, Reston, VA
Director, Sensis Reston Technology Center, 11111 Sunset Hills Road, Reston, VA
3
Project Manager, 11111 Sunset Hills Road, Reston, VA,
4
System Engineer, 11111 Sunset Hills Road, Reston, VA.
5
System Engineer, 11111 Sunset Hills Road, Reston, VA
6
Senior System Engineer, 11111 Sunset Hills Road, Reston, VA
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Copyright © 2009 by Sensis Corporation. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.
Recognizing the importance of these questions, NASA’s Aeronautics Research Mission Directorate (ARMD) started
two parallel research efforts aimed at analyzing the deployment of new vehicles with the advanced concepts in the
NextGen specification. The study scope includes the interactions, safety tradeoffs, and environmental implications
among operational procedures, new vehicle technologies, and the performance of NextGen. One of the two ARMD
studies is being conducted by Sensis Corporation, and is the focus of this paper.
This study is important for several reasons. First, inconsistencies between the NextGen definition and the
capabilities of the new vehicles are more easily rectified if identified early. Second, the performance and
environmental targets that are specified by NextGen are influenced by the types of aircraft that are expected to be
available in the future. Third, the NextGen terminal area procedures will be highly influenced by the performance
capabilities of the vehicles which operate in the airspace. Finally, the specification of NextGen itself can be
changed, if needed, to accommodate the capabilities and performance of the new vehicle designs.
The project outlined herein considers five specific types of future advanced vehicles: 90-passenger large civil
tiltrotors (LCTRs), unmanned aircraft systems (UASs), supersonic civil transports (SSTs), very light jets (VLJs),
and cruise-efficient short takeoff and landing vehicles (CESTOLs). These five vehicles are only a fraction of what
is currently being studied by industry today, but they do represent vehicles that have a reasonable probability of
being utilized in the decade of the 2020’s and beyond. Two of the aircraft—VLJs and UASs—are available today.
UASs are limited to flight in controlled airspace primarily due to their lack of sense-and-avoid technology, but that
restriction is likely to be lifted by the 2020’s if technology matures as expected. VLJs are being manufactured
today. As mentioned earlier, Bell/Agusta Aerospace is developing a 9-passenger civil tiltrotor, expected in operation
in a few years. By the decade of the 2020’s, much larger LCTRs, such as the 90-passenger version studied here,
may be in service. The CESTOL is under active consideration by aircraft manufacturers as a replacement for a
single-aisle large commercial transport, although CESTOL aircraft are not available today. Finally, the SST, the
vehicle requiring the most technological improvements among the five studied here, is nevertheless within
possibility of production in the next twenty years.
Of these five vehicles, performance results for four (CESTOL, LCTRs, UASs, and VLJs) are presented in this paper.
II. Previous Work
A summary of project progress through January of 2009 is given in a recently-published paper.v This paper and the
ones that follow provide more recent, and much more detailed, results from the project.
Studies of specific new vehicle technologies, independent of NextGen, have been ongoing for many years. For
example, NASA has studied civil tiltrotor (CTR) operations over the last two decades, both analytically and through
very high fidelity human-in-the-loop (HITL) motion simulation studies. Analytical studies have shown the
feasibility of CTR for short-haul (<500nm) operations, diverting short-haul travelers to the CTR’s vertiport, thereby
freeing arrival and departure slots on the main runway for more efficient longer-haul transport aircraft.vi This result
suggests that overall passenger throughput at vertiport-enabled airports can be increased with minimal impact on
flight delays. HITL simulators have shown that CTR conversion from “turboprop mode” to “helicopter mode” on
arrival is best achieved before acquiring the glideslope when instrument meteorological conditions (IMC) prevail.vii
This result has implications for the design of CTR instrument approaches.
In the UAS world, much attention is being devoted to the “sense and avoid” technology necessary to integrate them
into the National Airspace System (NAS) as well as best practices for UAS use prior to the availability of the senseand-avoid capability.viii Proposed UAS missions are plentiful: cargo systems operating continuously for guaranteed
next-day service for all freight,ix humanitarian and disaster relief operations,x high altitude long endurance missions
for communication support or surveillance,xi and meteorological sensor platforms, among many others.
Because VLJs are in commercial use today, there have been several studies focusing on the impact of VLJs
operating in the NAS. A study using the Transportation System Analysis Model (TSAM) at Virginia Tech showed
that VLJ on-demand air-taxi service becomes economically competitive with commercial air service if the VLJ cost
drops below $1.85 per passenger mile (2006 dollars).xii Although not targeting VLJs specifically, a recent paper on
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the NextGen early implementation effort in Florida suggests that VLJs might help climate change by avoiding
altitudes that cause cirrus-inducing contrailsxiii
In the SST world, studies have focused on producing a “quiet” sonic boom so that SST flights over land become
commonplace. Studies have also focused on the business case for such vehicles. Initially it is envisioned that small
SST business jets will be produced,xiv although there is some work on large commercial SSTs as well.xv
There have been numerous studies of CESTOL technologies in the last decade. Of particular importance is a study
of the short takeoff and landing (STOL) technology on a hypothetical single-runway airport.xvi The study affirmed
the commonly-held belief that differences in approach velocities negatively impact runway capacity, unless the
slower-moving aircraft can be separated from the rest of the arrival flow. Because of their short runway landing
capability, CESTOL vehicles tend to have much slower approach speeds than conventional aircraft.
Of particular note are previous studies focusing on the performance implications of a fully-implemented NextGen
system. The JPDO has studied the future with and without the NextGen transformation using only traditional
aircraft types. Their studies include aircraft such as the Boeing 787 and Airbus A380, but do not include any of the
vehicle technologies included in this study. The JPDO results show that the projected future travel demand (in
2025) is only 30% satisfied without NextGen, but 80% satisfied when NextGen is fully implemented.xvii An
interesting question arises as to whether these new vehicles, with new and different flight profiles and
arrival/departure requirements, can help bridge the remaining 20% gap in 2025 and the even larger gaps in 2040 and
beyond.
III. Research Method
The research question that this project addresses is the impact of the five new vehicles on NextGen for the time
period 2025-2040 and beyond out to three times today’s traffic. Simulation models of the National Airspace System
(NAS), configured for its expected behavior under NextGen, were used extensively for this analysis. Because there
does not exist a single simulation that provides all of the functions necessary to answer this question, the project
employed a number of different models and different simulations, connected manually, as shown in Figure 1.
The steps required to run this analysis are as
follows.
Step 1. Define the performance of the new
vehicles. For each of the five new vehicles, its
performance must be defined in enough detail
that the various simulation models can fly the
vehicle in the virtual world. In the aviation
analysis community, Eurocontrol’s Base of
Aircraft Data (BADA) is a standard for
describing vehicle performance. In this first step,
researchers at the Georgia Institute of
Technology’s Aviation Systems Design Lab
(ASDL) use their Environmental Design Space
(EDS) project each new vehicle’s performance
as needed for the BADA standard. For existing
vehicles
(conventional
aircraft),
BADA
performance
data
already
exists,
thus
only
the
Figure 1. Model Infrastructure for New Vehicle Analysis five new vehicles need to be modeled in this
step. When projecting the vehicle’s performance, its noise and emissions profiles are also estimated. These profiles
are needed to drive the Aviation Environmental Design Toolkit (AEDT), a standard suite of tools used by
researchers to generate noise contours and emissions profiles around airports.
Step 2. Generate new vehicle demand. In addition to vehicle performance data, the various simulation models need
a traffic demand file that specifies the specific flights flown by each aircraft (conventional and new aircraft). The
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project started with standardized data files that have been used by JPDO in their analyses. Those files are
subsequently modified to reflect the impact of each new vehicle on overall traffic demand. That impact is
influenced by the business model for each new vehicle, and some of the vehicles have multiple business models.
For example, CESTOL aircraft are capable of landing and departing on runways as short as 3,000 feet. As a result,
they can be used in the “business shift” business model in which highly congested airports shift excess flights to
suitable nearby airports. But because CESTOL also have slow approach speeds (necessary to land on a short
runway), they are capable of flying steep (4.5-degree) approaches as well as spiral, or helical, approaches. These
novel approaches can be used to utilize runways at congested airports more effectively in addition to utilizing nearby
airports.
Step 3. Develop terminal area procedures. Some of the simulations require detailed trajectories of aircraft in the
terminal area. These simulations need the specifics of the procedure design. Because some of the new vehicles
considered (CESTOL and VLJ in particular) have slow approach speeds, they must be segregated from the main
traffic. In this step, procedures for both conventional and new aircraft that are consistent with NextGen are
developed and put into a form amenable to detailed simulation analysis.
Step 4. Evaluate the safety profile of the new vehicles. With their performance, business case, demand, and terminal
area routing determined, the next step is to establish the difference in safety margin between the current system and
a NextGen system with new vehicles. The safety analysis consists of two parts. The first part is determining the
safety margin in the current system as compared to the margin in a NextGen system. The second part is determining
the safety margin of a NextGen system with the new vehicles. For this step, human factors models from the Georgia
Institute of Technology, as well as expert opinion and historical data, are used to determine the safety margins.
Step 5. Evaluate the efficiency of the terminal area procedures. This step can occur simultaneously with step 4. It
involves using the SIMMOD simulation to compute the trajectories, in the terminal area, of the conventional aircraft
with the new procedures. Metrics from the SIMMOD analysis include the traditional delay/capacity/throughput
numbers, as well as precise aircraft position and altitude information that can be passed to AEDT for environmental
impact (noise and emissions) analysis.
Step 6. Evaluate the performance of the entire NAS. In this step, the demand file (consisting of both the new
vehicles and existing conventional aircraft), the BADA performance of all vehicles, and the terminal area procedures
are combined to compute the expected system-wide impact of the new vehicles. Capacity and delay metrics as well
as environmental metrics (using AEDT) can be computed at this point, along with some level of controller workload
based on dynamic density of the airspace. The Airspace Concepts Evaluation System (ACES) software is used to
evaluate system performance at this step.
In parallel with these steps is a process in which the metrics and trade space were analyzed to specify metrics that
could be computed to illustrate the impact of the new vehicles. In addition, metrics that might not be able to be
computed today are identified and used to determine gaps in simulation capabilities.
IV. Results
In this section we will present significant results developed during this study. We will focus on the efficiency gains
expected from four new vehicles (CESTOL, CTR, UAS, and VLJ), with a focus on how much of the capacity gap
identified earlier can be filled. These results cover the performance of the vehicles in a system-wide context only;
other papers in this conference cover the environmental and safety aspects of these vehicles and detailed regional
impact studies. The project used three future demand files for baseline comparison, one for the year 2025, one for
the year 2040, and one for a hypothetical future year in which traffic demand has increased three times (3X) over an
average day in July 2006. The three demand files were supplied to the project by the JPDO’s Integrated Portfolio
and System Analysis (IPSA) group. These files were modified, as detailed below, to create future demand files for
CESTOL, CTR, and UAS vehicles.
A. Cruise Efficient Short Takeoff and Landing (CESTOL) Aircraft
A primary application for CESTOL technology is to offload flights from heavily congested airports. The 100passenger CESTOL aircraft is capable of arriving and departing at airports whose runways are 3,000 feet long or
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greater. Most aircraft of that size require at least 5,000 foot runways, and sometimes longer. As a result, the
CESTOL aircraft can arrive and depart at many more airports than conventional aircraft of the same size. This
characteristic can be exploited to relieve larger airports of flights in excess of their capacity. This business case is
motivated by a generalization of a network-based approach to airline scheduling, as opposed to the hub-and-spoke
method of scheduling. In this scenario, travelers would be routed more directly to their ultimate destinations by
offering them a myriad of choices to airports other than the dominant one in each metropolitan area.
To explore this concept, projected future traffic demand was modified by offloading flights from the top 35 major
airports whenever their demand to capacity ratio exceeded 90% in any 15-minute interval. The selected flights must
have a stage length less than 600 nm, which is the maximum range of the CESTOL aircraft. The flights were
offloaded to reliever airports within 70 nm of the primary airport, provided that the reliever possessed a paved
runway at least 3,000 feet long with a width of at least 100 feet.
Figure 2 shows the ACES performance for the future traffic projected for the years 2025 and 2040 using standard
FAA traffic growth rates. The performance is presented as a tradeoff curve between flight volume and system
delay. As flight volume grows, the system delay grows exponentially. The exponential relationship is not
surprising given that airports operate similar to a queuing system, in which the runways operate as servers and the
flights operate as customers using the servers.
Figure 2 contains many points that are
operationally infeasible, because average
delays and variances are unacceptably
large. It is therefore important when
interpreting Figure 2 to establish an
operationally feasible point on the
volume/delay tradeoff curves. One such
method is to select an operating point
where the average system-wide delay was
about equal to a recent actual year. In
2006, the ASPM data set records an
average delay at the 35 largest airports
around 6 minutes per flight, with three
airports operating as high as 9 minutes per
flight.xviii Using that criteria, there are
approximately 2,500 more flights per day
with CESTOL in 2025 and 5,000 more
flights per day in 2040.
Figure 2. Tradeoff curves between flight volume and delay for projected traffic in 2025 and 2040. Although the throughput increase for this
offloading scenario is significant, there are
several problems with this strategy. It is not clear that utilizing reliever airports is economically feasible in many
cases. For commercial flights to be profitable there must be sufficient demand to and from each airport to warrant
service. In addition to demand, most of the reliever airports currently lack infrastructure and supporting services: onsite emergency crews, passenger security checkpoints, and luggage handling facilities, to name a few. Therefore
significant airport infrastructure development will be needed to prepare reliever airports for commercial flights. In
addition, because many large airports tend to be hubs, there either needs to be sufficient local demand (nonconnecting passengers) or there must be a mechanism to shift connecting passengers from one flight to another if
their connecting flight is at another airport in the metroplex. The interconnection mechanism might be high-speed
rail or bus as it is unlikely that shuttle flights would be offered. Therefore the intra-metroplex infrastructure for
connections would likely also need to be improved before reliever airports could become attractive alternatives to
metropolitan hub airports. It is not clear whether demand growth by 2025 or 2040 would be large enough to drive
the investment required to support significant reliever airport growth as needed to utilize CESTOL vehicles under
this model.
B. Large Civil Tiltrotor (LCTR) Aircraft
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A second strategy for increasing operations without proportionally increasing delay is to use vertical takeoff and
landing aircraft, such as LCTRs, to arrive and depart at areas of an airport independent of the dominant runways. If
independent LCTR arrival/departure routes are procedurally separated from fixed-wing aircraft arrival/departure
procedures, then the LCTRs can perform runway-independent operations, thus adding capacity without adding to
delay. But because LCTRs have higher operating costs than their fixed-wing counterparts (the project herein
analyzed a 90-passenger tiltrotor), they become economically feasible only in high-density markets where fixedwing service is somewhat unreliable due to high congestion-related delays. City pairs that have “shuttle” operations
were targeted for LCTR service. Shuttle operations are defined here as having more than fifteen flights per day in
one direction. After making reasonable assumptions about LCTR production rates per year, 1,600 flights were
identified as being candidates for LCTR usage in 2025 and 4,300 flights were identified in 2040.
The impact of LCTR replacement for these flights is as follows. The original fixed-wing aircraft that serve these
high-density markets must compete with other fixed-wing aircraft for both airspace and runway slots (both departure
and arrival). When replaced by LCTRs, they can use the runway-independent arrival and departure procedures to
service the airport with little, or no, impact on the fixed-wing aircraft operations. The LCTR operations will
potentially interfere with each other, but will not impact fixed-wing operations at the airport. The result of such a
shift for the future demand years 2025and 2040 is shown in Figure 3.
Figure 3. Impact of CTR shuttle flights between high‐density airports. Figure 3 shows that the LCTR shuttle flights
increase system capacity substantially,
although the effect of replacing shuttle flights
with LCTRs is smaller than the effect of the
CESTOL business-shift strategy shown in
Fig. 2. At a constant average NAS-wide delay
of 6 minutes the LCTR scenario can handle
1,100 more flights than the baseline scenario
in 2025, and 2,700 more flights than the
baseline in 2040. Regardless of the state of
technology of LCTRs in particular, it remains
true that any vehicle capable of landing in a
very short (600 feet or shorter) landing pad
and capable of flying arrival and departure
routes that are procedurally separated from
those on the main runways, will increase the
capacity of the NAS significantly. Whether
business is willing to invest in a more costly
vehicle like the LCTR remains less clear.
C. Unmanned Aircraft System (UAS) Technology
UASs are interesting because they describe a level of technology, not a particular aircraft. UAS technology, if
perfected, could feasibly be used in any aircraft from light reconnaissance activities (for which they are used today)
through large commercial airliners. UAS requirements on this project included (1) a vehicle that weighed over 100
pounds; (2) a civilian mission; (3) a mission that impacts traffic levels in the NAS. To satisfy these three
requirements, a mission involving freight forwarding using small aircraft was analyzed.
Rapid freight delivery today involves large aircraft flying to many spoke airports. When packages arrive at a spoke
airport, if they are destined to a remote area, they can be forwarded by truck or by small aircraft. Which mode is
chosen is strictly a matter of cost. On one of the days analyzed—December 20, 2007—two-hundred fifty three
small-aircraft cargo flights were identified serving city pairs that began at a freight carrier’s “spoke” airport and
ended at a smaller airport, usually in a rural area. The preferred vehicle for these freight-forwarding flights was a
“Cessna Caravan Super Cargo Master” (C208) and its variants.
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Were UAS technology to be installed on C208 aircraft, it would have the following effects. First, all material
related to pilot comfort and safety—seats, seat belts, yokes, rudders, air conditioning, and most avionics—could be
removed from the aircraft. However, extra avionics required to securely communicate between a pilot on the ground
(remotely monitoring the flights) and the on-board flight control system would be needed as well as enhanced
automation. The project estimated that the weight savings from removal of pilot necessities balanced the weight
gain from additional communication avionics, resulting in no net increase in weight or cargo capacity.
The UAS would have some cost savings because one ground-based pilot could remotely monitor several vehicles.
Thus the breakeven point between using a truck and using a C208 for freight forwarding is likely to change in favor
of the C208. The project estimated that currently the breakeven point is roughly 120 miles, meaning that if a truck
must travel more than 120 miles along roads then the C208 is more cost effective. Because precise cost estimates of
UAS technology are difficult to forecast, the project developed UAS demand sets with distance ranges 30-60 miles,
60-90 miles, 90-120 miles, and 120-150 miles. Adding all four of these UAS demand sets to the 2025 and 2040
baseline demand sets gives the results shown in Figure 4.
The volume-delay tradeoff curve
for the UAS freight forwarding
scenario is essentially a shift of the
baseline to the right. This is
because the UAS business model
adds many small aircraft to the
system, but those aircraft depart
from relatively uncongested spoke
airports and arrive at small remote
airports with little traffic. As a
result, the entire volume/delay
tradeoff curve is simply shifted to
the right.
There is a slight
downward trend in the average
delay for the UAS curve due
entirely to mathematics: The UAS
scenario adds flights without
increasing total delay, resulting in
a slight decrease in average delay.
Figure 4. Effect of UAS freight‐forwarding operations on the NAS. Obviously this UAS scenario has
no impact on any measure of
passenger capacity as this is a freight carrying business model.
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D. Very Light Jet (VLJ) Technology
Very Light Jets are in commercial use today. Expanded use of VLJs assumes decreasing operating costs relative to
other forms of transportation. The VLJ schedules used in the New Vehicle NRA were created by researchers at
NASA’s Langley Research Center using Virginia Tech’s Transportation Systems Analysis Model (TSAM). Using
projected demand between city-pairs, the model computes the number of flights that could be flown in an
economically competitive manner by
a 4-passenger VLJ given certain
assumptions
regarding
airline
operating costs, the price of jet fuel,
and the cost of auto travel.
Figure 5 shows the results of adding
3,900 VLJ flights to the 2025
baseline schedule and 6,500 VLJ
flights to the 2040 baseline schedule.
Because few VLJs fly into major
hubs, their impact on delay is small.
Like in the UAS scenario, the VLJ
scenario shows a slight decrease in
average delay because many aircraft
were added without a significant
increase in total delay. Because the
VLJ only carries 4 passengers, it
does not substantially increase the
capacity of the NAS for carrying
passengers.
Figure 5. Effect of VLJ operations on the NAS. V. Conclusions
The research question posed at the beginning of this paper involved how much of the 20% gap between a full
NextGen implementation and the traffic demand of the future could be bridged by new vehicle technology. Not
surprisingly, the answer to this question lies in how the new vehicles are used to serve aviation demand. The unique
characteristics of each vehicle can be used to shift the demand/volume curve to the right (serving more demand with
the same performance).
For example, the CESTOL aircraft’s ability to land on a short (3,000 foot) runway can be used to offload
congested hub airports during periods of peak traffic volume. If that business model is adopted, and it has many
attractive features, then the results suggest that 2,500 to 5,000 more flights per day could be accommodated in the
fifteen major metropolitan areas. This is equivalent to 250,000 to 500,000 more passengers per day that could be
moved into and out of the fifteen major metroplexes—or 90 to 180 million more passengers annually traveling
through congested metroplexes.
The LCTR business case relies on the aircraft’s ability to land on a very short (600-foot) landing strip that can be
placed within an airport’s physical boundaries without interfering with the operation of the major runways. Using
the NextGen technologies, the approach and departure routes to the landing strip can be procedurally separated from
the existing fixed-wing approach and departure routes. The net effect would be the same as if a new runway were
added to an existing congested airport. Because LCTRs will be more costly to purchase and operate than
conventional aircraft, their main use would be at existing high-density corridors where fixed-wing aircraft would
experience considerable delay and schedule uncertainty. Our simulations suggest that the LCTR replacement
strategy could add 1,100 flights per day in 2025 and 2,700 flights per day in 2040, without increasing delay. This is
equivalent to 100,000 to 250,000 additional passengers per day.
For UASs, the business case revolves around using small aircraft more extensively for freight-forwarding
operations. Because these aircraft would operate at off-peak times and serve relatively uncongested airports, it is no
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surprise that their use adds demand (flights) to the system while leaving the performance (delay) unchanged.
Moreover, because they have no passenger capacity and create very little delay, they have no impact on the
passenger capacity of the NAS.
Like the UAS scenario, the VLJ scenario also adds relatively large numbers of aircraft to the NAS while adding
little delay. Because the VLJ only seats 4 passengers, its ability to increase the passenger-carrying capacity of the
NAS is limited.
The overall conclusion is that several of these new vehicles operate quite differently from conventional
operations—with short takeoff and landing capabilities and with a potential for independent and non-conflicting
operation—and combined with NextGen capabilities indicate that their utilization can be exploited in the future to
more fully satisfy future air traffic demand.
ACKNOWLEDGMENTS
The authors would like to acknowledge the guidance of our contracting officer technical representative, Mr. Harry
Swenson, as well as the guidance of the technical monitor, Mr. Phil Arcara. This work represents the cumulative
effort of many people from many organizations. In particular we would like to thank Michelle Kirby, Peter
Hollingsorth, Dimitri Mavris, Gaurav Nagle, Matt Elliott, and Vitali Volovoi of Georgia Tech; Mark Rodgers,
Alfredo Colon, and Alma Ramadani of CSSI Inc.; Wim den Braven and David Holl of ATAC; Rosa Weber of
Honeywell; and Randy Kelley.
Special thanks to Andy Hahn of NASA who proofread this paper and provided insights into the spiral procedures
and the CESTOL reliever airport scenario. We would also like to thank Dr. Frederick Wieland who led this project
for much of its duration.
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iv
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v
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