The Evolution of Transformational Flight - AIAA ARC

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The AIAA has officially approved a new Transformational Flight Program Committee whose mission is the. “shaping of a f
The Evolution of Transformational Flight Brien A. Seeley M.D.* CAFE Foundation, Santa Rosa, California, 95404 The Comparative Aircraft Flight Efficiency Foundation (“CAFE”) applies the principles of evolution and utilitarianism to define the core set of requirements for the future, ondemand, aviation-based transportation market as an ecological niche. In evolution, a niche is the sum of the habitat requirements for a species to emerge, persist and produce offspring. In the present analysis, the species that will produce offspring will be the new air vehicles (“Sky Taxis”) that reach mass production and that transform aviation as their niche grows from existing airports to future, more proximal “pocket airparks”. In order to be sustainable, this transformation must also respect the basic principle of utilitarianism: “the greatest good for the greatest number”. The consensus aviation future forecast by NASA’s Aviation Unleashed Program is a transformational one in which autonomous aircraft will carry both passengers and freight in a safe, quiet, on-demand, sustainable, fast (door-todoor), affordable, accessible, distributed, point-to-point, public acceptable, ubiquitous aviation-based transportation system. These many descriptors make the niche requirements self-evident and clearly dictate the practical “traits” essential to the “fitness” of air vehicles in this niche. A concerted program that will apply maximal effort to rapidly bring forth air vehicles with such traits is herein presented as a series of pragmatic, inter-dependent, costeffective technology prizes. The five-year program is one of spiral development that leverages fast prototyping to converge these several technologies in a process of planned evolution. It builds upon CAFE’s 33 years of designing and safely conducting technology prize competitions, including the 2011 Green Flight Challenge (GFC I). The prize program is founded on transportation statistics, extant and emerging technologies, human physiology, and prospective market research. This prize program will accelerate the growth of the mainstream market of transformational flight as well as its research funding and infrastructure. A detailed exploration of the costs, risks, benefits, alternatives and imperatives for an extensible near-term implementation of sustainable public Sky Taxi service into this niche is included.

Nomenclature 4D 6’ AFS AGL ATC BHP BMS CAFE CAS Cdo CCW CFD CFJ CGFCP CLmax

= = = = = = = = = = = = = = =

a three-dimensional path along which each point has a defined specific clock time 6 feet, with apostrophe indicating feet autonomous flight system height above ground level air traffic control brake horsepower battery management system CAFE Foundation, Inc., an all volunteer, 501c3 non-profit educational foundation calibrated airspeed zero-lift drag coefficient circulation-controlled wing computational fluid dynamics co-flow jet, a specialized high lift airfoil system CAFE Green Flight Challenge Program maximum lift-coefficient

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President, CAFE Foundation, 4370 Raymonde Way, [email protected], Senior Member AIAA.

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CNEL CO2 CTOL dBA DtD EAA ESTOL eta G GA GFC I GPS IFR kg kph kWh kW lb m mic MPG mph MSL NAS NTSB OSTP PAS pkmPL PSI RAS RITS ROI RPM STEM STS STZ TFR V VFR VMT VTOL Vmax Vso

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =

community noise equivalent level carbon dioxide conventional take off and landing decibel noise level, A-weighted scale door-to-door Experimental Aircraft Association extremely short take off and landing propeller efficiency the force of gravity at sea level on Earth general aviation the 2011 Green Flight Challenge sponsored by Google and prize-funded by NASA global positioning system instrument flight rules; e.g., flying with instrument guidance while immersed in clouds (see VFR) kilogram kilometers per hour kilowatt hour kilowatt pound meter microphone miles per gallon, typically referenced to 87 unleaded auto fuel miles per hour above mean sea level, describing elevation or altitude on a standard day National Airspace System National Transportation Safety Board Office of Science and Technology Policy propeller acoustics simulator passenger kilometers per liter pounds per square inch runway acceleration simulator runway-in-the-sky, a virtual airport runway situated in the airspace return on investment revolutions per minute science, technology, engineering and mathematics education Charles M. Schulz Sonoma County Airport simulated traffic zone temporary flight restriction volt visual flight rules; i.e., flying with visual guidance and not immersed in clouds vehicle miles traveled vertical take off and landing maximum velocity minimum velocity at 1 G at which an aircraft in landing configuration stalls

Evolution—Nomenclature artificial selection = the process by which humans intentionally select desired heritable traits competition = the process in which species and individuals compete for limited resources extinction = the disappearance of a species due to insufficient fitness, fatal genetic flaws, or natural disaster fitness = the average amount of reproductive success of individuals who share particular heritable trait(s) gene = a sequence of DNA base pairs that codes for a protein conferring a certain trait or action genetic hitchhiking = the process by which a selected gene brings others that are linked on the same chromosome genotype = the combination of genes that produce a certain phenotype or set of traits in an individual natural selection = the process by which heritable traits that confer fitness become more prevalent in a population niche = a place, habitat, market or ecological role in which a phenotype can survive according to its fitness

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phenotype = the combined observable physical traits of an individual conferred by particular genes sexual selection = the selection of male or female individuals with traits that increase mating and offspring speciation = the process by which individuals confined by geography, behavior or time form a distinct new species succession = The process of replacement of one dominant species by another in a habitat or ecosystem symbiosis = the process by which one species helps the fitness of another variation = the process by which selection, mutation and migration create several different phenotypes

I. Introduction The AIAA has officially approved a new Transformational Flight Program Committee whose mission is the “shaping of a future on-demand aviation-based transportation market opportunity”. This paper informs that shaping by drawing upon fundamental principles of evolution and utilitarianism to define the core requirements of that transportation market in terms of an ecological niche constrained by societal needs. These principles apply fitness for survival in that niche and “the greatest good for the greatest number” as the most essential considerations. This method results in a clear set of core requirements that distill the much-needed definition of transformational flight and that determine the primary design goals of the new aircraft that its niche will demand. Once these first generation primary design goals are determined, technology prizes can be devised to rapidly fulfill them. The succession of species in the new niche then largely becomes, like natural selection, a more teleonomic process without the limitations of any biased, single-minded, controlling agency or “watchmaker”. With clearly defined core requirements, technology prizes can evolve a diversity of innovative new traits and capabilities from which will emerge new phenotypes that will persist and be reproduced. Technology prizes maximize the speed with which successful traits can be brought forth while minimizing the time for non-fit traits to become extinct. For maximum diversity of innovations, technology prizes should seek a maximum-sized pool of eligible innovators—what evolutionists would call a ‘global gene pool’. Using this approach, this paper presents a series of global technology prizes that can rapidly bring forth the traits necessary for the main niche of on-demand transformational flight. Based upon the synchronicity of known and emerging technologies, our societal transportation needs and environmental concerns, the consensus of the experts at NASA’s Aviation Unleashed Program1 was that the future domain of transformational flight will inevitably be one of an safe, quiet, on-demand, sustainable, fast (door-todoor), affordable, accessible, distributed, point-to-point, public acceptable, ubiquitous aviation-based transportation system. (See “Defining the Core Requirements”, below) They also forecast a future that included non-transportation, sub-specialized aircraft designs with unusual traits that would fulfill several other novel uses apart from the main transportation system. Such novel aircraft, most of which would not carry humans, would perform functions such as firefighting, law enforcement, search and rescue, agriculture, resource management, scientific data collection, energy harvesting, police and military surveillance, exploration of ocean and other planets, border patrol and recreation. The traits and technologies developed for the future mainstream on-demand transportation market are very likely to also provide “technology pull” for unmanned aircraft that perform these novel, specialized uses, as well as for a wide variety of other civil aircraft.

II. A New Frontier in Aviation As described by biologist E. O. Wilson in “The Social Conquest of Earth”, the evolution of the large human brain conferred the unique advantages of memory, teaching and social cooperation. These traits proved so powerful, important and valuable that homo sapiens succeeded in rapidly dominating all other species on earth. This domination occurred even though humans did not evolve the specialized anatomical features necessary for bird-like flight. The human brain instead devised people-carrying flying machines that over the last 110 years evolved to far surpass the range, ceiling and speed of bird-flight. However, in all those years, our human-carrying, cross-country flying machines have never rivaled birds in terms of combining the following traits: 1. 2.

ultra-quiet flight vertical or extremely short take off and landing (V/ESTOL)

Creating small, new, moderately fast (> 193 kph or 120 mph) passenger aircraft with such combined traits would represent nothing less than a new frontier in aviation—one that could transform transportation. It would finally give humans the bird-like capability to fly, not drive, to nearly anywhere.

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This frontier was broached in 2011 by the remarkable performances achieved in the GFC I conducted by CAFE. Pipistrel’s winning electric aircraft achieved 172 pkmPL (403.5 pMPG). The second-place electric-powered eGenius aircraft achieved a combined 159 pkmPL (375 pMPG) at 169 kph (105 mph), take off noise of below 65 dBA at a 38 m (125 foot) sideline and a take off distance of less than 610 m (2000 feet) over a 15 m (50 foot) obstacle on a flight of nearly 322 km (200 miles). These performances inaugurated the Age of Electric Flight by proving that emission-free electric aircraft could achieve decent speed, adequate range, extraordinary energy efficiency and unprecedented quietness. They surpassed the energy efficiency and range of both the Nissan Leaf and the standard Tesla Model S electric cars, at about double the speed and in a vehicle that is immune to surface gridlock. Yet it is only the beginning of what can be accomplished if all of today’s emerging technologies are exploited. The $1.65M NASA-funded GFC I technology prize purse elicited a mix of 14 teams with members from across the globe, who built a remarkable array of innovative aircraft designs to compete in the GFC I. Combined private investment in the GFC I was over $7M. Several teams were supported by college students and nearly 30 graduate STEM theses resulted from the GFC I. Three teams were led by senior aeronautical engineers at major universities. Three teams represented leading small aircraft manufacturers. Team aircraft varied from 1 seat to 5 seats with powerplants from 37 to 149 kW (50 to 200 BHP). Safe, small, emission-free, personal air vehicles with ultra-quiet V/ESTOL capability, even if achieved at the sacrifice of high speed and long range, would be immediately attractive to time-starved users and provide significant benefits in today’s world of single-file surface gridlock, air pollution and climate change. With the appropriate additional features needed to fulfill the core requirements for public acceptance, they would open a new niche and confer enhanced fitness in terms of habitat, food sources, nesting locations, genetic influence and overall productivity. They would also naturally expand the diversity of our species’ gene pool and our opportunities to escape habitat destruction by natural disaster. In short, they would embody the evolution of transformational flight. In terms of vehicle fleet size, the fully developed on-demand, point-to-point air transportation system using Sky Taxis would dwarf that of all other aircraft types. A realistic relative magnitude of this succession is depicted in Figure 1., below, which depicts current vehicle fleet sizes for the main types of aircraft in the US.

Aircraft type versus fleet size, USA 1,200,000 Sky Taxis

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Figure 1. The strong market demand for transformative Sky Taxis predicts production numbers that would dwarf the known existing fleet size for all other aircraft types.

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Bringing forth the core capabilities necessary for ubiquitous Sky Taxi system deployment would have pervasive spin-off benefits. Similar to the way in which the enormous expansion of the US military aircraft industry during World War II led to a boom in general aviation for years afterward, the Sky Taxi system growth would powerfully restore growth in all facets of GA by making mass-produced, high quality aircraft parts, electric propulsion and autonomous-flight-capable avionics affordably available for personally owned aircraft, including LSAs and kitbuilts. This symbiosis would greatly improve aviation safety and re-invigorate the starkly under-utilized CTOL GA airports, as well as all of the related infrastructure and important support organizations such as NBAA, AOPA and EAA.

III.

Evolutionary Concepts

The gradual and unintentional process of natural selection has impeccable wisdom in bringing forth the traits necessary for fitness in a given niche or ecosystem. Deleterious or unfavorable traits are discarded during the process of survival of the fittest. The requirements of a niche that cause certain traits to emerge and survive can be clearly identified. With the exception of humans and few others, natural selection inherently produces living creatures that are exquisitely adapted to their environment in ways that sustain it rather than polluting or destroying it. The result has been an ecological homeostasis that was maintained over millions of years by intricate food chains that naturally recycle nutrients between plants and animals. However, such evolution is a very slow process and it has been disrupted by humans. The reverse of natural selection, artificial selection or selective breeding, involves humans choosing the desired biological traits and blending them into an individual, creature or organism of presumably exceptional fitness. Artificial selection can be accomplished very quickly, often in just one generation. Anticipating consequences of artificial selection is difficult in biologic systems due in part to the possibility of unpredictable mutations and other phenomena. Adverse consequences may be minimized if a holistic rather than narrowly selfish approach is used at the outset of any artificial selection process. The holistic approach necessarily includes the environmental and societal impacts of the approach. It is worth examining whether product development in free markets is analogous to the agentless process of natural selection. Adam Smith argued 240 years ago that the unconcerted “invisible hand” of unregulated free markets might exhibit a natural and fortuitous wisdom that would benefit everyone. Competition does cause better products to survive and inferior ones to become extinct while entrepreneurial strivings fortuitously create new jobs. However, for a variety of reasons, free markets have repeatedly failed to preserve the environment so as to respect the utilitarianism principle of the greatest good for the greatest number. The free market has not prevented the crisis in climate change, a four-fold increase in surface gridlock, and a marked worsening of air pollution. It has also not prevented a precipitous decline of general aviation in America. The free market in the USA has led to a staggering and adverse disproportion of wealth among its citizens, a glaring example of the unchecked effect of survival of the fittest without co-equal application of the principle of the greatest good for the greatest number. Well-intended government regulations, stimulus packages, government-directed research, procurement contracts, and grant-funding have also generally failed to solve these very large and longer term environmental and societal problems. In contrast, technology prizes have recently proven very successful in efficiently bringing forth the desired traits, capabilities or technological breakthroughs necessary to solve major problems. In March, 2012, a few months after the success of the 2011 Green Flight Challenge, the Obama Administration took the unprecedented step of authorizing all of its Cabinet-level agencies to employ technology prize competitions as legitimate alternative methods for solving major problems.2 In contradistinction to other instances of artificial selection driven by a profit motive or special interests (including selective breeding, the free market and government policies mentioned above) the technology prize method can altruistically apply a global pool of talent, ideas and resources to rapidly and publicly demonstrate diverse solutions to major environmental and societal problems. The global tech prize demands that by a date certain not only must a required achievement be demonstrated, but that to win the prize, a team’s achievement must surpass that of every other team from across the globe. Tech prize teams will exploit the internet to rapidly crowd-source the innovations that they seek, which enhances the prize mechanism’s transparent, naturalselection-like process of problem solving.

IV.

Utilitarian Concept

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John Stuart Mill is credited with the utilitarian concept of “the greatest good for the greatest number” as a guiding principle for policy-making, goal-setting or actions by individuals. The consistent application of this principle is a touchstone of democracy. It requires foresight and inherently provides a beneficent, holistic, systems approach to planning that admittedly downplays the strivings of special interests of individuals. It is important that this principle be applied when defining the core requirements for transformational flight in order to maximize its societal benefits and minimize any adverse impacts on the environment. The utilitarian principle would, for example, support having Sky Taxis be affordable and accessible for the general public, emission-free and subject to effective safety and noise standards. It would favor public, shared-use landing sites with noise ordinances rather than exclusive private ones. The relative allocation of airspace between commercial airline services, pleasure flying by private pilots and future Sky Taxi service would likewise need to be guided by this principle. In the face of today’s serious problems of climate change, air pollution, surface gridlock and a major decline in general aviation, the principle of the greatest good for the greatest number would urge the rapid development of transformational flight as an important and valuable course of action toward solving all of these problems.

V.

Defining the Core Requirements

The 11 core requirements for transformational flight are: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

safe quiet on-demand sustainable fast (door-to-door) affordable accessible distributed point-to-point public-acceptable ubiquitous

The essential nature of these requirements becomes obvious if one performs the thought experiment of inserting the word “not” in front of any one of these 11 adjectives. A safe, quiet, on-demand, sustainable, fast (door-to-door), affordable, accessible, distributed, point-topoint public-acceptable, ubiquitous, aviation-based transportation system does not exist today and would clearly be transformational. Each adjective for such a transformational system is crucial to its success. Examining the actual meaning inferred by each adjective helps define the core requirements of the system’s niche. Safe means both a public perception of safety and a risk of fatality or injury during flight that rivals that of commercial airline service. Quiet means that its take off, landing and flyover operations must be ultra-quiet enough to be accepted for continuous high capacity operations in areas close-by to where people live and work. On-demand means accessible whenever needed. Sustainable means successful as a business enterprise and compatible with both the environment and its resources. Fast (door-to-door) means that flying in its system can offer door-to-door trip speeds that are at least twice those of any other mode of travel for trips as short as 60 km. Affordable means that the cost of flying in such a system offers a value to the traveler that significantly surpasses the competing value of travel by car, bus, train or other means. That value will be primarily based upon the dollars per passenger per kph of door-to-door trip speed, but must also respect the comfort, privacy, availability of wi-fi and ease of use. Accessible means close to locations where people need and want to go. Distributed means that one can fly from near home to nearly anywhere else rather than flying only to large metro hub airports. Point-to-point means departing from and traveling to points that are generally within less than 6 minutes of one’s origin or destination, without need of a rental car or use of congested surface freeways. Such proximity is crucial to achieving fast door-to-door speeds. Public-acceptable means both embraced for use by the public and acceptable to the public for frequent, routine low altitude operations in and above their neighborhoods, towns, shopping centers, open spaces and parks. Ubiquitous means that the Sky Taxi system will succeed across the nation and in other countries. Aviation-based means that the major portion of each trip’s length is flown rather than traveled in ground vehicles. Transportation system means one whose

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capacity allows substantial numbers of people to make useful trips to and from multiple locations over a large region. A finer grain examination of each of the adjectives’ meanings can more clearly define the core requirements of the transformational transportation system and thereby reveal the practical capabilities or traits necessary in the species of aircraft that will succeed in that niche. A. Safe: To be safe enough to win the public trust necessary to succeed in its market, this mode of transportation must rival the safety of commercial airline service. To accomplish this in small aircraft would be transformative. This level of safety will demand the near total elimination of pilot error, which, in turn, will eventually demand highly reliable autonomous flight as the norm. The autonomous flight controls must include redundant components. In addition, the first generation Sky Taxis must be made even safer by having features that can prevent accident or injury in the event of a failure of the autonomous control system. Riding in a Sky Taxi must be considered like riding in a hotel elevator. It will require a near-perfect record of vehicle and pilot reliability, vehicle safety features, accident avoidance by currency training in use of emergency procedures and flawless coordination by the air traffic control system. People must always walk away uninjured from any Sky Taxi mishap, malfunction or vehicle impact. The safety features of the first generation Sky Taxi should include all of the following: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.

smart propellers or fans that do not start if anything obstructs their path; a highly reliable, fail-safe propulsion system; wheel motors for quiet take offs, anti-lock regenerative braking and propless autonomous taxiing; vehicle ballistic parachutes, which may eventually include automatic or remote activation; power-off glide ratios of at least 20:1; very slow touchdown speeds with Vso near 52 kph (32 mph); mechanical flight controls redundant to autonomous servo-controls; a currently trained, licensed, current human pilot to operate those mechanical controls; acceptable handling qualities including spiral, longitudinal and maneuvering stability; shoulder harnesses containing airbags; reliable battery management system (BMS); provision for battery fire containment or jettisoning; precision, fast-acting autonomous flight controls for both gust management and envelope protection; autonomous, on-board, air and surface traffic detection and avoidance equipment; autonomous, on-board self-diagnostics that perform extensive automated pre-flight inspection; avionics that can request and automatically receive and follow assigned 4D GPS flight paths.

These important features are especially important in the initial implementation of the system as it builds the public’s trust, when an accident could critically threaten the entire future of the Sky Taxi market. The fastest way toward a market-useful Sky Taxi will be via a technology prize to induce the implementation of all 16 of the safety features above into a fixed-wing, ultra-quiet, ETSOL, “Optionally Piloted Aircraft” (OPA) that can readily obtain its FAA certification using standard known pathways. Such an aircraft could bring the important benefits of autonomous flight safety into the domains of both GA and transformational flight at the earliest possible date. To be perceived as safe, the user of the Sky Taxi must be kept comfortable. This means that the aircraft must respect the limits of human physiology in terms of cabin noise, ride quality, G forces, seating comfort, field of view (orientation), oxygen supply and ease of entry-exit to the aircraft. B. Quiet: Aircraft noise has long been aviation’s nemesis, relegating airports to enormous land parcels that cannot be located near people’s destination doorstep. This subverts aviation’s most fundamental purpose; fast travel without roads. The advent of electric propulsion and the extremely quiet operations that it can achieve comprise the single most important feature of transformational flight. Extremely quiet operations will finally enable aircraft to be permitted to take off and land in close proximity to one’s destination doorstep. This proximity will allow travel in Sky Taxis to be faster in door-to-door trip speed than car, airliner or the fastest bizjet. The physiology of the human auditory system imposes absolute limits as to what sound pressure level of noise is tolerable. These have been quantified for decades by a variety of methods and metrics and have been applied by the

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FAA to determine allowable airport size. The FAA regulation is based upon the “Schultz Curve”, shown above in Figure 2.

Figure 2. FAA requires that no more than 10% of the population nearby an airport be highly annoyed by that airport’s operational noise. According to the FAA’s “Schultz Curve”, a DayNight Average Sound Level of 60 dB or less is generally accepted as the maximum noise level compatible with this requirement. Some communities have insisted upon more stringent limits, particularly when flight operations are frequent or nearly continuous. C. On-demand: On-demand means that Sky Taxi service can be immediately available to the general public 24 hours a day and 7 days per week. Immediate availability means no waiting for TSA security checks, nor waiting in lines based on boarding zones. Instead, without having to line up at a ticket counter, people can walk right in to the Sky Taxi loading area where a friendly conductor will direct them to the next available Sky Taxi in the queue, and will assist them in boarding, loading and buckling up as needed. People can use their smartphone to both pre-reserve and arrange ride-sharing for their Sky Taxi trip. They can select their flight destination on the Sky Taxi’s touchscreen map once buckled in. They can then pay for the trip with a credit card slot-wipe or wireless smartphone application. Such availability is transformative because it far surpasses the convenience and accessibility of both scheduled airline service and owner-flown aircraft. On-demand also implies that Sky Taxi service will generally remain available in mild IFR conditions of clouds, light rain and fog and that its pilots and the aircraft itself will be equipped to safely provide such service. Severe weather conditions can interrupt Sky Taxi service just as they currently do with airline service. For autonomous aircraft, flying in mild IFR conditions should be no more challenging than flying in VFR conditions. Users of Sky Taxis will not be required to have pilot’s licenses. This feature expands to the greatest number the user-base of Sky Taxis from the USA’s roughly 600,000 pilots to its 245 million people who are over 15 years of age. In the initial implementation of Sky Taxi service, users will demand that professional pilots be on-board to fly each trip. The salary of such pilots will significantly increase the fare price for each trip relative to a trip flown by a remote pilot. Market competition is therefore likely to rapidly bring forth demonstrably safe, remotely piloted Sky Taxis. On-demand will NOT allow Sky Taxis to be rented to even highly qualified licensed private pilots who want to pilot the them to a destination of choice. That would be akin to letting private individuals commandeer taxicabs or transit buses. It is important to recognize that the Sky Taxi system must be treated as a transit system that operates in parallel to the existing general aviation system in which private pilots can fly to public use airports. The pocket airpark, by contrast, will be a type of transit mall at which only specially certificated Sky Taxis can operate. Those Sky Taxis will make point-to-point trips on assigned 4D flight paths. The Sky Taxi will be a distinct new breed of

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small aircraft in that it must have extraordinary short runway capabilities combined with low noise emissions, and special flight controls that can reliably provide pinpoint landings. To distinguish them in the public eye in terms of safety, it may be appropriate for all Sky Taxis to be painted yellow and for private general aviation planes to not be allowed to be painted yellow. This intrusion on individual rights would be justified by the utilitarian principle as being of crucial importance of maintaining the public trust in Sky Taxis and not allowing a private pilot’s plane accident to impugn the safety record of Sky Taxis that operate to higher standards. D. Sustainable: Sustainability has two main aspects for transformational flight. The first is that regional Sky Taxi service must prosper enough to rapidly expand into new areas. The second is that its implementation must be environmentally friendly. From the sample business model presented in Appendix B, the prosperity appears reasonably assured. The environmental friendliness demands emission-free electric propulsion, public-acceptable levels of safety and low noise, along with ESTOL capabilities for very small, pocket airparks and some attentiveness to the life cycle analysis of the components used in Sky Taxis. Compared to the existing general aviation paradigm with its adverse environmental aspects of very large airports, loud noise emissions, low fuel efficiency, leaded fuel and diesel black carbon emissions, the ulta-quiet, electric ESTOL Sky Taxi system would be truly transformative. The advances in electric propulsion that will be spurred with the emergence of Sky Taxis will likely help accelerate the adoption of electric cars and renewable energy sources. Extensive use of Sky Taxis could exert favorable effects upon the need for building expensive new highways, rail lines and bridges. This could have a very large beneficial environmental effect in the BRICS countries of Brazil, Russia, India, China and South Africa, by helping to reduce their increase in fossil-fueled ground vehicles and the attendant need to build new highways. E. Fast (door-to-door): People choose their mode of transportation mainly according to its door-to-door (DtD) trip speed. Transformational flight promises unprecedentedly fast DtD speeds. Surface transportation gridlock, mode changes, and delays related to ticketing, security, and the boarding process have combined to severely reduce commercial air travel’s DtD speeds. A tally of the time required for each of the many steps encountered in commercial air travel underscores the areas in which transformational flight can excel in saving time: 1. airliner flight time; per scheduled flights for SFO to LAX: 2. ground travel time STS to SFO, including park & fly: 3. ground travel time LAX to El Monte: 4. additional uncertainty time of 43% for each ground leg: 5. ticketing counter time: 6. TSA security line time: 7. airport gate walk time + bathroom visit: 8. boarding time for 130 people: 9. unboarding time, unloading overhead bins: 10. car rental desk time: 11. car rental bus time: Total time for 819 km (509 mile) trip: Overall DtD trip speed:

80 min 120 min 60 min 77 min 20 min 20 min 10 min 30 min 10 min 20 min 10 min 457 min 108 kph (67 mph)

We can compare the steps above with the much abbreviated ones that will pertain to using a Sky Taxi at a pocket airpark. The large ground travel delays and the 43% uncertainty penalty due to surface transportation gridlock would be eliminated if the pocket airpark is within just 6 minutes of one’s home or one’s final destination doorstep. Ticketing for on-demand use could be accomplished either by using a smartphone app or by merely sliding one’s credit card in the instrument panel slot provided in the Sky Taxi. There would be no need for TSA security because the small, 2 or 3-seat Sky Taxis will ultimately fly designated, point-to-point 4D flight paths autonomously and these paths will be monitored by air traffic control. If ATC detects an off-path flight that is confirmed to be threatening, it can remotely deploy that Sky Taxi’s rooftop ballistic parachute to end the threat. One would not need to walk hundreds of meters to reach a departure gate at pocket airparks; instead, with the assistance of a conductor/attendant, fliers in ones or twos would board the next available Sky Taxi in the queue and depart. Upon landing and taxiing to the passenger lounge area at a pocket airpark quite close to their ultimate destination, the fliers would climb out of the Sky Taxi and either walk, bike or golf cart their way for the remaining

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short distance to their destination. There would be no rental car needed and no need to travel on gridlocked freeways. Trip Speed Enhancement by Sky Taxi based on Schedule Airline Flights in Boeing 737-300 Car only

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Figure 3. Analysis of the door-to-door trip speed of various length airline trips if made by any of four different modes. The green columns indicate the dramatic improvements in DtD trip speed if pocket airparks and Sky Taxis are used.

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NOTES: Car in urban use @ 35 kph Car in rural use @ 97 kph 29 kph golf-cart to/from ESTOL pocket airport ESTOL Sky Taxi: includes 6 min. walk to pocket airport + 2 min. to board Sky Taxi Airliner: includes 2 x 82 minutes ground travel in uncertain gridlock, plus 2 x 63 min. for ticketing/baggage/security, parking shuttles and car rental

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Assumptions: 48 km to airliner airports at 35 kph 4.8 km to ESTOL pocket airport 885 kph Boeing 737-700 -- LAX to SFO = 383 kph 193 kph Sky Taxi cruise speed @ 1220 m AGL

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Figure 4. The range over which a 193 kph Sky Taxi could deliver 2X faster DtD trip speeds extends from 60 km to over 800 km. The abysmally slow DtD speeds of airline travel could be markedly improved with Sky Taxis, if pocket airparks were placed on the rooftop of terminal buildings at major hub airports. If a 193 kph Sky Taxi were employed on both ends of the airline trip to largely replace the ground travel legs, then the DtD speeds shown in Figure 3., above

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could be achieved. This would be a symbiosis that enhanced both the airline and the Sky Taxi markets. If the entire trip could be made in a Sky Taxi, with a 6 minute walk from home to pocket airpark and from pocket airpark to destination doorstep, then even the rather slow 193 kph Sky Taxi would provide 2X improvement in the DtD speed of either car or airliner + car. The DtD speed advantage that the Sky Taxi could provide applies across a remarkably wide range of trip lengths, as shown in Figure 4., above. Particularly important is the finding that the Sky Taxi could offer its DtD speed advantage on trips as short as 60 km. This extends its usefulness into the realm of frequent commuter trips and shows that it could thereby capture a very large market in many metropolitan / suburban regions of the US. This is especially true in those regions where the central metropolitan area is bounded by a sizable body of water, such as San Francisco, Chicago, New York, Seattle, New Orleans, Cleveland, Milwaukee, Tampa, Boston, Miami, and Washington DC. 50

Trip length vs. percent of trips in USA, all modes. 80% of trips are less than 805 km Source: US BTS @ http:// www.rita.dot.gov/bts/ sites/rita.dot.gov.bts/ files/publications/ national_transportati on_statistics/html/ table_01_42.html

45

Percent of trips

40 35 30 25 20 15 10 5 400

500

600

1609-3217 km roundtrip

300

805-1608 km roundtrip

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483-803 km roundtrip

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322-481 km roundtrip

0

! 322 km roundtrip

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Figure 5. During its first several years of implementation, while battery energy densities are improving, the vast majority of Sky Taxi trips are likely to be those of less than 300 km. As shown above in Figure 5., transportation statistics show that more than 80% of trips have a roundtrip length of less than 800 km. The majority of those are round trips of fewer than 322 km. These are the very trips that Sky Taxis can perform with the greatest speed advantage. F. Affordable: To be affordable the aircraft must be small and popular enough to be mass produced. Transportation statistics show that most trips are made with less than 1.4 people per vehicle. Therefore, small, 2-seat aircraft will likely be sufficient for most trips. Affordability also demands electric propulsion because of its demonstrated extremely low energy cost relative to propulsion that uses combustible fuels. The dollars per mile of the winning aircraft in the GFC I was approximately 1 cent per mile. This figure was achieved by a sailplane like fixed-wing aircraft with a very high L/Dmax. Even with cruise speeds of just 120 mph, the overall dollars per kph figure for such aircraft can be far lower than that of other modes of transportation. Affordability, like accessibility, is also linked to flight operations being based at very small land parcels located near where people live and work. The take off and landing sites must be so close to one’s destination doorstep as to minimize the time and money spent on ground transportation. Such flight operations will demand ultra-quiet, V/ESTOL aircraft. Likewise, affordability demands there must be no TSA security delays with Sky Taxis. These aircraft should have the same security treatment by TSA as any taxi-cab; i.e., none. Affordability will depend upon the production cost of the aircraft, which in turn will be tied to its size, its production volume, its certification cost and product liability premiums. All of these will be reasonably affordable for a small two-seat fixed-wing electric aircraft with conventional mechanical flight controls. Such aircraft have a somewhat known actuarial experience, one that is improving as avionics improve. For such aircraft, the cost of certification to carry passengers for hire is currently estimated to be $40-100M. These costs are projected to be more than an order of magnitude higher for an autonomously controlled, multi-rotor electric VTOL or hybrid tilt-wing aircraft. However, the certification standards for such VTOL aircraft do not yet exist and the timeline for them to be

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created is uncertain. Absent any prior known actuarial or fleet experience, the product liability premiums for such VTOL aircraft would also tend to be much higher than for the familiar fixed-wing versions. Trip fuel cost: Dollars per passenger per kph for car, jetliner and sky taxi: based on Scheduled Airline Flights in Boeing 737-300, walkable pocket airparks for Sky Taxi. Dollars per Passenger per kph

0.9

Car only

0.8 0.7

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0.4 0.3 0.2 0.1 0 400

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1094 km SFO to SEA

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544 km SFO to LAX

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0

48 km to hub 2 passengers 11 km / liter car 0.24 km / liter 737 83% load factor 43 km / liter Sky Taxi Fuel @ $1.32 / liter

Figure 6. Cost per passenger per kph: By enabling public-acceptable operations at pocket airparks that are within a 6 minute walk of home, the potentially transformative cost and speed advantages of ultra-quiet ESTOL Sky Taxis are shown to apply across a wide range of trip lengths. The most insightful metric by which to judge the affordability of Sky Taxi use is that of dollars per passenger per kph, as shown above in Figure 6. By that metric, the Sky Taxi shows an enormous advantage in affordability. G. Accessible: Accessible in one sense means without barriers to use. This means that people can walk onto a Sky Taxi facility and proceed directly to a queue of waiting Sky Taxis. Accessibility also will demand many locations at which Sky Taxis can take off and land. These will include existing airports and new pocket airparks. The airparks must be neighborhood-compatible. USGS land-use maps that detail the areas of developed structures and hardscape show that these airparks must be kept as small as 1 hectare (2.5 acres) if they are to be located near where people live and work. See Image 1. Distributed locations will, in the early implementation of the system, consist mainly of existing CTOL airports, of which there are over 5000 in the USA. Sky Taxi service at those 5000 airports will provide transformative accessibility that does not exist today. That service will become markedly more popular when pocket airparks are added on piers or barges along the waterfront of major metropolitan cities. Such waterfront airparks will be extremely popular destinations. See Appendix B. The system must be so attractive to such a broad base of users that it consistently wins community support for adding future small airparks, including some in high traffic metro areas. To become so distributed, those new small airparks must be small enough land parcels to be affordable and must not annoy or frighten residents nearby (see Public-acceptance, below). Ideally, the pocket airpark will be pro-actively integrated into a community such as being co-located with coffee houses, shipping companies like FedEx, community gardens or sports fields and with nearby connection to surface transit or trains. H. Distributed: To maximize utility and time savings, Sky Taxis will need to access CTOL airports and future pocket airparks that are diffusely distributed. A network of these will naturally develop traffic patterns that reveal where additional landing sites are needed to meet demand. It is likely that pocket airparks will be placed near to amusement parks and tourist attractions, as well as on the rooftops of large shopping malls.

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I. Point-to-point: Flying point-to-point is routine for most birds. However, a multitude factors have prevented public acceptance of point-to-point use of VTOL aircraft. For the practical purposes of on-demand, accessible, distributed, affordable and sustainable air transportation, the term ‘point-to-point’ does not require VTOL operations. Instead, it can connote flying between approved, shared-use pocket airparks that are quite nearby to both one’s departure and destination doorsteps. “Nearby” may be defined as meaning within less than 6 minutes trip time by either walking, bicycle or golf cart. The key requirement is to save large amounts of time by circumventing the need of a modal change to a rental car or the use of congested surface freeways. In 6 minutes, most people can walk 0.5 km (0.3 miles). Spending 6 minutes on a bicycle should allow one to travel 2 km (1.2 miles). A 6 minute ride on residential streets in a DOT500-approved electric golf cart that is licensed for speeds up to 40 kph (25 mph) could produce a distance traveled of over 4 km (2.5 miles). Finding affordable land parcels for small airparks that are within 4 km of people’s destinations appears to be achievable if the parcels are small enough. Although, a clear requirement for these small airparks must be the capability for VTOL or ESTOL, the limiting case for the smallness of such parcels will be the noise footprint of the Sky Taxi. Image 1. below illustrates the critical relationship between parcel size and proximity to destination. It shows that a 2000 foot runway is much too large to be sited close to downtown or residential areas where the crucially important proximity to destination is most needed.

Image 1. Sonoma County hardscape and potential landing sites. Red depicts building structures, pink depicts development or hardscape, yellow is open space and brown is agricultural land. The dimensioned blue lines, circles and rectangles representing potential sizes for landing sites, reveal the ubiquity of siting opportunities for tiny pocket airparks. The cross-hatched area is the Sonoma County Airport (STS) with 1524 m (5000 foot) runways. J. Public-acceptable: The public must embrace flying in Sky Taxis as safe, comfortable, convenient, and affordable. To achieve convenience, the public must also accept Sky Taxi operations in their neighborhood as safe and non-annoying. Once accepted by the public, such operations will eventually be conducted at designated, use-permitted, shared-use airparks that are very near where people live, work and play. The public’s acceptance of those operations as safe will be transformative. It requires a collective perception that the risk of anything falling from the sky onto people or buildings is extremely remote, on the order of 1 in 106 or “six sigma” and that Sky Taxis have safety features that ensure that they can prevent such occurrences. That perception will require that Sky Taxis operations actually

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demonstrate and maintain that level of safety right from the inception of their use if the market is to survive and prosper. One horrendous ‘hardover’ fatal accident that kills the innocent passengers of a Sky Taxi would devastate the emerging market. The comfort of flying in Sky Taxis will affect their public acceptance. Commodious and acceptable passenger seating, as in airliners and most 2-seat aircraft, should be side-by-side and offer some adjustable tilt-back. Low cabin noise levels, a generous field of view, and cabin ventilation and temperature control all must be more than satisfactory. The ride quality in turbulence must also be acceptable, and this will demand that Sky Taxis have very effective high lift devices to provide sufficient cruise speeds while achieving a Vso of just 52 kph. Other, more advanced future technologies such as ‘morphing’ configuration change or computerized smart trimtabs may further enhance the ride quality of Sky Taxis. Non-annoyance is a special multi-factorial aspect that bears closer examination. Aircraft noise emissions are the main source of annoyance to airport neighbors. The noise varies in intensity, frequency spectrum, impulsivity and dominant tone. In some cases near large airports, noise complaints have included annoyance due to low frequency vibrations that shake the nearby walls and windows of people’s homes. In the case of small, ultra-quiet Sky Taxis that take off nearly every 30 seconds at the most popular pocket airparks, the allowable noise will have to be even lower than 60 dBA, and the quieter the better. Fortunately, preliminary evidence indicates that fixed-wing Sky Taxis that use quiet wheel motors for their initial take off run, may be able to achieve extremely low take off noise, on the order of just 48 dBA at a 38 m (125 foot) sideline, even without synchrophasing. Beyond the noise it emits, residents strongly resent any aircraft that unexpectedly lands in their neighborhood when there is no shared use public airpark present. This resentment is worsened if a VTOL aircraft’s downwash onto an unprepared surface creates a blast of wind, leaves and gravel into people’s yards or against their windows. Such resentment often demands that VTOL aircraft forsake their ‘land anywhere’ capabilities and instead use remote CTOL airport facilities. If residents see an aircraft hovering over their homes, they perceive this as a looming threat, or arrogant intrusion on their privacy and serenity. This is particularly true in light of the current news headlines regarding the expanding use of unauthorized camera-equipped drones. If the aircraft is instead recognized as a safe, people-carrying, publicly available Sky Taxi that can quickly and almost inaudibly pass overhead to shared use, approved landing sites, resentment will be far less likely. CAFE’s informal survey results in 2013 indicate that most people today demand that a pilot be on-board to fly their Sky Taxi rather than entrusting it to remote or pilotless operation. None have insisted on having two pilots aboard, so it appears that single pilot operation will be acceptable. The public acceptance of remotely piloted Sky Taxis will require time and an impeccable safety record for such operations. K. Ubiquitous: To be ubiquitous, Sky Taxi service must proliferate from its first market regions and be implemented across the nation and the globe. This might occur as a series of franchises, like Starbucks Coffee. For this transformational phenomenon to happen, Sky Taxi service must be profitable for its owners from the start and all of the other ingredients described above will be necessary, especially impeccable safety. See Appendix B. Ubiquity will also depend upon having Sky Taxis with the unique combination of ultra-quiet operation and ESTOL capability suitable for operations at pocket airparks that can be sited on land parcels of just 152 x 76 m (500 x 250 feet). As shown in Image 1. above, this seems to be the ‘just-right’ size to achieve point-to-point service. Larger parcels quickly become too big to be sited as needed and smaller ones confer almost no practical advantage. In addition, the 500 x 250 foot parcel size appears to offer the smallest one possible for which a fortuitous concordance can be achieved between tolerable levels of ultra-low noise and the G forces encountered during ESTOL operations. A community’s transportation system and its demand for Sky Taxi service will determine its collective willingness to dedicate land parcels for pocket airparks. L. Transportation system: A transportation system means a planned, meaningfully sized, coordinated network of locations, vehicles, energy sources, operations and staffing necessary for moving people and freight over substantial distances. Such a system cannot have bottlenecks; it must have sufficient capacity for consistent availability of on-demand travel. Such capacity will require a large number of operations per hour at each pocket airpark, which will demand aircraft that can vacate the designated landing area quickly during both arrivals and departures. To achieve and maintain a large number of operations per hour, the system must also achieve a high degree of public trust and acceptance with a minimum of complaints from airpark neighbors.

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Multiple agencies will regulate and draw revenue from the system, its traffic, its airparks and its vehicles, not least of which will be the Federal Aviation Administration. Fortunately, plans are underway to rewrite and update the FAA’s Part 23 certification regulations, and the CAFE Foundation and others are working to ensure that process includes consideration of the new species of transformative aircraft. The above discussion elucidates the core requirements for success in the on-demand market niche and reveals their inter-dependency. To successfully launch the domain of transformational flight, a concerted technology prize matrix must bring forth the traits for fitness in that niche as well as ensure a continuous record of impeccable safety. J. Summary: In summary, the core requirements necessary to rapidly bring forth transformative flight services are these: 1) small aircraft with the niche-defined combination of required performance capabilities (traits); a) emission-free electric propulsion; b) ultra-quiet propulsion, with ≤ 60 dBA at 38 m (125 foot) sideline take off noise; c) V/ESTOL capability; short (and quiet) take off ground roll of ≤ 100 feet to reach 45 mph; d) sufficient cruise speed of ≥ 120 mph; e) sufficient range of ≥ 200 miles; most trips will be less than 100 miles; f) at least 2 seats, side-by-side; g) safety features necessary for ensuring public acceptance; i. smart propellers or fans that do not start if anything obstructs their path; ii. autonomous, on-board, air and surface traffic detection and avoidance equipment; iii. wheel motors for quiet/short take off, braking and propless autonomous taxiing; iv. vehicle ballistic parachute; v. power-off glide ratio of ≥ 20:1; vi. stall speed or Vso ≤ 52 kph (32 mph); vii. mechanical flight controls redundant to autonomous servo-controls; viii. a currently-trained, licensed human pilot to mind those mechanical controls; ix. acceptable handling qualities including spiral, longitudinal and maneuvering stability; x. shoulder harnesses containing airbags; xi. reliable battery management system (BMS); xii. provision for battery fire containment or jettisoning; xiii. precision, fast-acting autonomous flight controls for both gust management and envelope protection; xiv. autonomous self-diagnostics that perform extensive autonomous pre-flight inspection; xv. avionics that can request and automatically receive and follow assigned 4D GPS flight paths; 2) rigorous operational measures to avoid accident, injury, discomfort, delay and annoyance; a) robotic battery pack swapping; b) ramp conductor to assist boarding, loading, pre-flighting, queue flow, ground control; c) passenger lounge with restrooms, snacks; d) automated monitoring and broadcast of airpark weather and runway incursion/blockage; e) convenient, near-by low-cost or no-cost parking for bicycles, scooters and golf carts. 3) highly profitable business model founded on affordability, accessibility and ease of use; 4) greatly expanded utilization of existing CTOL airport infrastructure; 5) symbiotic integration with commercial metro hub airline service; 6) strategically located waterfront airparks in major urban areas; 7) a public-use, on-demand, transit model of operations for Sky Taxis 8) a mobile phone app for pre-reservation of Sky Taxis and 4D flight paths; The additional features that will further enhance transformative flight services but are not essential to its initial implementation are difficult to predict, but may include things such as: 1. cooperative and streamlined Part 23 certification processes by FAA; 2. greatly simplified pilot training and pilot workload; 3. accelerated development of a compatible NextGen air traffic control system; 4. expanded use of and access to renewable energy sourced electric aircraft charging stations; 5. uninterrupted growth of public trust in autonomous flight control systems; 6. higher speed and greater range for Sky Taxis, without sacrifice of other essential traits.

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VI.

Core Requirements and Speciation

The particular and pragmatic traits necessary for first generation Sky Taxi fitness and ‘reproductive success’ (aka mass production) have been identified above. Though experts view the succession of some species of electric Sky Taxi as inevitable in light of market forces and environmental concerns, the selection pressure necessary to induce these core traits can be beneficially focused with a succession of inter-dependent, global technology prizes with large cash awards. The pool of global aeronautical talent who will be eager to compete for such prizes was clearly made evident in GFC I. Those future prizes can select traits that fortuitously produce ‘genetic hitchhiking’ by which, for example, the requirement of emission-free flight brings with it the enhanced safety, reliability, controllability, distributability and power density of electric motors. Once the fully capable first generation Sky Taxi is demonstrated, variations will emerge to suit market demand. Fixed-wing Sky Taxis designers can breed in homologous traits from conventional aircraft (stability, control, handling qualities, field of view, etc.) while innovating the new traits that are necessary to the new niche. Such aircraft can benefit from established, known and more affordable pathways toward the important and necessary certification to carry passengers for hire. The process of speciation will evolve 2nd generation Sky Taxis that will compete to succeed the first. This is likely to be a kind of sexual selection process in which the Sky Taxi with the most appealing shape, cabin noise, fare price, seat comfort, cup-holders, on-board wi-fi etc. becomes the one chosen to reproduce. The degree to which such variations occur will depend upon the sufficiency of the first generation and upon the significance of the improvements that can be offered without requiring recertification. It is difficult at this time to predict which features will prove to be the ones most crucial to improve in later variations of the Sky Taxi. However some likely scenarios can be explored here. In some performance parameters, the natural selection process will be one influenced by diminishing returns. This process will determine which version of 2nd generation Sky Taxi merits expensive investments for FAA certification costs. There are likely to be some ‘just-right’ or ‘sweet-spot’ values for Sky Taxi performance that are not enhanced by either increase or decrease. For example, it is unlikely that a Sky Taxi will need to achieve a minimum flight speed slower than 52 kph (32 mph) because the slower speed version would not significantly benefit the proximity siting of pocket airparks, yet it would likely constrain the new version’s top speed. A similar diminishing returns effect would likely affect any effort to boost the Sky Taxi’s L/Dmax much beyond 20:1 because the gains in pMPG and safe glide range would not significantly alter the user cost or safety record of the first generation Sky Taxi. Surpassing the proximity, range, speed, and cost advantages conferred by pocket airpark compatibility of the first generation, fixed-wing ESTOL Sky Taxi with a 2nd generation fully VTOL version does not appear likely and is therefore unlikely to warrant the costly $1.1 billion NASA-estimated cost for FAA certification of such aircraft. At present, the FAA does not have regulations for certificating a multi-rotor electric VTOL aircraft with an autonomous flight control system that relies upon differerntial rotor thrust for control rather than on mechanical flight controls (ailerons, rudders, etc.). Leading vehicle ballistic parachute maker BRS has no product or plans for engineering their parachute as a safety device to fit multi-rotor VTOL aircraft. Relative to the fixed-wing ESTOL version, such 2nd generation VTOL variations would likely come at the price of several dB higher take off noise, shorter range, lower pMPG, and the elimination of redundant mechanical flight controls. Sub-scale quadcopters are small and quiet enough to be non-threatening. But wide experience indicates that, except in emergencies, the public does not accept or authorize full-sized passenger-carrying VTOL aircraft exploiting their ‘land anywhere’ capability in their neighborhoods because it often inflicts unexpected, highly impulsive noise, hovering, and strongly blowing dust, leaves and gravel at unprepared landing sites. Prepared, shared-use pocket airparks which are perceived to provide the greatest good for the greatest number and where aircraft noise is expected to be happening will be the public authorized and acceptable solution. The cost of providing Sky Taxi service could be dramatically reduced if there were no need for an on-board pilot. The cost reduction would be substantial if the piloting could be done remotely by a shared crew of ‘bunker pilots’ whose job was to ‘mind’ several otherwise highly autonomous aircraft and intercede only when necessary. A step beyond this would be a Sky Taxi that was a 100% autonomous flight-capable aircraft with no human pilot involved, akin to riding in a hotel elevator. Introducing autonomous flight to the world of general aviation will be best accomplished by using optionally piloted aircraft (OPA) that can be flown by an on-board pilot with mechanical stick and rudder or can fly pilotless using on-board autonomous capabilities.

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Speciation may later proceed according to market analyses that indicate that the fare price reduction obtained using bunker pilots is so great as to render the additional savings from 100% autonomy unnecessary. The large cost savings and potential enhancement of safety from autonomous capabilities justify offering a substantial technology prize for a public, full-scale demonstration of fully autonomous capabilities in Safety-piloted, passenger-carrying aircrat, both to advance their technology and engender their public acceptance. The question of whether a larger, 4-seat or 6-seat Sky Taxi, the “mini-van of the sky”, would succeed as a 2nd generation Sky Taxi in the niche of transformational flight also deserves consideration. There may develop a finite number of popular “trunk routes” that could generate improved profits by utilizing a 6-seat aircraft. Families might use a 6 seat Sky Taxi for vacations on a frequent enough basis to support such vehicles. However, the vast majority of car trips are made with an average less than 1.4 people aboard, in accordance with the inherent scatter of destinations and discrete schedules for individuals. Ride sharing enjoys a very limited popularity, in part because people prize their privacy and personal space. In addition, 2-seat Sky Taxis will require much less powerful motors than larger aircraft, and this may mean that larger aircraft are unable to achieve the extremely low noise emissions that are an absolute requirement for operations at pocket airparks. In the case of improving a Sky Taxi’s speed, a 20 minute flight covering 40 miles at 120 mph then shortened to just 12 minutes by boosting the aircraft’s speed to 200 mph, might be deemed worthwhile for time-starved executives. But if the certification and other costs meant that the 8 minutes saved with the new, higher speed version required it to charge twice the fare price of the 1st generation model, most customers would likely choose the less expensive fare. Given the same battery energy density, the higher speed version would be likely to have a much shorter range than the lower speed Sky Taxi, and this too might limit its market acceptability. Since figures show that a modest 193 kph Sky Taxi using pocket airparks can deliver twice the DtD trip speed of a bizjet, additional speed for mass-market Sky Taxis may not merit any compromise in their economy or range. Even so, we should expect some “express” models to evolve. Boosting the newer Sky Taxi’s equivalent passenger miles per gallon from 200 up to 300 would increase its range, but would translate to a miniscule reduction in the fare price, because analysis shows that, for electric powered aircraft, the fare price is much more governed by pilot salaries and land use costs than by energy costs. Moreover, it appears that robotic battery swapping may provide a solution to range issues, at least until battery energy density increases to the expected level of 1000 wh/kg.

Image 3. In nature, large birds with high L/D use ESTOL, employing a short ground run to get airborne. The largest-ever flying bird, the prehistoric Argentavis magnificens, was mainly a glider, with its weight of 75 kg, its 7 meter wingspan and its 8.11 square meters of wing area making it incapable of taking off without a short ground run to generate sufficient lift. Its reliance upon ESTOL reflects the main basis for the natural absolute size limitations of birds: the Square-Cube Law articulated by Galileo and the limited power density of biologic muscle. Similarly, an upper size limit on electric powered aircraft is likely due to the combined effects of the Square-Cube Law and the limited density of electric energy storage. The Breguet Range Equation, elegantly restated by Martin Hepperle3 with terms that apply to electric powered aircraft, shows these influences more clearly. Its terms, shown below in Equation 1., also reveal which components of electric aircraft design are the most accessible and amenable to improvement.

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Range = Ed x !total x (1/g) x (L/D) x (mbattery/GW)

Eq. (1)

Where: Ed is energy density of batteries in J/kg or m2/sec2 !total is total combined efficiency from battery to thrust generated; g is the acceleration due to gravity in m/sec2 L/D is the cruise value for lift to drag ratio; mbattery is the weight of the battery pack in kg; GW is the gross weight of the aircraft in kg; Equation 1 reveals the primacy of L/D as the single most influential parameter by which a designer can control the aircraft’s range and/or gross weight. It also reveals that there will be a strong selection pressure for improvements to both battery energy density and airframe structural efficiency. The importance of achieving high L/D pushes the designs toward ones whose minimum sink speed is rather low and hence adverse to achieving highly desirable fast cruise speeds. This fact underlies the need for having a “Fast-ESTOL” technology prize in which competing ultra-quiet aircraft must demonstrate a high cruise speed in combination with a pocket-airparkcompatible low stall speed. Equation (1) can be rearranged into Equation (2) to allow scenario explorations of gross weight results for altered energy density, range, and weight fraction: GW = Wp/ (((1-(We/GW)-((g*R)/(Ed*!total *(L/D))))

Eq. (2)

R is the range in meters Wp is the weight of the payload in kg We is the empty weight of the aircraft in kg (not including batteries) This reveals that Sky Taxis with short range and today’s 200 wh/kg batteries can realistically achieve gross weights that fall below the 600 kg or 1320 lb level that defines the typical Light Sport Aircraft, while still having reasonable cruise L/D ratios.

Gross weight, kilograms

L/D versus gross weight for 200 wh/kg 0.79 eta, 0.53 We/GW, various ranges 1500 1400 1300 1200 1100 1000 900 800 700 600 500 400 300 200 100 0

Range 644 km (400 mi) Range 322 km (200 mi) Range 161 km (100 mi) Range 80 km (50 mi) Range 48 km (30 mi)

LSA weight

0

5

10 15 20 25 30 35 40 45 Lift to drag ratio

Figure 7. Shorter range can substantially reduce the L/D requirement for achieving gross weights below the 600 kg level of Light Sport Aircraft (LSA).

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To minimize the amount of parcel size necessary, pocket airparks will require that Sky Taxis perform steep departures and approaches. The steep departure can be achieved by aircraft with a high power to weight ratio. Electric motors can deliver power at levels nearly twice that of their continuous power rating if the power is only used for about 15 seconds. A Sky Taxi that is quietly accelerated on the ground to 72 kph (45 mph) in 4 seconds in only 27 m (90 feet) using its electric wheel motors can accomplish its initial lift off and climb to 76 m (250 feet) AGL in just 15 seconds of propeller operation, and that is a height safe enough to then throttle back to rated power for the remainder of the climb. At a height of 76 m, the Sky Taxi noise level on the ground below is likely to be below ambient levels and its ballistic parachute will have enough altitude to be effective if deployed. Steep landing approaches on the order of 20 degree glideslope will greatly reduce the parcel size necessary for a pocket airpark relative to conventional 4 degree glideslopes. Such steep approaches can be achieved with the use of either sailplane-like spoilers or, in the future, possibly by modulation of a co-flow jet airfoil. CAFE has proposed a “Runway in the Sky” software application that could portray a real-time moving image in a glass cockpit showing a virtual pocket airpark toward which Sky Taxi type aircraft could fly approaches and landings. The software would position this virtual airpark about 1220 m (4000 feet) AGL so that full stall landings could be performed safely. The software could record a highly skilled pilot’s control inputs along with the glideslope, the sink rate at touchdown, the winds aloft in that virtual landing pattern and any simulated crosswinds that the user cared to apply. These recorded inputs would provide valuable learning for the automation software, including information for both the development of high lift/high sink devices and the eventual autonomous control inputs necessary to repeat such pinpoint landings.

Image 2. Comparison of VTOL and ESTOL parcel sizes of equal operational capacity (4 per minute) with 60 dB noise boundaries. The 4 blue rectangles depict a 3.8 acre area containing 4 FAA-recommended safety zones for heliports, overlain on a 2.5 acre pocket airport runway. The green rectangle depicts the size of an NFL football field. The two red circles depict the larger parcel sizes necessary for aircraft take off noise that is louder by +6 dB or +12 dB (66 dB and 72 dB, respectively). Compare to parcel sizes in Image 1. The concept of operations at the busiest pocket airparks, such as those proposed on the waterfront in large cities like San Francisco, Chicago and New York, is one that crucially depends upon maximizing capacity by having minimum delay between take offs or landings. A maximum of 4 operations per minute per runway is projected for

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fixed wing aircraft, while VTOL aircraft are likely to be limited to perhaps 1 or less. Operations that use VTOL Sky Taxis with the added time needed to hover, touchdown, disgorge passengers and then clear the touchdown area for the next arriving VTOL Sky Taxi would be likely to seriously impair the busy airpark’s important throughput capacity. These concerns are reflected in Image 2, above:

VII.

Societal and Environmental Selection Pressures

A. Climate Change: The increasing adverse effects of climate change in terms of damage from severe storms, drought and oceanographic impacts needs no elaboration. Its global economic cost, according to DARA’s 2012 report, surpasses $1 trillion and this is forecast to double by 2030. Transportation is a substantial and growing emitter of greenhouse gases, and the majority of this adverse impact can be eliminated if electric propulsion is widely adopted. GHG effects and the five-fold rise of respiratory deaths due to particlates suggest that conversion to diesel or bio-diesel will not be a sufficient or sustainable remedy. Natural disasters such as floods and earthquakes often disable modes of surface transportation. Climate change is forecast to markedly increase the frequency of severe storms. A high capacity network of pocket airparks could help save many lives in areas of natural disaster. B. Surface Gridlock: Beyond its awful effects on ground transportation, surface gridlock regularly prevents commercial aviation from fulfilling its mission of providing “fast travel without roads.” Every day, people become stuck for hours in surface gridlock after landing in an 804.6 kph (500+ mph) aircraft. According to NASA, on trips of less than 402.3 km (250 miles), commercial air travel in 804.6 kph (500+ mph) aircraft delivers an average door-to-door trip speed of only 88.5 kph (55 mph). The 2009 annual amount of fuel wasted due to surface traffic congestion was 3.9 Billion gallons; this represents a four-fold increase since 1982. Gridlock, when coupled with the remoteness of hub airports, squander aviation’s speed advantage. The combined federal, state, and local government expenditures on transportation for the 5-year period of 2003 through 2007 totaled $1.2 Trillion. In spite of such spending, worsening traffic congestion has caused the U.S. to have 53.9 kph (33.5 mph) average door-to-door trip speeds for surface transportation. In addition, when schedule deadlines are involved, the FHWA.DOT recommends allowing 43% extra time to cope with the uncertainties that affect surface travel in metro areas. This extra time lowers commuter trips speeds to just 36 kph (22.4 mph). See Figure 4. The only logical and sustainable remedy for gridlock delays is 3D transportation using an emission-free Sky Taxi-based system of close-in pocket airparks. This remedy could offer DtD trip speeds that are twice that of the fastest bizjet at a tiny fraction of the cost. Road building is simply not possible in some poor countries and in remote rugged areas. With the building of a small, 1-hectare pocket airparks, Sky Taxis could provide valuable and affordable access to such areas for purposes of supply, med-evac, and other aid. C. Air Pollution: This issue begs for the use of emission-free vehicles wherever possible. A five-fold increase in respiratory disease deaths attributable to particulate air pollution during the 10-year period from 2000 to 2010 attests to this fact. Electric powered Sky Taxis will emit no in-situ carbon monoxide, nitrous oxides, or particulates. D. General Aviation Troubles: The OIG’s September 24, 2012 Report on Aviation Industry Performance4 indicates 2 ominous findings; a 36% reduction in general aviation operations and a 24% reduction in short-haul airline flights in the last 4 years. These findings, along with the dwindling population of student pilots suggest that only with pocket airparks can the speed and utility of GA travel be restored. However, if ultra-quiet, ESTOL Sky Taxis are created, the recovery and rejuvenation of GA could be rapidly implemented by linking existing CTOL airports with a single metropolitan pocket airpark. See Appendix B.

VIII.

Sky Taxi Habitat Capacity

The Rhinocorps study funded by NASA for the PAVE Program affirmed the potential capacity of a 3D air transportation system to accommodate thousands of Sky Taxis.5 Three dimensional space offers a practically

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unlimited number of ‘lanes’ compared to single-file surface transportation. Even with today’s, human-in-the-loop ‘see-and-avoid’ traffic avoidance, the sky offers more than enough capacity for the Sky Taxi travel paradigm to substantially benefit the entire transportation system. If any bottleneck will impede future Sky Taxi traffic, it is likely to be the capacity for take offs and landings at high traffic pocket airparks serving urban centers. Fully developed and facilitated, this capacity can reasonably be expected to reach 4 aircraft per minute per runway, i.e., a departure or landing every 15 seconds. In its initial implementation, an interval of 30 seconds per runway operation is more likely. When the runways are very small, adding runways may be the safest and most cost-effective way to increase capacity in such urban areas.

IX.

New “Genes”: Extant and Emerging Technologies

For the last 7 years, the annual CAFE Electric Aircraft Symposia have showcased many technologies that supply a rich array of new ‘genes’ to enable Sky Taxi development: • • • • • • • • • • • • • • • • • • • • •

electric motors—quiet, reliable, lightweight, regenerative and vibration-free; precise and reliable motor control technology; wheel motors that efficiently integrate tire and brake in a small, lightweight package; energy storage density, management systems, cycle life and burst power capability; solar energy capture, photovoltaics; ideal traction—tire pressure, compounding, profile, and grip; advanced structures including nano-technologies; ultra-quiet propulsion including ANR and synchro-phasing; high lift devices including vectored thrust, CFJ and CCW; high L/D and high pMPG sailplane technology; CFD guided drag reduction, laminar flow, and Goldschmied propulsion; vehicle parachutes; motor-in-wheel acceleration, braking, steering, and navigating; computerized flight decks with machine intelligence; advanced sensor systems and wireless communication/navigation; fast-acting servo flight controls effective at low slight speeds—”stability enhancers.” spoilers for steep approaches and glide path control gust and turbulence alleviation by smart tabs fast-charging of batteries robotic battery swap smartphone apps to reserve Sky Taxi services in advance.

X.

Human Physiologic Limitations

Sky Taxi operations must satisfy all of the limitations relating to human physiology. A list of these and some mitigating traits include: • • • • • • • •

noise levels; ≤ 80 dBA in cabin and ≤ 60 dBA at pocket airpark boundaries; G force limits; ideally kept less than 1 additional G on take off and landing; oxygen need; non-pressurized flights stay below 2438 m MSL (8,000 feet); bladder capacity limit; absent a lavatory, Sky Taxi range suits flights ≤ 3 hours duration; ease of entry-exit; similar to a car and some provision for ADA requirements; personal space boundaries; adequate seating comfort and capaciousness; motion sickness avoidance; large speed envelope with high lift devices, automated trimtabs; heating, ventilating and air conditioning; sufficient for both hot and cold days.

The CAFE-hosted GFC I imposed reasonable constraints on altitude, range, noise, seating size, field of view, speed envelope and take off distance (G) limits. The CGFCP will continue these and increase the stringency of the noise constraint.

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XI.

CGFCP Background

The CAFE Green Flight Challenge Program (CGFCP) was presented at the AIAA 51st Aerospace Sciences Meeting in Dallas in January, 2013 and is available as a manuscript.5 The manuscript provides comprehensive information about the CGFCP, which can be summarized here as follows: The CGFCP provides the series of inter-dependent technology prizes necessary to bring about OPAs whose traits will satisfy the core requirements for transformational flight. It aligns with NASA, FAA, EPA, DOE, OSTP, DOD and DOI goals and can provide numerous environmental, scientific, educational and commercial benefits. Its economic impact could lead to what NASA’s Chief Scientist, Dennis Bushnell, called a “one-trillion dollar market.” The model for an OPA Sky Taxi service is presented in Appendix B below, and, with a fleet of 250 aircraft, is projected to be capable of generating a $100M profit in one regional market in one year.

XII.

CGFCP: Technology Prize Matrix

CAFE designed the CAFE Green Flight Challenge Program (CGFCP) as a series of five stepwise, interdependent technology prizes (“missions”) necessary to bring forth the core requirements (“traits”) for a successful electric powered Sky Taxi. Missions II-VI of the CGFCP can be completed in 68 months from its announcement date. The core CGFCP missions are: MISSION: GFC I: CGFC II: CGFC III: CGFC IV: CGFC V: CGFC VI:

SPECIFIC TRAIT OR CAPABILITY: 2011, Speed, range and MPG: In emission-free electric aircraft; 2014, Wheel Motors for Quiet, Extremely Short Take Off and Landing (ESTOL); 2015, Ultra-Quiet Propulsion with sufficient thrust for operation at pocket airparks; 2016, Autonomous Flight in OPAs—Comprehensive Demonstration (with Safety pilot) 2017, Fast-ESTOL (Vmax with Quiet ESTOL, speed envelope and high lift contest) 2018, The Sky Taxi Finale: OPAs that are Quiet, ESTOL, Autonomous, and Fast.

Each mission brings forth one or more of the breakthrough air vehicle capabilities necessary for Sky Taxis that can transform aviation and transportation. Those essential capabilities and thresholds to be demonstrated are as follows: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.

take off distances of less than 128 m (500 feet) over a 38 m (125 foot) obstacle (i.e., ESTOL); take off noise emissions of less than 60 dBA at a 38 m (125 feet) sideline distance; extremely short (and quiet) take off ground roll of ≤ 31 m (100 feet) to reach 72 kph (45 mph); Vso ≤ 52 kph (32 mph) directed, autonomous flight with 4D navigation and ATOL (automatic take off/landing); cruise speed of at least 193 kph (120 mph) combined with ESTOL capability; energy efficiency better than 85 pkmPL (200 pMPG); electric propulsion, with BMS and battery fire safety provisions; ballistic vehicle parachute range of ≥ 322 km (200 statute miles); two seats, side-by-side, of adequate size and outward view, with 200 lb per seat payload capability; satisfactory basic handling qualities; mechanical flight controls; two seats, side-by-side; power-off glide ratio of ≥ 20:1; smart propellers or fans that do not start if anything obstructs their path;

XIII.

CGFCP Competitions

A. Wheel Motors: Using a test cart weighing 300 kg. and that provides the same battery pack energy source for each team, team wheel motors of prescribed small dimensions and weight that would fit a small aircraft’s landing gear will be bolted

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onto the cart and performance tested to determine their traction, power and acceleration capabilities. The winner will be determined using a formula that combines the wheel motor’s acceleration distance from rest to 72 kph (45 mph) and its achievement in saving weight below an allowable maximum of 30 pounds. According to the known boundaries of wheel motor technology, realistic goals for the winning wheel/motor/tire unit may be to achieve a 072 kph acceleration distance of less than 24 m (80 feet) and a weight of less than 18 pounds. The deliverable will thus be a wheel/motor/tire/brake unit that could fit existing GA wheel fairings and could serve as a direct replacement for existing GA landing gears. B. Ultra-Quiet Propulsion: In CGFC III, a specialized ground test vehicle built by CAFE and known as the Propeller Acoustic Simulator (PAS), will allow accurate and safe measurement of the noise emissions of several different ultra-quiet electricpowered propulsion systems suitable for use on small aircraft. The PAS will be a steerable, 600 kg, four-wheel cart with a 400-volt battery pack to power the propulsion systems being tested. The 600 kg weight of the PAS matches the gross weight limit for Light Sport Aircraft because future 2-seat Sky Taxis are expected to be of similar weight. Competing teams will supply propulsion systems consisting of propellers, propeller spinners, propeller shaft extensions, motors, support struts, span-wise mounting structure, and controllers whose combined weight is ≤ 135 kg and that can be quickly installed onto the specified bolt pattern/mounting points on the PAS. Because propeller noise is proportional to power, to conduct a fair low-noise propeller competition demands that the noise of each team’s propulsion system be measured while producing a prescribed level of thrust, speed and acceleration under realistic and relevant conditions. Score will be weighted in the same fashion as the iARPA Great Horned Owl noise competition and winner will be the quietest one. Innovations of several types are expected to be brought to bear in this competition, including synchrophasing, co- and counter-rotating blades, ducted fans and automatic noise cancelling software. The ultimate goal will be to create the requisite thrust while emitting a nearly homogenous wake of uniform velocity. The deliverable will be both enhanced understanding of ultra-low noise propulsion and possibly a variety of bolt-on ultra-quiet propellers for current and future GA. C. Autonomous Flight: In CGFC IV, small civil “optionally piloted aircraft” (OPAs) will be required to perform autonomously (without any physical intervention by the Safety Pilot(s)) a series of tasks essential to safe operations at pocket airparks. Points will be given for each task in proportion to its difficulty and the precision with which it is performed. The winner will be the team aircraft with the most points. The tasks are chosen because they are the ones that GA accident statistics (e.g., Nall Report, NTSB) indicate as most subject to human error, and/or are those that future Sky Taxis must perform safely and routinely. The tasks include: 1) autonomous navigation; 2) autonomous taxiing, take off, and pin-point landing; 3) automated enhanced vision capable of ‘detect and avoid’ for both ground and air traffic; 4) envelope protection, including unusual attitude recovery; 5) precision 4D trajectory management with fly-by-wire throttle; 6) precision autonomous ‘engine-out’ landing at a virtual airport (“Runway-in-the-Sky” or RITS). Team aircraft will be required to use an “autonomous flight system” (AFS) to accomplish these tasks and will have a mechanical stick and rudder control system so that its on-board Safety Pilots can override the AFS. The deliverable is expected to be a plug-and-play suite of autonomous flight hardware and software that can provide immediate safety improvements to a wide array of GA aircraft. D. Fast-ESTOL: The purpose of this competition is to bring forth ultra-quiet aircraft that optimally combine the two inherently conflicting capabilities of slow flight and high speed flight. Such combined capabilities are essential for Sky Taxis to operate at pocket airparks and to have acceptable ride quality. Team aircraft must first demonstrate level flight at ≤ 52 kph (32 mph) CAS while performing a 360° turn. Next they must demonstrate ≤ 60 dBA noise emissions at 38 m (125 feet) radius in 72 kph (45 mph) CAS during fly-by. To win, they then must demonstrate the highest speed during a closed course speed measurement on an NAA-approved 3 km test range. The deliverable will be the demonstration of devices that can greatly improve the ride quality and expand the speed ratio of light aircraft.

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E. The Sky Taxi Finale: In CGFC VI, the finale in Sky Taxi development, small, ultra-quiet, electric-powered Sky Taxis from competing teams will be required to demonstrate the combined capabilities essential for them to operate at pocket airparks. The final score of each team’s Sky Taxi will be computed by the following formula, similar to that used for the successful GFC I, using its maximum achieved average speed and take off noise measurement from its flight attempt: 1/((1/mph)+(1/(360-(4*dB)))) Eq. (2) The deliverable will be one or more prototype Sky Taxis with all of the capabilities necessary for operation at pocket airparks.

XIV.

Conclusion

The core requirements necessary for the evolution of the on-demand aviation market for transformational flight are defined from the consensus paradigm predicted by NASA’s Aviation Unleashed Program. The traits necessary to fulfill those requirements are clearly identified and the existing and emerging technologies that can create those traits are explored. The prospects for speciation and subsequent improvements to a new species of optionally piloted aircraft called a “Sky Taxi” are described. A series of technology prizes known as the CAFE Green Flight Challenge Program (CGFCP) is presented as a rapid means to bring about a diversity of new OPAs with those traits. Global environmental, societal, transportation and economic problems urgently demand a concerted solution. The launch of this technology prize matrix can help provide that solution and reinvigorate aviation. The business case and economic model favoring a Sky Taxi system of transportation are presented in Appendices A and B, below. The ultimate economic and industrial impact of the Sky Taxi system is projected to result in a Sky Taxi aircraft fleet whose numbers exceed by 100 fold those of most other aircraft types. See Figure 1.

APPENDIX A: Business Case for Sky Taxis The value proposition of any mode of transportation can be graded by its dollars per mph. The Sky Taxi could deliver a dollars per mph that far surpasses any other form of transportation. Time is a non-renewable resource and is the scarcest commodity for an increasing portion of our ever-busier population. Unlike cars that demand ‘hands on wheel’, Sky Taxis can offer the user continuous productive time for reading or laptop computer use that can include use of the Internet. As the Sky Taxi system reduces or eliminates the need for operating, parking, maintaining or owning a car, it will offer users additional savings. The direct operating cost of a Sky Taxi if inferred from that experienced in the GFC I, entails an energy cost of less than $0.01 per passenger mile. Electric propulsion can offer major advantages in both cost and reliability. The affordability and energy density of advanced batteries is rapidly and substantially improving. According to the DOE, the average service life of an electric motor is 20 years. In clean conditions and within temperature limits, electric motors can operate continuously for more than 60,000 hours between bearing replacements, and unlike piston engines, require no oil changes, spark plug replacement, tune-ups, hose replacements or compression testing. The NEMA standard for premium efficiency for electric motors is 90.2%, compared to less than 30% for internal combustion engines. The cost per horsepower of a 200 BHP electric motor is less than 20% that of a new 200 BHP certificated aircraft piston engine. These factors all favor electric propulsion as a reliable and affordable alternative to internal combustion propulsion for small aircraft.

APPENDIX B: Sky Taxi Service Model The map image below shows with red dots the 99 CTOL airports within 100 miles of SFO. Congested metropolitan areas offer a strong pent-up need for gridlock relief and an opportunity for the rapid implementation of a Sky Taxi service network. Such a network could exploit the existence of many nearby existing CTOL airports as feeders for a major downtown area, if that downtown can provide a small waterfront pocket airpark. Numerous major cities are at least partially bounded by waterfront areas at which such pocket airparks could be sited on a pier or barge.

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CAFE Foundation Board Member Bruno Mombrinie developed a model for Sky Taxi service in the San Francisco Bay Area using Pier 17 in San Francisco as a prospective landing site. Pier 17 houses the very large, popular Exploratorium and the plan is for the Sky Taxi landing sites to be on its roof. Officials at the Port of San Francisco have informed this model by providing facts and figures relevant to the leasing costs and regulations necessary to this model. In the image below, the two green segments represent 450 foot long runways for Sky Taxi operations at Pier 17 in San Francisco, connecting to any of the 99 existing CTOL airports that lie within 100 miles of that city. The traffic patterns for flight operations at these waterfront runways would be kept mainly over the water and waterfront, and the noise of these aircraft would be much less than the car and bus noise along the 4-lane yellow embarcadero boulevard. These two runways could provide 240 operations per hour. Support staff would, like a typical queue of taxi-cabs at a metro airport, include 2 conductors to assist people with boarding and exiting the aircraft. Another staff person would monitor the operation of the robotic battery pack swapping operation, which could compete a swap in just 2 minutes. This model relies upon a motto of “keep ‘em flying” as a means to extract maximum productivity from each Sky Taxi in the fleet. Electric propulsion is well suited to such nearly continuous use. As the initial Sky Taxi service became popular, additional piers could be converted to landing sites to increase system capacity. Most major cities have waterfronts that would allow such expansion. This model, using ultra-quiet Sky Taxis with large, slow-turning, low-noise propellers, projects a very attractive consumer cost that would offer far more speed per dollar than any other travel mode. The service would offer, in general terms, a 20-minute flight in place of a 100-minute car trip, at the same cost. This would deliver a 5X improvement in the important “dollars per mile per hour” metric that defines transportation value.

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Taking into account all costs, including insurance, staffing, facilities leases, the use of well-paid commercial pilots and the leasing of the aircraft, this model indicates a potential profit of $100M per year for the San Francisco region alone. This would be only one of many such Sky Taxi franchises around the nation, where a large market for such high speed, gridlock-free travel is anticipated. The implementation of such service could occur very rapidly by employing already licensed pilots using the existing FARs and air traffic system. This rapid implementation, made possible by just a single, ideally located pocket airpark, would provide a compelling substrate for growing the transformational flight system’s capacity, autonomy, safety and future landing sites.

Acknowledgments B.A.S. author is particularly indebted to CAFE Foundation Board members for their ideas, research, advice and innovations that contributed to this paper: Bruno Mombrinie, Dr. Larry Ford, Stephen Williams, Johanna Dempsey, Mike Fenn, Alan Soule, John Palmerlee, and Wayne Cook. Valuable editing was provided by Anne E. Seeley. Significant contributions were made by Damon Seeley of Electroland.net, Dean Sigler (CAFE Blog editor), CAFE Advisory Board Members: David Calley of Planet-Rider, Dr. Case van Dam of UC Davis, Dr. Eric Darcy of NASA, Dr. Krish Ahuja of Georgia Tech, Dr. Ajay Misra of NASA Glenn Research Center, Tyler MacCready, John Vian of the AIAA TF PC + Boeing, John Langford of Aurora Flight Sciences, Dr. Gecheng Zha of University of Miami, Charles Darwin and Daniel Raymer. Valuable input was provided by noise technology consultant David Josephson from the AIAA TF PC, and Dr. Werner Wilcke of IBM labs. Information and inspiration were drawn from all of the teams that competed in the GFC I and the many esteemed faculty who have participated in the CAFE Electric Aircraft Symposia I-VII.

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References And Bibliography 1

Hinton, David, NASA Langley Research Center, November 20, 2010, Summary report for NASA’s Aviation Unleashed Program. URL: http://cafefoundation.org/public/2013_07_22/Aviation.Unleashed.Day3.Summary.pdf 2 Kalil, Tom, and Dorgelo, Cristin, White House Office of Science and Technology Policy “Identifying Steps Forward in Use of Prizes to Spur Innovation”, April 10, 2012, URL: http://www.whitehouse.gov/blog/2012/04/10/identifying-steps-forwarduse-prizes-spur-innovation 3 Hepperle, Martin, “More Efficient Aircraft Configurations-Dream or Reality?” presented at NATO UAS Meeting on Energy Efficient Technologies and Concepts of Operation, Lisbon, Portugal, October 22, 2012, URL: http://www.mhaerotools.de/company/paper_14/09%20-%20Electric%20Flight%20-%20Hepperle%20-%20DLR.pdf 4 OIG’s September 24, 2012 Report on Aviation Industry Performance, URL: http://www.oig.dot.gov/node/5948 5 NASA PAV Simulation Effort, RhinoCorps Ltd. Study, September 2005, URL: http://cafefoundation.org/v2/pdf_tech/SATS.demographs/PAV.RhinoCorps.Simulation.pdf 5 Seeley, Brien, CAFE Foundation, January 8, 2013, AIAA 51st Aerospace Sciences Meeting, Dallas, TX., “The CAFE Green Flight Challenge Program (CGFCP)” URL: http://cafefoundation.org/public/2012_12_31/CGFCPAIAA122712fff.pdf

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