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Aeronautical Technologies for the Twenty-First Century 4 SHORT-HAUL AIRCRAFT INTRODUCTION This chapter provides an assessment of the technology needs of short-haul aviation in the United States. It focuses on government research and technology development actions required over the next 10 to 20 years, with emphasis on the role of the National Aeronautics and Space Administration (NASA). The Committee believes that the recommended actions will provide U.S. manufacturers and operators with the technology necessary to take advantage of major opportunities projected for 2000 to 2020, and will help bring to the American public the benefits of a greatly improved short-haul air traffic management (ATM) system. The chapter is presented in four sections: current industry status and environment, future needs and opportunities, barrier issues, and recommended NASA actions. In each section, items common to more than one category of short-haul aircraft are discussed first, followed by items specifically applicable to the individual aircraft categories. The boxed material summarizes the primary recommendations that appear throughout the chapter, with specific recommendations given in order of priority, and the benefits that can be expected from research and development efforts devoted to short-haul aircraft. CURRENT INDUSTRY STATUS1,2,3,4 The category of short-haul aircraft includes commuter aircraft, rotorcraft, and general aviation (GA) airplanes. Also, although not strictly short-haul aircraft, business and private jets are included in this category to distinguish them from large transport aircraft. There are roughly 1 Aerospace Industries Association of America. 1991. Aerospace Facts and Figures 91–92. Washington D.C. 2 Regional Airlines Association. 1991. 1991 Annual Report of the Regional Airlines Association. Washington, D.C. 3 Regional Airliner Census. 1991. Aerospace World Business & Technology. 5 (April). 4 General Aviation Manufacturers Association. 1991. General Aviation Statistical Databook, 1990–1991 Edition. Washington, D.C.
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Aeronautical Technologies for the Twenty-First Century Recommendations General NASA should enlarge its support of the key technologies for general aviation, commuter aircraft, and rotorcraft through extensive validation, and should both sponsor and participate in comprehensive system studies to define total aircraft systems, with investigations into their technical and economic characteristics. Specific NASA should undertake an aggressive safety research program focused on cognitive engineering and the features that are unique to the operation of commuter, rotorcraft, and general aviation aircraft. NASA's unique capabilities in simulation and training should be used to help enhance the initial training and skill maintenance programs of all aircraft pilots and mechanics. NASA's extensive capabilities in aerodynamics, structures, and acoustics should be applied toward major improvements in rotorcraft economics, speed, and efficiency. NASA and the FAA should undertake a study to establish the degree to which existing airport capacity could be increased by shifting some short-haul traffic to helicopters and tiltrotors, using vertiports integrated into available airport real estate. NASA should undertake an extensive research and technology development effort to improve rotorcraft passenger comfort. 220,000 short-haul aircraft in the United States, making up 98 percent of the total civil aviation fleet.5 Short-haul aircraft operations are projected to continue to grow with expansion of the national economy and growth of population and industry in communities remote from urban centers. The greatest growth is projected for the commuter sector, where passenger enplanements are expected to double during the 1990s. European manufacturers in recent years have made major inroads in the markets for the various categories of short-haul aircraft. Foreign manufacturers, many of whom are subsidized by their governments, dominate the commuter market; currently no commuter aircraft for more than 19 passengers is being built in the United States today because manufacturers have found that they cannot compete in airframe manufacturing. However, a majority of commuter aircraft are powered by engines made in the United States or made elsewhere by U.S.-owned companies. 5 Aerospace Industries Association, op. cit.
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Aeronautical Technologies for the Twenty-First Century Benefits of Short-Haul Aircraft Research and Technology Development Cost/Convenience Development costs Low cost components Technology validation Reduced operating costs Lower fuel consumption Reduced maintenance Longer airframe and component life Reduced liability costs Increased comfort levels for crew and passengers System Capacity Reduced aircraft separation (takeoff and landing, on the ground, and in flight) Reduced complexity of ATM system Enhanced Category III operations Environment Reduced noise Safety Lower accident rate Reduced human error Reliable automated systems Reduced and predictable aircraft fatigue Aircraft Performance Greater fuel economy Greater speed and range The following factors contribute to a continuing deterioration of the position of the U.S. manufacturers: the lack of capital in small U.S. aircraft companies, the establishment of a number of foreign consortia for development and production of commuter aircraft and rotorcraft, and the coordination and expansion of European technology development.
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Aeronautical Technologies for the Twenty-First Century The April 1988 Euromart Study report6 cited total research and technology development expenditures for commuter aircraft in Europe at $450 million in 1986–1987; and recommended an immediate 25 percent increase, a 50–60 percent increase in 5 years, and a doubling in 10 years. These numbers include civil and military aircraft but exclude engine and equipment development. The Commuter Market The commuters (regional airlines) provide air service to and from small- and medium-size communities. During the 1980s the developing ''hub and spoke'' patterns created a growth opportunity for commuters to feed the hubs. It created a growing interest by major air carriers in "code sharing" with regional carriers to provide integrated reservations, ticketing, and other services for traffic feed between major hub cities and smaller communities. Today, 94 percent of all commuter enplanements in the United States are made by code-sharing partners of major carriers. Commuters are the fastest growing segment of the airline industry. During the past 10 years, there has been a threefold increase in the U.S. commuter airline business, from 14 million passengers annually to 42 million, and from 1.7 billion passenger-miles to 7.6 billion. The Federal Aviation Administration (FAA) forecasts7 future growth at a somewhat lower rate, 7–8 percent per year, which is still a twofold increase over the next 10 years. Even this rate of growth is higher than that projected for the major carriers. The average seating capacity of commuter aircraft today is 22.1 seats. They account for only 2 percent of scheduled carrier revenue passenger-miles flown but for 8 percent of passengers, 35 percent of the aircraft in the fleet, and 40 percent of departures for scheduled air carriers. They are significant contributors to congestion at busy hubs and must compete for slots at capacity-controlled terminals. As of February 1991, there were 2,534 commuter aircraft in service, of which 1,505 were in North America (see Table 4-1A). Only 565 of the 2,534 were manufactured in the United States. These aircraft carry 19 passengers or less, are made by Beech and Fairchild, and are based on original designs more than 20 years old. There are 1,363 announced orders for commuter aircraft, with only 87 of these orders placed with a U.S. company (see Table 4-1B). Based on a forecast of the future commuter fleet by the Regional Airlines Association,8 the U.S. market for commuter airplanes during the 1990s is estimated to be $20 billion: 60 percent of the commuter market ($12 billion) is projected for airplanes having a capacity of 40 passengers or more. 6 EUROMART Study Report. 1988. Loughton Essex, U.K.: Specialized Printing Services, Ltd. 7 Federal Aviation Administration. 1991. Aviation Forecasts, Fiscal Years 1991–2002 (FAA Report FAA-APO-91-1). Washington, D.C.: U.S. Government Printing Office. 8 Regional Airlines Association, op. Cit.
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Aeronautical Technologies for the Twenty-First Century TABLE 4-1(A) Short-Haul Aircraft Delivered, by Region (as of February 1, 1991) Category Europe Middle East Africa South America Caribbean North America Asia Pacific Total % Share 10–19 passengers BAe Jetstream 31 29 2 — 251 8 290 30 Beech 1900C 5 13 — 176 12 206 22 Dornier 228 47 32 13 39 53 184 19 Fairchild Metro III 30 2 5 235 3 275 29 Subtotal 111 49 18 701 76 955 % share 12 5 2 73 8 20–40 passengers DHC Dash 8-100 28 3 5 158 13 207 23 Embraer Brasiliaa 42 1 10 155 2 210 23 Saab 340 A/B 85 — 3 117 14 219 24 Shorts 330/360 71 1 4 167 37 280 31 Subtotal 226 5 22 597 66 916 % share 25 1 2 65 7 More than 40 passengers ATR 42 57 13 10 92 15 187 28 ATR 72 13 — — 2 5 20 3 BAe ATP 22 2 — 6 0 30 5 BAe 146-100 8 5 — 3 14 30 5 BAe 146 200 28 1 5 53 11 98 15 BAe 146-300 16 — — 5 15 36 5 CASA/IPTN CN-235b 20 13 6 — 14 53 8 DHC 8-300 12 — 4 19 2 37 6 Fokker 50 65 5 — — 35 105 16 Fokker 100 26 2 2 27 10 67 10 Subtotal 267 41 27 207 121 663 % share 40 6 4 31 18 Total 604 95 67 1,505 263 2,534 % share 24 4 3 59 10 Source: Aerospace World Business and Technology a Plus two undisclosed b Plus one undisclosed
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Aeronautical Technologies for the Twenty-First Century TABLE 4-1(B) Short-Haul Aircraft on Order, by Region (as of February 1, 1991) Category (passengers) Europe Middle East, Africa South America, Caribbean North America Asia Pacific Total 10—19 BAe Jetstream 31 2 — — 27 3 32 Beech 1900Ca — — — — — — Beech 1900Da — — — — — — CBA-123 Vectorb — — — — — — Dornier 228 — — — — 5 5 Fairchild Metro III — 1 27 59 — 87 Subtotal 2 1 27 86 8 124 20—40 BAe Jetstream 41 — — — 10 — 10 DHC Dash 8-100 8 — — 32 — 40 Dornier 328 3 1 — 33 4 41 Embraer Brasilia 6 1 1 98 — 106 Saab 340 A/B 16 — — 92 7 115 Shorts 330/360 — — — 4 — 4 Subtotal 33 2 1 269 11 316 More than 40 ATR 42 72 3 11 51 8 145 ATR 72 88 1 2 80 15 186 BAe ATP — 1 — 8 — 9 BAe RJ70c — — — — — 0 BAe 146-200 16 — — — 1 17 BAe 146-300 4 — — — 9 13 Canadair RJd 55 — — 50 4 109 CASA/IPTN CN-235 29 53 — — 38 120 DHC 8-300 39 — 5 21 6 71 Fokker 100 67 — 2 95 15 179 Fokker 50 23 — — — 2 25 Saab 2000 34 — — 13 2 49 Subtotal 427 58 20 318 100 923 Total 462 61 48 673 119 1,363 Source: Aerospace Wold Business and Technology a Beech Aircraft does not release order data. b Embraer has 99 options. c BAe had 10 options. d Includes orders and commitments.
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Aeronautical Technologies for the Twenty-First Century FIGURE 4-1 Commuter fleet forecast. The industry has been moving rapidly toward large aircraft, with the hub bypass market being a significant growth opportunity. Worldwide, 923 of the 1,363 commuter aircraft on order are 40- to 107-passenger aircraft, and 318 of these are for the North American market (Table 4-1B). With the emerging fleet, the average capacity will grow from 22.1 to more than 40 seats. The aircraft on order include 328 jets; 219 of these are 100-passenger class, and 109 are 50-passenger aircraft. A newly formed European consortium led by Deutsche Aerospace, along with Aerospatiale and Alenia, seeks to bring together a family of existing and new aircraft types to meet nearly all the requirements of regional airlines. This organization would parallel the Airbus Industries consortium which has complete medium- and long-haul product lines. They plan two basic new regional jetliners, one carrying 85–90 passengers and the other 120–125 passengers.
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Aeronautical Technologies for the Twenty-First Century The forecast of jet deliveries to regional airlines (Figure 4-1) indicates that between 70 and 135 jet aircraft are expected to be delivered each year for the next 20 years by European manufacturers. The 219 100-seat aircraft on order illustrate the market trend. Once technical suitability has been established, price and financing terms are the primary determinants of purchase, with operating costs secondary. Government-subsidized foreign manufacturers dominate the market, and competition among them is fierce. There are five manufacturers in the 10- to 19-passenger and six in the 20- to 40-passenger category. Seven manufacturers offer 12 models in the over-40 passenger category; however, there are currently only two competitors making 100-passenger jets, British Aerospace and Fokker; Canadair is developing a 50-passenger jet. The market for smaller, less than 50-passenger aircraft is shrinking and at the same time is crowded with competitors. Thus, it is unlikely that a U.S. manufacturer would undertake an initiative to attempt to compete for this market. The market for future deliveries of 80- to 125-passenger jet aircraft is significant and may represent an opportunity for U.S. manufacturers to reenter the regional market. However, the only small U.S.-built jet, the 115-passenger Boeing 737-500, has not yet been sold to a regional airline. The Rotorcraft Market Civil rotorcraft are operated today in a number of fields: energy, news, agriculture, executive transport, business, public service, police, and firefighting. There are currently 4,232 turbine-powered and 3,244 piston-powered helicopters in the civil fleet. Few helicopters operate as commuter carriers today, primarily because of the high operating costs. Scheduled passenger operations have been successful only where geographic barriers and lack of airports prevent ground transportation or fixed-wing aircraft from operating effectively. Still, a steady growth of civil helicopter markets is projected.9 The value of the worldwide civil helicopter production in 1990 was $1.0 billion and is projected to grow at an average rate of about 7 percent annually (Figure 4-2). This growth would result in a $2 billion civil rotorcraft market by 2001, not including advanced vertical takeoff and landing (VTOL) aircraft such as the tiltrotor. Of the total world helicopter production, including military, the civil sector accounted for 17 percent in 1990 and is projected to account for 25 percent by 2001. U.S. manufacturers delivered 570 civil helicopters in 1990, with a value of $350 million (34 percent of the worldwide market). As shown in Figure 4-2, U.S. market share is projected to increase through the mid-1990s and then to decline to approximately 30 percent by the end of the decade. 9 National Research Council. 1991. Worldwide Civil Helicopter Forecast by Weight Class. Washington, D.C.: National Academy Press.
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Aeronautical Technologies for the Twenty-First Century FIGURE 4-2 World civil rotorcraft production forecast. Recent U.S. helicopter exports, including military, have been in the $300 million to $400 million range annually. They are expected to increase to about $700 million annually by the mid-1990s, due in part to increased export of civil helicopters. Most civil helicopters, especially medium- and large-sized craft, are derivatives of military aircraft. There is only one new U.S. military development program in sight, a light attack helicopter, the Boeing/Sikorsky RAH-66 Comanche. European governments are proceeding with the development of an entirely new generation of military and commercial helicopters, which will cut heavily into U.S. market share in the late 1990s and after the turn of the century. Civil, as well as military, helicopter programs are funded by governments in Europe. Recently announced European procurement plans include more than 1,000 20—30-passenger machines (military NH90s and EH-101s). A German company MBB has announced the production of the BO-108, an advanced composite light twin-turbine helicopter. Aerospatiale, jointly with Singapore and China, is proceeding with a light single-turbine civil helicopter, the P-120 L. The Eurocopter Tiger attack helicopter made its first flight in April 1991; 430 production units are planned. The BO-108 and P-120 will penetrate the lower end of the market, whereas civil versions of the NH-90, EH-101, and Tiger helicopters will fill market needs for intermediate- and large-size helicopters. Eurocopter is a French/German company resulting from spin-off and merger during 1991 of the helicopter divisions of Aerospatiale and MBB. Dornier's helicopter activities will be included in Eurocopter after 1994. With the merger, Eurocopter has essentially a complete line of civil helicopter products. In addition to the Eurocopter merger, there is an increasing trend
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Aeronautical Technologies for the Twenty-First Century toward international collaboration in the development of new rotorcraft, as illustrated in Table 4-2. The civil helicopter market should continue to grow at a substantial rate beyond the $2 billion level early in the next century. European and Japanese competition is intensifying rapidly with the formation of consortia, mergers, and government-funded development programs. U.S. industry will require very substantial research and development support if it is to remain technologically competitive and obtain a significant share of the civil helicopter market after the year 2000. One rotorcraft area in which the United States has a significant lead is the tiltrotor, with a good technology base provided by the successful XV-15 research program and the V-22 military development project. Additional research, technology development, and system studies are needed to address the remaining questions regarding civil application of tiltrotor aircraft. If this effort provides positive results relative to the basic technical, environmental, operational, and economic issues, a major opportunity should develop for U.S. industry. The General Aviation Market General aviation consists of the civil fixed-wing fleet, including business jets but excluding scheduled air carriers and noncertificated types. Thus, general aviation aircraft range from two-place trainers to wide-body turbofans used in business. The current U.S. GA fleet exceeds 200,000 airplanes for a variety of business and personal uses. As shown in Figure 4-3, the GA manufacturing industry was devastated during the 1980s. From a peak of nearly 18,000 units in 1978, which were mainly personal aircraft, U.S. production declined to less than 1,100 units in 1987. During 1990, only 1,144 GA airplanes were produced in the United States. The turbine-powered business aircraft manufacturing sector recovered somewhat in recent years (449 turbine units in 1990 versus 372 in 1986). However, current production is less than half the number of units in the peak years 1978–1981. The piston powered sector remains depressed, with only 705 units produced in 1990, or about 5 percent the production of the peak years 1977–1979. Revenues of GA manufacturers did not drop as drastically as did the number of units produced because of the increased prices and production of a larger portion of more expensive models. Unpredictable costs of product liability, totally unrelated to product safety (Figure 4-4), have caused many manufacturers to cease production of light aircraft and their component parts. European manufacturers are strong competitors in the business jet sector. They are expanding into the light aircraft sector previously dominated by U.S. manufacturers. Notwithstanding increasing costs and complexity of operation in the national airspace system, utilization of general aviation airplanes has remained relatively strong. Following a 15 percent drop in the early 1980s, total annual flight hours by piston airplanes has remained level at approximately 27 million. Total flight hours for the general aviation turbine fleet increased steadily during the 1980s at a rate of about 4 percent per year, to approximately 5 million hours in 1990.
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Aeronautical Technologies for the Twenty-First Century TABLE 4-2 International Consortia for New Helicopters and VTOL Aircraft Aircraft U.S. U.K. France Germany Italy C.I.S. Holland Spain Japan China India Singapore TW 68:4-engine tilt wing VTOL, 12,000lb, 8–14 passengers √ UROFAR: 30-passenger tiltrotor transport √ √ √ √ √ A129/T800: LH-engine-powered Mangusta antitank helicopter √ √ Battlefield Lynx: LH-engine powered Westland helicopter √ √ EH-101: large, multiengined, civil and military transport helicopter √ √ NH-90: medium tactical and transport helicopter √ √ √ √ Tiger: combat helicopter √* √ √ Advanced light helicopter 14-passenger transport √ √ BK-117: Turbomeca Arriel-powered utility helicopter √ √ √ P120L: five place executive helicopter √ √ √ Rolls-Royce-powered Kamov Ka-62R helicopter √ √ Source: American Helicopter Society * British Army Combat Helicopter Competition, only.
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Aeronautical Technologies for the Twenty-First Century FIGURE 4-3 General aviation unit shipments/billings. However, the general aviation fleet is aging rapidly. Currently the average ages of active airplanes are 14 years for turbojets, turbofans, and turboprops; 25 years for piston, single-engine aircraft; and 22 years for piston, multiengine aircraft. Given these average ages, the refurbishment and upgrading of equipment in the older airplanes have become major activities for maintenance organizations. General aviation manufacturers have depended primarily on NASA and other elements of the aircraft manufacturing industry for technology input. The application of advanced technology in general aviation varies widely with category, with the largest application in turbine powered airplanes. The installation of relatively low-cost advanced avionics in older airplanes, as well as new, is significantly improving the usefulness of the GA fleet. Progress in the application of technology advancements in other areas has been slow in piston-powered types, where utilization of advanced technology is sharply controlled by considerations of cost versus benefit. In contrast, turbine-powered business aircraft designs have incorporated advanced technology to a fairly high degree and have even provided the first production application of some advancements. Market Forecast The growing population and the increasing demand for air transportation of people and goods are projected to continue the need for expansion of short-haul air transport in all categories. The need for short-haul service is increased further by mounting pressures to decentralize industry and population from troubled urban centers where it is costly to operate.
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Aeronautical Technologies for the Twenty-First Century FIGURE 4-4 General aviation fatal accidents and paid claims. Because of congestion at busy hub airports, there is a developing need for air service between smaller communities that bypasses congested hubs. There also remains an unfulfilled need for efficient VTOL transport, both for interconnection with long-range air service and for direct city-center to city-center transportation. The developing congestion of the airspace and airport system at busy hub areas needs to be addressed with new and emerging technologies to bring about a quantum improvement in the efficiency and capacity of the system. These needs, and many others, provide great opportunities for the development and application of advanced aeronautical technologies by NASA and U.S. manufacturers. Forecast for Commuter Aircraft The commuter market is projected to remain the fastest-growing portion of U.S. airline traffic. Foreign manufacturers are expected to continue to dominate the supply of commuter airplanes for more than 20 passengers, unless the structure and requirements of the regional carriers change significantly. U.S. equipment and engine makers will continue to supply their products to international manufacturers. However, competition from subsidized foreign manufacturers will probably make the development and production of current-technology turboprop transports in the 20- to 50-passenger range economically unattractive to U.S. manufacturers.
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Aeronautical Technologies for the Twenty-First Century Several factors are present that may offer new or expanded opportunities for the application of U.S. technologies to the commuter aircraft area. There appears to be a sizable market developing for 50- to 100-passenger turbofan commuter aircraft, primarily for use in ''hub bypass'' operations. Larger, faster, and more comfortable aircraft are needed for routes with longer stage lengths and higher traffic density. If advanced U.S. technology is made available for commuter airplanes and high bypass ratio turbofan engines, it appears likely that good opportunities could exist for U.S. industry. Continued growth of traffic congestion at the major hubs will serve to limit growth of commuter airline traffic unless actions are taken to significantly improve both air- and ground-side systems. Satellite-based navigation and communication systems, combined with advanced ground and airborne computers, have great potential for improving the capacity and safety of the traffic system in terminal areas, en route, and on the ground. Implementation of these systems will be a major factor enabling orderly growth of the commuter airline market. Such growth is essential to meet national transportation needs, and with it will come opportunities for application of advanced technologies by U.S. manufacturers of engines, equipment, and hopefully, complete aircraft. Integrating VTOL operations into existing airports, by the use of helicopters and tiltrotors has the potential to reduce commuter traffic on congested runways and on approach and departure paths, thus increasing the capacity of these airports. Rotorcraft also have the potential of providing hub bypass commuter operations in dense traffic areas. Key to realizing the potential of advanced rotorcraft in commuter applications is demonstration of the technology, environmental and passenger acceptability, operational suitability, and economics. Such demonstration is necessary to convince manufacturers and operators of the viability of commuter rotorcraft operations. The potential of advanced VTOL aircraft in commuter operations and other sectors of the air transportation system is discussed in more detail in the next section. Forecast for Rotorcraft Civil use of rotorcraft is presently limited by external noise constraints, operating costs, lack of public heliports and associated ATM systems, and the perception that rotorcraft are less safe than conventional aircraft. U.S. industry is heavily challenged by foreign manufacturers and is losing market share to that challenge. However, on the demand side, there are several promising potential opportunities for application of advanced rotorcraft. Recent studies conducted by NASA and the FAA show a potentially large market for tiltrotor aircraft. Major markets include "urban area to urban area" and "high-density hub feeder." Realization of these markets would require the total system and infrastructure for such operations to be developed, including the ability to operate separately from fixed-wing traffic, into vertiports located near populated areas, with acceptable noise, economics, passenger acceptance, and safety. The United States currently has a substantial lead in the development of tiltrotors for military use. As mentioned in the previous section, advanced rotorcraft offer the potential for making a major contribution to the commuter sector and reducing congestion at busy hubs. A significant
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Aeronautical Technologies for the Twenty-First Century contribution should be possible even without a whole new complex of vertiports and large improvements in external noise required for public acceptance of new vertiports. In addition, rotorcraft offer the promise of relieving the congestion of ground transportation feeding airports in major urban areas, both by providing air access to the hub from surrounding communities and by providing a route structure that bypasses the hub for travel from communities in the hub region to spoke destinations. Demand for the unique capabilities of rotorcraft in a variety of mercy missions continues to increase. A new concept, now in the earliest discussion stage, stems from the need for a massive international disaster response capability, with both long-range and VTOL short-range airlift capability. Currently and in the near term, military agencies of the major powers will provide air transport resources for disaster relief. In the longer term, it appears that a vertical lift disaster relief force built around air-transportable, advanced rotorcraft could provide major advancement in international disaster relief. Opportunities for research and technology development that can contribute to fulfillment of the needs for improved rotorcraft capabilities include (1) vibration and noise reduction; (2) improved productivity and reduced operating costs; and (3) development of satellite-based navigation, communication, and control systems. This includes the accompanying rotorcraft control systems and techniques that will allow safe operation of rotorcraft, independent of fixed-wing traffic. This technology is necessary to allow exploitation of the rotorcraft's vertical takeoff and landing capability in all-weather operations from nonrunway-type facilities, and it will improve both utility and safety. Forecast for General Aviation Aircraft Continuing long-term growth in the use of GA airplanes in corporate and utility applications is projected by the FAA. The agency predicts a 50 percent increase in turbine-powered GA flight activity over the next 12 years. For piston-powered airplanes the FAA predicts that flight activity will remain level over the next 12 years. Increasing problems with the infrastructure and quality of life for many people in major urban areas bring increasing pressures to decentralize industry and population. In the long-term, this should stimulate a significant increase in the use of GA airplanes to provide the necessary point-to-point, on-demand air transportation for outlying communities and dispersed businesses and industries. A large increase in the need for GA airplanes for training purposes is expected to continue. This increase results from the demand for new pilots caused by continued growth of the scheduled air carriers, the retirement of large numbers of pilots during the 1990s, and a reduction in the supply of pilots from the military services. As discussed above, a number of factors constrained the growth of GA aircraft operations and caused a decrease in personal aircraft operations in the early 1980s. If these constraining factors were effectively addressed, general aviation could make an increasingly important contribution to the national transportation system. Improvement in the health and growth of GA
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Aeronautical Technologies for the Twenty-First Century flight operations should reflect directly on the manufacturing sector, especially in view of the need to replace the aging fleet. An infusion of new technology could make a major part of the existing GA fleet obsolete. A significantly improved low-cost power plant to replace the piston engine is an example of the type of technology that could rejuvenate light aircraft design and manufacturing. BARRIERS The Committee believes that the biggest barrier to meeting future needs for short-haul air transport is the complex and costly airspace and airport traffic management system. This problem is especially severe at busy hubs and is rapidly getting worse. However, each of the five areas of need defined in Chapter 1 is relevant to the advancement of short-haul aircraft (i.e., cost, environmental impact, safety, performance, and capacity). These issues are discussed in the following sections. Barriers to Commuter Aircraft Profitability and the associated availability of capital were, for a long time, deterrents to growth of the commuter airline industry. In recent years these issues have been mitigated somewhat by mutually beneficial associations between commuter and major airlines. However, economic issues remain a major constraint on the application of advanced technology in commuter airplanes, and shortage of capital inhibits U.S. builders of such aircraft. The rapid growth of both the major and the commuter airlines has resulted in increasingly serious congestion at the busiest hubs. The commuter system, which has served all of its constituents well by providing safe, reliable, high-frequency service between small communities and hubs, has now become a major part of a rapidly worsening national problem. Both the land-side and the air-side have become overly congested, partly as a result of the success of the commuter concept. A commuter passenger requires the same parking space, the same driving space, and the same terminal facilities as other passengers. Commuter air operations require the same attention and the same airspace, and in some cases more time to fit into the system, whereas productivity in terms of passengers per airport operation is lower. Realization of the full potential contribution of commuter, to the national transportation system depends on finding a solution to the hub congestion problem. Although environmental considerations are not a major factor with commuter aircraft as currently used, they are likely to be of increasing concern with the emergence of advanced rotorcraft as economical modes of transportation. Relatively little work has been done on the human/machine interface (cognitive engineering) for the class of equipment utilized by the commuter industry. As cockpit technology moves ahead, a better understanding of this area is needed. The major source of commuter pilots is general aviation, and the transition from a simple airplane to a highly sophisticated cockpit is a radical change that must be eased as much as possible.
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Aeronautical Technologies for the Twenty-First Century Barriers to Rotorcraft Before rotorcraft can be used to help solve the runway capacity problem by absorbing a significant part of the short-haul traffic, a number of serious barrier issues will have to be overcome. The first of these is high operating cost. There are many contributors to the cost problem. The initial capital investment is large. Helicopters are expensive because production runs are small and development costs are high, partly because of the empirical, trial-and-error aspects of so much of the design and development process. Production is expensive because of the large number of complex parts and, again, because production runs are relatively small. Maintenance is also expensive because of the complexity and the flight-critical nature of so many highly stressed fatigue-loaded parts, which has always required very conservative "safe life" parts retirement. For missions of any significant range, relatively poor cruise lift-to-drag ratio results in limited payload fractions, and low cruise speed further decreases productivity. Convertible rotorcraft, such as the tiltrotor, can improve the lift-to-drag ratio and cruise speed, and reduce the fatigue loading of components. However, with current technology the higher empty weight fraction of tiltrotors tends to erode part of the benefit. Rotorcraft must justify their higher operating costs by operating from convenient, close-in vertiports. Community acceptance is a critical vertiport consideration, and noise is a major problem. Even with current technology, noise can be reduced by designing for lower tip speeds and lower disk loadings, but this further penalizes efficiency and productivity. Steep-gradient curvilinear operations can reduce the noise footprint considerably and help avoid noise-sensitive areas, but this introduces instrument flight rules, flight path control, and ATM system challenges. Because rotorcraft will probably want to take advantage of unused low-altitude airspace in congested urban areas, cruise noise is also an important issue. It is evident that the rotorcraft commuter problem must be attacked on many technical fronts. The public perception of safety risks continues to serve as a barrier to both passenger acceptance of rotorcraft and acceptance by potential vertiport neighbors. The safety record of commercial passenger helicopter operators compares well with commuters, especially on the basis of accidents per departure. However, the fact remains that the safety record, as well as the perception of it, must be improved before broad public acceptance can be expected. Another potential barrier to passenger acceptance is comfort. Current helicopter vibration levels, although greatly improved in modern designs, are still frequently well above the threshold of comfort, especially at high-speed and during landing approach. Although the tiltrotor has a basic advantage in vibration over the helicopter at high-speed, it still requires vibration control design and treatment to meet passenger acceptance standards. It is clear that abatement of internal noise, for both helicopters and rotorcraft, will require significant attention to new soundproofing techniques. For trips of more than 150 miles, current modern helicopter cruise speeds (typically 150–160 knots) will probably be too slow for ready acceptance by the traveling public, whose expectations are based on higher fixed-wing speeds. The application of rotorcraft by commuter
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Aeronautical Technologies for the Twenty-First Century airlines, other than for short trips, depends either on achieving a significant increase in helicopter cruise speed or on effective application of the tiltrotor. Barriers to General Aviation Aircraft A number of issues form major impediments to realization of the opportunities provided by general aviation. These include price increases above the general rate of inflation caused by soaring product liability costs, loss of suppliers, changes in laws governing investment tax credits, weakening of the general economy, shortage of technical improvements, and the increasing complexity and cost of operation in the national airspace system. Each of these has in some way limited the growth of GA operations and drastically reduced the production of new aircraft. NASA'S CONTRIBUTIONS TO SHORT-HAUL AIRCRAFT Short-haul aviation can benefit greatly from a broad-based NASA research and technology program in both the classical and the more exotic aeronautical disciplines. For the sake of clarity, the features of an effective program, as they pertain specifically to short-haul aircraft, are broken down into the categories of need described in Chapter 1. As mentioned there, these categories are not independent, they overlap to a significant degree, and technologies that contribute to furthering one need are likely also to further another. Table 4-3 shows the current (1992) funding for short-haul aircraft by discipline. As discussed in Chapter 1, the Committee was not constituted to recommend specific funding levels for the technologies discussed in this report. However, from the information shown in Table 4-2 and in Appendix C it is clear that NASA's emphasis in the short-haul aircraft category is on rotorcraft. In fact, of the $32.0 million specifically devoted to this category, $23.8 million was allocated to the rotorcraft research and technology base (see Appendix C) and $5.2 million for "advanced rotorcraft technology." The remaining $3.0 million was spent on propulsion technology for general aviation and commuter aircraft. Although the Committee believes that development and validation of rotorcraft technology is a worthwhile goal, and recognizes that much of the technology developed for larger subsonic aircraft will apply to commuter and general aviation aircraft, the nation would certainly benefit from a more balanced short-haul program. Better balance could be achieved through reallocation of a portion of rotorcraft funding to conventional takeoff and landing aircraft or, preferably, as part of an overall increase in the NASA civil aeronautics budget that keeps rotorcraft funding near current levels but increases funding for other short-haul aircraft. Many of the advances that address these categories of needs are likely to be applicable to other categories of aircraft discussed in this report. In the experience of the Committee, broad-based technology development programs will tend to uncover applications in areas that were unforeseen at the beginning of the program. So, although consistent focus is needed to address the special needs of short-haul aircraft as one part of the total NASA program, care
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Aeronautical Technologies for the Twenty-First Century TABLE 4-3 Short-Haul Funding by Discipline Discipline Current NASA Program (millions of 1992 dollars, percent of total)a,b Systems and operationsc $5.9 18.4% Aerodynamics $16.5 51.6% Propulsion $3.0 9.4% Structures and materials $3.3 10.3% Controls, guidance, and human factorsd $3.3 10.3% Total $32.0e 100.0% Source: NASA Office of Aeronautics and Space Technology a 1992 funding in real-year dollars, excluding fundamental research not tied to a specific application. b Percentages may not add to 100% due to roundoff error. c Includes both flight systems research and systems analysis studies. d Includes the Avionics and Controls and Cognitive Engineering categories discussed in this report. e Of the $32.0 million total, $29.0 million was devoted to rotorcraft technology and $3.0 million to general aviation technology. should be taken to ensure that the full range of applications of each technology is well understood. Cost/Convenience Developing cost-effective aircraft is not necessarily the role of NASA. However, developing the technologies that lead to cost-effective aircraft is a proper role. Thus, development of a technology that promotes longer aircraft lifetimes, reduces engine fuel consumption, improves lift-to-drag ratios, reduces structural weight, or improves passenger comfort through reduction in noise or vibration levels can and should be undertaken by NASA. Research on continued airworthiness of aging aircraft, including aging characteristics of composite materials, inspection/nondestructive evaluation methods, and cognitive engineering, continues to be needed to make U.S. commuter aircraft commercially viable. Practical alternatives to arbitrary life limits are essential for older commuter airplanes, which were designed to airworthiness standards that are now obsolete. Improvement is needed in predictive analysis and model test techniques to increase the efficiency of the rotorcraft development process and thereby reduce acquisition cost. Also, to produce simpler designs that are cheaper to build and maintain, NASA's support is needed for
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Aeronautical Technologies for the Twenty-First Century development of design concepts that take advantage of new materials, especially composites, to replace bearings with flexures and to tailor rotor blade dynamic characteristics. Increased confidence is needed in definition of life cycle costs of new technologies, such as the tiltrotor, before the regional airline industry can be expected to invest in them. The Committee believes that NASA can help build this confidence by validation of the critical technologies to minimize risk and by sponsorship of, and participation in, comprehensive system studies to define the total system and its technical and economic characteristics. Research and technology development is needed to improve rotorcraft passenger comfort. Primary areas in which NASA effort is necessary are vibration prediction methods, vibration reduction concept development, machinery noise reduction and suppression, and gust alleviation. System Capacity Although the administration of the national airspace system is primarily the province of the FAA, the Committee believes that NASA has capabilities that could augment and complement those of the FAA. Thus, NASA can make a major contribution to increasing the capacity and efficiency of the system by developing technology that reduces the complexity and cost of access to that system. Advancements are badly needed, not just by the short-haul segment but by all users of the airspace system. Areas in which NASA can provide significant contributions are: position determination and flight path guidance; traffic awareness and collision avoidance, both in the air and on the ground; and availability of real-time weather information for the flight crew. Advancements in computational capabilities and the maturation of new technologies such as satellite navigation, advanced Doppler radar, and satellite communications can be applied to provide a quantum improvement in the system. Significant cost and reliability improvements should be possible by automating many functions that are currently very labor intensive. The Committee also believes that a study is needed to establish the degree to which existing airport capacity could be increased by shifting some short-haul traffic to helicopters and tiltrotors, and having vertiports integrated into available airport real estate. Environment The emissions that are generated by rotorcraft, general aviation, or even commuter aircraft are minimal compared to those generated by large subsonic transports or potential supersonic transports. The primary impact of short-haul aircraft on the environment then is the generation of noise. The Committee believes that NASA's excellent capabilities in acoustics should be applied to reducing both exterior and interior noise of rotorcraft, GA, and commuter aircraft. This effort should be an essential part of a comprehensive noise research and technology development program, including research in the fundamentals of noise phenomena and the development of improved noise prediction methods; development and substantiation of technologies for reducing engine, rotor, and propeller noise; research on human response to noise and development of noise measurement criteria; research and
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Aeronautical Technologies for the Twenty-First Century technology for active control of noise; and development of U.S. capabilities for large-scale acoustic wind tunnel testing. Furthermore, to help reduce terminal area noise and maximize the utility of rotorcraft, there is a need to develop operations-enhancing technologies such as steep-gradient curvilinear instrument flight rules approach guidance systems, ATM system integration techniques, and improved pilot/vehicle interfaces. Safety Because flight crew error continues to be the primary cause of fatal accidents and addressing this cause can potentially make the largest contribution to short-haul aviation safety, NASA should undertake an aggressive safety research program, focused on cognitive engineering, and should address the features that are unique to the operation of commuter, rotorcraft, and general aviation aircraft. In addition, the development of fail-safe designs, integrity monitoring systems, and damage-tolerant gears and shafts for on-condition removal are needed to reduce maintenance costs and increase the safety of rotorcraft. Particularly challenging is the need for a real-time condition monitor for metallic rotating structural elements. Acoustics emissions and laser information transfer offer intriguing possibilities in this area. NASA has unique capabilities and facilities and can make a significant contribution to GA safety in the future, as it has in the past. Research and technology development in GA safety should be rejuvenated at NASA. Some of the items that should be included are cognitive engineering, flying qualities, departure from controlled flight, and spinning. Another major contribution needed from NASA toward general aviation safety is the development of the basic technology for advanced low-cost on-board systems, including flight path guidance and control, information transfer, traffic awareness and collision avoidance, and real-time weather presentation. Application of these technologies, in combination with a greatly improved airspace management system, could bring about a dramatic improvement in the usefulness and efficiency of general aviation operations. Finally, the Committee believes that NASA's capabilities in simulation and training could help enhance the initial training and skill maintenance programs of all aircraft pilots and mechanics. Emerging computation and simulation technologies could provide the basis for low-cost personal training aids and simulators that could aid in keeping more sophisticated aircraft well maintained and help alleviate the primary factor in GA, rotorcraft, and commuter accidents—pilot error. Aircraft Performance All categories of short-haul aircraft can benefit from advances in performance. NASA's role as the primary provider of advances in the traditional aeronautical disciplines (propulsion, aerodynamics, materials and structures) will continue to provide incremental improvement in the speed, range, and payload of short-haul aircraft. Furthermore, it can be expected that NASA will play a major role in advancing the more exotic technologies associated with cognitive
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Aeronautical Technologies for the Twenty-First Century engineering, and advanced avionics. Each category of aircraft considered in this section will require advances in performance to remain viable in future markets. In particular, it is the belief of the Committee that NASA's very extensive capabilities should be applied toward major improvements in rotorcraft speed and efficiency. The research and technology effort should range from studies of improved aerodynamics, dynamics, materials, structures, and machinery, to investigation of promising new VTOL configurations. RECOMMENDED READING American Institute of Aeronautics and Astronautics. 1990. The Role of Technology in Revitalizing U.S. General Aviation: Report of a Workshop , December 12–13, 1989. Washington, D.C. National Research Council. 1981. NASA's Role in Aeronautics: Report of a Workshop. Aeronautics and Space Engineering Board. Washington, D.C.: National Academy Press.
Representative terms from entire chapter: