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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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3
Naval Air Platform Technology

OVERVIEW OF FUTURE NAVAL AIR TECHNOLOGY

Initial Observations

In reviewing relevant technologies and formulating its findings, the panel took special note of significant trends in employment concepts for air platforms:

  • Increased emphasis on long-range, precision weapons, launched from both aircraft and surface vessels;

  • Expanded consideration of off-board sensing and targeting; and

  • Growing concerns about employing manned aircraft in combat operations over land, particularly during daylight hours.

It will be important to strike a balance among tactical air platforms, sophisticated weapons, and off-board sensors in order to provide the most cost-effective approach for the future. Acknowledging calls for increased emphasis on unmanned aerial vehicles (UAVs) for a variety of support and lethal missions, the panel believes that the argument over manned and unmanned aircraft—although an important one—is not the real watershed decision for 21st-century naval aviation. The cardinal aircraft issue for future decision-makers is that of tactical aviation (Navy, Marine Corps, Air Force) versus standoff weapons, long-range bombers, and ship or shore basing. This issue is not addressed here, but nevertheless must underlie any consideration of the future character of naval aviation.

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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Vision of Naval Air Platforms for 2035

A More Vertical Force

Naval aviation, both afloat and ashore, is likely to become a more vertical force in the future. There will be increased reliance on air vehicles, both manned and unmanned, with short takeoff and vertical landing (STOVL), vertical takeoff and landing (VTOL), and short takeoff and landing (STOL) characteristics that have excellent payload, range, and low-signature capabilities. Takeoff and landing footprints will be much less than today's conventional takeoff and landing aircraft, thereby opening up design space for future aircraft carrier development.

Unmanned Aircraft

Naval aviation will employ UAVs for a variety of missions, beginning with reconnaissance, surveillance, and targeting, and later expanding to include such familiar aircraft carrier (CV) support tasks as tanking, electronic warfare (EW), antisubmarine warfare (ASW), and airborne early warning (AEW). Some of these unmanned aircraft will fly from aviation ships and surface combatants, whereas others, some possibly operated by the Air Force, may be based ashore at great distances from the supported battle group or expeditionary task force. As UAVs become more reliable and gain operational acceptance, unmanned tactical aircraft will be employed for selected lethal purposes, both air-to-air and ground attack. The panel believes that the introduction of unmanned tactical aircraft as substitutes for today's fighter and attack planes will be a slow ''fly-before-buy" process, and that a place will remain in the naval aviation arsenal for piloted tactical aircraft for many years to come.

Aerial Trucks

The introduction of subsonic, stealthy-when-required, aerial trucks is seen as a major positive development for the future. These aircraft—manned and unmanned—and employing STOVL, VTOL, and in many instances, STOL capabilities could constitute the backbone of naval aviation for the missions cited above. These workhorses would be mission configured using modular packages that could be changed in a reasonable time aboard ship and at advanced shore bases.

Broadened Aircraft Basing Options
Carrier Size

Because of the trend toward a more vertical force of aircraft with attendant reduced demands for takeoff and landing deck space, the spectrum of acceptable

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×

aircraft carrier sizes and configurations is broadened considerably. Seakeeping characteristics of aviation ships are also less constraining on STOVL and VTOL aircraft—and to some extent STOL—a fact that contributes to lowering the ship tonnage threshold below that for which safe air operations are now viable.

Vertical aircraft also contribute to cost-effectiveness in other important ways—in sortie generation and the attendant quantity of munitions delivered on target. A ship with a vertical air wing can carry more such aircraft than conventional takeoff and landing (CTOL) aircraft and, for short to medium ranges, STOVLs and VTOLs can cycle at a greater rate. This adds up to more sorties and more ordnance delivered in a given period of time.

Distribution of Air Assets

The panel sees aircraft, some with considerable combat capability, being distributed more widely among ships of the fleet. Improved system reliabilities and the greater prevalence of vertical aircraft will make such distribution feasible in many instances, at least on a temporary basis, as dictated by the tactical situation.

Flexible Carrier Deck Loads

Although commanders have always been able to tailor the mix of aircraft types in a carrier air wing, force options of unusual flexibility will be open to the Navy in 2035 if the requisite enabling technologies are developed and exploited. For example, support aircraft functions—tanking, EW, ASW, AEW—could be provided by shore-based air platforms, the majority unmanned, that operate from airfields perhaps thousands of miles away and remain on station in support of battle groups for periods of two days or more. A CV in this instance could function as an all-fighter attack base and munitions magazine, greatly increasing the striking power of the all-fighter battle group. Alternatively, under a different tactical scenario, the carrier could serve principally as a support and/or reconnaissance and surveillance base, operating troop lift and logistics aircraft as well as special mission planes that provide reconnaissance and targeting support for expeditionary forces ashore and control long-range missiles launched by bombers and surface ships.

TECHNOLOGY DEVELOPMENT PLAN

The panel believes that a plan to develop future technologies for naval aviation should embrace the following elements:

  1. Make maximum use of technological advances in the commercial aviation sector, as well as advances developed by the Air Force, Army, and NASA.

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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Interservice cooperation has improved over the years, and the Navy has benefited considerably from R&D conducted by NASA and by the other military services. This policy should be continued and, indeed, information exchange and sharing, including joint technology planning and development, should be enhanced whenever possible. Navy R&D planners should seek to maintain and improve strong working relationships with NASA R&D planners to encourage recognition of Navy needs within NASA and to maximize the utilization of technology available from the relevant NASA programs.

  1. Continue the general course of Navy-funded R&D as outlined in current plans, but also maintain a healthy watch for the occasional nonessential pet projects that can creep in and soak up resources. By maintaining the current path, the Navy will be assured of having technologies in hand that facilitate evolutionary development of current air platforms should this course of action be chosen in the future; however, the panel believes that this course alone is inadequate to met the challenge of the future.

  2. Implement new, focused R&D thrusts in the following air platform technology areas, building on current progress within the Navy and in joint efforts with the Air Force, the Army, and NASA:

  • Aerodynamics,

  • Structures,

  • Propulsion,

  • Flight and mission control,

  • Signature reduction, and

  • Design and manufacturing processes.

Technology Toolbox/Buffet Line

The panel suggests that the Navy view its future R&D challenge as one of developing tools, including borrowing, wherever possible, those funded and developed by civil aviation, the Air Force, and the Army. These tools would then be placed in a toolbox ready to be used or presented on a technology buffet line. Thus, when the time comes to develop a tactical aircraft after the joint strike fighter (JSF) or a follow-on support aircraft, the Navy will have the option to pursue either a traditional evolutionary path or one that exploits the enabling technologies identified in this report, with the attendant new platform concepts identified by the panel.

Key Enabling Technologies

The panel identified 12 key enabling technologies (Table 3.1) that are uniquely applicable to naval aviation platforms and may be underemphasized within the Navy Department's current R&D portfolio.

Investment by the Navy Department in the 12 enabling technologies that

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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TABLE 3.1 Key Enabling Technologies

Technology Focus Area

Key Enabling Technology

Aerodynamics

Laminar flow control

High-lift aerodynamics

Structures

Lightweight, high-strength composites

Propulsion

Core engine performance

Variable cycle engine

Adapting large-engine technology to small engines

Flight and mission control

Integrated flight and propulsion control

High-capacity, long-range data links

Signature reduction

RF signature reduction

IR signature reduction

Design and manufacturing processes

Dynamic electronic prototyping

 

Reduced-cost, low-rate production

capitalize on and leverage the established aerospace R&D path could broaden the air platform and aircraft basing options for naval forces in the year 2035. By exploiting these enablers, and as success is demonstrated, those officials who set operational requirements and formulate acquisition programs will be afforded increased flexibility in fashioning designs of aircraft and aviation ships to meet future needs of the Navy and Marine Corps. These needs will embrace a wide mission spectrum in an era of rapid change in information technologies, increased reliance on precision-guided munitions, and demands for lower cost and possibly fewer aircraft and base ships.

The panel believes that developing and deploying more cost-efficient air platforms and supporting sea bases are feasible and necessary goals. These aircraft and aviation ships will confer warfighting benefits that will be unattainable if R&D proceeds solely along the traditional path, wherein each aviation community (i.e., fighters, strike, reconnaissance, surveillance, ASW, EW, and troop lift) seeks a successor model possessing increased performance.

The enabling technologies and their impact on future air platform designs are discussed in the context of the technology focus areas for future naval air platforms described below.

Integrated High-Performance Turbine Engine Technology

The Defense Department's very successful Integrated High-Performance Turbine Engine Technology (IHPTET) program, which was initiated in 1988 and will proceed in phases until 2003, constitutes an excellent model for a technology

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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development program. Its success is attributable to four crucial elements: (1) the subject is seen as important; (2) clearly defined technical and schedule goals are specified; (3) the effort is a government and industry partnership; and (4) stable funding profiles are established and adhered to. The panel believes very strongly that IHPTET should serve as the model for air platform technology development.

TECHNOLOGY FOCUS AREAS

Aerodynamics

Laminar Flow Control

The most significant air platform performance parameter for mission capability is range and, alternatively, endurance—both of which are major functions of cruise efficiency. From an aerodynamic perspective, this relates to low cruise drag.

Current Situation and Constraints

Many factors can dominate cruise drag: shape (or fineness), wing platform and aspect ratio, airfoil design, size, gaps and protuberances, surface roughness, engine inlets and nozzles, and control or trim surfaces. It is well known that a particular design to accomplish a specific mission is a compromise among mission elements such as maneuver performance, takeoff and landing performance (especially for sea-based air), and cruise performance. In addition, for fighter, attack, and reconnaissance aircraft, external stores are often used to increase payload and/or range at the expense of cruise drag.

Many advances in technology have enabled refinement of aerodynamic shape for the basic platform as well as the external pylons and stores and their integration. Flight control technology has led to reductions in trim drag. Sophisticated analytical tools and design codes have facilitated optimum wing designs and inlet and nozzle integration based on dominant elements of the mission profile. As analytical tools continue to be refined, so does the understanding of flow phenomena, flow interactions, and drag. Computer-aided design tools facilitate moldline definition (and build) with unprecedented fidelity. New structural design techniques and composite structure process development are enablers for high-aspect-ratio wings to extend both the altitude and the endurance envelopes for special-purpose aircraft. These kinds of improvements are addressed almost daily and can be classified as business as usual from an aerodynamic perspective. There is, however, one particular aerodynamic technology with tremendous potential to improve cruise performance that is not business as usual. This is the area of laminar flow control.

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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FIGURE 3.1 Potential gains from laminar flow control. SOURCE: NASA Langley Research Center Web site at http://128.155.35.117/LFC_www/LFC.html.

Key Enabling Technology

Laminar flow control is a technique to control the boundary layer or the airflow closest to the skin. By maintaining laminar flow in the boundary layer and controlling the transition to turbulent flow, drag can be reduced significantly, buffet onset and flow separation can be delayed, and the flight envelope can be extended efficiently. Usually this is best accomplished by venting or bleeding the boundary layer via suction through a porous skin. An alternate technique is pulse blowing at frequencies tailored to unstable fluctuations in the location of boundary-layer transition. Interaction of the secondary flow with the primary airflow stabilizes the boundary layer and maintains laminar flow. Yet another technique, primarily useful at low Reynolds numbers, is to tailor the airfoil shape to maintain laminar flow. Figure 3.1, provided by NASA and based on work conducted at the NASA Langley Research Center and the Boeing Company, illustrates significant potential gains from the application of laminar flow control to both subsonic and supersonic flight. Fuel savings of the order of 10 to 20 percent can be realized for subsonic narrow-body transports, whereas fuel savings in excess of 20 percent are projected for wide-body transports with ranges greater than 4,000 nautical miles. Alternatively, research studies on high-speed flight indicate that supersonic cruise lift-to-drag ratios can be increased on the order of 10 percent at speeds of Mach 2.5, depending on the transition Reynolds number.

The feasibility of these concepts has been demonstrated in both laboratory and flight research. For example, Figure 3.2 depicts one of the flight test vehicles, an F-16XL at the NASA Dryden Flight Research Center, that has been modified to conduct supersonic laminar flow control research. Close inspection of the port wing reveals the test panels in the enlarged glove area. Other flight

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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FIGURE 3.2 NASA laminar flow flight test vehicle at the Dryden Flight Research Center. SOURCE: NASA Langley Research Center Web site at http://128.155.35.117/LFC_www/LFC.html.

test research has been conducted using a Boeing 757 for investigating laminar flow control in the subsonic regime.

Recent accomplishments have been facilitated by a greater understanding of the flow phenomenology via development of CFD codes and breakthroughs in processing technology. Outstanding analytical and empirical correlation has been demonstrated for the F/A-18. Physical implementation of laminar flow control technology requires exacting external moldline (skin) definition, fabrication, preparation (hole location and size), and operation (vent flow control). As noted above, computer-aided design and manufacturing (CADAM) is a significant enabler in attaining the necessary fidelity for the moldline surface and for vent (port) locations. Control of the secondary flow through these vent holes is now feasible and manageable using advanced digital electronic controls and modern processing capabilities. Specific matching of the secondary flow management to the moldline shape and flight condition remains a challenge. These elements should be areas of continued Navy focus.

However, much work remains to enable full integration into aircraft design.

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×

Issues range from those associated with product definition in the laboratory to those associated with operational employment in the fleet. Analytical and experimental work to refine the moldline definition, vent hole distribution, and flow control based on specific design applications (fighter, support, surveillance) and platforms, wind tunnel validation of numerical codes, and the definition of robust scaling laws for naval air vehicle applications are all required before laminar flow technology is mature enough for full implementation. Operational issues include maintaining adequate bleed port operation (size and number of ports) and vent control, given the potential for surface contamination by rain, dirt, or salt spray. A range of solutions should be examined, including surface treatment, redundancy management for the ports, characterization of failure modes and effects, and maintenance and repair concepts. These efforts should not be conducted at the expense of pressing for continued progress in product definition, manufacturing, or flow control quality. Efforts should be coordinated with applicable work in contributing materials, structures, and manufacturing technology program elements.

Other Contributing Technologies

There is a distinct interaction between laminar flow control technology and several other technologies described in this report. Many of the wind tunnel and CFD tools used in laminar flow control R&D are applicable to high-lift aerodynamics issues as well. Large, complex unitized composite structures play a role in moldline and surface fidelity, and new processes enable very-high-aspect wing development. These have to be tied together from a Navy applications perspective for common support aircraft and UAVs. The variable cycle engine enables mission matching and may be valuable to offset traditional vent and bleed losses, depending on the specific breadth of Navy platforms and tailored mission applications. Integrated flight and propulsion control facilitates attainment of efficient trim conditions and integration of vent port flow control as a function of flight or maneuver envelope for all vehicles. Techniques to provide radio-frequency (RF) signature reduction will also reduce gaps and protuberances and should be considered when implementing laminar flow control methods in applications where stealth may be an issue, particularly for new-design fighter or attack aircraft and UAV applications. Dynamic electronic prototyping is an essential tool for evaluating particular designs, as are many of the tools used to facilitate reduced-cost, low-rate production.

Potential Payoffs for Future Air Platforms

Improved aerodynamic cruise performance has a first-order, fundamental effect on all aircraft design. Reduced drag and improved cruise efficiency provide design options to (1) increase endurance and operational altitudes for UAVs or

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×

surveillance aircraft; (2) increase payload or range for the same size and weight platform in remaining naval air applications; or alternatively, (3) reduce platform size and weight with increased efficiency. All of this equates to decreased acquisition (size) and operational costs (fuel) for the life cycle of the vehicle.

Recommendations

To realize the potential offered by laminar flow control, several technology areas should be pursued to round out the fundamental understanding and provide for operational applications and transition:

  • The Navy aerotechnology base should provide validated product definition and analysis tools, including shape, location, flow port patterns, and flow control. The Navy materials technology base should be tasked to provide coatings to prevent contamination and blockage of the secondary flow ports.

  • Elements of the Naval Air Warfare Center (NAWC) and the Naval Air Systems Command (NAVAIR) should explore specific vehicle and mission applications. Research and development efforts on an integrated systems basis should provided parameters for control system development, critical operational (and failure) modes, and repair and maintenance techniques. These integrated efforts should extend to operational control and integration with variable cycle engine technology and should draw on advanced composite structures technology for characterization of new classes of air vehicles such as common support aircraft or surveillance UAVs.

High-Life Aerodynamics

One of the fundamental issues in carrier aviation is the ability to generate high lift at low speeds for takeoff (catapult) and landing (trap), particularly at maximum payload and bring-back weights typical of fighter or attack aircraft and fleet support carrier aviation. From an aviation safety perspective, lower approach speeds are desirable. Level 1 handling qualities at any approach speed are mandatory.

Current Situation and Constraints

Providing good high-lift capability for shipboard operation is a demanding task, particularly for modern supersonic jet aircraft. High-lift requirements for catapult and for approach or arrestment are different. Launch requirements typically are accompanied by lift and acceleration demands at heavy gross weights. For arrestment, maximum bring-back loads are important, but the requirements are to maintain a steady approach angle and altitude at low speeds through to arrestment. These high-lift requirements often introduce constraints and aircraft

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×

design considerations that conflict with other mission design requirements. In particular, a wing optimized for high-speed flight should be very thin and highly swept, with little camber and twist. Low-speed aerodynamic efficiency, on the other hand, requires a relatively thick upswept wing, with high camber at the leading edge, preferably for full span. Many complex solutions have evolved over the years, including variable incidence (with respect to the fuselage) nose strut extension for catapult such as that used on the F-8; variable sweep as with the F-14; and numerous flap, slat, and slot arrangements on the wing's leading and trailing edges—some of them augmented by a complex active boundary layer control and blowing systems (e.g., the F-4). Increased flap area or deflection also has an effect on wing pylon and external stores integration (e.g., F/A-18) due to the physical clearances required for full flap conditions. Leading and trailing edge flaps are typically complex, have bulky drive systems creating external bumps, add significant weight to the airplane, and are a high-maintenance item. Often, developing excellent handling qualities for low-speed flight conditions is an exacting job because of the significant change in lift distribution and lift as a function of both airspeed and angle of attack. A fundamental issue is the ability to characterize the high-lift flow field, including repeatable flow through flap vents and slots, especially as it is affected by flow from the main wing or flow shed from the fuselage. Analytical tools for this complex flow field are not fully developed, yet this condition is fundamental to effective and safe CV operations. Researchers are gaining a greater understanding and appreciation of shed vortices from complex fuselage shapes, chines, or windscreen and canopy every day.

Achieving a better understanding of high-lift aerodynamics and flow field interactions with and through deployed surfaces can provide a major breakthrough for simplification of wing design while maintaining repeatable low-speed handling qualities, high bring-back weights, and safe boarding rates. It is critical to maintain nonseparated flow over the deployed flap system. This requires further aerodynamic code development and an intense empirical interaction (i.e., wind tunnel test) for reduction to design practice. Figure 3.3 illustrates some of the outstanding problems that have yet to be solved.

Key Enabling Technology

Significant experimental work has been conducted in conjunction with the F/A-18 E/F program. Computer-aided design and analysis has enabled major progress for characterization of the high-lift flow field. An operable Reynolds-averaged Navier-Stokes turbulence model (both two dimensional and three dimensional) has been developed and validated to a large extent in wind tunnel tests. This has been facilitated by developments in processing capability and the ability to define a single three-dimensional solid geometry analytical and design data base for wing-flap-slot systems. Further, advanced test and flow field measurement techniques, such as a laser Doppler velocimeter, have been integrated

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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FIGURE 3.3 High-lift system design problems for current and future fighter configurations. SOURCE: Courtesy of McDonnell Douglas Corporation.

into wind tunnel testing using variants of F/A-18 wing system models at NASA Langley and have added immensely to the understanding of the flow phenomenology. So-called smart structures and shape-memory materials may facilitate implementation of an effective and repeatable design.

Many technical challenges remain. Researchers need to gain a fundamental understanding of off-body flow field bubble formation and its prevention. Vortex control research should be conducted to better understand and facilitate flow field control, as well as repeatable gap vent flow control (between flap surfaces and wing), and solid analytical or empirical correlations are yet to be developed into a closed form design process. This requires extended analysis and wind tunnel testing for a variety of wing and wing flap configurations applicable to carrier-based fighter, support, and surveillance UAV aircraft, in the presence of fuselage or other body flow (e.g., pylon landing gear, door shed flow) at full-scale Reynolds numbers and incidence angles typical of approach conditions. These efforts could be undertaken as part of the naval aerotechnology base maturation efforts and for related programs such as the JSF and the common support aircraft (CSA).

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×
Other Contributing Technologies

A distinct interaction exists between this technology and others described in this report. Many of the wind tunnel flow measurement and analysis tools are applicable to aerodynamic cruise performance research. Lightweight, high-strength composites may be used for complex wing-slat-flap system design and development for all carrier-based aircraft. Integrated flight and propulsion control may be used to maintain excellent handling qualities off the catapult and through trap in the high-lift configuration, including automatic flap control. Dynamic electronic prototyping can be a significant benefit for definition of mechanisms and flap motion for implementation of the particular design, as can many of the same techniques used to facilitate reduced-cost, low-rate production.

Potential Payoffs for Air Platforms

Greater (and repeatable) high lift efficiency is a fundamental design parameter for carrier suitability, especially in the power approach condition. The benefits are direct in terms of lift capability (bring-back load) and approach speed for fighter squadron (VF), attack squadron (VA), and CV-based support aircraft. Such capability provides the naval aircraft designer options to balance payload and approach performance with wing high-lift system design complexity, size, weight, and cost. This extends also to greater safety in carrier operations and could facilitate STOL applications for CVs, air-capable platforms, and land-based patrol squadron (VP) aircraft as well. Successful implementation could also alleviate future shipboard catapult and arrestment gear design requirements (soft cat and trap) to provide significant life-cycle cost savings.

Recommendations

The Navy aerotechnology base should provide validated analytical tools for the complex flow fields (including vortex flow surrounding the fuselage and wings) at high-lift carrier approach conditions. This includes research in flow measurement instrumentation, extension of current laser velocimeter techniques, and testing of complex airfoil and wing-body shapes. Further attention has to be given to development of flow control techniques in this environment.

Extension of the technology into practical solutions and vehicle applications by NAWC and NAVAIR is fundamental to the successful transition of the technology to future operations systems such as the CSA, JSF, and beyond. It is appropriate for systems integration efforts to tie this technology to smart structure developments.

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×

Structures

Lightweight, High-strength Composites

Composite structural materials have long held the promise of significant weight reduction for combat aircraft. Nominally, 10 to 15 percent (by weight) of modern tactical aircraft structure is made of composite materials. The AV-8B and AV-8B+ Harrier aircraft contain roughly 26 percent composites by weight, ostensibly to capture the weight savings leverage for tactical VSTOL capability. Unfortunately, composites are still relatively costly, although they are likely to be more affordable with dedicated attention to capturing the inherent benefits of the material in design, fabrication, assembly, and support.

Current Situation and Constraints

In the majority of applications to date, designers have been inhibited by the availability of proven automated fabrication processes and the need for autoclave cure at relatively high temperature and pressure. As a result, many applications consist of material substitution (i.e., composites for aluminum) with the resultant unimaginative structural design concepts referred to simply as black aluminum. Larger flat skins have been used for wing and tail surfaces, although automated tape lay-up processes enabled introduction of significant curvature for the B-2 bomber and for the AV-8B forward fuselage. Much effort has gone into cocuring skin and stiffeners in the autoclave, but both tools and inspection are expensive and defect correction is even more costly. For the most part, fabrication of composite structures is labor intensive and expensive. Adding to cost and quality issues are considerations of material storage at 0°F and limited storage life (pre-cure). Application of specific materials (fiber and resin combinations) is temperature and load dependent, with high-temperature applications requiring special formulations and load applications requiring attention to fiber strength properties and orientation. In fleet operation, special attention must be given to corrosion prevention and to maintenance and repair techniques applicable to the specific materials used.

Attention to affordability has given rise to new design, manufacturing, assembly, and inspection processes. Through the use of advanced finite element codes and computer-aided engineering, designers are able to use the material properties to produce nonconventional, lighter, and less expensive designs. A number of recent composite structure programs including those at Navy ManTech (the Navy's manufacturing technology development program), NASA, and the composite structure programs associated with development of the JSF are addressing new design fabrication and tooling techniques to realize both weight and cost savings. Navy efforts are focused on V-22, F/A-18, and JSF. Navy ManTech efforts are focused through the Great Lakes Composites Consortium and are

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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making good progress in determining new materials and manufacturing processes.

Certain key characteristics have become apparent across these programs from a technology perspective, most of which relate to the automated production of relatively large unitized structures to deliver the fundamental process quality and reduced numbers of parts, tools, and fasteners.

Key Technology and Enabler: Lightweight, High-strength Composite Structures

Many enablers come into play in this technology. Arguably, it may begin with new high-modulus carbon fibers and new resin systems from the Navy's materials technology base programs, tailored to strength and temperature applications. For stiffened skins, this can include new core material formulations of either foam or honeycomb. Another key is the evolution of design and analysis codes using high-speed processing and facilitated by a single three-dimensional digital solids model for a database to capture feature-based design techniques. This allows the exploitation of material properties for an efficient integrated structural design. These elements are the basis for the newly initiated Advanced Lightweight Affordable Fuselage Structures (ALAFS) program, whose goal is to reduce cost by 30 percent and weight by 20 percent for a major structural element. This structural element will extend from wing-fold to wing-fold and will integrate the fuselage and wing carry-through structure. Figure 3.4 illustrates a

FIGURE 3.4 ALAFS structural concept. SOURCE: Joint Strike Fighter Program Office, Office of the Assistant Secretary of the Navy for Research, Development, and Acquisition, Washington, D.C.

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×

FIGURE 3.5 Fiber-reinforced single-piece inlet duct. SOURCE: Courtesy of McDonnell Douglas Corporation.

concept for a structure for the ALAFS program. The ALAFS structural concept includes titanium hot isostatic press (HIP) cast main landing gear support bulkheads and pylon support fittings, resin transfer molded (RTM) spars and fuselage frames, and unitized syntactic core sandwich inlet ducts and outer moldline skins. The RTM spars are co-bonded to a single-piece fiber steered lower wing skin. The RTM spars contain hybrid laminates for survivability and three-dimensional preforms for out-of-plane loads. The fuselage center section is capped with a cocured dorsal assembly, including skins and substructure.

Of course, the designs must capture the full benefit of available fabrication and tooling concepts, such as advanced fiber placement, stitched resin film infusion, and arc-sprayed composite autoclave tooling. Such manufacturing processes lend themselves to process control and operator verification, rather than postfabrication inspection. Large unitized structures such as single-piece spars, complex single-piece inlet ducts, and skins (with numerically controlled or placed apertures for doors and other access) have been demonstrated in the laboratory to yield first-time quality, with further cost reduction in assembly. Figure 3.5 shows a fiber-reinforced composite single-piece inlet duct.

For more heavily loaded structures, there have been significant improvements in processes for co-cure reinforcement and bonding techniques. Other developments, taken from outside the aerospace industry, show promise for non-critical structural elements. These include chopped fibers, from short-length random orientation to distributed directionally oriented multiple-length fibers, and resin transfer molding.

Much of the effort described is in the concept analysis, laboratory demonstration, or prototype machine stage. Some of this technology has already been incorporated into products such as the C-17, F/A-18, V-22, and F-22. More advanced elements will be incorporated into the JSF, with potential backfit to the

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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F/A-18 E/F. A continuing technical challenge remains to define and characterize material properties throughout a wide temperature range and to evolve designs that can exploit existing and new material properties. This challenge should be at the heart of the Navy's material technology base program. Fabrication process development must be continued and expanded via Navy ManTech programs to reduce the touch labor content and to provide built-in quality using advanced automated process control techniques. For the assembly phase, continued effort must also address joining and bonding techniques and reduced-cost tooling, all worthwhile Navy ManTech objectives. Providing the technology in a state of readiness for platform application and use is the expensive R&D proposition, including investment in technology base and machine tools; it requires a long-term stable commitment by NAWC and NAVAIR and a commitment to transition the technology, as in ALAFS. Finally, no development can be considered complete without a substantial companion effort to improve the damage tolerance and fleet reparability of the resulting products. The processes should be an integral part of the navy technology base.

Other Contributing Technologies

There is a distinct interaction between this technology and others described in this volume. In many respects, this technology will enable attainment of the aerodynamic and signature performance goals by providing a high-fidelity, stable external moldline and tailored apertures. Implementation of this technology is enabled by the use of dynamic electronic prototyping and reduced-cost, low-rate production concepts. Electronic prototyping provides a stable design and analysis tool for the products. At the same time, continued development will require the capability both to model the process technology and to diagnose fabrication process parametrics and implementation. Development of reduced-cost, low-rate production methods goes hand-in-hand with successful implementation of this technology.

Potential Payoffs for Air Platforms

Lightweight, high-strength composites have been proven to have a first-order performance payoff (i.e., weight and size for tactical, vertical lift, and high-altitude surveillance UAVs). Attainment of the goals noted here for this technology would provide a needed extension (i.e., reduced acquisition and life-cycle cost for all air platforms). Success with this technology provides leverage for high-aspect-ratio stiffness critical designs (i.e., it facilitates development and introduction of UAVs) and for very weight critical designs (i.e., it facilitates development and introduction of aircraft employing STOVL, STOL, and VTOL concepts). In addition, the technology can be expanded to submarine, surface

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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vessel, and vehicle applications where balance, corrosion control, or survivability issues may benefit.

Recommendations
  • The Navy materials technology base program explained above should continue to define and characterize materials properties through a wide temperature range. Materials should include high-modulus fibers, high-temperature and extended-shelf-life resin systems, and chopped fiber concepts.

  • The technology base programs have to be integrated with new fabrication and manufacturing processes to eliminate touch labor and emphasize process control for quality. Companion efforts should include fabrication and assembly tooling, and bonding and joining techniques.

  • Additional ManTech program emphasis should be given to integrated design, fabrication, and analysis efforts to provide relatively large unitized structures (reduce the number of parts and fasteners) and employ feature-based design. Both the material technology base and the ManTech programs should focus on damage tolerance design, as well as repair and maintenance techniques.

  • NAWC and NAVAIR should continue efforts to explore design applications to transition the technology and to provide enhanced cost and weight performance for future air vehicles such as CSA, JSF, and surveillance UAVs.

Propulsion

Early jet engines had a single spool where the high-energy exhaust or jet was utilized directly to provide propulsive thrust. The single-spool jet engine consisted of a compressor, combustor, and turbine (generally termed the high-pressure spool). Because of the high-energy jet exhaust velocity, propulsive efficiency was low, particularly at lower aircraft speed. By introduction of a second spool called the low-pressure spool, a portion of the exhaust energy of the high-pressure spool can be used to drive a low-pressure turbine that in turn drives a low-pressure fan, or propeller in the case of turboprop engines, thereby reducing the engine jet velocity and achieving significantly greater propulsive efficiency, particularly at subsonic speeds. However, the technology programs that led to the development of the low-pressure spool were not well coordinated, and progress was slow and costly.

In 1988, the IHPTET program, a joint Air Force, Navy, Defense Advanced Research Projects Agency (DARPA), NASA, and industry effort, was initiated to better coordinate development of more affordable and robust higher-performance turbine engines. Phase I of the program was successfully completed in 1991; Phases II and III are scheduled for completion in 1997 and 2003, respectively. Phase III goals are very aggressive and include improvements of 100 percent in the ratio of thrust to weight for turbofan and 120 percent in the ratio of power to weight for turboshaft engines. Phase III embraces many technologies and is a

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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very comprehensive program for the entire government-industry propulsion team involving all six major U.S. turbine companies. The IHPTET program is an excellent example of the kind of progress that can be made through a coordinated goal-oriented team approach to R&D and is a good model to be used in other technology pursuits besides engines.

Core Engine Performance

In the more than 50 years since the jet engine was first developed, materials technology has contributed more to the steady and dramatic progress in performance, durability, maintainability, and cost than any other technology. During various periods, as much as 50 percent of the improvements made in performance resulted from advances in materials technology, particularly improvements in high-temperature nickel-based superalloys for the hot section and high strength-to-weight titanium alloys for the cold section (less than 1,000°F). The original Whittle and Von Ohein engines were limited to turbine inlet temperatures of about 1,400°F. Today's commercial engines operate at more than 2,800°F. Although turbine airfoil cooling techniques have certainly contributed to this truly noteworthy improvement, most of the increased capability continues to come from materials technology. An increase in turbine rotor inlet temperature is the single most powerful factor in maintaining the steady increase in specific core horsepower generated. Depending on the cycle and configuration, the improvement in specific core horsepower (horsepower per pound-second of airflow) has been utilized for a higher thrust-to-weight ratio in turbojet engines, better fuel consumption in high-bypass turbofan engines, and/or higher turboshaft horsepower per engine weight in turboprop engines.

Before discussing specific recommendations for propulsion technology investments beyond Phase III of the current IHPTET program, consideration should be given to utilizing a more fundamental metric by which to chart progress, as well as to judge whether further technology investments would be fruitful. The metrics of thrust-to-weight ratio and specific fuel consumption have been entirely appropriate for more than 50 years, as long as the configurations have been fairly stable and the only change has been from the original pure turbojet to the turbofan. However, as aircraft configurations evolve to incorporate augmented lift features (e.g., STOL, STOVL, or VTOL and directed energy), the ratio of thrust to weight may no longer be a fundamental measure of platform performance for tactical air platforms and is certainly not a good measure of engine performance. Specific core power and specific weight (weight per pound-second airflow) would be more fundamental measures of engine performance whether the core exhaust gas energy is used to drive a high-bypass fan propulsor, a shaft such as in a helicopter or turboprop, a lift augmentation fan, or a directed-energy weapon.

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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Improving specific core power is dependent primarily on operating at higher turbine inlet temperatures up to the theoretical limits of stoichiometric combustion. Based on current engines in production—if hydrocarbon fuels are assumed—the theoretical limit is up to four times higher than current specific core power figures. Successful achievement of the aggressive IHPTET Phase III goals would result in a specific core power improvement factor of about two, or roughly half of the theoretical limit. Achieving this goal would result in a dramatic improvement in air platform capabilities.

Ideal core performance is based on the ideal Brayton cycle, which assumes 100 percent component efficiencies and no parasitic air consumption (e.g., for cooling and leakage). The foregoing discussion has focused on core engine performance because it is the key enabling technology with the broadest applicability. The technical challenges associated with its achievement are presented below. Several other key enabling technologies and technical challenges are also presented.

Achieving IHPTET Phase II and Phase III Goals
Current Situation and Constraints

The aggressive Phase II goals, and particularly the more aggressive Phase III goals, currently depend heavily on nonmetallics technology. This quest for high-temperature, lightweight nonmetallics has been going on for many years with very limited success—clearly not enough success to permit incorporation into an engine for a manned tactical aircraft. The complete lack of ductility characteristics in nonmetallics has thwarted their utilization in most engine applications to date except for low-strain applications such as cold static parts.

Key Technology Enabler: High-temperature Metals

Conventional wisdom in the industry has been that metals have reached their peak. Consequently, substantial research and development for high-temperature metals basically has been abandoned. However, there are some credible activists in the industry who hold strongly to the view that metals could still be enablers in providing further increases in turbine temperature if R&D levels were increased to stimulate the necessary breakthroughs.

Other Contributing Technologies

Other technology thrusts that could contribute significantly to improved core engine performance include the following:

  1. Improvements in aerodynamic component efficiencies. Aerodynamic  

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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modeling within an engine is far more complex than the already difficult problem of modeling the external flow around an aircraft. Results of these efforts to date have produced dramatic improvements not only in reducing the design or development cycle but also in improving aerodynamic efficiency. It is believed that far more improvements in this technology are possible and could lead to additional improvements in core engine efficiency, not only for steady state but for off-design and transient conditions as well.

  1. Active closed loop flow path control. Unequal heating and cooling of the rotor and stator drive the need for larger tip clearance to prevent case rubs and possible blade failure. By controlling the tip clearance throughout the operating engine, significant improvements in component efficiencies and thus in core engine performance could be achieved. Additionally, surge margin currently must be built into compressors to accommodate transients, inlet distortion, and deterioration. Improvements in closed-loop flow path control could provide overall improvements in efficiency and operability, as well as smaller, lighter components.

  2. Improved cooling. Advanced high-temperature metals technology plus advanced turbine cooling are both critical to increasing turbine temperatures until uncooled metallics or nonmetallics become feasible and practical. The melting point of refractory metal alloys is more than 7,000°F. Currently 20 to 30 percent of core flow is used to cool the turbine metal parts. This represents a substantial penalty when the air that is compressed using turbine energy cannot be used in the cycle to produce core power and, in turn, thrust or shaft horsepower. Improved turbine cooling must therefore be pursued until such time as metallic or nonmetallic materials can be developed that do not require cooling.

  3. Variable cycle engines. Requirements for takeoff, cruise, high-altitude operation, and supersonic operation are different, and ideally, engine cycles should be adjusted for each of these operating conditions. Since this has not been possible in the past, engine cycle selection for any given propulsion system has necessarily been a compromise. A variable cycle engine, in theory, would allow the propulsion system to be optimized for each specific flight condition. This of course is very simplistic and may not be entirely possible. Variable cycle engines, however, have been studied for many years in an effort to achieve some degree of cycle flexibility. To date, the complexity required to achieve a variable cycle engine appears to outweigh the benefits. However, most of the work to date has been proprietary to each propulsion company, and it has been difficult to obtain a fully objective assessment of the practicality of a variable cycle engine. An appropriate forum should be established involving the industry and other experts to examine variable cycle concepts realistically and fully for the purpose of making such an assessment. Figure 3.6 shows a schematic diagram of a variable cycle engine.

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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FIGURE 3.6 Schematic of a variable cycle engine. SOURCE: Courtesy of General Electric Aircraft Engines.

Potential Payoffs for Air Platforms

The payoff in improved core engine performance from aggressive pursuit of these technologies would have a dramatic effect on increasing the range and payload capabilities and reducing the size and therefore life-cycle cost of carrier-based CTOL and STOL or STOVL tactical aircraft, as well as removing other surface constraints to effective VTOL tactical aircraft operations.

Recommendations

The panel recommends that a comprehensive program be established modeled after the highly successful IHPTET program, to organize and fund coordinated research into each of these technology areas for improving core engine performance with goals for specific core power and specific weight that are 50 percent better than the IHPTET goals for 2003. Specifically, this program should address the following:

  • High-temperature metals and nonmetals. It is strongly recommended that basic R&D in metals technology be significantly increased without restricting funding for what may be the very long term solution, namely, nonmetallics. The difficulties associated with practical designs utilizing nonmetallic materials that have almost no ductility are monumental, and these materials have yet to demonstrate sufficient progress for the majority of aircraft engine requirements. It is therefore recommended that R&D on nonmetals be targeted initially for use in expendable engines. Since the parts are smaller and development turnaround time is faster, the technology could be advanced more rapidly and at a more reasonable cost in expendable engines. In the meantime, research on high-temperature

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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metals has to be accelerated if progress is to continue in improving core engine performance.

  • Component efficiencies, flow path control and cooling improvements . Continued R&D in these areas is essential to achieving the potential payoffs that lead to realizing the panel's vision of a lower-cost, more vertical and dispersed naval air capability at sea.

  • Variable cycle engines. Although the chances of achieving a cost-effective variable cycle engine in the near term are probably remote, the payoff could be extremely significant to the air platforms of 2035, and it is therefore recommended that R&D be continued in variable cycle engines through a multicompany demonstrator engine program to fully explore and validate promising design concepts.

  • Environmental implications. The panel was charged to consider environmental implications for new platforms and technology thrusts. From a propulsion perspective, the panel recommends that specific goals be established, as part of further IHPTET phases, for reduction in turbine engine emissions: NOx reductions for aircraft engines and CO reductions for surface engine applications.

Adapting Large-engine Technology to Small Engines
Current Situation and Constraints

Scale effects make it difficult to apply large-engine technology to small engines. Clearance tolerances, which account for leakage losses, tend to remain constant regardless of engine size, and their impact relative to the small size of each airfoil or similar element is proportionally greater. Therefore, reductions in manufacturing tolerances and improved closed-loop flow path control can provide even greater improvements in transient aerodynamic modeling. For similar reasons, full-range aerodynamic modeling is even more important in small engines than in larger ones.

Technology Enablers

Additional R&D in full-range transient modeling and in reducing manufacturing tolerances is needed to enable small engines to benefit fully from technology improvements in large engines.

Potential Payoffs for Air Platforms

The Navy has unique requirements for small, heavy-fuel engines compared to land-based engines that run on light fuels. Engines for ship-based UAVs are but one example of this need. The inherent advantages in performance, weight, and reliability of turbine-powered engines, compared to reciprocating engines, coupled

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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with the adaptation of large-engine technologies would provide a very attractive and effective engine option for ship-based UAVs for reconnaissance and tactical strike, as well as for powering marine ordnance. For example, modest technology advances could yield significant improvements over today's small engines, including greater than 2:1 power-to-weight ratio, fuel economy competitive with diesels, and high reliability (time between overhaul > 3,000 hours).

Recommendation

Apply large-engine technology to small engines by funding a heavy-fuel (JP5), small-engine demonstrator program with the following goals:

  • Installed horsepower per weight ≥ 2.0,

  • Specific fuel consumption ≤ 0.5, and

  • Time between overhaul > 3,000 hours.

Integrated Flight and Mission Control

Integrated Flight and Propulsion Control

Air vehicle designers have traditionally sought to provide inherent static and dynamic stability as well as controllability through fixed and movable airfoils. A good balance between inherent stability and controllability, based on consideration of size, operating speeds, and mission maneuvering requirements, was the measure of a designer's success. The objective in design integration of the propulsion system was to minimize the impact of propulsion on these other important design objectives, that is, to decouple propulsion from the stability and control equation and let the pilot be the flight integrator of control and propulsion through manipulation of stick and throttle. This traditional approach to the design of air vehicles has limited the space available to tactical aircraft designers.

Current Situation and Constraints

Current technology in aerodynamics; high-strength, lightweight materials; computers; and high thrust-to-weight ratio engines has greatly expanded the potential design space for combat aircraft. Evolutionary improvements in flight and propulsion control—from manual and boosted controls to digital, fly-by-wire systems—have allowed static and dynamic stability margins to be relaxed, which has opened up some of this new design space to designers. It has, for example, allowed the size, weight, and resultant structural strength requirements of aerodynamic stability and control devices to be reduced, making possible lower-cost, lighter-weight, high-performance fighters such as the F-16 Falcon. It has also allowed the use of destabilizing leading-edge extensions (e.g., on the F/A-18

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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Hornet) and canards (e.g., on some European fighters), to be used effectively to enhance maneuverability.

Although digital fly-by-wire control may have opened up additional design space for low-cost, high-performance aircraft in the heart of the flight envelope and at higher speeds, traditional aerodynamic stability and control devices lose effectiveness at extremely low speeds. VSTOL or VTOL aircraft such as the U.S. Marine Corps AV-8 Harrier and Russian YAK-38 Forger have overcome this problem by integrating, to some degree, the use of thrust vectoring both for propulsion or lift and for stability and control of takeoff and landing, and they have operated very successfully aboard ship. However, they still depend on conventional aerodynamic surfaces for stability and control at higher speeds and thus incur a penalty in range, weight, complexity, and cost for their VTOL capability over conventional tactical aircraft. The F-22 has taken integrated flight control a step further through the introduction of flight and vehicle management system concepts and mechanical pitch thrust vectoring, which is a by-product of its low signature afterburner nozzle design.

Key Technology Enabler: Multiaxis Thrust Vectoring

The X-31 program demonstrated the potential for multiaxis thrust vectoring to increase the maneuvering capability of conventional jet aircraft designs dramatically. The stability and control power of multiaxis thrust vectoring not only eliminate the drag, structural, signature, and weight and balance impacts of traditional tail section design but also greatly expand the usable flight envelope, particularly on the low-speed end. Designs having vectoring nozzles, particularly when combined with canards, enable thrust to augment lift for STOL and tighter low-speed tactical maneuvering. Vectoring nozzle designs open the door to thrust reversing for landing, which may also be employed beneficially in tactical maneuvering. The key is to approach flight control and propulsion from an integrated design perspective. This requires not only additional R&D but also further relaxing of existing stability and control requirements if designers are to take full advantage of these and other technology advances in future Navy tactical aircraft.

Other Contributing Technologies

The challenge in any design effort is to use available technologies creatively to achieve a high degree of synergism between the technical approaches employed to satisfy competing requirements. Nowhere is this more true than in aircraft design, where the cost, weight, and performance penalties of design compromises are so high. As in the F-22, there is potentially a high degree of synergism between vectoring nozzles and signature suppression. Likewise, there is potentially a high degree of synergism between signature reduction and the use

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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of thrust vectoring for stability and control of tailless aircraft, as well as enhancing cruise performance. Strong synergistic effects between thrust vectoring both for lift augmentation and stability and for control and improved low-speed aerodynamic performance, including STOL and VTOL performance, are also possible. In thrust vectoring itself, there is the potential to reduce synergistically the weight, complexity, and cost of mechanical vectoring, as well as the signature, through the use of fluidics. However, achieving this level of design integration and optimization in a timely manner and at an affordable cost is going to depend on the development of advanced design tools such as dynamic electronic prototyping.

Potential Payoffs for Air Platforms

The potential payoff of integrated flight control for ship-based tactical aviation includes not only the air platform itself but also the carrier. Reducing the vehicle weight, complexity, cost, and performance penalties for STOL could significantly reduce ship catapult and arresting gear performance requirements and, in turn, carrier aircraft structural weight and cost penalties, making common Navy, Marine Corps, and Air Force tactical aircraft designs a truly achievable objective. Stealthy, tailless STOL airplanes having good low-speed, level 1 handing qualities and improved cruise performance in reasonably sized, affordable, and survivable manned tactical aircraft would go a long way toward restoring the Navy's deep-strike capability. Even greater increases in range and reductions in size and cost could be achieved by manning such aircraft remotely. The key to achieving these payoffs, however, is well-coordinated, objective-oriented, long-term R&D in integrated flight control and design tool technologies.

Conclusions

The principal technology shortfall in flight control today is in low-speed stability and control. Achievement of a more affordable, vertical STOL or STOVL capability in the future will require substantial improvement in the technical approaches to attaining low-speed level 1 handling qualities, particularly for takeoff and landing under adverse conditions, that do not compromise stealth. A follow-on to the X-31 technology demonstration program has to be pursued to develop and exploit the applications of thrust vectoring to integrated flight stability and control for both signature reduction and STOL or STOVL capabilities beyond that currently planned for JSF.

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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High-capacity, Long-range Data Links
Current Situation and Constraints

Increasingly, the Navy is shifting to an operational concept wherein surveillance and targeting sensors are separated physically from the command node location, which in turn may be remote from the weapons launch platform. In the case of air platforms, no longer will the sensors, commander (pilot), and weapons necessarily be co-located in a single aircraft. Further, third-party targeting data sources and weapons magazines are proliferating. Examples of this evolving trend appear in such concepts as forward pass, cooperative engagement capability (CEC), the arsenal ship, and the piping of tactical situation data derived from a variety of off-board sources directly into cockpits.

This evolution offers promise for major improvement in the tactical flexibility and combat effectiveness of air platforms. Realization of this promise is not without challenges, however, because the operational concept is inhibited by the gross inadequacy of traditional communications equipment. To realize the potential benefit of this new concept, communications systems must be capable of reliable transmission of large amounts of data. They are now constrained by a lack of (1) bandwidth necessary to accommodate high-resolution imagery transfer; (2) processor capacity needed for target recognition and interpretation; (3) memory sufficient to handle massive amounts of archival data; (4) software to search the network quickly in order to provide commanders with tailored tactical information in a timely manner; and (5) for stealth reasons, the means to minimize signal emissions and the adverse impact of aperture size.

Key Technology Enablers

The Navy requires high-capacity, long-range data links that are reliable, secure, and supported by intelligent control, processing, and information search software. Fortunately, commercial technology in this area is experiencing explosive growth and the Navy can therefore leverage this development. Such data links can be leased directly or derived technically from the evolving worldwide, wideband commercial satellite and fiber networks, and from their supporting commercial terminals, switches, and stewardship software. Bandwidths have already grown from tens of kilobits to tens of megabits per second in five years; network routing is increasingly flexible and transparent to the user; addressing and formats are routine and network independent; and software agents routinely aid in search and analysis of data and in executing orders.

Payoff Potential for Air Platforms

High-capacity, long-range data links will permit physical separation of command,

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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targeting, weapons control, and weapons delivery functions from the platforms performing these functions. Operational commanders will therefore be accorded vastly increased flexibility in employing air platforms. Introduction of this technology will accelerate the acceptance and employment of UAVs by the Navy and Marine Corps and will make available real-time tactical information to air crews and commanders. In summary, high-capacity, long-range data links that are reliable, secure, survivable, and countermeasure resistant are essential to opening up new air platform options for naval forces in the year 2035.

Recommendations

The Navy's task is to exploit commercial wide-band space and surface networks as well as special-purpose systems being developed by other Department of Defense (DOD) agencies. It must do this while maintaining the demanding link survivability and countermeasure-resistant performance required by mobile naval forces. This will involve the following:

  • Monitoring industry and DOD organizations closely to keep abreast of fast-paced developments there;

  • Encouraging industry to install features funded by the Navy that will facilitate Navy-unique exploitation of the technology; and

  • Investing directly in focused projects that adapt these commercial technologies to the needs of naval aviation platforms, including developing antennas to prevent compromising stealth features of air and ship system nodes.

Signature Reduction

RF Signature Reduction

Reduced radar signature has been recognized for a number of years as a tactical advantage when operating against a radar-equipped enemy. A reduced signature enables combat leverage by collapsing an enemy decision and reaction time line. The leverage is beneficial for both improved lethality and improved survivability.

Current Situation and Constraints

A number of reduced radar signature aircraft are operated today—some reduced to a greater extent than others. Many would suggest that we are in the third generation of the applying this technology. First-order effects are attained through shaping, then by application of radar-absorbing materials and/or use of specially designed radar-absorbing structure. A corollary benefit may be to enhance the effectiveness of electronic warfare systems as an integrated package. The open

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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literature suggests that countertechniques may employ bistatic (receiver in a different location than transmitter) and electro-optical or infrared systems. These add to the challenge of providing a robust solution but are not without their own physical and operational difficulties. Analytical and design codes have been useful in determining proper moldline shapes and material applications and in characterizing new material and structural systems. These codes are challenged by the breadth of the problem to be addressed when considering bandwidth and the number of potential design solutions or material applications. Massive processing capability is imperative, and next-generation code development must be addressed. Of course, a companion issue is validation, which brings into focus the necessary test, modeling, scaling, and diagnostic capabilities necessary for effective and affordable design solutions. Finally, field experience suggests the need for improved fleet diagnostic, maintenance, and repair capability, as well as improved damage tolerance for some of the materials.

Key Technology Enabler: New Design and Analysis Codes

Advanced code development is progressing, enabled by substantial improvements in computational technology. Such systems employ massive core capability and provide for relatively rapid processing. This technology may be the fundamental enabler for continued progress in signature reduction as well as for product definition. Application of codes and processing techniques facilitates definition of new material properties, manufacturing processes, system applications, and test measurement techniques.

Remaining challenges, from both a design and a technology perspective, include reducing the number of apertures; elimination or mitigation of gaps and protuberances; providing lightweight, robust materials and attachment systems; and analytical or empirical correlation of test results to full-scale applications. Additional issues include maintaining a balance between shape and aerodynamic, structural, and vehicle handling performance.

Other Contributing Technologies

Signature reduction interacts with several other technology areas discussed in this report. An integrated vehicle design demands attention to aerodynamic cruise performance, high-lift aerodynamics, and IR signature reduction. Aerodynamic codes have an analogue in electromagnetic codes. Some particular vehicle applications may be facilitated by incorporation of integrated flight and propulsion control. Certainly, the technological progress in lightweight, high-strength composites; dynamic electronic prototyping; and reduced-cost, low-rate production facilitates development and incorporation of this technology.

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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Potential Payoff for Air Platforms

Continued progress and successful incorporation into new vehicle design will provide improved lethality and survivability of tactical combat and airborne reconnaissance systems, with attendant reduced acquisition and support costs. Application of the technology to other naval systems should provide a greater combat detection edge across the board.

Recommendations
  • RF signature reduction efforts should be focused on providing advanced, wide-band, material systems as an integrated design solution. This implies continued advance code development and validation, including improved experimental modeling, scaling, and diagnostic techniques.

  • Additional efforts are required to provide quick turnaround and user-friendly fleet diagnostic, damage repair, and maintenance techniques.

  • Integrated R&D and design efforts should be focused on reducing the number of apertures and generally providing greater moldline fidelity and continuity. The design and application effort should include integration of vehicle shaping and material systems for future air vehicles such as the JSF and advanced combat and surveillance UAVs.

IR Signature Reduction

Infrared signature reduction has lagged RF signature reduction in the past, largely because of the weight, complexity, and cost of the technical approaches pursued, such as direct shielding and active cooling. The relatively higher IR signature levels have tended to compromise achievements in RF stealth by enabling IR detection and tracking for missiles and cueing for RF sensors to counter RF stealth. Reducing IR detectability, especially in the medium- and long-wave spectra (3 to 5 and 8 to 12 µm, respectively), to levels comparable to RF detectability would eliminate the use of IR as a countermeasure to RF stealth and greatly increase the overall effectiveness of current RF stealth technology as well as reopen low-altitude airspace to strike operations. However, achieving these levels of IR stealth will require a complete rethinking of the problem and a coordinated R&D program to bring together all of the technologies that can contribute in a synergistic way to a more cost-effective IR stealth approach.

Current Situation and Constraints

To some extent, special paints or coatings can reduce airframe emissions at their design wavelengths, but not to levels of detectability comparable to RF stealth. Special passive surface treatment of exposed metal engine parts potentially

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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can do the job in the rear quadrant, but the physics employed in this surface treatment is not a practical solution for the rest of the airplane. There are also manufacturing challenges and questions about long-term degradation in a sooty, hot gas environment that still have to be resolved, and further R&D is needed before such surface treatments can be put to practical use on engines.

Key Technology Enabler: Thin-film Coatings

The Department of Commerce is currently pursuing an advanced technology program (ATP) in thin-film technologies to replace paint on aircraft. Preliminary results indicate that thin-film coatings will be more durable than paint, will offer savings of up to 25 percent in unit cost and 50 percent in life-cycle cost over conventional aircraft painting, and will virtually eliminate the toxic vapor and waste problems associated with painting and stripping operations. In addition, additives can be put in the film adhesive to inhibit corrosion, which when coupled with a more protective coating could provide very significant reduction of aircraft skin corrosion problems. However, the most significant aspect of film coatings for military aircraft is that the same passive surface treatments used for engine parts could easily be applied to film surfaces in the manufacturing process and potentially produce the same results that have been achieved on engine parts. Used together, surface treatment of exposed engine parts and airframe film coatings could have the potential to reduce the level of IR detectability to that of RF.

Other Contributing Technologies

Although the physics of the passive surface treatments involved is understood, substantial R&D work remains to be accomplished to get them into production. The techniques used to fabricate treated metal surfaces for testing are not necessarily suitable for manufacturing actual engine parts. The effects of exhaust gas contamination need to be investigated and ways found to mitigate this if it proves to be a problem. Likewise, film top coatings have to be optimized for the long-term durability of the film and the effectiveness of surface treatments in an operating environment, which includes intense sun and rain exposure, as well as exposure to dust, salt, solvents, and other contaminants. Techniques for application, repair, and removal likewise have to be optimized. Although some of this is being addressed in the Commerce Department's ATP, signature aspects are not. These aspects include not only the environmental effects on surface treatments but also the development and refinement of analytical tools to model and optimize such treatments in both the IR and the visual spectra.

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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Potential Payoff for Air Platforms

There is potentially a very strong synergistic payoff for naval aviation in thin-film technology as a replacement for paint, in terms of both life-cycle costs and corrosion protection and of significant reductions in IR and visual signatures for no more weight and half the life-cycle cost of paint, excluding the hazardous materials cost aspects of paint. The potential payoff is even more dramatic when the cost, weight, and impracticality of active cooling required to achieve the required levels of IR signature reduction are considered; these are well beyond the capabilities of today's special paints. Bringing IR detectability back into balance with RF would leverage the investments already made in stealth and could nullify the shoulder-mounted IR missile threat in the types of Third World challenges where the risk to U.S. aircrew is an important political consideration in deciding whether or not to engage. This technology would also be applicable to ships and other craft or vehicles needing protection against IR detection and IR missiles.

Recommendation

The Department of the Navy should initiate a comprehensive IR signature reduction program to coordinate research in film coatings, as well as other surface treatment techniques, with the objective of reducing aircraft detectability by IR sensors to levels commensurate with current and projected detectability by RF sensors. The opportunity exists for the Navy to leverage ongoing research into thin-film coatings as a paint replacement by investigating how such coatings can be used for signature control as well as corrosion protection.

Design and Manufacturing Processes

Dynamic Electronic Prototyping

Tremendous strides have been made in advancing the state of the art in computer-aided design and manufacturing. Designers can now work in a three-dimensional design environment that automatically highlights component fit and interference problems, which greatly accelerates the design process. Completed CADAM designs can now be transmitted directly to automated production equipment on the factory floor to fabricate parts and speed up the manufacturing process. However, aircraft design is still dependent on building developmental flying prototypes to validate performance and weed out functional integration problems. This process adds years and billions of dollars to development time and cost, and to life-cycle costs, and mission performance can be affected when basic design problems are discovered too late in the development process to be fixed properly. The current, iterative design, build, test, analyze, and fix approach

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×

to aircraft development is expensive and time consuming and accounts for a significant percentage of the 15 years typically required to field new aircraft.

Current Situation and Constraints

Commercial advances in modeling and simulation software over the past few years, particularly in support of the entertainment industry, have far outstripped those made in the previous 20 years in support of defense aerospace. Although much of this commercial progress has been in visual effects, the underlying software is equally applicable to defense modeling and simulation needs and has, in fact, contributed to our current national war gaming simulation capabilities. Virtual reality, a laboratory novelty five years ago, has already been employed effectively in evaluating human factors aspects of NASA space station designs and commercial ship designs. Campaign models, such as those used to plan Desert Storm operations, and, to a lesser extent, system effectiveness evaluation tools have also benefited. Despite the advances in modeling and simulation capabilities and in CADAM capabilities, the two have not been integrated, and aircraft designers and engineers still rely on separate specialized software tools for just about every aspect of design development.

Key Technology Enabler

The three principal software tools used in aircraft development are three-dimensional CADAM for design, finite element analysis for structural engineering, and computational fluid dynamics for aerodynamic optimization. A number of additional software tools are used in the process, however. For example, there are separate codes for modeling RF stealth effects and computational means of modeling just about every other conceivable aspect of aircraft design from airframe aeroelasticity and avionics to hydromechanical subsystems and basic material properties. There has been no strong commercial incentive, however, to commit the talent, time, and money to pull all of these tools together into a common, integrated, user-friendly program for designers and engineers, and this is unlikely to happen anytime soon without strong government sponsorship and funding support.

The computational power and modeling codes required for electronic prototyping already exist and, if properly integrated, would allow the Navy to build high-fidelity fully functional prototypes in cyberspace and test them for proper operation under simulated dynamic environmental conditions. This would allow the design and engineering to be refined and matured on the computer an order of magnitude faster than the design, build, test, analyze, and fix process used today in the development of new aircraft. Subcontractors could submit functional software models of their proposed components in a standardized format that

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×

would permit rapid installation and functional checkout in the electronic prototype. Weight and balance and cost data could be updated, and subsystem and component failure modes could be exercised in a total system context. Fault isolation system checkouts could be performed, and component installation, removal, and replacement could be evaluated to optimize maintainability. In fact, the entire manufacturing process could be planned, evaluated, and optimized on the computer well in advance of committing to tooling.

Other Contributing Technologies

Although many of the engineering software tools already exist, their integration will likely require development of a prototyping software architecture and a user-friendly system of templates for inputting design, material, functional characteristics, and other data. The underlying models need to be compatible with the new modeling architecture, and new models may have to be created to fill in any missing elements such as gust loading, carrier wake turbulence, and field runway effects. The objective would be to model both the aircraft and its operating environment as closely as possible yet still allow lower-fidelity preliminary designs to be exercised to facilitate the design and engineering optimization process. The concept is to provide engineers with a means of quickly quantifying performance, weight, producibility, and cost tradeoffs as the detailed design evolves.

Potential Payoffs for Air Platforms

Historically, new aircraft development programs get into trouble because the performance, weight, and cost implications of the selected design and technical approach are not known in sufficient detail early enough in the development process to achieve the stated operational requirements within the program's schedule and remaining funds. Dynamic electronic prototyping would close this information gap. The performance, weight, and cost of the selected design and technical approach could be quantified early, allowing program time and budget to be spent productively on achieving stated requirements and making a smooth transition to production. High-fidelity dynamic electronic prototypes would also facilitate the development of variants and, if maintained for each operating configuration, could be used to engineer and test engineering change proposals, update support, and investigate in-service problems. Thus, electronic prototyping not only would reduce development time costs and risks but also would reduce life-cycle costs and facilitate in-service improvements in combat capability and readiness to extend the airplane's useful service life. These benefits would apply to the use of electronic prototypes in the design, development, and life-cycle support of ships and submarines as well.

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×
Recommendation

The development and integration of the software necessary to perform dynamic electronic prototyping must be recognized as a major software engineering undertaking and handled in much the same way as other major new acquisition programs. To be successful, it must be pursued as a team effort, combining the talents of the aerospace industry and the ultimate user, as well as expertise from the commercial software industry, universities, and government. The panel recommends that such a program be organized and funded as a multiyear effort, with high-level Navy Department or DOD sponsorship. The program will require a well-staffed Navy program management office, capable of organizing, integrating, and contracting for the scope of effort required from the exceptionally wide range of technical expertise that must be brought to bear to define the requirements, do the research, design the architecture, set the standards, and write the core software and application programs necessary to achieve a true high-fidelity dynamic electronic prototyping capability.

Reduced-cost, Low-rate Production

A dramatic change has occurred in the defense industry: namely, rates of production have reached record lows, and affordability, or cost, is a dominant parameter. Conventional wisdom suggests that costs increase naturally as the quantity and rate of production decrease. Significant advances in design, fabrication, assembly, and tooling process technology are needed to enable affordable modernization of our combat forces.

Current Situation and Constraints

Most air vehicle production practices are the outgrowth of those employed while the United States was increasing force structure significantly in response to a Cold War threat and to serious regional conflicts (e.g., Korea and Southeast Asia). Significant defense buildups resulted in significant quantities of weapons systems and weapons. For example, in the late 1960s, the F-4 Phantom production rate reached 72 per month. Today's production rate peaks at 24 per year for the F/A-18 and less for other systems. In addition, the aerospace industry has experienced massive contraction (40 percent reduction in jobs) and consolidation, raising significant issues of maintaining job skills on the shop floor and retraining the current production work force. Legacy systems, processes, and production operations are labor intensive by tradition. Reworking and cost of quality have been the norm. Traditional approaches led to a high number of parts, tools, fasteners, and station moves (of subassemblies) and to the introduction of errors. Having more operations required in the system is a fundamental contributor to more mistakes.

Quality-enabling techniques, first introduced into the commercial world, are

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×

FIGURE 3.7 Design for manufacturing and assembly: the F/A-18 E/F, a true success story. SOURCE: F/A-18 E/F Program Office, Naval Air Systems Command, Arlington, Va.

now finding their way into the defense business. The use of computer-aided design is a basic enabler for development of a single, three-dimensional, solid model database used for design, analysis, tooling design, and manufacturing (both fabrication and assembly). A fundamental requirement for achieving high-quality, low-cost, low-rate production is to exploit the digital database and its resultant electronic mockup. Techniques include feature-based design and design for fabrication and assembly using the most modern fabrication and tooling processes to facilitate cost savings, as well as a step function reduction in the number of parts, tools, and fasteners in an assembly or subassembly. An example is the F/A-18E/F, where concentration on design for manufacturing and assembly and new fabrication techniques have led to increased quality and a significant reduction in parts count; see Figure 3.7.

Key Technology Enabler: Large Unitized Structures

The panel has chosen to label large unitized structures as a key technology. More appropriately it may be labeled a key technology result or a technology process driver. This means that large unitized structures represent an approach to significant quality improvement and cost reduction, enabled primarily by

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×

computer aided design technology and, as an adjunct, dynamic electronic modeling.

These elements lead to a definition of the required process technology for integrated design, machines (fabrication), tooling, and assembly processes. These draw on such technological progress as high-speed machining and superplastic forming for metals, fiber placement and stitched resin infusion for composites, development of composite tools with a metallic vapor barrier for the autoclave, use of laser theodolites for assembly with a closed loop to the design database, computer-aided work instructions and superimposed virtual image registration for assembly, and use of stereolithographic processes to develop investment castings. These examples, some of which are depicted in Figure 3.8, are merely starting points. Significant challenges remain for joining technology (welding, bonding, electromagnetic drives for rivets); high-speed machining and cutter development for hardened metals (titanium and steel); tooling (expendable tooling, tool costs, and tool life); and supportability and maintainability of large unitized structures. All of these elements should be the focus of an enduring Navy Man Tech program.

FIGURE 3.8 Examples of manufacturing process initiatives. SOURCE: Courtesy of McDonnell Douglas Corporation.

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×

FIGURE 3.9 Bottom line results: benefits of design in manufacturing and assembly realized in the C-17 transport program. SOURCE: Courtesy of Wright Laboratory Manufacturing Technology Directorate, Wright Patterson AFB, Ohio.

Other Contributing Technologies

The above technology set interacts with several others in this report. Principal enablers exist via dynamic electronic modeling. Results of progress here affect virtually every element previously noted and have a direct interplay with the area of lightweight, high-strength composites.

Potential Payoffs for Air Platforms

Success in this area can have a first-order effect on force structure modernization through reduced cost of acquisition and ownership. Product quality and performance (weight) should also improve markedly. This may, indeed, be the single most important leverage for future defense systems, not only for air platforms but also across the board as the principles are applied. One prominent example is a newly redesigned C-17 horizontal tail, which has realized significant cost and weight reductions; see Figure 3.9.

Recommendations
  • Navy Man Tech efforts should emphasize the principle of reduced parts, tools, and fasteners in the development and manufacturing processes for both metallic and composite structures. Manufacturing process development should be conducted to extend high-speed machining from aluminum to hard metals

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×

such as steel and titanium. Joining techniques, such as diffusion bonding and friction-stir welding, should be exploited to provide quality subassemblies and assemblies and to provide leverage for the use of near net shape casting and HIP forgings. Advanced casting and forming techniques should be exploited for repeatable large-part production, and should focus on producing near-net-shape parts to eliminate both material waste and machine time.

  • Advanced tooling concepts should be explored in conjunction with the fabrication and assembly techniques noted here and in the discussion of composite structures. The guiding principles should be expandable-rate tooling (i.e., suitable for low rate, modified at some later point for increased rate) and reduced number of unique tools (via design for assembly and integrated manufacturing processes to obviate assembly steps, e.g., high-speed machine subassembly to eliminate sheet metal buildup).

  • Integrated design and production efforts should be modeled, along with process cost, to allow cost-based decisions up to and including factory layout to reduce production cost and cycle time.

SUMMARY OF ENABLING TECHNOLOGIES

Table 3.2 lists the 12 key enabling technologies identified by the panel and indicates their impact on important air platform characteristics and costs. Aggressive development of these technologies will affect acquisition and life-cycle costs positively and in a major and fundamental way. Developing these technologies is essential to improving key aircraft design attributes such as cruise, takeoff, and landing performance and to enhancing combat survivability, particularly in subsonic speed regimes.

Applications of Enabling Technologies

These enabling technologies are applicable to manned and unmanned designs, and to conventional as well as various short or vertical takeoff and landing concepts. Further, they permit physical separation of command, targeting, sensor, weapons carriage, and weapons control functions from the platforms, air or surface, that perform the functions. Table 3.3 shows how these technologies affect the development of new concepts.

Although these technologies also apply to the kinds of aircraft operating or being developed today, they were selected because they open up future aircraft and carrier platform options that are not otherwise attainable with current programs and R&D plans. Developing the proposed enabling technologies and exploiting the platform options thus opened up could move naval aviation, in the years ahead, in the following directions:

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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TABLE 3.2 Air Platform Characteristics and Costs: Impact of Enabling Technologies

Enabling Technology

Greater Endurance and Range

Higher Thrust-to-Weight Ratio

Lower Landing Speed

Enhanced Survivability

Less Development Time

Reduced Acquisition Cost

Lower Life-cycle Cost

Laminar flow control

X

X

X

High-lift aerodynamics

X

Lightweight, high-strength composites

X

X

X

X

X

Core engine performance

X

X

X

X

Variable cycle engine

X

X

X

X

X

Adapting large-engine technology to small engines

X

X

X

Integrated flight and propulsion control

X

X

X

X

High-capacity, long-range data links

X

X

RF signature reduction

X

X

X

IR signature reduction

X

X

X

Dynamic electronic prototyping

X

X

X

X

Reduced-cost, low-rate production

 

 

 

 

X

X

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×

TABLE 3.3 Aircraft and Air-Capable Ship Concepts: Application of Enabling Technologies

Enabling Technolgy

Subsonic Aerial ''Truck"

STOL

Enhanced VTOL

Enhanced STOVL

UAV Long Endurance

UAV Sea-based Support

UAV/Sea-based Strike Fighter

Reduced Dependence on catapults and Arresting Gear

Broadened range of Viable CV Sizes

Increased CV Configuration Options

CV/LHD Hybrid

Laminar flow control

X

 

 

X

High-lift aerodynamics

X

X

X

X

X

X

X

X

Lightweight, high-strength composites

X

X

X

X

X

X

X

X

X

X

X

Core engine performance

X

X

X

X

X

X

X

X

Variable cycle engine

X

X

X

X

X

X

X

Adapting large-engine technology to small engines

X

X

X

Integrated flight and propulsion control

X

X

X

X

X

X

X

X

X

High-capacity, long-range data links

X

X

X

X

RF signature reduction

X

X

X

X

IR signature reduction

X

X

X

X

Dynamic electronic prototyping

X

X

X

X

X

X

X

Reduced-cost, low-rate production

X

X

X

X

X

X

X

 

 

 

 

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×
  • Systems that embody performance enhancements principally in air weapons and sensors instead of the platforms themselves.

  • Subsonic aerial trucks as weapons carriers, target designators, and sensor platforms. Here, speed and maneuverability would no longer be principal design drivers. Also, the truck concept will facilitate improved cruise and endurance characteristics and make signature reduction more easily achievable and less costly.

  • A more vertical force—VTOL, STOVL, and STOL. The mix of such platforms and CTOLs will be determined by the success of vertical designs in fleet operations and the size and configuration of future aviation ships.

  • Widespread use of land- and sea-based UAVs for surveillance, reconnaissance, targeting, and a variety of support missions. UAVs for lethal purposes may follow.

  • Reduced dependence on high-capacity catapults and arresting gear.

  • A mix of aircraft carrier sizes.

Fighter and Attack Missions

Exploiting the enabling technologies will facilitate a shift in emphasis from an overfocus on platform performance to a focus on weapons, sensors, and communications. Thus, a fighter or attack aircraft in the future need not be a wholly self-contained system that can do everything on its own. Instead, it can serve as a de facto reusable intermediate stage of a broader weapons system in, for example, the role of weapons carrier, or solely as a sensor platform controlling missiles launched from ships, land sites, or arsenal airplanes. Such platforms also can be manned or unmanned.

Subsonic Aerial Trucks

The need for high-speed, very maneuverable, and, consequently, expensive air platforms would be minimized by substituting utilitarian subsonic trucks that incorporate modular mission change packages where sensible. These trucks may or may not have on-board sensors, depending on the mission. They could draw on tailored off-board information derived from long-endurance UAVs, satellites, Air Force platforms, national technical means, and other battle group assets. The aerial truck concept is also an attractive candidate for the several nonlethal support missions now flown by sea-based aircraft.

The subsonic truck has the cost advantage of being less expensive to develop, manufacture, and operate than vehicles in today's high-speed fleet. Given improved laminar flow techniques and advances in engine efficiency, improved cruise and endurance performance is ensured. Placement of propulsion components is simplified, which in turn will facilitate the development of STOL vehicles and improvements in VTOL and STOVL designs.

A shift to predominately subsonic air platforms also facilitates the achievement

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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of reduced RF and IR signatures in future designs. This is attributable to greater flexibility in airframe shaping, application of signature-reducing coatings, placement of engine inlet and exhaust ducts, placement and shaping of sensor and communications apertures, and in the instance of a weapons-only arsenal truck, elimination of radiation by sensors and communications.

More Cost-efficient Systems

The acquisition cost for future aircraft needed to carry out today's fighter and attack missions can be reduced by eliminating the high-speed flight requirement, no longer essential tactically or for survivability and employing advanced design and manufacturing processes. Operating costs will be lower because of the better aerodynamic cruise performance of new subsonic designs, as well as improvements in engine-specific fuel consumption. Combining these attributes with reliable and secure, high-capacity, long-range data links will yield a force that is less costly overall to procure and operate, on a dollars per target killed basis, than today's technology allows.

Unmanned Aerial Vehicles

UAVs offer obvious great potential benefits in surveillance, reconnaissance, and targeting, although these are only beginning to be demonstrated in the field. Additionally, UAVs promise reductions in aircrew manning and attendant training costs, as well as elimination of political risk associated with current manned aircraft reconnaissance missions and one-time punitive strikes in which downed aircrews are in danger of becoming hostages. Exploiting the enabling technologies will assist the Navy and Marine Corps to benefit from the kinds of concepts that spring from the high level of interest in UAVs by Congress and other DOD components.

Long-endurance Systems

Very long endurance or long-range UAVs that often can operate only from distant airfields, offer great promise to naval forces at sea despite their inability to fly from ships. Technical advances such as improved subsonic laminar flow; high-strength, low-weight composite airframes; improved propulsion efficiency; and reliable, secure, high-capacity data links over long distances give these systems their unusual performance and make operations in support of air and surface naval forces feasible.

As an example, the Tier II+ High Altitude Endurance system, now being developed by DARPA, can fly 2,500 nautical miles to an operating area and remain on station for two days before returning to base, all the while providing area and spot data from synthetic aperture radars, moving target indicators, and

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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electro-optical and infrared sensors via satellite or direct line-of-sight downlink to naval commanders at sea and Marine Corps air-ground task forces ashore. Matters of ownership, tasking authority, flight control, payload control, and imagery access must be worked out, but integration into the Navy and Marine Corps of commercial data link and satellite technology will make possible full exploitation of the potential of very long-range or long-endurance UAV systems.

Sea-based Systems

The panel sees VTOL, STOVL, and STOL designs as the sea-based UAVs of choice, with VTOL solutions going beyond current rotary wing technologies such as the tilt rotor and conventional helicopter. Air vehicles with ability to take off and land vertically or in short distances make sense for naval applications because they can operate from flattop aviation ships and other surface vessels with smaller, partial helicopter-like flight decks.

UVAs Permitting Offloading Functions

By employing land- and sea-based UAVs for a variety of support missions—reconnaissance, surveillance, targeting, weapons control, EW, tanking, and long-range ASW and AEW—the flexibility of a naval task force at sea can be enhanced considerably. Commanders could offload certain support functions from carriers and amphibious aviation ships, thereby freeing flight and hangar deck space and turning these air-capable ships into all-strike or all-assault lift platforms. When naval forces operate at great distances from friendly airfields, the long-endurance UAV assures the commander of needed support while still permitting him to engage in high-intensity strike operations and ship-shore assault.

Lethal UAVs

Unmanned vehicles designed for lethal purposes are concepts to be explored as the enabling technologies mature, experience is gained in nonlethal applications, and trade studies help identify the most cost-efficient approaches. Such concepts range all the way from stealthy, loitering, long-endurance UAVs that dive into targets of opportunity to a highly capable air vehicle much like today's F/A-18 that is flown remotely by a pilot located in a command module on board a ship. In between these extremes might be a Tomahawk-like missile equipped with dynamic retasking capabilities and a large, possibly stealthy, subsonic aerial arsenal truck, described above, carrying weapons that can be launched on remote command.

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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Networked Warfare

The Navy is currently leading development efforts in CEC as part of its air defense approach. The recent introduction of an airborne mode in the network will now enable ships best positioned to engage a threat to do so on the basis of tracking and fire control data contributed by other ships in the task group.

At the present time the development effort in CEC is focused on integrating the air node into the network strictly as an airborne relay. The next step is to enable the air node to contribute fire control quality data to the net from its own on-board sensors, with a vision of eventually adding airborne shooters to the netted air defense capability. The panel believes that the current focus of netted warfare should be expanded to include offensive operations against surface targets by aircraft, submarines, and surface ships, with airborne sensor platforms—very likely UAVs—performing terminal guidance where necessary in a forward pass mode of operation.

The netting of all warfare platforms by a common cooperative engagement architecture for both defensive and offensive combat operations would greatly expand the inherent warfighting capabilities of all platforms for littoral warfare, including support of Marine Corps forces ashore. Air platforms in particular would benefit greatly from the ability to employ off-board weapons. Aircraft size, weight, and cost could be greatly reduced since ordnance payload and carrier bring-back weights are design drivers in size and strength requirements and, consequently, in cost—including the cost of stealth.

Support and Special-mission Aircraft Functions
Challenge and Opportunity

Perhaps the greatest potential for effecting beneficial change exists in providing the functions now resident in support and special mission aircraft. Mission categories include patrol, antisubmarine warfare, tanking, airborne early warning, surveillance, reconnaissance, electronic warfare, and logistics support. Some of these planes are not carrier capable and operate solely from shore bases; others, such as fixed-wing logistics aircraft, cycle to and from the fleet. However, significant numbers of support and special-mission planes are regular elements of the carrier air wing, constituting about 25 percent of the wing's complement. The functions they perform give the carrier battle group flexibility, including its ability to operate independently of other forces if required, an attribute much valued by senior commanders.

However, this flexibility comes at a price. The support elements occupy 35 percent of available deck space aboard carriers, space that might be used to embark additional strike fighters. If the support functions can be offloaded but still remain available to the commander, the CV could be turned into a pure strike

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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ship. Here, it would serve as a refueling site and munitions magazine proximate to the target area, reloading and rapidly cycling fighter and attack aircraft. Battle group combat effectiveness would be enhanced, and the cost per target killed should be reduced.

Commanders now have the option to change the mix of aircraft in an air wing and offload support aircraft. However, provisions must be made for the kinds of support these planes provide, support that is not available if the battle group is operating at a distance from friendly airfields. Hence, as a practical matter, creation of an all-attack carrier is not feasible today in many tactical situations.

New Option—Off-board Support

The enabling technologies that facilitate development of long-endurance or long-range UAVs, sea-based UAVs, and the aerial truck make possible offloading these functions to the degree desired. Support mission functions are naturals for unmanning, with very long-endurance or long-range UAVs that remain on station two days or more, constituting the backbone capability. The generally nonlethal nature of support functions also should facilitate early introduction of unmanned aircraft as current programs demonstrate reliability and UAVs therefore gain broader acceptance.

Long-dwell surveillance or reconnaissance aircraft, with large-aperture antennas, would provide continuous tactical intelligence to both battle group and expeditionary force commanders without any necessity for sea-based flight operations. Also, naval expeditionary task forces without CV battle group support would benefit from improved situational awareness of their own and enemy forces without the interference to ship-shore lift operations that carrying organic reconnaissance platforms would induce. Patrol squadron (VP) could easily evolve into such a support force, becoming a shore-based element of the carrier's air wing.

Sea-based manned and unmanned support aircraft could be positioned on ships other than CVs and LHDs. In concert with long-range systems operating from shore, this would reduce or eliminate flight deck congestion on both aviation ship types and would speed up turnaround of strike aircraft and troop life rotorcraft.

Implications for Aircraft Carriers

Introduction of new air platform concepts made feasible by development of the 12 key enabling technologies described above will have a profound effect on the design of future aircraft carriers and amphibious aviation ships. A more vertical aircraft complement broadens considerably the range of viable CV and LHD size options in the following ways:

  • Nimitz size. New air platform concepts would enable a large CV to  

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×

generate significantly more sorties than can an air wing patterned after today's CTOL wing configuration. Sortie totals also can be increased dramatically by offloading support functions as noted above. The operational flexibility and economies of scale inherent in a large carrier likewise remain factors to be considered.

  • Medium-tonnage CV. With a vertical air wing, a medium-tonnage carrier could generate sorties equivalent to today's Nimitz air wing.

  • Small CV. Operating a vertical air wing reduces the tonnage threshold below which a carrier is considered nonviable.

  • CV-LHD (amphibious assault ship) hybrid. A mission-flexible carrier suitable for littoral warfare might be possible. Depending on the task force mission, such a ship could embark strike fighter aircraft, Marine Corps lift and attack rotorcraft, or a mix of types. Since the next-generation aircraft envisioned by the panel can operate from aviation ships across a wide spectrum of sizes, this opens up the possibility of the Navy buying a high and low mix of aviation ships. These ships could include Nimitz-like CVs suitable for large-scale operations and smaller flattop aviation ships for less demanding situations.

Payoff: A Potential Sea Change in Naval Aviation

The benefits resulting from aggressively developing the key enabling technologies outlined in Table 3.3 will have a significant impact on both air platforms and their base ships, as summarized in Box 3.1. The Navy and Marine Corps have an opportunity to effect a sea change in the naval aviation of 2035 if the requisite technologies are developed and the platform options that spring from them are exploited. This force would differ materially from one that would result from the normal requirements and acquisition process; it would be different in character, composition, capability, flexibility, and cost. In turn, it would have a dramatic and positive overall impact on future naval forces.

RECOMMENDATION

The R&D path now being pursued by the Department of the Navy may limit its choices for air platforms that will follow on current development programs such as the Joint Strike Fighter program and a possible common support aircraft.

Accordingly, the panel recommends that an air platform technology development plan be undertaken that comprises R&D funded by non-Navy entities, traditional Navy-funded programs centered on needs unique to the Sea Services, and most importantly, the 12 enabling technologies identified in this chapter, whose development should be vigorously pursued in IHPTET-like fashion. By doing so, Navy and Marine Corps leadership will have in hand a range of options on its technology buffet line when the time comes to develop platforms to enter operational status in the year 2035 and beyond.

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×

BOX 3.1

Naval Aviation of the Future

  • Moving toward a more vertical force—STOVL, VTOL, and STOL

  • Subsonic aerial trucks as new, utilitarian naval air platforms

  • Very long-endurance, long-range UAVs a principal naval forces asset

    • High-quality surveillance, reconnaissance, and targeting information in real time

    • Capability for offload of support aircraft from carriers

  • More flexible carrier deck loading

    • CVs as all-fighter or attack warfighters, or as

    • Littoral warfare support ships with few or no VF or VA

  • Broad range of viable aircraft carrier sizes and configurations

    • Large CV to small CV with same aircraft types embarked

    • Hybrid, multimission aviation ship (CV-LHD) as littoral warfare platform

  • More cost-efficient force as a result of the following:

    • Lower aircraft acquisition and life-cycle costs

    • Greater aircraft deck loads per ship ton than today

    • Increased CV sortie generation rates

    • Efficiency of all-strike “arsenal” aircraft carrier

    • Reduced manning due to more reliable systems, introduction of UAVs

    • Lower training costs because of unmanning, less CV landing training for “vertical” air wing

  • New air platform decisions necessary only as enabling technologies are proven

Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×
Page 37
Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
×
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×
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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Suggested Citation:"3 Naval Air Platform Technology." National Research Council. 1997. Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force: Volume 6: Platforms. Washington, DC: The National Academies Press. doi: 10.17226/5839.
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