tion of aerodynamic characteristics at high angles of attack, stall/spin-prevention concepts and the development of criteria for emergency spin recovery systems are areas of research now being pursued in addition to the previous efforts in developing test techniques, defining normal spin recovery design criteria and consulting with the industry on specific problems. Following the FY 1978 flight evaluation of a modified high-wing aircraft, the FY 1979 program will include a T-tail configuration and begin the study of light twin-engined aircraft.

As illustrated in Figure 35, ongoing efforts in the development of more efficient aerodynamic components, such as airfoils and high-lift devices, will continue in FY 1979. The concentration on drag reduction techniques is intended to provide a generalized design procedure that will reduce the need for the current cut-andtry flight test approach to drag clean-up. In addition, results of ongoing work in the conventional-takeoff and landing (CTOL) area to develop low drag coatings for aerodynamic surfaces will be examined for applicability to light aircraft.

Benefits from a particular aerodynamic improvement, such as a high-lift airfoil or reduced drag through the use of winglets, will not necessarily be achieved when integrated into an aircraft as a modification. Beginning in FY 1978, and continuing, is an effort to provide guidelines for optimum integration of new aerodynamic capabilities into current configurations. A similar effort will explore potential efficiency improvements from new or novel configurations.

Illustrated in Figure 36 are several areas that are being investigated in an effort to provide greater propulsive efficiency. Turbine engines, both fan and shaft versions, appear to be gaining acceptance across a wider spectrum of aircraft types. Less maintenance, lower cost of turbine fuel, broader tolerance to fuels, and high combustion efficiency make these engines potentially viable alternatives to reciprocating engines in the above-400-horsepower class.

The Quiet, Clean, General Aviation Turbofan (QCGAT) engine will be completed in FY 1979. Following the evaluation tests by the two contractors, the engines will be delivered to NASA. Subsequent efforts beyond FY 1979 will concentrate on in-house verification testing and performance evaluation at the Lewis Research Center.

Existing turbine engines are too large for application to all but the largest general aviation aircraft. In FY 1978, four contractors have undertaken preliminary definition studies of small, 400-horsepower, 800-pound-thrust turbine engines. In FY 1979, detailed definition studies will be initiated including a careful evaluation of the airframe requirements to properly incorporate such an engine into the aircraft.

During FY 1979, design and fabrication of model hardware for propeller/ nacelle flow field investigations will be underway, as will research on advanced blade sections.

More basic studies of fuel tolerance and cycle efficiency, including evaluation of diesel and rotary engines, will continue during FY 1979.

As illustrated in Figure 37, the utility of light aircraft as a mode of transportation is heavily dependent upon the ability to operate in adverse weather and a complex air traffic system. While accomplished routinely by the airlines, the differences in airborne equipment, operational requirements, ground facilities and flight crew make general aviation instrument operations considerably more challenging. Continuing research on advanced integrated avionics, studies of advanced navigation concepts and previous work on handling qualities for general aviation, as illustrated in Figure 38, represent a technology base that is available for improving the safety and reliability of instrument flight.

Information available through the Aviation Safety Reporting System (ASRS) and other sources indicates a number of problems exist with single-pilot instrument-flight-rule (IFR) operations. During FY 1979, efforts will be initiated to isolate the most critical problems so that NASA may begin, in consultation with users and FAA, to explore concepts for resolving them.

The approach will be to establish realistic operating scenarios and, through simulation, identify the operating and procedural conditions adversely affecting the single pilot's flying task. Although premature to speak about specific areas to be investigated to resolve such problems, it is envisioned that such matters as charting, training requirements, and air traffic control (ATC) procedures would be explored. In addition to the work outlined here. NASA also will be defining plans for examining single-pilot IFR issues within the context of the cockpit-displayed traffic information program.

The utility and productivity of aircraft dedicated to the performance of a special mission can be enhanced if the aircraft is specifically tailored to the requirements of the task. Such is the situation with aircraft used to apply agricultural materials.

Since the primary transport mechanism for the materials, once ejected from the aircraft, is wake generated by the aircraft, the width of the pattern and its evenness are directly influenced by the uniformity of the downwash. The wake of the aircraft and the propeller slipstream seriously detract from the ability to apply a uniform layer of material.

Relying on facilities and techniques developed in the study of trailing vortices, model tests and analytical studies will be carried out to define acceptable modifications to current aircraft that will improve the uniformity of the pattern by tailoring the wake characteristics. While a relatively low-level effort, it does capitalize on a unique area of expertise within NASA and does hold the promise of significant return if successful.

In summary the general aviation research and technology program planned for FY 1979 is well balanced and is addressing the most critical problems identified as future limits to growth. This shift in emphasis away from the near-term problems to a next-generation timeframe in aerodynamics, propulsion and avionics is compatible with the time required for the evaluation and incorporation of new technology by the industry.

VERTICAL TAKEOFF AND LANDING (VTOL)

The NASA technology programs on VTOL have been oriented primarily toward civil transport aircraft concepts until recent years. During this time, the NASA efforts, together with the work by the military and industry, have resulted in a steady advancement of the VTOL technology state of the art. These encouraging technology advancements have been a strong factor in the Navy's more immediate commitment to related vertical and short takeoff and landing (V/STOL). In describing NASA broad-based VTOL technology programs, a review will be given first of a few NASA accomplishments of the past year on the lift/cruise fan-powered aircraft concept, which is likely to be a strong contender for the Navy V/STOL "A" prototype and for follow-on civil applications. Then some planned activity in other elements of the NASA's broad-based VTOL programs having general applicability to longer term VTOL applications such as a supersonic fighter will be described.

In conclusion, some brief remarks will be provided regarding potential NASA involvement in V/STOL "A" technology development. This activity is under active negotiation with the Navy at this time.

Lift/cruise fan VTOL aircraft are generally characterized by utilizing highbypass-ratio fans for thrust in cruise, and for lift in terminal-area flight.

Small-scale lift/cruise fan model tests have been valuable for first-order investigations of configuration aerodynamics, including propulsion system and air-. frame interaction, and ground-effect flows such as suckdown, fountain effect, reingestion and so forth. Despite the value of the small-scale powered models for rapid, systematic, and exploratory research of a broad magnitude, there always remains the necessity for some large-scale wind-tunnel and static testing of aircraft models to validate and guide the utilization of the small-scale research in design. This is particularly true with V/STOL concepts because of the extreme complexity of the aircraft flows, their susceptibilty to scale effects, and the difficulty in properly simulating them with small models. Accordingly, the Ames Research Center during the past year conducted additional configuration research with a large-scale three-fan aircraft model in the 40x80-foot tunnel, and on the static test facility to investigate ground effects.

The effect of operating near the ground has always been a major concern for VTOL. Ground effect can introduce large negative or positive increments to engine thrust and aircraft lift. Typically, it is influenced heavily by small configuration details and ground height. It cannot yet be predicted assuredly by theoretical means, and large-scale results are often markedly different from smallscale. For this reason, considerable effort has gone into investigation of the model at the two heights shown, as well as at an intermediate height. The results have indicated a thrust loss of up to 7 percent at the intermediate and low heights. However, this particular configuration exhibited a large buoyant

force (sometimes called fountain effect) which exerted induced lift on the vehicle so that its net suckdown was never more than about 1 percent of the fan thrust at any ground height.

As indicated in Figure 39, NASA is continuing broad-based VTOL research programs applicable to highly-maneuverable fighter-attack aircraft. Included are small-scale tests of VTOL models incorporating several different propulsive-lift concepts in subsonic and high-speed tunnels with emphasis on investigation of the complex flow interactions between the propulsion system and the airframe. Large-scale low-speed aerodynamic tests will be carried out in the Ames 40x80-foot tunnel of representative complete powered VTOL configurations incorporating jet-lift augmentor concepts shown to be promising in preliminary analytical and experimental studies.

A major effort will be made to extend available methods of calculating VTOL aircraft jet flow characteristics, covering such aspects as jet-lift thrust augmentation, inlet reingestion, ground effects including "fountain" interactions, and transition flight.

In regard to the Navy V/STOL Type "A" program, the Navy has determined that the current VTOL data base must be expanded to support development of its Type "A" prototype aircraft. Some representative possible Type "A" configurations are shown in Figure 40. These include various lift/cruise fan and rotorcraft concepts. A Navy/NASA agreement was formalized in October 1977, setting forth a general understanding of a joint program directed at Type "A" technology needs. A detailed program plan is being defined, under which the Navy will provide financial support for NASA effort which is generally beyond that customarily provided for important military aircraft development programs. Four categories of NASA involvement are scheduled to mesh with the Navy's first two primary Type "A" milestones, namely, completion of concept formulation by 1982 and advanced development of the Type "A" prototype by 1988. These categories are: (1) evaluation support to the Navy during and immediately following its contracted conceptual design studies, (2) support to the Navy and to the two primary contratcors it selects for the prototype development phase, (3) technology support in key areas identified by the Navy and (4) required major upgrading of some NASA facilities and equipment.

NASA evaluation support in the concept formulation phase will include (as indicated in Figure 41) small-scale model aerodynamic tests of the four Navy contractor conceptual designs at low-speed and transition flight conditions in the Langley Research Center's 4x7-meter V/STOL subsonic wind tunnel and at high speed in the Ames Research Center's 11-foot unitary tunnel. Large-scale tests of key components of these designs in the Ames 40x80-foot tunnel and piloted flight simulator studies of the designs on the Ames Flight Simulator for Advanced Aircraft also are planned. As indicated previously, details of the joint program in this and the other phases are now being defined.

SHORT TAKEOFF AND LANDING (STOL)

The NASA STOL technology program is directed at providing, by the early 1980's, design and operational data for the United States aerospace industry to be able to develop quiet, short-haul transports and for the Federal Aviation Administration (FAA) to establish appropriate certification standards. The major elements in this program include construction and research testing of the Quiet Short-Haul Research Aircraft (QSRA) and the Quiet, Clean Short-Haul Experimental Engine (QCSEE). In addition, NASA has been participating with the United States Air Force in flight tests of their Advanced Medium STOL Transport (AMST) prototype aircraft. Generalized activities have also been underway in the Research and Technology Base program and in the STOL Operating Systems Technology program.

In response to Congressional action which resulted in a $3 million reduction in FY 1978 appropriations, NASA has reevaluated its STOL ativities to determine which efforts could be reduced while, at the same time, maintaining a satisfactory level of cohesive activities necessary to achieve its primary goals and objectives. This assessment has resulted in terminations, reductions and rescoping of some specific efforts. At Ames Research Center, most of the contracted and in-house work on reduced- and short-takeoff-and-landing aircraft performance and handling qualities was terminated, as was almost all of the research on aeroacoustics and loads at Langley Research Center. Reductions in the STOL

Operating Systems Technology program will result in early termination of the DHC-6 Twin Otter effort and reduction in the Augmentor Wing Jet STOL Research Aircraft STOLAND flight research activities. Flight validation of the Microwave Landing System for STOL operations will be reduced in scope, and piloted simulation studies of advanced digital avionics systems will not be conducted.

These reductions result in substantial curtailment of the in-house research efforts, thus impacting the far-term STOL research and technology. NASA will, however, maintain activities to achieve its near-term goals and objectives through the continuation of the flight experiments programs to provide the critical technology for future civil and military short-haul transport developments.

The restructured current program emphasizes the Quiet Short-Haul Research Aircraft (QSRA) project and the Quiet, Clean Short-Haul Experimental Engine (QCSEE) program.

The QSRA is being developed to obtain research and technology data for design and certification criteria applicable to future quiet, propulsive-lift shorthaul transports. With the goal of a 90 EPNdB noise footprint of less than one square mile, the unique QSRA aircraft has been designed with a wide range of lift and control capability to thoroughly investigate terminal area operational characteristics. The propulsive-lift technology obtained with the QSRA should be applicable to a wide range of civil and military high-performance jet STOL, reduced-takeoff-and- landing (RTOL), and conventional-takeoff-and-landing (CTOL) transports.

Figure 42 shows the QSRA in the final stage of assembly. Rollout is scheduled for late March 1978 and the aircraft should be delivered to NASA in the fall for initiation of flight tests in FY 1979 to document the aircraft's performance capability and operating characteristics. Also, during FY 1979, research experiments requiring special instrumentation and test hardware and equipment will be developed for follow-on QSRA flight investigations needed to verify and correlate ground-based analytical, wind tunnel and piloted flight simulator-derived predicted characteristics.

NASA has participated with the Air Force in its Advanced Medium STOL Transport (AMST) flight test and evaluation program. This cooperation has permitted NASA to acquire operational flight data needed for civil transport technology for the two different AMST prototype designs. Since the report to Congress at this time last year, NASA has measured aerodynamic and acoustic loads in critical areas of the flaps and fuselage on the Boeing YC-14 aircraft (Figure 43), as was done and reported to Congress earlier on the Douglas YC15 aircraft. In addition to these measurements, data were also obtained on the acoustic environment in the aircraft crew compartment and the main fuselage area to assess the effects of interior acoustic treatment techniques. These data will be compared with predicted values based on static ground tests and analytical methods for use in developing improved design methods for reducing acoustic fatigue and interior noise.

NASA planned to perform follow-on tests as part of its participation in the Air Force's development phase, the next step after the AMST prototype effort. However, in January 1978, the Office of the Secretary of Defense announced the decision to cancel further development in the AMST program. As a result of this decision, NASA has initiated in-house studies to determine cost-effective means by which it could satisfy the primary needs for propulsive-lift technology using the AMST prototype aircraft. NASA expects that these studies will provide it with the technical and cost information for alternative courses of action regarding further flight activity with the AMST aircraft. NASA has been in close contact with the Air Force and plans to meet with them and possibly other interested agencies in the near future to establish a national plan for AMST prototype aircraft utilization.

The Quiet, Clean Short-Haul Experimental Engine (QCSEE) program, now in its fourth year, has as its primary objective the demonstration of major noise reduction technology, along with other propulsion innovations, in ground tests of both over-the-wing (OTW) and under-the-wing (UTW) engine configurations representative of possible future jet-STOL transports.

Tests at General Electric with the OTW and UTW propulsion systems were successfully completed in June 1977 and January 1978, respectively. The results indicated that all major performance goals were achieved. The specific noise

technology that was achieved could provide a four-engine, 150-passenger STOL aircraft with a 90 EPNdB noise footprint of less than one square mile. Both QOSEE configurations are at Lewis Research Center for tests with appropriate wing flap sections as shown in Figure 44. These tests, which will verify nacelled engine/wing flap section acoustic and aerodynamic characteristics, are scheduled to be completed during early fiscal year 1979.

In its STOL Operating Systems Technology program, NASA has been conducting simulations and flight experiments at Ames Research Center under a joint agreement with the Federal Aviation Administration (FAA) to define methods by which STOL aircraft can be operated effectively and safely in potential future air traffic environments. The program is primarily concerned with the airborne elements that will be needed for operations of short-haul aircraft in terminal areas.

An example of the type of activity underway is a recently completed simulation investigation of operational procedures and fuel savings for a profiled descent and delayed-flap approach into a high-density terminal-area environment. This study included participation of air traffic controllers at the FAA National Aviation Facilities Experimental Center (NAFEC) who, as shown in Figure 45, were coupled to two ground-based piloted simulators flown by commercial airline pilots at Ames. This arrangement permitted the simulator pilots to participate simultaneously in dynamic air traffic control simulations being conducted at NAFEC. The results of this simulation are currently being analyzed and will be documented in the near future.

The main theme of the fiscal year 1979 flight experiments in the Operating Systems Technology program will be control of powered-lift aircraft in a manner which preserves adequate performance and safety margins during autoland, auto approach, night operations and descent profiles which are fuel/noise optimum from cruise to touchdown. It is anticipated that these experiments and the others described above will be completed by the end of fiscal year 1979.

HIGH-PERFORMANCE AIRCRAFT

The High-Performance Aircraft (HPA) technology element of the NASA program primarily consists of those activities oriented toward increasing the maneuverability and high-speed performance characteristics of aircraft and, for the most part, is focused on advancing the technology for future generation military aircraft.

The work is coordinated very closely with the DOD and emphasizes “new” technologies or potential "breakthrough" technology areas where new technologies or concepts are tried for the very first time. Thus, the High-Performance Aircraft program provides the cutting edge of our advanced aeronautics technology program. In many cases, these technologies are applied first by the military and then applied by the civil sector after the military operational experience has proven and matured the technology, approximately one generation after it has been developed for the military.

The strength of the HPA program is the work that is conducted in the discipline areas of aerodynamics, structures, avionics, and propulsion in the R&T Base and in the interdisciplinary activities, where the interactions between the disciplinary considerations are considered as a total concept.

The thrust of the R&T Base program is to promote new ideas and concepts, with the next step to flight test being taken only for those concepts showing the most promise for future payoff and where the critical aspects cannot be adequately investigated and validated in ground facilities.

Low-Speed Aerodynamics, Stall/Spin

Experience with highly maneuverable military airplanes has shown that aircraft of this type are quite susceptible to loss of control and entry into unrecoverable spins during high angle-of-attack maneuvering. As a consequence, aggressive stall/spin research and research application over the past 5 to 10 years by NASA, DOD, and industry have resulted in new fighter designs (F-14, F-15, F-16) with greatly improved high angle-of-attack characteristics over the previous generation of fighter aircraft. The general objective of NASA's research is to establish guidelines for the design of spin-resistant military airplanes through both airframe design and automatic control systems concepts (Figure 46).

Work will continue in the area in fiscal year 1979. Wind tunnel and dynamic model flight tests will be used to investigate the stall/spin characteristics of the