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A historical view of multi-jet engine installations is given that emphasizes integration of the powerplant and the airframe in aircraft design for improved reduction in external nacelle drag and interference drag characteristics.
Research related to reliable aircraft design is summarized. Topics discussed include systems reliability optimization, failure detection algorithms, analysis of nonlinear filters, design of compensators incorporating time delays, digital compensator design, estimation for systems with echoes, low-order compensator design, descent-phase controller for 4-D navigation, infinite dimensional mathematical programming problems and optimal control problems with constraints, robust compensator design, numerical methods for the Lyapunov equations, and perturbation methods in linear filtering and control.
A method is suggested for predicting the stability of automatically controlled aircraft by a comparison of calculated frequency-response curves for the aircraft and experimentally determined frequency-response curves for the automatic pilot. The method is applied only to stabilization in roll. The method is expected to be useful as a means of establishing the specifications of the performance required of the automatic control device for pilotless aircraft designed as missiles.
A simple, systematic, optimized vortex-lattice approach is developed for application to lifting-surface problems. It affords a significant reduction in computational costs when compared to current methods. Extensive numerical experiments have been carried out on a wide variety of configurations, including wings with camber and single or multiple flaps, as well as high-lift jetflap systems. Rapid convergence as the number of spanwise or chordwise lattices are increased is assured, along with accurate answers. The results from this model should be useful not only in preliminary aircraft design but also, for example, as input for wake vortex roll-up studies and transonic flow calculations.
Despite significant advancements in controls configured vehicles/active controls technology (CCV/ACT) in the past decade, few applications of this promising technology have appeared in recent aircraft designs. The status of CCV/ACT is summarized, and some of the constraints which are retarding its wider application are described. Suggestions toward establishing an increased level of confidence in the technology are given.
The potential of applying advanced technology to a single engine trainer configuration is investigated. The analysis is performed in a parametric manner to evaluate the individual and combined effects of various aerodynamic and propulsion technology considerations. The analysis is accomplished using a computerized aircraft synthesis model that simulates the aircraft design and mission. The resulting performance characteristics are compared with a current trainer design to identify the performance improvements or penalties.
The results of four years research on technology are synthesized in an advanced supersonic cruise aircraft design. Comparisons are presented with the former United States SST and the British-French Concorde, including aerodynamic efficiency, propulsion efficiency, weight efficiency, and community noise. Selected trade study results are presented on the subjects of design cruise Mach number, engine cycle selection, and noise suppression. The critical issue of program timing is addressed and some observations made regarding the impact that timing has on engine selection and minimization of program risk.
The objectives of the Ames ACA program are to develop the active control technology (ACT) for short-haul aircraft, to evaluate existing methods, to develop new techniques, and to demonstrate the readiness of the technology in operational environment. Two concepts are basic to ACT: integrated aircraft design and integrated flight-control-system design.
A comparison is made between airplane productivity and utilization levels derived from commercial airline type schedules which were developed for two subsonic and four supersonic cruise speed aircraft. The cruise speed component is the only difference between the schedules which are based on 1995 passenger demand forecasts. Productivity-to-speed relationships were determined for the three discrete route systems: North Atlantic, Trans-Pacific, and North-South America. Selected combinations of these route systems were also studied. Other areas affecting the productivity-to-speed relationship such as aircraft design range and scheduled turn time were examined.
The feasibility and possible significance of aerodynamic simulations are considered. Despite certain limitations, there is reason to believe that many useful and important flows containing turbulence can be computed with an accuracy acceptable for use in aircraft designs. Attention is given to the equations for unsteady fluid flow, the direct calculation of unsteady viscous flows, the direct calculation of nonlinear equations, the computation of flows about bodies using turbulence modeling, future developments in numerical methods, and future developments in computers.
A method of optimization of the direct operating cost (DOC) and the effective perceived noise (in units of EPNdB) in aircraft is proposed. A computer program was used to generate a variety of aircraft designs meeting certain specifications, where wing loading, aspect ratio, cruise altitude, wing sweepback, and speed was varied, and DOC for each case was calculated. The higher aspect ratio, in combination with the appropriate wing loadings, cruise altitudes and wing sweep, is found to reduce the noise and the fuel used.
Powered-lift concepts are utilized in aircraft currently under development for STOL application. One of the concepts, upper surface blowing, places the jet exit just above the upper surface of the wing to produce powered lift from the jet exhaust blowing over the deflected flap. New data are presented to show the effects of airspeed, angle of attack, and angle of jet impingement. Scaling relationships are investigated concerning their applicability for extrapolating data to a different model size. The effects of a number of test parameters are examined and full-scale spectra are predicted from model data. It is concluded that scale models are an effective means for obtaining fluctuating pressure spectra for use in aircraft design. The prediction of full-scale loads from model data will require geometrically accurate models and closely spaced measurement locations.
More realistic guideline data must be developed for use in aircraft design in order to comply with recent changes in British civil airworthiness requirements. Unrealistically pessimistic results were obtained when the methodology developed during the Concorde SST certification program was extended to assess catastrophic risks resulting from uncontained engine rotors.
An aircraft's influence on lightning-strike occurrence was investigated. The compression of an electric field around an aircraft was considered in mathematical calculations of an aircraft's ability to store charge. Model test results were used to predict lightning-strike attachment zones in an analysis of aircraft design.
An analytical model developed for evaluating and verifying advanced rotor concepts is discussed. The model was used during in both open loop and real time man-in-the-loop simulation during the rotor systems research aircraft design. Future applications include: pilot training, preflight of test programs, and the evaluation of promising concepts before their implementation on the flight vehicle.
The V/STOL operational capability is reviewed with emphasis on pilot workload and all-weather landing guidance systems. A research and development program to correlate and integrate the development of all systems and techniques involved in enabling the pilot to fly V/STOL aircraft onto ships and tactical sites is described. Aircraft design parameters that affect its control in the vertical takeoff and landing flight regimes are emphasized. Topics considered include: (1) integrated flight controls and displays; (2) low speed sensor; (3) air traffic control appraoch and landing guidance systems; (4) visual landing aids; (5) ground effect induced thrust variation problems; and (6) handling qualities.
The proceedings of a workshop of many disciplines of the aviation community are presented. The general topics addressed were general, services, aircraft design, simulation, and general aviation.
Sessions were held with the standing committees on aircraft design, simulation, general services, and general aviation. It was stated that current procedures for designing structural components with respect to turbulence forcing functions were adequate. It was agreed that the ultimate goal of aviation weather services was the delivery of accurate and timely information to the cockpit flight crew.