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Discussion and author closures on Viscometry and its Applications to Automotive Lubricants provides a supplement to SAE SP-382 which included all papers presented at the ASTM-SAE Symposium during the National Automotive Engineering Meeting held in Detroit, Michigan, May 14-18, 1973. The format of this paper follows that of the Symposium which was divided into two sessions: Effects of Low Temperature and Shear Rates on Lubrication, and Effects of High Shear Rates on Lubrication.

An aircraft maintenance program can be one of the most valuable economic tools available to a commercial air transport operator. It is the area that offers management the most opportunities to control costs. Current commercial aircraft design plus recent regulatory changes have combined to place an increasing burden on management, accompanied by the potential for an increasing economic return.

A program has been undertaken to develop new airfoil sections suitable for general aviation aircraft, utilizing theoretical and experimental advanced technology developed in recent years primarily for subsonic jet transport and military aircraft. The airfoil development program is one component of the Advanced Technology Light Twin (ATLIT) program sponsored by NASA Langley Research Center. Two-dimensional tests of a new airfoil at NASA and Wichita State University have demonstrated high cruising performance over a fairly wide C1 range, and a C1max value of 3.69 with Fowler flap and no leading-edge devices. Experimental and theoretical development of additional configurations is under way.

A totally integrated design-to-cost program was undertaken at Westinghouse to derive a basic, standardized line of spray oil-cooled generators having optimized performance and maximum reliability over a wide range of output ratings and customer applications. The development of the spray cooled generators resulted in unique design configurations that also warranted development of new manufacturing facilities.

An overview of avionics maintainability, as indicated from airline operating statistics, shows improvement in some elements and degradation in others, but a slowly degrading overall trend. Maintainability elements and trends are identified and discussed. Principal problems are the shop labor expended for the high proportion of removed equipment found to be in satisfactory condition, and the increasing line maintenance effort required by wide-body aircraft. Built-in test equipment (BITE) or monitoring within the system, if properly designed, appears to be a good approach to improve this situation. Design guidance for effective BITE or monitoring objectives is provided.

The question has been asked whether the airline industry is gaining or losing in the design of new aircraft for maintainability. The Lockheed L-1011 aircraft is examined by an operator resulting in two answers: yes-for routine maintenance; and no-for nonroutine maintenance. Areas for investigation for further improvement, particularly in the wide-body aircraft, include the care of passenger cabin and associated appliances and amenities. The airlines have increased interior maintenance by brightening up the interiors-trading dark colors, which do not show abuse, for the lighter, more attractive colors. The same principles and criteria need to be applied to cabin interior design as have been used to develop the reliable structures, systems, and powerplants now in operation.

This paper will discuss the procedures used for material selection that were developed and used for two Advanced Metallic Structures, Advanced Development Programs (AMS/ADP) sponsored by the Air Force Flight Dynamics Laboratory (AFFDL) under joint management and direction of AFFDL and the Air Force Materials Laboratory, Wright-Patterson Air Force Base, Ohio. The relationship of structural properties and the role of fracture mechanics in material selection are covered. The application of the selection criteria is demonstrated as it was applied to the Advanced Metallic Air Vehicle Structure.

Results of a brief study program to devise and evaluate new structural materials and concepts for a subsonic, transport-type aircraft are presented. Comparisons of several wing concepts to the state-of-the-art baseline concept indicate a weight saving of 10%, but with corresponding total cost increases of 50-75%. One fuselage concept indicates a 7% weight saving with a 5% total cost saving. Corresponding aircraft performance payoffs with and without resizing are also established. The overall payoffs are somewhat nominal, based on the new concept impact on participating structure only. Both baseline and new concept analyses are based on a common set of requirements for ultimate strength, fatigue life, damage tolerance, and flutter rigidity. The study is directed to metallic concepts.

This paper describes the results of parametric design studies of the application of filamentary composite materials in the structure of high-subsonic-speed transport aircraft. System costs and weight savings are presented as a function of percent utilization of composite materials from zero to 80%. The weight savings potential of composites for direct material substitution and for resized aircraft show gains of up to 25 and 50%, respectively. The state-of-the-art in structural design, analysis, fabrication, and test is discussed. Structural design concepts are shown and test validation is given, along with cost analyses.

The YF-16 lightweight fighter prototype program contracted by the U.S. Air Force (USAF) in April 1972 established a dollar ceiling on the design, manufacture, and test of two prototype aircraft, and also established a flyaway cost goal for production aircraft should the USAF elect to procure the aircraft for its force structure. With cost as a factor coequal with performance, innovative design features were incorporated in the basic configuration during preliminary design to minimize the size, weight, and cost of the aircraft, yet meet the desired performance goals. Simplicity and elimination of unessential features were also given primary consideration. The execution of the detail design, tooling, and manufacturing program was oriented toward low cost concepts and rigorous adherence to established budgets. Multiple use of parts and assemblies, use of low cost materials, and standardization of hardware items contributed to low tooling and manufacturing cost.

A decision tool utilizing the magnitudes of system parameters and an associated set of weighting factors has been developed to compare alternative design concepts for new systems. The weighting factors are computed from data describing the system requirements, and they are not assigned a priori. The magnitudes for the system parameters and the weighting factors are combined in a new, unique manner, not by direct multiplication. Both of these operations can be implemented on a computer; consequently, alternative design concepts can be compared rapidly in the presence of and in response to changing system requirements. This decision tool is primarily for use during the preliminary design phase of a system.

Increasing concern has been shown at all levels of government over the rising cost of major weapons systems. The implementation of the “design to cost” approach is intended to reverse this trend by placing greater emphasis on the cost elements during systems design and by restraining the natural desire for maximum performance if the technology required involves the risk of cost escalation. These factors, however, must not detract from the basic goal-the production of a weapons system with acceptable, reliable performance within cost guidelines. The application of design to cost and the effect of prototyping are described as they apply to the A-10 close air support aircraft.

A review of the structural design and material selection in the YF-17 airplane is presented. Emphasis is placed on the choice of those design concepts and materials that are unique, and the effect on these choices of the prototyping philosophy is described. Special emphasis is placed on the use of graphite materials, but the use of other nonmetallic materials and the considerations involved in the selection of metallic alloys and heat treatments are also discussed.

A new passive vibration isolation method has been developed which offers less static deflection and lower transmissibility at the operating frequency than conventional passive isolators. The method consists of attaching the object to be isolated to nodal points which are developed when an elastic beam is excited by a vibrating source. Attachment at the nodes dynamically decouples the driving and driven systems in a frequency band making isolation independent of the mass of the driven system. The immediate application is to eliminate helicopter fuselage vibration; however, because of its generality, it can be used wherever conventional isolators are used in isolating a limited range of vibration frequencies.

The requirements of higher aircraft availability, lower maintenance costs, and a more comfortable passenger/crew environment demand low vibration in helicopters. To meet this objective, Sikorsky Aircraft has developed and reduced to practice the main rotor head bifilar absorber. The bifilar absorber reduces vibration directly at the source-the main rotor. It cancels the rotor system exciting forces before they are transmitted into the airframe, and thus effectively controls vibration throughout the helicopter. Reduced vibration levels translate directly into improved reliability and maintainability. The principle of the bifilar absorber and the vibration reductions achieved in production installations are described. The quantitative improvement in reliability and reduction in maintenance resulting from the reduction in vibration are presented. The field data were collected from 15 aircraft without the bifilar absorber and from 15 aircraft with the bifilar absorber.

A parametric computational concept has been developed that facilitates rapid and accurate generation of AST engine data suitable for mission analysis. This calculation tool, in the form of a computer program, considers the aerothermal, mechanical, installation, and noise aspects of different types of AST engines, while calculating installed performance, weight, and physical dimensions in a specified airflow size.

Operation of a U.S. developed supersonic transport must and will meet community noise standards. This paper examines the airport noise problems of large transport aircraft, highlights critical considerations, and then studies possible solutions available from advanced propulsion technology. Engine sizing requirements to meet SST payload-range and airport performance criteria are reviewed first, and the impact of noise on the engine size and aircraft performance is then identified. Relief offered by noise suppressor development and technology advances that can be foreseen in the next decade for turbojet and turbofan engines are described. The advantages offered by a duct heating turbofan engine cycle are discussed. The potential offered by variable cycle engines to provide low noise characteristics with minimum penalty on performance are shown, and the practical restraints imposed on this potential by airframe aerodynamic noise is illustrated.

Nitinol, a nickel-titanium alloy, exhibits the unique property of undergoing a temperature-dependent phase transformation. Associated with this phase transformation is a significant shape change that has led to the common designation of “memory material.” This shape change has been utilized to design mechanical fasteners which expand radially on transformation to produce interference fits for increased fatigue life components, give effective length reductions for high clamp-up forces, and form a rivet tail for low-cost installation. Various design concepts, manufacturing techniques, and mechanical properties are discussed.

No greater contribution seems to exist for improving supersonic transport economics than by improving the state of the art of jet noise suppressors. Exact matching of thrust requirements for supersonic cruise, transonic acceleration, climb, and especially takeoff-climb is complex. The present design becomes an equivalent five-engine configuration, where the extra thrust is required to enable environmental levels of FAR Part 36 to be achieved. The added size is required first to allow for engine throttling during takeoff run to provide reduced exhaust velocity and exhaust gas temperature consistent with suppressor structural limits, and secondly to make up for suppressor losses at takeoff flight speeds. As the engine selection must be closely tied to airplane selection, substantiation of the 2.2-M airplane selection is described.

Performance and cost improvements force the development and implementation of new fasteners into production. Total internal company organization participation is essential. Industry cooperation and use can be vital to economic success. Production feasibility tests to establish installation costs and production suitability must be established. These include: cost of inventory of existing on-going system; cost of surplus; tool cost for changeover; floor space required; inventory of parts in process; and cost of installation. Technical solutions should be flexible to minimize personal bias of participants.