SEARCH · Engineering Papers
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Data collection and analysis in the areas of air transportation, aircraft manufacturing and sales, airline operations, market projections, internal trade, and energy consumption; legislation and regulations, technology needs; surveys; decision-making; cost analyses; and technology transfer are discussed.
As a part of the EET aerodynamics program an out-of-house program was developed and monitored to provide theoretical procedures useful in the design of transport aircraft. The focus of the effort was to provide tools valid in the nonlinear transonic speed range. The effort was divided into two basic areas, inviscid configuration analysis and design procedures and viscous correction procedures.
The implementation of software fault tolerance is investigated for critical modules of the Software Implemented Fault Tolerance (SIFT) operating system to support the computational and reliability requirements of advanced fly by wire transport aircraft. Fault tolerant designs generated for the error reported and global executive are examined. A description of the alternate routines, implementation requirements, and software validation are included.
The overall objectives of this research effort have been to develop and evaluate algorithms and flight management concepts for minimization of fuel or direct operating costs. These concepts are to be used for flight planning or for on-board computation and steering of turbojet transport aircraft in the vertical path. Within this research context, a computer program, called OPTIM, has been developed to use these algorithms to generate near-optimum vertical reference profiles. OPTIM contains control options to examine effects of various flight constraints on cost performance. A companion program, called TRAGEN, was developed to simulate an aircraft flying along a given vertical reference profile. TRAGEN is used to verify OPTIM's output , to examine the effects of parameter value uncertainty (such as prevailing wind), and to compare cost performance of profiles generated by different techniques. This paper describes OPTIM and TRAGEN and presents examples of the programs utility.
The Fault-Tolerant Multiprocessor (FTMP) is a highly reliable computer designed to meet a goal of 10 to the -10th failures per hour and built with the objective of flying an active-control transport aircraft. Fault detection, identification, and recovery software is described, and experimental results obtained by injecting faults in the pin level in the FTMP are presented. Over 21,000 faults were injected in the CPU, memory, bus interface circuits, and error detection, masking, and error reporting circuits of one LRU of the multiprocessor. Detection, isolation, and reconfiguration times were recorded for each fault, and the results were found to agree well with earlier assumptions made in reliability modeling.
NASA has undertaken development and test programs in collaboration with the large transport aircraft construction industry, in order to remove existing barriers to the use of composite material primary structures and to assess their advantages in terms of both acquisition cost and mission performance. These programs are expected to reach design technology readiness for wing and fuselage structures by 1988, paving the way for the validation of design and manufacturing methods in the early 1990s. While composites promise a reduction in fuselage manufacturing costs, it is judged that the relative cost of a metallic wing will be more difficult to surpass. Nevertheless, a 40 percent wing weight saving may more than compensate for increased wing structure cost.
A summary assessment is made of foreign civil aviation as it relates to the posture of the United States civil aviation industry. Major findings include: (1) Main competitors - European Economic Community (EEC) and Union of Soviet Socialist Republics (USSR). (2) Largest commercial market - Transport aircraft. (3) Current market status and projections - U.S. currently dominates the civil aviation market but foreign markets show greater growth trends. (4) Competitive comparisons - Status comparisons are made in technology (aerodynamics, structures and materials, propulsion, avionics, systems, design coordination, and manufacturing); production runs; marketing; and postsales support. The U.S. generally leads except in aerodynamics and propulsion. (5) Multinational ventures - Joint U.S. industry/foreign government development of advanced technology engines is well developed; airframe industry discussions are now underway. (6) Implications - Although the U.S., is currently preeminent in most areas, this may be only a temporary condition. Past U.S. success in aviation has provided many benefits to the nation. These benefits may be lost.
The rapid advance in microprocessor technology has made it possible to automate many functions that were previously performed manually. Several research areas have been identified which are basic to the question of the implementation of automation in the cockpit. One of the identified areas deserving further research is warning and alerting systems. Modern transport aircraft have had one after another warning and alerting systems added, and computer-based cockpit systems make it possible to add even more. Three major areas of concern are: input methods (including voice, keyboard, touch panel, etc.), output methods and displays (from traditional instruments to CRTs, to exotic displays including the human voice), and training for automation. Training for operating highly automatic systems requires considerably more attention than it has been given in the past. Training methods have not kept pace with the advent of flight-deck automation.
An Energy Efficient Engine program has been established by NASA to develop technology for improving the energy efficiency of future commercial transport aircraft engines. As part of this program, a new turbofan engine was designed. This report describes the fuel and control system for this engine. The system design is based on many of the proven concepts and component designs used on the General Electric CF6 family of engines. One significant difference is the incorporation of digital electronic computation in place of the hydromechanical computation currently used.
The software developed for the Fault-Tolerant Multiprocessor (FTMP) is described. The FTMP executive is a timer-interrupt driven dispatcher that schedules iterative tasks which run at 3.125, 12.5, and 25 Hz. Major tasks which run under the executive include system configuration control, flight control, and display. The flight control task includes autopilot and autoland functions for a jet transport aircraft. System Displays include status displays of all hardware elements (processors, memories, I/O ports, buses), failure log displays showing transient and hard faults, and an autopilot display. All software is in a higher order language (AED, an ALGOL derivative). The executive is a fully distributed general purpose executive which automatically balances the load among available processor triads. Provisions for graceful performance degradation under processing overload are an integral part of the scheduling algorithms.
The task of flying a multipilot transport aircraft is a classic small-group performance situation where a number of social, organizational, and personality factors are relevant to important outcome variables such as safety. The aviation community is becoming increasingly aware of the importance of these factors but is hampered in its efforts to improve the system because of research psychology's problems in defining the nature of the group process. This article identifies some of the problem areas as well as methods used to address these issues. It is argued that high fidelity flight simulators provide an environment that offers unique opportunities for work meeting both basic and applied research criteria.
The structural response of internally pressurized composite cylindrical panels, representative of a transport aircraft's fuselage skins, is predicted by means of a one-dimensional, geometrically nonlinear analysis. An analytical study is conducted for the response of 4-, 8-, and 16-ply graphite/epoxy skins. The results obtained indicate that the response is geometrically nonlinear, and that a boundary layer with a severe bending gradient exists at the panel edges. The importance of through-the-thickness shearing deformations in the bending boundary layer is illustrated through comparison of analyses based on Kirchhoff-Love and shear deformation theories. Numerical results for the bending boundary layer lengths of the different panels are presented, and two bending boundary layers are predicted with the shear deformation theory.
An experimental investigation was recently conducted in the NASA-Langley Research Center 4- by 7-Meter Tunnel to explore the effects of aft-mounted advanced turboprop installations on the low-speed stability and control characteristics of a representative transport aircraft configuration. For the conditions investigated, the experimental results indicate that the longitudinal and directional stability of the configuration was not adversely affected by aft-pylon-mounted single-rotation tractor or counter-rotation pusher propeller installations. The results indicate that for the single-rotation tractor configuration the propeller induced aerodynamics are dominated by the interaction of the propeller slipsteam with the pylon, and that the propeller contribution to the stability characteristics for the counter-rotating pusher configuration is dominated by propeller normal forces. The longitudinal and directional control effectiveness, engine-out characteristics, and ground effects are also presented.
The Advanced Information Processing System (AIPS) is designed to provide a fault tolerant and damage tolerant data processing architecture for a broad range of aerospace vehicles, including tactical and transport aircraft, and manned and autonomous spacecraft. A proof-of-concept (POC) system is now in the detailed design and fabrication phase. This paper gives an overview of a preliminary fault detection and error handling philosophy in AIPS.
In response to rising fuel costs and reduced profit margins for the airline companies, the optimization of the paths flown by transport aircraft has been considered. It was found that application of optimal control theory to the considered problem can result in savings in fuel, time, and direct operating costs. The best solution to the aircraft trajectory problem is an onboard real-time feedback control law. The present paper presents a technique which shows promise of becoming a part of a complete solution. The application of singular perturbation techniques to the problem is discussed, taking into account the benefits and some problems associated with them. A different technique for handling the descent part of a trajectory is also discussed.
Computer technique aids joint optimization. Load-sharing between fasteners in multirow bolted composite joints computed by nonlinear-analysis computer program. Input to analysis was load-deflection data from 180 specimens tested as part of program to develop technology of structural joints for advanced transport aircraft. Bolt design optimization technique applicable to major joints in composite materials for primary and secondary structures and generally applicable for metal joints as well.
The effects of fatigue loading on the behavior of graphite/epoxy panels with either S-Glass or Kevlar-49 buffer strips is studied. Buffer strip panels are fatigued and tested in tension to measure their residual strength with crack-like damage. Panels are made with 45/0/-45/90 sub 2s layup with either S-Glass or Kevlar-49 buffer strip material. The buffer strips are parallel to the loading direction and made by replacing narrow strips of the 0-degree graphite plies with strips of either 0-degree S-Glass/epoxy or Kevlar-49/epoxy on a one-for-one basis. The panels are subjected to a fatigue loading spectrum MINITWIST, the shortened version of the standardized load program for the wing lower surface of a transport aircraft. Two levels of maximum strain are used in the spectrum with three durations of the fatigue spectrum. One group of panels is preloaded prior to the application of the fatigue cycling. The preload consists of statistically loading the spectrum in tension until the crack-tip damage zone reaches the ajacent buffer strips. After fatigue loading, all specimens are statistically loaded in tension to failure to determine their residual strengths.
As part of a program to evaluate high-temperature advanced composites for use on supersonic cruise transport aircraft, two graphite/polyimide composites have been aged at elevated temperatures for times up to 5.7 years. Work on the first, HT-S/710 graphite/polyimide, was started in 1974. Evaluation of the second polyimide, Celion 6000/LARC-160, began in 1980. Baseline properties are presented, including unnotched and notched tensile data as a function of temperature, compression, flexure, shear, and constant-amplitude fatigue data at R = 0.1 and R = -1. Tensile specimens were aged in ovens where pressure and aging temperatures were controlled for various times up to and including 50,000 hours. Changes in tensile strength were determined and plotted as a function of aging time. The HT-S/710 composite aged at 450 F and 550 F if compared to the Celion 6000/LARC-160 composite aged at 350 F and 450 F. After tensile testing, many of the thermal aging specimens were examined using a scanning electron microscope. Results of these studies are presented, and changes in properties and degradation mechanisms during high-temperature aging are discussed and illustrated using metallographic techniques.