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There are no standards that directly consider practical reliability testing technology (methods and equipment). This void needs to be filled. The SAE G-11 division has approved the development of six new standards to fill this void. This paper discusses these six standards: 1) Reliability TestGlossary; 2) Reliability Testing-Strategy; 3) Reliability Testing-Procedures; 4) Reliability Testing-Equipment; 5) Reliability Testing-Statistical Criteria for Comparison of Reliability Testing Results and Field Results; 6) Reliability Testing-Collection, Calculation, and Statistical Analysis of Reliability Testing Data, Development Recommendations for Improvement of Test Subject Reliability, Durability, and Maintainability.

In this work we discuss the fault avoidance and the fault tolerance approaches for increasing the reliability of aerospace and automotive systems. This includes: the basic definitions/concepts (reliability, maintainability, availability, redundancy, etc.), and characteristics (a priori analysis, a posteriori analysis, physical/hardware redundancy, analytical/software redundancy, etc.) of both approaches, their mathematical background and models (exponential, Weilbull, etc.), their basic theory, their methods and techniques (fault trees, dependence diagrams, Markov chains, etc.), some of their standards (SAEARP4761, AC 25.1309, etc.) and simulation environments (Cafta, etc.), and their applications to the reliability analysis and reliability improvement of aerospace and automotive vehicles. This is illustrated by some examples driven from the aerospace and automotive industries.

The current interest in Extreme STOL technology is intended to develop technology to provide future fixed-wing transport aircraft with very high lift capability for very short (

Fastening metallic structure for aerospace applications is relatively straightforward and has been done for some time. Dealing with advanced composites, though, requires a significantly different technological approach, especially primary structure. Although composite material utilization has increased enormously in civil and military aircraft in recent years, the application of composite materials to primary aircraft structure has not kept pace and is still greeted with some skepticism in the aerospace community. In particular, no major transport manufacturer has yet employed composite components for fuselage or wing primary structure. This appears to be changing rather rapidly with the introduction and the evolution of new airframes such as the 7E7 and Blended Wing Body (BWB) concepts. This paper presents recent developments in the design, fabrication, and testing of composite fasteners and, in particular, solid rivets and hybrid blind fastener assemblies, for use in the mechanical joining of composite and composite/metallic aircraft structural assemblies. It identifies major reasons for the general reluctance of airframers to take advantage of the durability and weight-savings afforded by composites, such as joint integrity, repairability, and maintainability, and addresses how these issues are related to the structural mechanical joining considerations.

Fuel cell systems emerge as a new technology, which is expected to play an important role for future powertrain applications. To enable this technology’s entrance into the market, new developments to improve robustness, cost efficiency and maintainability are necessary. Besides the stack itself, several subsystems are required to operate a fuel cell system. The technical challenges for developing and optimizing these subsystems are comparable to the challenges in the stack development itself. The air delivery system is considered to have a major impact, subject to overall efficiency, noise emissions and costs. These properties are determined not only by the system hardware, but also by the chosen control strategy. This paper describes an intelligent model based control strategy, which enables the system to use optimal operation points of compressor and motor. The quantities to be controlled are air mass flow and pressure. The precise achievement of the desired values is crucial for proper stack functionality and stack lifetime. The controlled parameters are the compressor speed/torque and the opening of the return manifold pressure valve. The paper considers all aspects of the controller development and the implementation of such a system including controller hardware and hardware-inthe-loop simulation. The results presented in this paper were achieved in simulations and on a real system.

The design of a mechanical assembly such as an automotive disc brake involves a host of considerations aside from the necessary performance and cost objectives. Other aspects, which define a successful design, relate to maintainability, robustness over the product life, and NVH characteristics. The conflicting goals and objectives that define a successful design cannot be achieved without compromise, and determining the most suitable configuration to best balance these conflicting goals defines the optimal brake design. To evaluate these characteristics at the earliest stages of design, a general parametric disc brake model has been developed for single and twin-piston pin-slide brakes, and embedded in a multibody dynamic analysis environment. The utility of the parametric model relates to the large number of variables that may be considered in automated sensitivity studies, design of experiment, and optimization efforts. To outline the capabilities of this approach, a trade study for a twin-piston pin-slide disc brake is described. The evaluation of pad load distribution is considered, where piston diameter, piston location, and caliper finger placement are considered as design variables, with the goal of achieving optimal pad load uniformity under a prescribed operational condition.

In recent years, the design and development of military propulsion systems have greatly benefited from advancements in analytical modeling and prediction tools. However, flight testing continues to play an integral role in the maturation of fighter engines. The severity of the fighter mission role dictates the need for capabilities beyond those normally attributed to commercial propulsion systems. While comprehensive static and simulated in-flight engine testing are key elements in developing these capabilities, flight testing provides the avenue for verification that all engine and control functions operate as intended in an integrated environment and that the propulsion system meets with customer, and specifically, pilot approval. In addition to the role that flight testing plays in introducing new propulsion technology into operational service, an equally critical function is served by providing the opportunity for component improvement verification. The USAF CIP program, aimed at establishing and satisfying the requirement for continuous improvement of propulsion system capabilities, has resulted in numerous upgrades to fighter engines such as the Pratt & Whitney F100-PW-229 for the McDonnell-Douglas F-15E Strike Eagle and the Lockheed-Martin F-16C/D Fighting Falcon aircraft. At present, more than 300 PW-229 engines are installed in USAF and foreign military service (FMS) F-15E and F-16 aircraft and have accumulated more than 310,000 flight hours since operational introduction in 1991. In general, engine improvements center on the areas of durability/maintainability and operability. Using the PW-229 Increased Performance Engine as its example, this paper will focus on various enhancements incorporated

The Reliability and Maintainability Assessment Tool is a stochastic, event-oriented simulation model that has been developed to analyze the functional reliability, availability, and maintainability characteristics of the Space Station Freedom. This tool simulates failures and performs corrective and preventive maintenance tasks, utilizing user-specified maintenance resources, including crewmembers and/or robotics, and accommodates the growth of the station. The model dynamically interfaces with minimal cut sets derived from reliability block diagrams to assess functional status and to determine queuing priorities.

This paper describes the NASA/JSC Research Technology Opportunity Program (RTOP) activity to assess the supportability of space systems throughout their life cycles. Supportability analyses for space systems present unique attributes and problems. The OSMOSSYS (Object oriented Simulation of Maintenance and Operations for Space Systems) was developed using object-oriented design concepts to provide NASA an analysis tool which addresses the question `Will a proposed space facility be able to successfully perform the missions for which it is designed?' This model integrates the complete configuration of the system including the reliability and maintainability characteristics of each component, the logistics support, and the mission operations of the facility to assess the success rate of the planned mission(s). Two parallel design processes are being utilized; developing core modules utilizing C++, and incorporating as much code and ideas as possible from existing NASA models. The space station was used as a test case to demonstrate the applicability of the model.

The development of more electric technologies for future military aircraft promises to provide significant redundancy, reliability, maintainability, and performance benefits. Advanced Cooling For High Power Electric Actuators particularly address the use electro-mechanical actuators (EMAs), and an approach for cooling EMAs using the combined concepts of passive reflux cooling and phase change materials (PCMs) for energy storage. The planned program involves four Phases: Phase I Requirements and Trade Studies. Phase II Detailed Design. Phase III Fabrication and Test Plans. Phase IV Test/Data Correlation. During Phase I Sundstrand identified actuator cooling requirements and evaluated the effects of several critical parameters on the use of passive reflux cooling in combination with PCM.

Current research in intelligent control systems at the Lewis Research Center is described in the context of a functional framework. The framework is applicable to a variety of reusable space propulsion systems for existing and future launch vehicles. It provides a 'road map' technology development to enable enhanced engine performance with increased reliability, durability, and maintainability. The framework hierarchy consists of a mission coordination level, a propulsion system coordination level, and an engine control level. Each level is described in the context of the Space Shuttle Main Engine. The concept of integrating diagnostics with control is discussed within the context of the functional framework. A distributed real time simulation testbed is used to realize and evaluate the functionalities in closed loop.

The HL-20 early lifting-body personnel launch system (PSL) research, expected PSL mission requirements, the HL-20 concept design status, and those features which enhance aerodynamic and aerothermodynamic performance, operation, efficiency, maintainability, reliability, and crew safety are described. Results of the HL-20 PLS research to date show that the concept has definite advantages for efficiently satisfying future needs for assured manned access to space. The vehicle is designed with operational efficiency, low life-cycle costs, reliability, and safety as the primary criteria. It is shown that the HL-20 PLS can be developed and put into operation in the same timeframe that the Space Station Freedom is deployed.

The AX-5 is an all metal Extra-vehicular (EVA) space suit currently under consideration for use on Space Station Freedom. A reliability model was developed based on the suit's unique design and on projected joint cycle requirements. Three AX-5 space suit component joints were cycled under simulated load conditions in accordance with NASA's advanced space suit evaluation plan. This paper will describe the reliability model developed, the results of the cycle testing, and an interpretation of the model and test results in terms of projected Mean Time Between Failure for the AX-5. A discussion of the maintenance implications and life cycle for the AX-5 based on this projection is also included.

NASA's Space Station is viewed as the beginning of man's permanent presence in space. This paper presents the guidelines being developed by NASA's medical community in preparing a quality, permanent health care delivery system for Space Station. The guidelines will be driven by unique Space Station requirements such as mission duration, crew size, orbit altitude and inclination, EVA frequency and rescue capability. The approach will emphasize developing a health care system that is modular and flexible. It will also incorporate NASA's requirements for growth capability, commonality, maintainability, and advanced technology development. Goals include preventing unnecessary rescue attempts, as well as maintaining the health and safety of the crew. Proper planning will determine the levels of prevention, diagnosis, and treatment necessary to achieve these goals.

At a major or system contractor level approximately 80% of what is delivered to the customer is obtained from suppliers. The successful procurement of hardware items with reliability R, maintainability M, and system safety SS requirements of R, M, and SS program requirements involves no particularly new or unusual techniques. It does require the consistent, disciplined use of several of the tools presently available, i.e., the item specification, a really comprehensive statement of work and a data reuqirements list. These all must be closely coordinated so that they "track together" . Clear distinctions between tasks to be accomplished, requirements for the design, and data items to be prepared are essential. Also, most system contractors need to better inform their potential suppliers.

This report documents a study to find overruning clutch concepts suitable for use in helicopters. Ten designs were selected for in-depth evaluation, and from these, three were selected for fabrication and testing: the spring, the sprag, and the ramp-roller clutches. These performed satisfactorily in the tests, and a design guide was compiled for them (USAAMRDL-TR-77-18). (Author)

Using the systems approach, the human factors engineer stands ready to assist the design engineer in providing the vehicle driver with an optimum workplace. A human factors checklist has been devised for the design engineer to alert him to the major areas where troubles for the human operator generally develop. This preliminary checklist has been applied to the design of a pickup truck cab to illustrate its use. The terms "average" and "percentile" are explained. Sources of human factors data are suggested where the design engineer may find specific information as to spatial requirements for U.S. adult men and women, automotive driver controls, deiver seating, environmental considerations within the vehicle, including conditions of heat, cold, and high humidity, ventilation, noise, vibration, and vision capability. When a particular component or control is the subject of a Federal Motor Vehicle Safety Standard, the pertinent standard is identified by number and title. Maintenance and maintainability considerations are emphasized, since all products must be repaired eventually. The Combination of good human factors engineering and vehicles that are easy to repair can greatly improve public acceptance of the automotive design engineer's product.

An investigation is conducted concerning the extent to which a program for rotorcraft research presented by NASA meets the user needs. Problems of civil operators are examined, taking into account powerplants, reliability and maintainability, environment, noise and vibration, and lack of space for passengers' baggage. A description of applicable technology is provided, giving attention to aerodynamics and structures, propulsion, power transfer methodology, flight control, avionic systems, human factors, and vehicle configurations. One of the most difficult challenges in trying to bring research to bear on operator problems is that in general researchers are working on long-term solutions while operators are seeking short-term answers. Attention is also given to potential technological bright spots, higher risk technologies, highest technological risks, and advanced vehicle configurations.

The Electronic Control Unit (ECU) required the development of special-process test equipment capable of ensuring necessary levels of performance, throughput, reliability, and maintainability. This paper details the development of one part of the overall test facility, the Final Test Station. /GMRL/

NASA's development of electrochemical CO2 concentration technology has led to the creation of subsystem hardware and control and monitoring instrumentation that are ideally suited to Space Station program applications; only seven orbital replacement units, for instance, are required for the performance of process functions. This process simplification leads to superior reliability and enhanced maintainability. Hardware and software features that enhance subsystem reliability through fault detection and isolation have been emphasized in the course of development. Further power, weight, and volume savings, together with enhanced maintainability, are also foreseen in prospective developments of these subsystems.

This paper provides the general descriptions of HSST-5 system and summarizes data of HSST systems developed to date. HSST-5 is the first MAGLEV train licensed as a public transport system by MOT of Japan. If the system can achieve good results in system reliability and maintainability, the system will be approved as a commercial line in the near future.

The zero-prebreathe Mark III, 8.3-psi EVA-capable space-suit assembly represents a significant evolutionary development stage toward the creation of an operational space-suit system for the NASA Space Station Program. The unique implementation of the Ortman cable coupling arrangement allows rapid assembly and disassembly of major suit component hardware; this will in turn facilitate on-orbit maintainability and resizing operations. Advanced thermal/micrometeoroid garment-type protection features were investigated in anticipation of Space Station construction-related EVA hazards, and duly incorporated in the final Mark III suit design.

The Stirling Powered Van Program (SPVP) is a multiyear, multiphase program to evaluate the automotive Stirling engine (ASE) in Air Force vans under realistic conditions. The objective of the SPVP is to transfer to manufacturer and end user(s) (i.e., on the path to commercialization) the second-generation Mod 2 ASE upon completion of the Automotive Stirling Engine Program in 1987. In order to meet this objective, the SPVP must establish Stirling performance, integrity, reliability, durability and maintainability. The ASE program background leading to the van program is reviewed and plans for evaluating the kinematic Stirling engine in Air Force vans examined. Also discussed are the NASA technology transfers to industry that have been accomplished and those which are currently being developed.

The Bosch process, which catalytically reduces CO2 with H2 to solid carbon and water, is a promising technique for the reduction of the CO2 removed from the Space Station atmosphere and the subsequent water formation for O2 recovery. A Bosch engineering subsystem prototype CO2 reduction unit was developed to demonstrate the feasibility of the Bosch process as a viable technology for Space Station application. A man-rated prototype unit is then described as part of the ECLSS Technology Demonstrator Program. The goal was to develop a Bosch subsystem that not only meets the performance requirements of two 60 person-day carbon cartridge capacities, but also satisfies inherent man-rated requirements such as offgassing characteristics, fail-safe operation, and ease of maintainability. It is concluded that the technology is at a state of maturity directly applicable to flight status for the NASA Space Station program.

A summary of the potential requirements, proposed configurations, inherent development problems, and technologies to be considered for future space transportation systems is presented. Such systems will include the improved Space Shuttle, new and derivative cargo launch vehicles, new propulsion systems, orbital transfer and maneuvering vehicles, and a second-generation Space Shuttle. It is concluded that more efficient and capable systems can be developed by placing strong emphasis on high reliability, safety, and improved ground and flight operations. These improvements can result from the introduction of advanced technologies and vehicles designed for operations and maintainability with the flexibility to adapt to mission needs.