This article provides non-proprietary and non-competition-sensitive information related to aircraft applications. It presents an overview of reliability and commonly used measurements. Failure modes that cause the negative performance are reviewed based on many types of sources. These include manufacturer service bulletins, reliability and customer service departments, literature reviews, demonstration programs, in-service evaluations, design guides, and surveys of commercial and military aircraft maintenance organizations. The article also describes lessons learned while attempting to avoid overlapping maintainability, reparability, and materials choice.

This article describes the various environments affecting corrosion performance, corrosion protection, and corrosion control. These include freshwater environments, marine environments, and underground environments. The article provides information on corrosion in military environments and specialized environments, representing less-well-known environments with more limited applications.

Maintainability is a function of the durability, damage tolerance, and repairability of a structure. This article discusses the configurations of composite structures, such as sandwich, stiffened-skin, and monolithic structures, used in commercial aircraft composites. It describes the considerations for maintainability of the composite structures during the conceptual design phase. Sources of the defects and damage, such as manufacturing defects and in-service defects, are reviewed. The article describes the nondestructive inspection methods that are used in the repair of composite structures to locate damage, characterize the extent of damage, and ensure post-repair quality. It lists suggestions that can be used as design guidelines for adhesive bonding, general composite structure, sandwich structure, material selection, and lightning-strike protection. The article also provides the basic considerations for personnel, facilities, and equipment during maintenance.

Corrosion, fatigue, and their synergistic interactions are among the principal causes of damage to aircraft structures. This article describes aircraft corrosion fatigue assessment in the context of different approaches used to manage aircraft structural integrity, schedule aircraft inspection intervals, and perform repair and maintenance of aircraft in service. It illustrates the types of corrosive attack observed in aircraft structures, including uniform, galvanic, pitting, filiform, fretting, intergranular, exfoliation corrosion, and stress-corrosion cracking. The article discusses geometric parameters such as pit dimensions, surface roughness, loss of metal thickness, and volume increase due to pillowing to quantitatively characterize the types of corrosion. It also explains the two most common fatigue life assessment methods used in the military aerospace industry: fatigue crack initiation and crack growth analysis.

Aging is a process where the structural and/or functional integrity of components will be continuously degraded by exposure to the environmental conditions under which they are operated. This article discusses aging mechanisms in various components of military systems such as structural parts, engines, and subsystems. It describes the aging management processes such as full-scale structural testing and practical life-enhancement methods. The article reviews control and prevention systems such as usage and health monitoring systems necessary to provide effective corrosion maintenance on military systems. Failure prediction techniques, namely, the equivalent pre-crack size approach, life-cycle cost modeling and simulation, and holistic life-prediction methodology are also discussed.

This article provides a summary of the concepts discussed in the articles under the Section “Product Reliability, Maintainability, and Repair” in ASM Handbook, Volume 21: Composites. The Section covers a range of topics that include the general issues for reliability, maintenance, and repair of composite structures. Specific structural applications, including marine, infrastructure, and aircraft related issues, are discussed. Operators of equipment employing composite structures in primary load applications must understand the issues with respect to maintenance and repair action. The Section also provides information on these requirements.

This article reviews corrosion problems in the U.S. Department of Defense (DoD) and discusses management and maintenance aspects of the practices that address the cost and readiness. It describes the plans to institute corrosion prevention and control strategies under DoD directives in engineering design, material selection, and fabrication processes for new acquisitions. The article also suggests a long-term strategy to reduce the cost of corrosion control.

This article focuses on failure analyses of aircraft components from a metallurgical and materials engineering standpoint, which considers the interdependence of processing, structure, properties, and performance of materials. It discusses methodologies for conducting aircraft investigations and inspections and emphasizes cases where metallurgical or materials contributions were causal to an accident event. The article highlights how the failure of a component or system can affect the associated systems and the overall aircraft. The case studies in this article provide examples of aircraft component and system-level failures that resulted from various factors, including operational stresses, environmental effects, improper maintenance/inspection/repair, construction and installation issues, manufacturing issues, and inadequate design.

The inclusion of damage tolerance design and a systematic review of design procedures allow the U.S. Air Force to design, manufacture, and maintain systems that are structurally safe and economically prudent. After a brief introduction of fracture mechanics, this article describes the particular aspects that relate to damage tolerance in aircraft design. It discusses the use of fracture mechanics as a method of predicting failure, understanding failure mechanisms, and suggesting inspection methods to protect against failure in pressure vessels. Various programs of U.S. Air Force to design aircraft structure, namely, airframe structural integrity programs, engine structural integrity program, and mechanical subsystems structural integrity program are also discussed.

This article discusses corrosion fatigue, its effects on the damage tolerance of aircraft, and its predictive modeling. A conceptual framework is presented that incorporates two distinctive cyclic-based life-prediction philosophies and expands them both to include the time domain in order to consider the effects of corrosion. These philosophies include crack initiation used for safe-life design and crack growth used for damage tolerance. The article presents the methodology for computing the effects of real-time age degradation on an aircraft structure for two different corrosion types: crevice and pitting corrosion. It describes the rationale and techniques needed to apply the age-based structural integrity processes to in-service structures in order to realize the benefits throughout the full structural life cycle.

This article describes the commonly observed forms of airplane corrosion, namely: general corrosion, exfoliation corrosion, pitting corrosion, microbiologically induced corrosion, galvanic corrosion, filiform corrosion, crevice corrosion, stress-corrosion cracking, and fretting. It discusses the factors influencing airplane corrosion from the manufacturing perspective: design, manufacturing, and service-related factors. The article explains the collection of corrosion data and provides an overview of the implementation and evolution of airline corrosion prevention and control programs and directions being considered in the design for corrosion prevention of airplanes.

This article describes the types of repair and presents reasons for avoiding damage to a structure or component during repair. It discusses the major standardization issues with emphasis on design, repair materials, repair techniques, and inspection.

Corrosion monitoring is important in the operation of modern industrial plants and in the use and maintenance of expensive assets such as bridges and aircrafts, because the damage caused by corrosion and the rate of the deterioration can be huge and the risks devastating. This article discusses the system considerations and installation techniques of different types of direct and indirect techniques in electrochemically based on-line corrosion monitoring process. It describes the importance of probe location and on-line corrosion monitoring techniques with examples.

This article describes the influences of the operational environments of U.S. Navy aircraft during corrosion-control process. The most widely used materials in airframe structures and components, such as aluminum, steel, titanium, and magnesium alloy systems, are reviewed. The article provides information on the inspections steps, corrosion-control issues, and corrosion-prevention strategies for naval aircraft. It contains a table that lists typical locations of corrosion on the aircraft. The article also provides examples of aircraft corrosion damage.

This article describes two analysis methods that are used to determine the life of aircrafts: fatigue life and fracture mechanics methods. The life limiting factors that control the durability of the aircraft are also discussed. The article provides an overview of the various approaches to corrosion identification and prevention. These include safe-life, fail-safe, and damage tolerance approaches. The article discusses their application to the process of extending the life of aircraft structural components.

Reliability-centered maintenance (RCM) is a systematic methodology for preventing failures. This article begins by discussing the history of RCM and uses Society of Automotive Engineers (SAE) all-industry standard JA1011 as its model to describe the key characteristics of an RCM process. It then expands on questions involved in RCM process, offering definitions when necessary. Next, the article describes the approach of RCM to failure modes and effects analysis (FMEA), the failure management policies available under RCM, and the criteria of RCM for deciding when a specific failure management policy is technically feasible. Then, after discussing the ways that RCM classifies failure effects in terms of consequences, it describes how RCM uses failure consequences to identify the best failure management policy for each failure mode. Next, the building blocks of RCM are put together to create a failure management program. The article ends with a discussion on some practical issues pertaining to RCM that lie outside the scope of SAE JA1011.

This article discusses three typical repair types for composite structures: temporary repairs, adhesively bonded repairs, and bolted repairs. It contains a table that lists general design requirements and considerations for the repair of composite structures. The article describes ten steps for an engineering repair approach to effectively restore structural integrity to damaged composite components. Management, validation and certification of repairs are also discussed. The article presents the design guidelines for analyzing the damage and possible strategies for making a repair. It reviews three repair schemes used in repair design analysis, namely, core replacement, adhesively bonded patch, and mechanically fastened patch. The article also emphasizes the various pitfalls and problems in repair design for composite structures.

This article describes the protective coatings technology used in naval aircrafts. It reviews the future needs and trends of the protective coatings technology based on advancing technology, environmental concerns, and operational requirements. The article discusses the standard finishing systems for aircrafts: the surface pretreatment system, primer, topcoat, advanced-performance topcoat, self-priming topcoat, and specialty coatings. It presents safe compliant solutions to environmental problems associated with the protective coatings technology. These solutions include the use of environmental regulations and hazardous materials, nonchromated pretreatments, waterborne technology, high-solids technology, and touch-up paints. The article also deals with the use of electrodeposition coatings, powder coatings, adhesive films, paint application equipment, and non-chromated sealants in the protective coatings technology.

This article introduces the concept of condition monitoring (CM) and summarizes various techniques used for CM across the industrial sectors. The techniques include visual inspection, performance monitoring, vibration condition monitoring, vibration condition monitoring, lubricant oil analysis, acoustic emission testing, temperature monitoring, motor current signature analysis, and ultrasound emission. The article describes the evolution of condition-based maintenance in CM. It also describes the basics of integrated vehicle health management, a capability that enables a number of maintenance philosophies. The article concludes with a discussion on various condition monitoring in industrial sectors, including condition-monitoring techniques in nuclear power plants, road condition monitoring, and condition monitoring in wind turbines.