Systems Engineering for Commercial Aircraft

A Domain-Specific Adaptation

Scott Jackson

• Editore: Routledge
• Anno: 2020
• ISBN:
  9781000152050
• Edizione: 2
• Argomento: Technology & Engineering
• Categoria: Engineering General

The key principle of systems engineering is that an aircraft should be considered as a whole and not as a collection of parts. Another principle is that the requirements for the aircraft and its subsystems emanate from a logical set of organized functions and from economic or customer-oriented requirements as well as the regulatory requirements for certification. The resulting process promises to synthesize and validate the design of aircraft which are higher in quality, better meet customer requirements and are most economical to operate. This book is more of a how to and a why to rather than a what to guide. It stresses systems engineering is an integrated technical-managerial process that can be adapted without sacrificing quality in which risk handling and management is a major part. It explains that the systems view applies to both the aircraft and the entire air transport system. The book emphasizes that system engineering is not an added layer of processes on top of the existing design processes; it is the glue that holds all the other processes together. The readership includes the aircraft industry, suppliers and regulatory communities, especially technical, program and procurement managers; systems, design and specialty engineers (human factors, reliability, safety, etc.); students of aeronautical and systems engineering and technical management; and government agencies such as FAA and JAA.

1
Introduction

The primary purpose of the book is to provide the reader with the information to apply the systems engineering process to the design of new aircraft, derivative aircraft, and change-based designs. A second purpose is to provide guidance that will allow the reader to adapt this process to the commercial aircraft domain through judicious selection of those aspects that would provide the highest leverage of benefits and the lowest risk of adversities. It is assumed that the reader either already has a basic understanding of the process or can obtain that information from further reading of other sources, such as the ones discussed later in Section 1.3. Although there are many interpretations of systems engineering, the principles discussed are generally universal. This book attempts to stress those which are most relevant to aircraft design.

For brevity, the initials SE will be used for systems engineering throughout this book.

1.1 Definition of a System

A system is anything with many parts, like an airplane, a wrist watch, the human body, or the US government. The parts of a system are hierarchical: that is, the airplane parts can be subdivided into subsystems, sub-subsystems, and so forth. However, the principles described here apply equally well to the design of a subsystem as to a system. The official definition of a system adopted by the International Council on Systems Engineering (INCOSE) is as follows: A system is:

… an integrated set of elements, subsystems, or assemblies that accomplish a defined objective. These elements include products (hardware, software, and firmware), processes, people, information, techniques, facilities, services, and other support elements. (2010, p. 5)

In the commercial aircraft industry the term system is normally used for electrical systems, hydraulic systems, and so forth. The term can also refer to the global aviation system. However, in this book system will be used in the SE context: that is, for the entire aircraft and its supporting elements. Subordinate elements will be referred to as subsystems, such as the electrical subsystem.

This definition, though, includes non-technical aspects, such as people. It may seem contrary to the classical definition of engineering to include these aspects. However, this definition is consistent with the modern definition of SE which deals with the effort to define such systems.

1.2 Definition of Systems Engineering

It is difficult for two systems engineers to agree on a definition of SE. There are many definitions and many theories on the implementation of SE. We will look at only a few definitions here.

As the discipline began to take form, the search for a definition also began. The need for such a discipline has resulted from a worldwide trend of devoting an increasingly larger portion of the engineering effort towards pre-design requirements definition. SE is a key methodology in that trend.

The Systems Engineering Body of Knowledge (SEBoK) defines three types of SE: product SE (PSE), enterprise SE (ESE), and service SE (SSE). The SE of an aircraft is product SE. Product in this context can broadly be interpreted to include the operators and maintainers. Product SE is the primary, but not exclusive, focus of this book. Enterprise SE includes the developer, the suppliers, and the carriers. This book does incorporate aspects of enterprise SE, for example, in Chapter 14 which discusses large-scale system integration (LSSI) with an emphasis on supplier management, an important element in enterprise SE.

SE is a discipline which has the goal of arranging the parts of a system in such a way that the entire system does something optimally, such as to get from A to B in a minimum time, or at a minimum cost. That is, SE optimizes the system’s performance. However, SE goes even further. Major goals of SE are: first, to define the system’s requirements so well that the product will never have to be redesigned; secondly, to make the product as reliable as possible; and finally, to make the customer happy. In practice, these goals may seem impractical. However, SE provides some methods which may bring the design closer to the goals.

The official definition of SE adopted by INCOSE is as follows:

Systems Engineering (SE) is an interdisciplinary approach and means to enable the realization of successful systems. It focuses on defining customer needs and required functionality early in the development cycle, documenting requirements, and then proceeding with design synthesis and system validation while considering the complete problem: operations, cost and schedule, performance, training and support, test, manufacturing, and disposal. SE considers both the business and the technical needs of all customers with the goal of providing a quality product that meets the user needs. (INCOSE 2010)

This definition raises some important points: First, it points out that SE addresses the entire life-cycle of the system, not just the operational phase. This book addresses the life-cycle functions of an aircraft system in Section 3.1. Secondly, it states that SE assigns requirements to people and processes, not just the aircraft. Section 5.5 discusses the ability and limitations of assigning requirements to people. Section 5.14 discusses how SE can assign requirements to the fabrication and assembly processes.

An earlier definition was given by Simon Ramo (1973) as follows:

Systems engineering is a branch of engineering that concentrates on the design and application of the whole as distinct from the parts … looking at a problem in its entirety, taking into account all the facets and all the variables and relating the social to the technical aspects.

Note Ramo’s inclusion of social factors in the design of a system. This definition indicates the possible breadth of SE.

The term systems engineering has also been used to pertain to computer systems, for example, or to subsystems, such as electrical or hydraulic systems. It will be used in this book in the broadest possible sense, that is, to pertain to any system.

The term system engineering has also been used. However, SE has become the industry standard. Although treatises have been written breaking down SE into many steps, let’s just consider five, for simplicity, as shown in Figure 1.1. Notice the iterative nature of the first three steps. We will discuss each of these throughout the course of this book. The FAA Systems Engineering Manual (2014, p. 5) contains a more expanded view of the SE process.

Figure 1.1 Steps in the SE process

Another graphic often used in the description of SE is the famous Vee model. This model is more appropriate when applied to the discussion of requirements; hence, Chapter 4 discusses this model and its implications.

1.3 Historical Background

Early authors to recognize the value of SE and describe the process include A. D. Hall in his book A Methodology for Systems Engineering (1962). Other early descriptions of the process include the Army Technical Manual TM 38-760-1, A Guide to System Engineering (1973) and the Army Field Manual 770-78, System Engineering (1979). The EIA published SYSB-1, System Engineering (1989). Other standards followed, culminating in MIL-STD-499B, Systems Engineering, which was never formally adopted.

Eventually various professional societies joined together to publish ANSI/EIA 632 (1999), Processes for the Engineering of a System. The purpose of ANSI/EIA 632 was to create a standard which would be useful for both military and civilian applications. In addition, the Institute of Electrical and Electronic Engineering (IEEE) has published IEEE Standard 1220-2005, Application and Management of the Systems Engineering Process (2005). The standards, in general, pertain to product systems engineering (PSE) as defined in the SEBoK, described above.

The term SE is sometimes used in different contexts to mean different things, even within the commercial aircraft domain. For example, it can be used to mean the development of subsystems, as in the term avionics systems engineering. In addition, it is sometimes used to mean software engineering. This book uses the term in the broader sense which is consistent with the INCOSE definition discussed above and with the international standard ISO/IEC (2008).

SE is reaching a stage of maturity where its application in specific industries, such as commercial aircraft, can be defined and documented, as described by Petersen and Sutcliffe (1992). The first major guideline is the Society of Automotive Engineers (SAE) publication, ARP 4754 (1996), which applies the principles of SE to the development and certification of commercial aircraft. The later document ARP 4754A (2010) superseded the earlier guideline and contains many aspects of SE compared to the FAA manual with an emphasis on safety and certification.

1.4 Overview of this Book

The overriding SE principle stressed in this book is that the aircraft should be viewed as a whole and not as a collection of parts. Each chapter looks at a different aspect of SE and shows how that aspect would be reflected in the systems engineering of commercial aircraft. Chapter 2 looks at the commercial aircraft industry, describes the levels of aircraft development (new, derivative, and change-based) to which SE would be applied, and shows how the aircraft component architecture fits into the SE hierarchical model. This chapter also describes new technologies which would be applied to aircraft of the future. Chapter 3 introduces the SE concept of functions and shows how to apply functional analysis to the entire life-cycle of the aircraft, to the aircraft as a whole, and to the aircraft’s subsystems. The SE concepts of performance requirements and constraints are the subject of Chapter 4. This chapter also shows how these requirements can be allocated to the aircraft’s subsystems. Chapter 5 addresses constraints and specialty requirements and focuses on some key aircraft specialty areas, such as weight and reliability. The importance of the human factors aspect of cockpit design and the concept of organizational safety and its importance to the aircraft industry are also discussed in this chapter. Chapter 6 describes the SE concepts of functional and physical interfaces and shows how these concepts would apply to both external and internal aircraft interfaces. Chapter 7 shows how the SE concept of synt...

Indice dei contenuti

• Cover
• Half Title
• Dedication
• Title Page
• Copyright Page
• Table of Contents
• List of Figures
• List of Tables
• Acknowledgments
• Acronyms and Abbreviations
• Symbols
• Preface
• 1 Introduction
• 2 Commercial Aircraft
• 3 Functional Analysis
• 4 Requirements and Needs
• 5 Constraints and Specialty Requirements
• 6 Interfaces
• 7 Synthesis
• 8 Top-Level Synthesis
• 9 Subsystem Synthesis
• 10 Certification, Safety, and Software
• 11 Verification and Validation
• 12 Systems Engineering Management and Control
• 13 Adapting Systems Engineering to the Commercial Aircraft Domain
• 14 Large-Scale System Integration
• 15 Risk Management
• 16 Resilience of the Aircraft System
• Final Comments
• Appendix 1 The Mathematics of Reliability Allocation
• Appendix 2 Example Commercial Specification Outline
• Appendix 3 Systems Engineering Automated Tools
• Bibliography
• Glossary
• Index