Aircraft Manufacturing Considerations

17.1 Overview

Cost analysis and manufacturing technology are subjects that require specialized instruction in academies, and they are not the main topics of this book. They are included to make readers aware that the classical aeronautical subjects of aero­dynamics, structures, and propulsion are not sufficient for a successful aircraft design. Cost analysis and manufacturing technology must be considered during the conceptual design study and integrated with classical aeronautical subjects. The following terms are used extensively in this chapter; some were referred to previously:

Design Built Team (DBT): This is a team of hand-picked, experienced engi­neers and specialists drawn from various related disciplines, who synthesize design for DFM/A considerations in multidisciplinary interactions with the classical subjects.

Design for Manufacture and Assembly (DFM/A): This is an engineering approach with the object of minimizing costs of production without sacrificing design integrity.

Integrated Product and Process Development (IPPD) (also known as Con­current Engineering): This offers an environment in which DBT uses IPPD to synthesize the trade-off studies in a multidisciplinary study to arrive at the best value for the product as a global optimum, rather than optimizing to a particular design study. DFM/A is part of IPPD.

Design for Six Sigma (DFSS): This is an integrated approach to design with the key issue of reducing the scope of mistakes and inefficiencies – that is, making a product right the first time to prevent the waste of company resources. It is a management-driven task to extract more from employees in order to find new ways to improve on routine approaches. In this way, the product is of the highest quality and lowest cost, satisfying all of a customer’s requirements.

Lean and Agile Manufacturing (LAM): This is a management tool to mini­mize costs by effective personnel management for improvements in the areas of assembly, system profitability, and the working environment.

Product Life-Cycle Management (PLM): This is a business strategy that helps companies share product data, apply common processes, and leverage cor­porate knowledge to develop products from conception to retirement, across the extended enterprise.

Manufacturing Process Management (MPM): This is a management strategy that provides a common environment for manufacturing, preplanning, and cost estimation, as well as detailed production planning, reconciliation analy­sis (i. e., estimate versus actual), and shop-floor work-instruction authoring.

Product, Process, and Resource (PPR): This is the hub environment, which provides a direct use of CAD-based data as a basis for work instructions. Emphasis is on use of single data set feeding all user systems.

Commercial aircraft design strategy is steadily evolving. It was initially driven by the classical aeronautical subjects, but recently it is customer-driven design strate­gies that consider DFM/A problems with the object of minimizing production costs without sacrificing design integrity and specifications. Manufacturing methodolo­gies, jigless assembly, and “flyaway” tooling concepts facilitate DFM/A. Designing for ease of assembly can be improved in the areas of assembly effectiveness and product quality.

Chapter 16 stresses the importance of rigorous costing as an integrated tool embedded in the multidisciplinary systems architecture of aircraft design to arrive at a best value. Cost estimation is used to trade-off studies between the classical aeronautical subjects and DFM/A methodology, with its guiding principles of parts count and manhour reduction, standardization of parts, and emphasis on designing for ease of assembly, which has wider implications for engineers and managers in the manufacturing industry. Whereas specialist groups concentrate on design for their task obligations – whether technology – or manufacture-driven or any other demand – the IPPD environment must synthesize the trade-off studies for the best value of a product as a global optimum rather than optimizing to a particular design study.

The paradigm of “better, faster [time], and cheaper to market” has replaced the old mantra of “higher, faster [speed], and farther” [6]. Aircraft manufactur­ers are meeting the challenges of this new paradigm by assessing how things are done, discarding old methods and working practices for newer, right-the-first-time alternatives. An increase in product value is achieved through improved perfor­mance (better), lower cost (cheaper), and in less time (faster). The paradigm shift from classical aeronautical studies led to new considerations for various types of design for… terms, more so in the academic circle (see Section 17.7). This chap­ter takes a holistic approach to aircraft design by consolidating various design for… considerations. The author suggests the introduction of an index of “Design for Customer” as a measure for establishing a product value.

The digital design and manufacturing process (see Section 17.9) leads to paper­less offices. The advent of the digital-manufacturing process greatly facilitated the DFM/A concept by addressing the role of MPM in the industry. MPM provides a common environment for manufacturing, preplanning, and cost estimation, as well as detailed production planning, reconciliation analysis (i. e., estimate versus actual), and shop-floor work-instruction authoring. It provides a means to integrate across the full product life cycle, ranging from concept to field maintenance to retirement (i. e., “cradle to grave”). Shop-floor execution systems are fed directly from the PPR – hub environment, providing a direct reuse of CAD-based data as a basis for work instructions. As-built data are captured and available for use within the PPR hub for follow-on planning and validation as the product evolves throughout its life cycle.

In some ways, automobile-manufacturing technology is ahead of the aerospace industry by successfully implementing digital-manufacturing technology and ad­vancing to futuristic visions. A successful automobile design can sell a million per year and last for a decade with minor modifications; whereas, in peacetime, fewer than 500 per year of a successful high-subsonic commercial transport aircraft are produced and none has yet reached the 10,000 mark in terms of total aircraft sales. The automobile industry can invest large sums in modern production methods yet keep amortization costs per car low.

17.1.1 What Is to Be Learned?

This chapter covers the following topics:

Section 17.2:	Manufacturing considerations
Section 17.3:	DFM/A
Section 17.4:	Manufacturing practices
Section 17.5:	DFSS concept
Section 17.6:	Tolerance relaxation
Section 17.7:	Reliability and maintainability
Section 17.8:	Designs for consideration: a holistic approach
Section 17.9:	Index of design for customer
Section 17.10:	Digital manufacturing

17.1.2 Coursework Content

Readers may compute the index of the design for customer. However, it is neither essential nor important because the industry is not adopting this system at this stage; more study is needed. However, the DFM/A considerations can be addressed in a second term. Such studies need not alter the finalized and substantiated configura­tion obtained thus far through the worked-out examples (in the industry, DFM/A is carried out in parallel during the conceptual design stage). It is beneficial to have an idea of DFM/A implications in aircraft design and operation. However, if it is a second-term topic, it may not be practical without specialist instructors using real­istic data. This chapter provides only a glimpse of the scope of DFM/A during the conceptual study phase.

17.2 Introduction

Today, it is not the operators who are the only customer. The future trends suggest the entire society as a customer of the high-tech aerospace engineering, which could “make or break” any society depending on how the technology is used. This also is true for other types of technology, including nuclear and bioengineering.

In the past, trade-off studies were limited to the interaction among aerody­namics, structures, and propulsion, as discussed through Chapter 13 of this book.

Subsequently, during the 1990s, the need for DFM/A considerations in an IPPD environment gained credence. The IPPD process continues to evolve for the customer-driven design trends in order to minimize ownership costs without sac­rificing integrity, performance, quality, reliability, safety, and maintainability. The recent economic downturn demands general and significant cost-cutting measures, severely affecting the commercial aircraft industry. In this economic climate, the roles of reliability, maintainability, recyclability, and so forth are design – and manufacturing-process-dependent. This chapter introduces an index of design for customer and incorporates value engineering.

The eventual affordability for operators as the “best buy” (i. e., product value), in turn, will allow manufacturers to thrive. Design considerations should not impose difficulties in their manufacturability. The associated aerodynamic-shape and structural-design concepts facilitate parts fabrication, their assembly, enhanced interchangibility, and so forth. Bought-out items should be selected for efficient and cost-effective system integration that leads to better reliability and maintainability during the aircraft lifespan. Recent events have resulted in the additional constraints of cost-effectiveness and environmental issues, requiring increased attention. The issues of global sustainable-development and anti-terrorism require additional design considerations. The choice of materials from a recycling (i. e., disposal) perspective is an additional issue when the use of composites gains ground over metals.