This paper examines the role of Statistical Process Control (SPC) and variation management in satisfying AS9103 requirements within the aerospace, aviation, and defense industries. It traces the evolution of SPC from its origins at Bell Laboratories through its modern application in aerospace quality management, and explains how standards such as AS9100 and AS9103 establish a uniform framework for managing Key Characteristics (KCs) across the supply chain. The paper details the core SPC tools — including control charts, process capability indices (Cp, Cpk), and x-bar and R-charts — and argues that their systematic application is essential to reducing production variation, achieving zero defects, and maintaining compliance with international aerospace quality standards.
To assure customer satisfaction, the space, aviation, and defense industries must produce safe, reliable products that meet applicable customer and regulatory requirements. However, globalization and the diversity of national and regional requirements have complicated these objectives. Organizations face challenges in purchasing products globally across all levels of the supply chain, and suppliers must deliver consistent products to multiple customers with varying expectations.
To address these challenges, the aerospace industry established the IAQG (International Aerospace Quality Group) to drive significant improvement in quality throughout the production process. A central part of this quality management strategy is the application of AS9100, which specifies the international standard for aerospace products and systems.
The international standard specifies quality management systems designed to produce products that meet customer requirements and statutory regulations. AS9100 is a widely adopted, standardized quality management system for the aerospace industry, released in October 1999 through collaboration between the SAE (Society of Automotive Engineers) and the European Association of Aerospace Industries. AS9100 replaced the earlier AS900 standard and incorporates the current version of ISO 9000. Major aerospace suppliers and manufacturers are required to comply with AS9100 as a condition of doing business. Its primary purpose is to improve the effectiveness of quality management systems in meeting customer requirements and satisfaction. In addition to AS9100, aerospace organizations are also required to meet AS9103 requirements.
One of the major objectives of the International Aerospace Quality Group is to establish common industry quality requirements across the aerospace sector. The primary objective of Key Characteristics (KCs) under AS9103 — Variation Management is to provide a common standard and set of expectations within the aerospace industry. Key Characteristics focus on establishing common requirements at all levels of the supply chain in order to improve safety and quality while reducing costs. The standard laid down by AS9103 provides a uniform process for documentation, control, identification, and guidance within the space, aviation, and defense industries.
The purpose of AS9103 is to enhance aerospace standards and drive improvement in production and manufacturing through effective management of Key Characteristics. The scope of AS9103 applies to all production processes in the aerospace industry that influence KC variation. AS9103 is designed for the following stakeholders:
Producers: Organizations that perform processes affecting the manufacturing of a part.
Customers: Organizations that provide parts via purchase orders, contracts, engineering drawings, and specifications.
Process Control Document (PCD): A written document describing a manufacturing plan to control variation in Key Characteristics.
The requirements of AS9103 are as follows:
Variation management activities shall be performed on KCs. An appropriate monitoring methodology shall be used to ensure continued performance. Lower-level KCs shall be identified where necessary to control variation in higher-level KCs. Appropriate documentation shall be created and maintained. Process capability shall be established when a KC is in statistical control.
Statistical Process Control (SPC) is a statistical technique used to enhance quality control and make products conform to required standards. As defined by Wiley (2009, p. 173): "Statistical process control (SPC) involves inspecting a random sample of the output from a process and deciding whether the process is producing products with characteristics that fall within a predetermined range. SPC answers the question of whether the process is functioning properly or not."
In the aerospace industry, SPC is an effective tool for controlling Key Characteristics. The following requirements shall be met through SPC application:
1. Process capability indices (e.g., Cpk and Cp) shall be calculated only when the process is in statistical control and shown to be stable using appropriate control charts or statistical methods.
2. The process shall be specified by the customer and be considered capable when Cpk > 1.33. A Key Characteristic is considered capable if its Cpk equals or exceeds 1.33.
3. Characteristics shall be traceable to the specific product or part, and similar variability shall be demonstrated when similar Key Characteristics from different products are combined on the same control chart.
Statistical methods are used to justify reduced frequency of inspection (Crossley, 2008). In the manufacturing process, attribute data are collected during production, and by establishing upper and lower control limits it becomes possible to control variations before they lead to defective output.
Walter A. Shewhart pioneered SPC at Bell Laboratories in the 1920s. AT&T, together with Harry Romig and Harold Dodge, subsequently formed a team to develop sampling inspection on a rational statistical basis. In 1934, SPC was applied in the U.S. Army for the manufacturing of ammunition and the development of control charts. The successful application of SPC led Army Ordnance to engage George Edwards as a consultant on SPC use across Army departments.
Since the 1970s, SPC has been widely applied in the manufacturing industry to enhance the quality of finished products. SPC uses statistical tools to monitor production process performance and to predict significant variations that may result in sub-standard output. SPC is also applicable to post-manufacturing inspection, where each product is accepted or rejected based on whether it meets design specifications (Fontanares, 1997).
The control chart is a statistical tool used to determine whether a manufacturing or business process is in a state of statistical control. Control charts measure variations in the production process and can differentiate common-cause variation from assignable (or "special") causes. Common causes are inherent to the process, while special causes are more actionable in the manufacturing context. A control chart indicates that a process is under control when it is stable over time.
Process capability indices are used to compare two or more processes. The common indices include:
Pp — a simple indicator of process performance; Ppk — Process Performance Index; Cp — Process Capability; Cpk — Process Capability Index.
When data plotted on a control chart falls within the control limits, the production process is operating as expected. Any process falling outside the control limits produces non-standard product.
Variable data control charts are used to monitor the mean, the process target, and process variation. The x-bar and R-chart are the most common types of variable control charts; the centerline and standard deviation are the tools used to construct them. Product measurements should remain within the centerline boundaries to avoid violating control chart rules (Yang, 2011).
"How AS9103 integrates SPC to control KC variation"
"Research gap, problem statement, and study objectives"
"Hypothesis, chapter outline, and study limitations"
You’re 41% through this paper. Sign up to read the remaining 3 sections.
Sign Up Now — Instant Access Already a member? Log inAlways verify citation format against your institution’s current style guide requirements.