How does it impact maintenance?
By Chris Grosenick
Quality can be described in a number of different ways depending on the perspective and the product or process involved. Quality is defined as "an inherent feature, a degree of excellence, having certain properties and grade." Webster's Dictionary defines quality control as "an aggregate of activities (as design analysis and statistical sampling with inspection for defects) designed to ensure adequate quality especially in manufactured products." While quality means different things to different people, AMTs should define quality as a collection of processes designed and implemented to ensure adequate quality exists in both aviation maintenance processes and products.
Let's go back a few years to the time when Quality Control (QC) was introduced as a product-oriented concept. Picture an inspector sitting at the end of an assembly line looking at each widget as it came down the chute. Inspectors looked for obvious defects and checked dimensions with some sort of "go/ no-go" gauge. The aviation equivalent would be a team of inspectors in a large operation, or an IA inspecting an aircraft after a major repair or phase inspection. This type of inspection looked at the finished product with little emphasis on the process that produced that product. Depending on the "product," this system worked quite well for a long time, but as manufacturing complexity evolved, end of assembly line inspection was not sufficient. Into that equation was also thrown cost, economies of scale, new materials, and new manufacturing processes.
One component of a quality management system is Quality Assurance (QA), and is most closely identified with ISO-9000, Six Sigma, and its successors. It is a process-based system that places more emphasis on how something is made rather than the final product. The rapid evolution of computers and their widespread use in manufacturing has allowed the process to become the focus of quality assurance, because computers can perform the same function many times with little or no error. One example is the modern CNC milling machine. Not only can these machines make parts with tolerances down to the fifth decimal place (.0000X), but they are smart enough to sense when the cutting tool starts to become dull.
Statistical process control has become the standard for manufacturing operations that use high technology machinery, and this quality process has been applied to the balance of quality programs in many different industries.
How does it apply to aviation?
How do new quality assurance processes apply to the aviation industry? It has been more difficult to apply these principles to aviation, mainly because of the small numbers of aircraft and components relative to other manufacturing processes for which quality assurance was originally designed. It has been relatively easy to apply these principles to the aircraft manufacturing process because of the intense automation and use of computers in the industry. One problem remains however, and that is that aircraft are still pieced together by hand, despite the assembly line appearance of aircraft factories.
And how does the quality assurance process apply to aviation maintenance? This is more difficult to answer because aviation maintenance is governed by several factors: statutory requirements (the FARs), original equipment maker (OEM) maintenance schedules and requirements (aircraft maintenance manual), industry standards and specifications (SAE, ANSI, NAS), and general maintenance practices (AC 43.13-1B, 337 and field approvals, etc.). When a maintenance situation is not covered by any of these documents or procedures, the AMT must rely on either experience or guidance from another technician or inspector to accomplish the repair. As a general rule, aviation maintenance should be done in accordance with the applicable OEM maintenance manual and the supporting OEM processes and procedures for general repairs. When this guidance does not exist, an AC 43.13 repair, or MIL-STD/MIL-SPEC procedure is warranted, depending on the certification system for the subject aircraft. An industry standard process can be used if no other information is available, and for certificated aircraft, a 337/field approval is one solution. Most of the time an OEM repair is available, and there is little need to find another solution. The reason an OEM solution is preferred is because an inspector/IA will use the maintenance manual set to perform an annual or sign off a major repair.