The Complete Handbook of Aircraft Parts & Accessories

Chapter 1: Understanding Aircraft Parts & Accessories

The first thing to understand about aircraft parts and accessories is that you are not buying a commodity. A bolt that holds a wing strut to a fuselage is not the same as a bolt from a hardware store, even if the threads match and the dimensions are identical. What makes an aircraft part different is its provenance, its traceability, and its compliance with a defined standard. This is not bureaucracy for its own sake. These three attributes directly affect whether the part will perform as expected under the unique stresses of flight, and whether the installation is legally airworthy.

In the world of aviation, parts fall into two broad categories: those that are acceptable for installation in a type-certificated aircraft, and those that are not. A type-certificated aircraft is one that was designed, built, and approved to a specific set of engineering standards, such as a Cessna 172, a Piper Seneca, or a Beechcraft King Air. If you install a part in that aircraft that is not approved, or not approved in that specific position, the aircraft is no longer airworthy in the legal sense. It does not matter if the part was better, cheaper, or stronger. The regulations define what is acceptable, and deviating from that puts the aircraft outside the law and outside any valid insurance coverage.

Consider a practical example. A Cessna 172 requires a specific oil filter adapter gasket. You can go to the Cessna parts dealer and