PMA Parts Make Improvements Possible

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Any aircraft is the sum of its parts, and if any one of them is not designed, tested, and approved for use on a specific make and model, the airplane cannot legally earn its keep. Airframe and powerplant OEMs are the primary source of approved parts, but usually they do not accommodate capabilities beyond those that existed when the aircraft earned its type certificate.

Incorporating new technology after an aircraft earned its TC requires a supplemental type certificate (STC). And the parts that bring everything from glass cockpits and NextGen avionics to cabin in-flight entertainment systems earn their right to fly through the Parts Manufacturing Approval (PMA) process.

As the PMA flowchart suggests, it’s an involved process. Often it starts with an approval from an Aircraft Certification Office (ACO). Most STCs involve major changes to an airplane’s capabilities, and the FAA requires proof that they do not adversely affect the airplane. As part of its STC efforts, ASIG works with the necessary FAA offices.

Developing PMA parts not only makes STC’d improvements possible, it creates the parts that maintain the new capabilities. ASIG engineers design needed parts as they develop an STC, but their work goes well beyond laying out an instrument panel or wiring harness that connects it to the airplane. In transport-category aircraft each new part must meet the requirements of Part 25. In other words, the new part must be equal to—or better than—the part it replaces.

A new part proves itself through drawings, specifications, and documents that include all required computations and the results of an exhaustive testing plan. To be eligible for installation the part must be made of the appropriate materials. It must perform its intended function and be compatible with the parts or components to which it is connected. Tests must prove that the part performs reliably under all mission profiles, cyclic loads, the stress of pressure and temperature, and all other applicable operating conditions.

From this design and testing work ASIG creates the required plan for continued operational safety (COS). Central to this effort is determining how critical a part is by assessing the consequences of its failure. Starting with the part’s fatigue life, engineers apply the appropriate margin of safety by establishing its airworthiness lifespan. Further, they identify failure modes, provide corrective actions, and generate instructions for continued airworthiness. And they include a recordkeeping plan that starts when the part is manufactured and legibly numbered with permanent markings.

An FAA Manufacturing Inspection District Office (MIDO) examines every scintilla of a PMA application. This can be time consuming, but ASIG’s designated engineering representatives approve much of the work before it goes to the FAA, significantly reducing the time to the MIDO’s final approval—and the time it takes to introduce new capabilities to your fleet.

Until next time, stay 5x5, mission ready, and Wired!