Aero-Terms!

Aero-Terms are designed to be a daily reminder of the terms, names, acronyms and explanations of the unique language that populates the aviation world. Aerospace, sport aviation, fixed wing, helo, you name it... it's all fair game.

Aero-Terms should serve as a quick but intriguing reminder of the terms you may use every day, or an introduction to an aspects of the Aero-World you may not yet be familiar with. ANN also encourages readers to go beyond the FMI link, and further research any intriguing terms.

Suggestions for future Aero-Terms are ALWAYS welcome, as are additions or discussion of the explanations given for each Aero-Term.

Critical Structure

A load bearing structure/element whose integrity is essential in maintaining the overall flight safety of the aircraft. Note that there are differences in the definitions of primary structure, secondary structure, and principle structural elements (PSE) when considering the different categories of aircraft. For example, PSE’s (principle structural elements) are critical structures for Transport Category Aircraft.
 
This definition is important in determining whether a repair or alteration is considered either Major or Minor. If a item of structure is considered “critical”, “primary” or a “PSE” the repair of that item would be considered Major thus neccesitating the use of Approved repair data.

FMI: http://aviationglossary.com/federal-aviation-administration-faa-definition/critical-structure/