AC

Advisory Circular

In the context of aviation and aerospace, an Advisory Circular (AC) is a document issued by a national aviation authority, such as the Federal Aviation Administration (FAA) in the United States, to provide guidance and information on a specific topic or regulation.

Alternating Current

In the context of aviation and aerospace, "Alternating Current" (AC) refers to a type of electrical current that periodically reverses direction, unlike direct current (DC) which flows in one direction only. In aircraft and spacecraft systems, AC is used to power various equipment and systems, such as: