Definition
An FAA Advisory Circular that establishes the standards and procedures for a Surface Movement Guidance and Control System (SMGCS), which allows aircraft and vehicles to operate safely on airport movement areas during low-visibility conditions (typically when runway visual range is below 1,200 feet).
Plain English
An FAA guidance document that tells airports and pilots how to safely move around on the ground when visibility is very poor, such as in heavy fog. It covers the special lighting, signs, markings, and procedures used so aircraft and ground vehicles don't collide while taxiing.
Context Anchor
Seen in discussions of SMGCS plans, low-visibility taxi procedures, and airport surface movement guidance.
Derivation
An 'Advisory Circular' (AC) is the FAA's standard format for issuing non-regulatory guidance. The number '120-57' identifies its subject series (120 covers air carrier operations) and its sequence within that series. Knowing this helps pilots recognize that an AC is official FAA guidance, not a regulation, but is still the accepted method for meeting related rules.
Why Pilots Care
Following the procedures in this circular reduces the risk of runway incursions and keeps ground movement safe when visibility is too low for normal taxi operations.
Intuition Check
Do not read advisory as meaning unimportant. An advisory circular is usually guidance rather than a regulation by itself, but its procedures can still shape the rules a pilot must follow through airport, company, or approved operating procedures.
Example Sentence 1
Before conducting low-visibility taxi operations, the crew reviewed the SMGCS chart developed under Advisory Circular 120-57.
Example Sentence 2
Airport operations referenced Advisory Circular 120-57 to confirm lighting and marking requirements for the active SMGCS plan.