Definition
ARINC 424 is the international industry standard that specifies the format and content of navigation data used by airborne navigation systems, including FMS and GPS units. It defines how waypoints, airways, airports, runways, terminal procedures (SIDs, STARs, approaches), and path-terminator codes are encoded so that any compliant avionics system can read and fly the data consistently.
Plain English
It is the agreed-upon data format that tells flight management computers how to store and interpret navigation information, so that every approach, departure, and route looks the same to the avionics no matter who built them.
Context Anchor
Seen in instrument procedure design, navigation database discussions, and avionics systems that load routes or instrument approaches.
Derivation
ARINC stands for Aeronautical Radio, Incorporated, the company that originally developed standards for airline radio and avionics. The number 424 is simply the catalog number of this particular specification within the ARINC standards library.
Why Pilots Care
Accurate, standardized navigation data is required for reliable instrument approaches and enroute navigation; using ARINC 424 ensures the database works the same way across different aircraft systems.
Intuition Check
ARINC 424 is not an approach chart or a procedure itself. It is the data format used to code that procedure into a navigation database.
Example Sentence 1
The RNAV approach in the FMS is built from ARINC 424 path-terminator codes, which is why the aircraft turns at a specific point rather than simply flying direct to the next fix.
Example Sentence 2
Each 28-day AIRAC cycle updates the navigation data according to the latest ARINC 424 rules.