Final answer:
The DME Radial Waypoints are displayed in the FMS using the ARINC 424 standard as a five-letter code, consisting of the DME station's identifier, a radial direction, and the distance from the station. This format supports navigation during various phases of flight.
Step-by-step explanation:
The DME Radial Waypoints are expressed in the Flight Management System (FMS) using the ARINC 424 navigational data standard, which is the aeronautical industry's principal standard for the formatting and transmission of data to onboard navigation systems. DME Radial Waypoints are typically designated by a five-letter code within the FMS. The code usually consists of the three-letter identifier of the DME station followed by a two-digit radial and may include an extension that indicates the distance from the station along that radial. For example, a DME Radial Waypoint might be displayed as "ABC45/15" in the FMS. Here, "ABC" represents the DME station, "45" represents the radial direction degrees from the station, and "15" signifies the distance in nautical miles along the radial from the DME station to the waypoint. These waypoints are crucial for pilot navigation as they dictate specific positions of aircraft in three-dimensional space (latitude, longitude, and altitude) and help in managing the aircraft's path during a flight, especially when flying along Standard Instrument Departures (SIDs), Standard Terminal Arrival Routes (STARs), or approach procedures.