Definitions
Heading: This is the direction the aircraft’s longitudinal axis points, usually measured in degrees from North (true, magnetic, compass, or grid).
Track: This refers to the projection on the Earth’s surface of an aircraft’s path, with the direction expressed in degrees from North (true, magnetic, or grid).
Radial: A magnetic bearing that extends from a VOR/VORTAC/TACAN.
Bearing: The horizontal direction to or from any point, typically measured clockwise from true north, magnetic north, or another reference point through 360 degrees.
Description
Heading vs. Track
The heading of an aircraft can differ from its track due to wind, which creates a drift angle. For most airliners flying at cruising speed, this difference is often within 5 degrees. However, under certain conditions, such as a true airspeed of 400 knots with a 100-knot crosswind, the drift angle can increase to 15 degrees.
Heading, Track, and Drift Angle
While the heading is essential for vectoring, the track is not. When an aircraft follows a specific track, its path remains a straight line. Conversely, if it flies on a heading, the line may curve left or right due to changing winds. Thus, an aircraft flying on a track may require multiple heading adjustments to counteract wind-induced drift.
Radial vs. Bearing
A radial is a specific type of bearing, always linked to the magnetic direction from a radio aid. In contrast, bearing is a broader term that can be measured from any reference point—whether it’s a radio aid, navigation point, the aircraft itself, or a point with coordinates. Bearings can relate to any North, not just the magnetic one.
Heading vs. Radial
The radial provides the relative position of an aircraft in relation to a VOR, but there is no mathematical relationship between the radial and the aircraft’s heading or track. For instance, if an aircraft is on the 360-degree outbound radial (to the north of the VOR), it can be flying on any heading or track, at least for a short duration.
Continuous Flight on a Radial
When flying continuously on a radial, the aircraft’s track aligns with either the inbound or outbound radial. A pilot heading toward a VOR has two choices: fly on the inbound radial (where the “TO” flag of the VOR receiver lights up) or on the outbound radial (where the “FROM” flag activates). The outbound radial is shown on many arrival and approach charts.
Conversely, a pilot flying away from a VOR also has two options: fly on the outbound radial (with the “FROM” flag on, which is the usual scenario) or on the inbound (reciprocal) radial (where the “TO” flag is lit). Although the latter is technically feasible, it can cause confusion and is generally not recommended.
