TRIANGLE OF VELOCITIES
Track: It is the actual path traversed over the ground. It may be track required, track desired or Track Made Good (TMG).
– The Americans use the term True Course for Track required.
– It is indicated by two arrows on the track line.
Ground Speed: The actual speed of the aircraft over the ground, covered or expected to be covered in a specified time.
Heading: The direction of the longitudinal axis of the aircraft from a known reference direction is called aircraft heading. It may be True heading (HdgT), Magnetic heading, (HdgM), Compass heading (HdgC) or Grid heading (HdgG).
– It is indicated by a single arrow on the heading line
Wind Direction: The direction from which the wind is blowing. The direction is always True direction.
– It is indicated by three arrows on the wind vector.
Wind Speed: The speed at which the wind is blowing.
Wind Velocity (W/V): Wind direction and speed when represented as vector is called wind velocity
Triangle of Velocities: The six components, Heading & True Air Speed, Track & Ground Speed and Wind Direction & Wind Speed form the 3 sides and 3 angles of a triangle. This triangle is called triangle of velocities.
– In this triangle the heading and track are the directions towards progress of the aircraft were as wind direction is the direction from which wind is blowing.
– In Navigation this triangle is continuously solved to know the position of the aircraft.
– In pre-flight planning the triangle of velocities is solved for every leg from the four known elements ie. Track required, TAS and forecast W/V. Heading and Ground Speed are calculated.
– If any of the four elements are known, other two elements may be calculated.
Drift: It is the angular difference between Heading and Track, measured in degrees port or starboard of the heading.
Bearing: The direction of one object from another, measured from a reference direction clockwise through 360º is called bearing.
– It may be True, Magnetic, Compass, Grid or Relaltive Bearing depending upon the reference direction chosen.
Relative Bearing (RB): The direction measured with respect to the longitudinal axis of the aircraft is called Relative Bearing.
Radial: The magnetic direction emanating from a radio station is called radial.
– It is always magnetic.
– Reciprocal of the radial is called anti-radial