Some terms are most commonly used in aviation centers for Air navigation purposes. The definitions of the terms are given in the subsequent paras.

Air Navigation Terms

Course.    The course is the direction in which an aircraft is heading. Courses are always expressed in three ways and are known as True Course, Magnetic Course and Compass Course.

Track.  The direction of the path of an aircraft over the earth is called track. Tracks are also expressed in three ways and are known as True track, Magnetic track and Compass track.

Drift.   The angular difference between the course of an aircraft and its track is called the drift.  Drift is measured in degrees to port (P) or starboard (S) from the aircraft’s head.  Drift is also named plus (starboard) or minus (port) and can be applied directly to the course to obtain the track.

Bearing.   The direction of one point from another is termed as bearing. Bearings may be measured from true north, magnetic north, or compass north but are normally plotted on a chart from true north. Sometimes the direction of a point from the aircraft is measured in relation to the forward axis of the aircraft. In this case the bearing is called a relative bearing. Relative bearings are measured clockwise from the forward axis of the aircraft through 360° and are frequently labeled with the letter (R). Thus, an object in line with the plane’s starboard wing has a relative bearing of 090(R). Similarly, an object in line with the port wing has a relative bearing of 270(R). When the relative bearing is known, the true bearing of an object from the aircraft can be calculated and depends upon the plane’s heading.

Back Bearing.    The direction observed from an aircraft of a place over which it has previously passed without any intervening alteration of course is called Back bearing.  It should be noted that a back bearing is the reverse direction of the track of an aircraft and may be expressed in true, magnetic and compass bearing.

Wind Direction. The direction from which the wind is blowing is called the Wind Direction.

Axis of Earth.     The diameter about which the earth rotates. 

Flight Plan.     Specified information relative to the intended flight of an aircraft filled either orally or in writing with air traffic control.  Also that portion of a flight log that is prepared before a flight.

ETA (Estimated Time of Arrival).     The predicted time at which an aircraft will reach a given point.

Knots.      A speed of one nautical mile per hour.

Pin Point.   The ground position of an aircraft determined by direct observation of the ground.

QFE.    Represents the atmospheric pressure at official aerodrome level.

QFF.      Represents the atmospheric pressure converted to mean sea level in accordance with meteorological practice.

QNH.     Represents the pressure value at which the subscale of an altimeter must be set that the altimeter will indicate the actual runaway elevation on landing.

Radar.  Radio detection and ranging equipment that determines the distance and usually the direction of objects by transmission and return of electromagnetic energy.

Radio.      A descriptive term applied to the use of electromagnetic waves between 10 kilocycles per second and 3,000,000 megacycles per second.

Search.    The organised employment of aircraft to find an objective whose position is unknown or uncertain.  But which has not been located on ETA.

Endurance.        The time an aircraft can continue flying under given conditions without refuelling 

Heading.  The course of an aircraft is called heading.    

Air Position. At any time the position of the aircraft whose progress is imagined to have been unaffected by the wind is called it’s air position. 

Indicated Air Speed (IAS). The speed of the aircraft shown by airspeed indicator uncorrected for positional and instrumental errors.

True Air Speed (TAS).  The speed of an aircraft corrected for positional and instrumental errors.

 Ground Speed.  The speed at which an aircraft travels over the ground is called its ground speed or the speed of an aircraft in relation to the earth is called ground speed.

 Cruise Control.   The method of operation of an aircraft to produce optimum fuel consumption with respect to time and/ or distance.

 Rhumb Line .     A line on the surface of the earth cutting all meridians at the same angle.

Compass Rose. Compass Rose is a design on a chart that shows direction. It points which way is north, south, east, west, and some intermediate directions.

Dead reckoning. Dead Reckoning determines a position by plotting courses and speeds from a known position.

Global Positioning System (GPS).   Global Positioning System (GPS) is a system which uses information broadcast from orbiting satellites to calculate the longitude and latitude of a receiving device.

 Parallax.  Parallax is the apparent differences in the positions of objects viewed along different lines of sight.

Sextant.   Sextant is an instrument used to measuring angular distances, like the altitude of the sun, moon and stars for navigation.