Triangle of Velocities – Ibex Aviation Academy

Triangle of Velocities or Vector Triangle or Wind Triangle

Plotting is the means of keeping track of aircraft position at all times during a flight
Pilots are legally mandated to be aware of their position at all times during a flight
Track and Air Plot are the two means of keeping track of aircraft position

Track plot is maintained by connecting the ground positions of aircraft
Track plot is the simplest means of keeping track of an aircraft position
Planned track (PT)or Track Required (TR)is intended flight path of the aircraft over surface of earth
Track Made Good (TMG) is the actual path of aircraft over ground
TMG is obtained by connecting the ground positions of aircraft at regular intervals
Track error is the angle made between Track Required (TR)and Track Made Good (TMG)
Track error is measured in degrees and expressed as TMG being Port (Left) or Starboard (Right) of TR

Track Plot is simple to maintain and is useful for pilot navigation
It is sufficient for short distance flights if frequent ground position is available
Useful in Clear Weather or Visual Met Conditions where ground is visible
Track Plot can be effectively used to alter headings during Terminal Navigation

Track plot would not be sufficient for all flights
It would not be usable in bad weather where we need to alter heading frequently
Track plot is unfit for long distance and oceanic flights with limited ground fixes
Track plot is not usable when ground is not visible throughout the flight time

Air Plot is the method of keeping track by plotting Air Positions
Air Vector, Ground Vector and Wind Vector are the three vectors in an air plot
Air Vector consists of Heading and True Air Speed (TAS) denoted by one arrow
Heading is the direction of the longitudinal axis of the aircraft and TAS is the speed of aircraft in nil wind
Ground vector consists of Track and Ground Speed denoted by two arrows
Track is the path of the aircraft over the surface of earth and Ground speed is the speed of aircraft in relation to ground positions
Wind Vector consists of Wind direction and Speed denoted by three arrows
Wind direction is indicated from the direction where wind blows and the wind speed is the speed of wind

Triangle of Velocities is used in Air Plot to find Drift Angle, Winds and the required Alteration of Heading
Wind Speed and Direction can be found by plotting the known vectors of the velocity triangle to scale
Drift Angle is the angle made between the Heading and Track of the Aircraft
Track could be Track Required (TR) during planning stage or Track Made Good (TMG) during flight
Drift angle is expressed in degrees and whether the Track is port (left) or starboard (right) of Heading
Port drift means the Track is to the left of heading which implies that winds are blowing the aircraft from right to left
Starboard drift means the track is to the right of heading which implies that winds are blowing the aircraft from left to right

Air Plot is the preferred method of maintaining position for long distance flights
Usable in bad weather where we need to alter heading frequently
Suitable for long distance and oceanic flights with limited ground fixes
Usable when ground is not visible throughout

Assume that an aircraft is maintaining Heading of 000 (T) and TAS of 100 Knots
Wind direction is 240° and Speed is 30 knots as per the Meteorological Briefing
Use Protractor and Scale to draw the air vector
Direction of the air vector would be 000° and the length of vector should be 100 mm represents 100 knots
Draw the wind vector in the similar manner
Direction of wind vector should be from 240 or will point towards 060
Length of wind vector would be 30 mm represents 30 knots
To get the ground vector
Join the start of air vector and end of wind vector
Measure the direction using protractor to get 012 and measure the length using scale to get 118 mm
The vector triangle tells you that Aircraft Track will be 012 (T) and Ground Speed will be 118 knots