In
air navigation, the wind triangle is a graphical representation of the relationship between
aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engine ...
motion and
wind
Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few ho ...
. It is used extensively in
dead reckoning
In navigation, dead reckoning is the process of calculating current position of some moving object by using a previously determined position, or fix, and then incorporating estimates of speed, heading direction, and course over elapsed time. ...
navigation
Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navigation, ...
.
The wind triangle is a
vector
Vector most often refers to:
*Euclidean vector, a quantity with a magnitude and a direction
*Vector (epidemiology), an agent that carries and transmits an infectious pathogen into another living organism
Vector may also refer to:
Mathematic ...
diagram, with three vectors.
*The air vector represents the motion of the aircraft through the airmass. It is described by
true airspeed
The true airspeed (TAS; also KTAS, for ''knots true airspeed'') of an aircraft is the speed of the aircraft relative to the air mass through which it is flying. The true airspeed is important information for accurate navigation of an aircraft. Tr ...
and
true heading.
*The wind vector represents the motion of the airmass over the ground. It is described by
wind speed
In meteorology, wind speed, or wind flow speed, is a fundamental atmospheric quantity caused by air moving from high to low pressure, usually due to changes in temperature. Wind speed is now commonly measured with an anemometer.
Wind speed ...
and the inverse of wind direction. Note that by convention wind direction is given as the direction the wind is ''from''. In a vector diagram such as the wind triangle, wind direction must be stated as the direction the wind is blowing ''to'', or 180 degrees different from the convention.
*The ground vector represents the motion of the aircraft over the ground. It is described by
ground track
A ground track or ground trace is the path on the surface of a planet directly below an aircraft's or satellite's trajectory. In the case of satellites, it is also known as a suborbital track, and is the vertical projection of the satellite's ...
and
ground speed
Ground speed is the horizontal speed of an aircraft relative to the Earth’s surface. It is vital for accurate navigation that the pilot has an estimate of the ground speed that will be achieved during each leg of a flight.
An aircraft diving ve ...
. The ground vector is the resultant of algebraically adding the air vector and the wind vector.
The wind triangle describes the relationships among the quantities used in
air navigation. When two of the three vectors, or four of the six components, are known, the remaining quantities can be derived. The three principal types of problems to solve are:
#''Solve for the ground vector''. This type of problem arises when true heading and true airspeed are known by reading the flight instruments and when wind direction and speed are known from either the meteorological forecast or from determination in flight.
#''Solve for the wind vector''. This type of problem arises when determination of heading and true airspeed can be done by reading the flight instruments and ground track and ground speed can be found either by measuring the direction and distance between two established points of the aircraft or by determining the drift angle and ground speed by reference to the ground.
#''Solve for true heading and ground speed''. This type of problem arises during
flight planning
Flight planning is the process of producing a flight plan to describe a proposed aircraft flight. It involves two safety-critical aspects: fuel calculation, to ensure that the aircraft can safely reach the destination, and compliance with air tr ...
or during a flight, when there is a need to determine a true heading to fly and a ground speed with which to compute an
estimated time of arrival
The estimated time of arrival (ETA) is the time when a ship, vehicle, aircraft, cargo, emergency service, or person is expected to arrive at a certain place.
Overview
One of the more common uses of the phrase is in public transportation where the ...
.
The traditional method of solving wind triangle equations is graphical. The known vectors are drawn to scale and in the proper direction on an
aeronautical chart
An aeronautical chart is a map designed to assist in the navigation of aircraft, much as nautical charts do for watercraft, or a roadmap does for drivers. Using these charts and other tools, pilots are able to determine their position, safe alt ...
, using
protractor
A protractor is a measuring instrument, typically made of transparent plastic or glass, for measuring angles.
Some protractors are simple half-discs or full circles. More advanced protractors, such as the bevel protractor, have one or two sw ...
and dividers. The unknown quantities are read from the chart using the same tools. Alternatively, the
E6B flight computer (a circular slide rule with a translucent "wind face" on which to plot the vectors) can be used to graphically solve the wind triangle equations.
On aircraft equipped with advanced navigation equipment, the wind triangle is often solved within the
flight management system
A flight management system (FMS) is a fundamental component of a modern airliner's avionics. An FMS is a specialized computer system that automates a wide variety of in-flight tasks, reducing the workload on the flight crew to the point that mode ...
, (FMS) using inputs from the
air data computer
An air data computer (ADC) or central air data computer (CADC) computes altitude, vertical speed, air speed, and Mach number from pressure and temperature inputs. It is an essential avionics component found in modern aircraft. This computer, rath ...
(ADC),
inertial navigation system
An inertial navigation system (INS) is a navigation device that uses motion sensors (accelerometers), rotation sensors ( gyroscopes) and a computer to continuously calculate by dead reckoning the position, the orientation, and the velocity (dir ...
(INS),
global positioning system
The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite sy ...
(
GPS
The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite sy ...
), and other instruments, (
VOR), (
DME), (
ADF). The pilot simply reads the solution provided to them.
See also
*
Set and drift are used to describe the current vector in marine navigation, analogous to wind in air navigation.
*
E6B flight computer.
*
Drift meter
A drift meter, also drift indicator and drift sight, is an optical device used to improve dead reckoning for aircraft navigation by measuring wind effect on flight.
Design
A drift meter consists of a small telescope extended vertically through th ...
References
*{{cite book , date=1 December 1989 , title=Air Navigation , publisher=Department of the Air Force, id=AFM 51-40
External links
A Javascript wind triangle calculator
Air navigation