In
aerodynamicsAerodynamics is a branch of dynamics concerned with studying the motion of air, particularly when it interacts with a moving object. Aerodynamics is a subfield of fluid dynamics and gas dynamics, with much theory shared between them. Aerodynamics is often used synonymously with gas dynamics, with...
, a
headwind is a
windWind is the flow of air or other gases that compose an atmosphere . On Earth, wind consists of the bulk movement of air...
that blows against the direction of travel of an object. A headwind reduces the object's speed and increases the time required to reach its destination. Headwinds are commonly measured in relation to the speed of vehicles — commonly air and watercraft — as well as in
runningRunning is a means for an animal to move on foot. It is defined in sporting terms as a gait in which at some point all feet are off the ground at the same time. This is in contrast to walking, where one foot is always in contact with the ground, the legs are kept mostly straight and the center of...
events — particularly
sprintA sprint is a sharp burst of forward movement.Sprint may refer to:*Sprint , a type of short race in athletics*Sprint, a major Cellular and Tier 1 telecommunications company in the United States originally called Sprint until July 2005...
s. The opposite wind is a
tailwindA tailwind is a wind that blows in the direction of travel of an object. A tailwind increases the object's speed and reduces the time required to reach its destination. Tailwinds are commonly measured in relation to the speed of vehicles — commonly air and watercraft — as well as in running events...
.
In aeronautics, a headwind is favourable in
takeoffTakeoff is the phase of flight in which an aircraft goes through a transition from moving along the ground to flying in the air, usually starting on a runway. For balloons, helicopters and some specialized fixed-wing aircraft , no runway is needed...
s and
landingthumb|right|A [[Mute Swan]] alighting. Note the ruffled feathers on top of the wings indicate that the swan is flying at the [[Stall |stall]]ing speed...
s.
In
aerodynamicsAerodynamics is a branch of dynamics concerned with studying the motion of air, particularly when it interacts with a moving object. Aerodynamics is a subfield of fluid dynamics and gas dynamics, with much theory shared between them. Aerodynamics is often used synonymously with gas dynamics, with...
, a
headwind is a
windWind is the flow of air or other gases that compose an atmosphere . On Earth, wind consists of the bulk movement of air...
that blows against the direction of travel of an object. A headwind reduces the object's speed and increases the time required to reach its destination. Headwinds are commonly measured in relation to the speed of vehicles — commonly air and watercraft — as well as in
runningRunning is a means for an animal to move on foot. It is defined in sporting terms as a gait in which at some point all feet are off the ground at the same time. This is in contrast to walking, where one foot is always in contact with the ground, the legs are kept mostly straight and the center of...
events — particularly
sprintA sprint is a sharp burst of forward movement.Sprint may refer to:*Sprint , a type of short race in athletics*Sprint, a major Cellular and Tier 1 telecommunications company in the United States originally called Sprint until July 2005...
s. The opposite wind is a
tailwindA tailwind is a wind that blows in the direction of travel of an object. A tailwind increases the object's speed and reduces the time required to reach its destination. Tailwinds are commonly measured in relation to the speed of vehicles — commonly air and watercraft — as well as in running events...
.
In aeronautics, a headwind is favourable in
takeoffTakeoff is the phase of flight in which an aircraft goes through a transition from moving along the ground to flying in the air, usually starting on a runway. For balloons, helicopters and some specialized fixed-wing aircraft , no runway is needed...
s and
landingthumb|right|A [[Mute Swan]] alighting. Note the ruffled feathers on top of the wings indicate that the swan is flying at the [[Stall |stall]]ing speed...
s. As a result,
aviatorAn aviator is a person who flies aircraft for pleasure or as a profession. The first recorded use of the term was in 1887 as a variation of the French 'aviation', from the latin 'avis', coined 1863 by G. de la Landelle in "Aviation ou Navigation Aérienne"...
s and
air traffic controllerAir traffic controllers are the people who operate the air traffic control systems to expedite and maintain a safe and orderly flow of air traffic and help prevent mid-air collisions. They apply separation rules to keep aircraft apart from each other in their area of responsibility and move all...
s commonly choose to takeoff or land in the direction of a
runwayA runway is a strip of land at an airport on which aircraft can take off and land and forms part of the maneuvering area. Runways may be a man-made surface or a natural surface .By extension, the term has come to mean, in addition, any long, flat, straight area, such as that used in fashion...
that will provide a headwind. In sailing, a headwind may make forward movement difficult, and necessitate tacking into the wind.
Aeronautics calculations
Pilots calculate the Headwind Component, Tailwind Component and Crosswind Component of any wind, if they do exist. Headwind and Tailwind are cosine functions of the wind while Crosswind Component is a sine function. Headwind and Tailwind do not occur together in normal conditions. Determining the
ground speedGround speed is the speed of an aircraft relative to the ground. It is the sum of the aircraft's true airspeed and the current wind and weather conditions; a headwind subtracts from the ground speed, while a tailwind adds to it...
of an aircraft requires the calculation of the head or tailwind.
Assume:
A=Angle of the wind from the direction of travel
WS=The measured total wind speed
CW=Crosswind
HW=Headwind
Then
CW=Sin(A)*WS
HW=Cos(A)*WS
For example if the wind is at 24015 that means the wind is currently from heading 240
degreesA degree , usually denoted by ° , is a measurement of plane angle, representing 1⁄360 of a full rotation; one degree is equivalent to π/180 radians...
with a speed of 15
KnotsThe knot is a unit of speed equal to one nautical mile per hour, which is equal to exactly 1.852 km/h and approximately 1.151 mph. The abbreviation kn is preferred by American and Canadian maritime authorities, and by the Institute of Electrical and Electronics Engineers; however, the...
and the aircraft is taking-off from runway 18; having heading of 180.
Crosswind = Sin(240-180)*15 ≈ 13
Headwind = Cos(240-180)*15 ≈ 7.5
The aircraft is said to have 13 knots of crosswind and 7.5 knots of headwind.
Aircraft usually have maximum headwind and crosswind components which they cannot exceed. If the wind is at eighty degrees or above it is said to be full-cross. If the wind exceeds 100 degrees it is common practice to takeoff and land from the opposite side of the runway, it has a heading of 360 in the above mentioned example.