Headwind
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A headwind is a wind that hits an aircraft in the front. This reduces the aircraft's ground speed and increases the time to reach a destination. It is favourable in takeoffs and landings where aviators and Air Traffic Controllers choose the side of the runway with the wind coming against the aircraft.
[edit] Headwind Component
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
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 degrees with a speed of 15 Knots 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. Aircrafts 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.
[edit] See also
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