Apparent wind
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1. speed - 2. fair wind - 3. wind - 4. Apparent Wind |
Apparent wind is the breeze felt by an observer. It is created both by the movement of the observer, and by the true
wind. For a stationary observer, both apparent wind and true wind are the same. Apparent wind is calculated by the sum of two
vectors. The first vector is the true wind velocity. The second vector is the velocity of the observer. By adding these two vectors together, one can determine the apparent wind.
In
sailing, and especially in
sailboat racing, apparent wind is a vitally important factor, since it determines the
points of sail on which the sails can efficiently generate forward motion.
In
fixed-wing aircraft, apparent wind determines the necessary speeds for takeoff and landing.
Aircraft carriers generally steam directly upwind at speeds of up to 35
knots, in order to increase apparent wind and reduce the necessary takeoff velocity. Land-based
airport traffic generally take off and land facing upwind for the same reason.
