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Blade pitch or simply pitch refers to turning the angle of attack of the blades of a propeller or helicopter rotor into or out of the wind to control the production or absorption of power. Wind turbines use this to adjust the rotation speed and the generated power. A propeller of a ship uses this effect to control the ship's speed without changing the rotation of the shaft and to increase the efficiency of streaming fluids. == Aircraft == In aircraft, blade pitch is usually described as "coarse" for a coarser angle, and "fine" for a finer. For an aircraft that is stationary the angle of pitch of each blade of a propeller fitted to that aircraft equates to the angle of attack. Blade pitch is normally described in units of distance/rotation assuming no slip. Blade pitch acts much like the gearing of the final drive of a car. Low pitch yields good low speed acceleration (and climb rate in an aircraft) while high pitch optimizes high speed performance and economy. A propeller blade's "lift", or its thrust, depends on the angle of attack combined with its speed. Because the velocity of a propeller blade varies from the hub to the tip, it is of twisted form in order for the thrust to remain approximately constant along the length of the blade; this is called washout. This is typical of all but the crudest propellers. It is quite common in aircraft for the propeller to be designed to vary pitch in flight, to give optimum thrust over the maximum amount of the aircraft's speed range, from takeoff and climb to cruise. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「blade pitch」の詳細全文を読む スポンサード リンク
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