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A Machmeter is an aircraft pitot-static system flight instrument that shows the ratio of the true airspeed to the speed of sound, a dimensionless quantity called Mach number. This is shown on a Machmeter as a decimal fraction. An aircraft flying at the speed of sound is flying at a Mach number of one, expressed as ''Mach 1''. ==Use== As an aircraft in transonic flight approaches the speed of sound soon after its takeoff, it first reaches its critical mach number, where air flowing over low-pressure areas of its surface locally reaches the speed of sound, forming shock waves. The indicated airspeed for this condition changes with ambient temperature, which in turn changes with altitude. Therefore, indicated airspeed is not entirely adequate to warn the pilot of the impending problems. Mach number is more useful, and most high-speed aircraft are limited to a maximum operating Mach number, also known as MMO. For example, if the MMO is Mach 0.83, then at where the speed of sound under standard conditions is , the true airspeed at MMO is . The speed of sound increases with air temperature, so at Mach 0.83 at where the air is much warmer than at , the true airspeed at MMO would be . 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「Machmeter」の詳細全文を読む スポンサード リンク
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