Airspeed and Mach number indicator

The airspeed and Mach number indicator displays the speed of the aircraft in relation to the air in which it is flying. In some instances, the speed of an aircraft is shown in Mach numbers. The Mach number of any moving body is its speed compared to the speed of sound in the surrounding medium (local speed). For example, if an aircraft is flying at a speed equal to one-half the local speed of sound, it is flying at Mach 0.5.

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GYROSCOPIC EQUIPMENT A gyroscope is a device for measuring or maintaining orientation, based on the principles of conservation of angular momentum. A mechanical gyroscope is essentially a spinning wheel or disk whose axle is free to take any orientation. This orientation is changed by external torque, but when it is minimized orientation restores because of a high rate of disk. But it’s not only principle on which gyroscopes are based. The ring laser gyroscope (RLG) consists of a ring laser having two counter-propagating modes over the same path in order to detect rotation. It operates on the principle of the Sagnac effect. A certain rate of rotation induces a small difference between the time it takes light to traverse the ring in the two directions. This introduces a tiny separation between the frequencies of the counter-propagating beams, a motion of the standing wave pattern within the ring, and thus a beat pattern when those two beams are interfered outside the ring. Therefore the net shift of that interference pattern follows the rotation of the unit in the plane of the ring.