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Airspeed Indicator (ASI)

Airspeed Indicator (ASI)

  • The ASI is a sensitive, differential pressure gauge which measures and promptly indicates the difference between pitot (impact/dynamic pressure) and static pressure.
  •  These two pressures are equal when the aircraft is parked on the ground in calm air.
  •   When the aircraft moves through the air, the pressure on the pitot line becomes greater than the pressure in the static lines.
  •  This difference in pressure is registered by the airspeed pointer on the face of the instrument, which is calibrated in miles per hour, knots (nautical miles per hour), or both.
  • The ASI is the one instrument that utilizes both the pitot, as well as the static system. The ASI introduces the static pressure into the airspeed case while the pitot pressure (dynamic) is introduced into the diaphragm.
  •  The dynamic pressure expands or contracts one side of the diaphragm, which is attached to an indicating system. The system drives the mechanical linkage and the airspeed needle.

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