page_title: Pitot-static system
section_title: Airspeed indicator
hierarchical_section_title: Pitot-static system / Pitot-static instrument / Airspeed indicator
caption_attribution_description: English: Internal workings of an altimeter.
context_page_description: A pitot-static system is a system of pressure-sensitive instruments that is most often used in aviation to determine an aircraft's airspeed, Mach number, altitude, and altitude trend. A pitot-static system generally consists of a pitot tube, a static port, and the pitot-static instruments. Other instruments that might be connected are air data computers, flight data recorders, altitude encoders, cabin pressurization controllers, and various airspeed switches. Errors in pitot-static system readings can be extremely dangerous as the information obtained from the pitot static system, such as altitude, is potentially safety-critical. Several commercial airline disasters have been traced to a failure of the pitot-static system.
context_section_description: The airspeed indicator is connected to both the pitot and static pressure sources.  The difference between the pitot pressure and the static pressure is called dynamic pressure. The greater the dynamic pressure, the higher the airspeed reported. A traditional mechanical airspeed indicator contains a pressure diaphragm that is connected to the pitot tube.  The case around the diaphragm is airtight and is vented to the static port.  The higher the speed, the higher the ram pressure, the more pressure exerted on the diaphragm, and the larger the needle movement through the mechanical linkage.
caption: Aneroid Wafer of an altimeter
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