The Airspeed Indicator

During a typical flight operation, knowing the airspeed that the aircraft is traveling at is important for carrying out a number of standard procedures. Whether maintaining a level speed for fuel efficiency, reducing it before a turn or landing, or increasing speed to ready for a liftoff, knowing how fast the aircraft is moving assists in upholding safe and efficient piloting. With an instrument known as the airspeed indicator, pilots are provided with the speed that the aircraft is moving at in relation to its surrounding air. As the airspeed indicator serves as one of the primary aircraft instruments, having an understanding of its functionality is very important for any pilot.

In order for the airspeed indicator to provide its readings to the pilot, the instrument relies on static and ram pressure gathered by the pitot-static system. The pitot-static system is a set of pressure-sensitive instruments and equipment, and it consists of the pitot tube, static port, and various pitot-static instruments. With a pitot tube located in an area where it is exposed to relative wind, ram air pressure is collected for the means of garnering total pressure. The static port, on the other hand, is often located in an undisturbed area of the fuselage and gathers static pressure. Unlike all the other aircraft instruments, the airspeed indicator utilizes both the pitot tube and static port for its measurements.

With a diaphragm located within the airspeed indicator case, static pressure enters the case while the pressurized air from the pitot tube enters the diaphragm itself. Based on the difference between the two pressures, the diaphragm will either begin to expand or contract and a pointer will move across a dial in response. Generally, the difference between the two pressures will be negligible while stationary on the ground, as ram air pressure increases with forward movement and static pressure increases with altitude. As measurements require air to be collected from tubes and ports located on the fuselage, all openings should be inspected before each flight to ensure there are no blockages that would create a major safety hazard.

The reading displayed on the airspeed indicator is known as the indicated airspeed (IAS), and it is important to know that this speed does not account for any errors or air density variation. With the use of airspeed calibration charts and other correction tools, calibrated airspeed (CAS) can be attained. By further correcting the reading with altitude and nonstandard temperatures, true airspeed (TAS) is determined. TAS is very beneficial for flight planning, and it may be determined by the flight computer.

On aircraft that do not have an airspeed indicator, other instruments or equipment may be used to either measure or control airspeed for flight. The airspeed sensor is a component that is regularly used for VTOL aircraft, and they utilize the pitot tube, static port, a temperature sensor, and two pressure sensors in order to measure pressure differences for speed readings. A controller airspeed or airspeed controller device is often found on UAVs, and they serve the autopilot system for speed adjustments as needed to accommodate different flight phases and stability.

With the use of the airspeed indicator or similar devices, pilots can ensure that they operate within safe speed ranges throughout the duration of a flight. Aerospace Buying is an online distributor of aircraft parts, offering customers competitive pricing on airspeed indicator, airspeed sensor, and controller airspeed components sourced from leading global manufacturers. As you peruse our expansive listings, you may request a quote at any time through the submission of an Instant RFQ form. Once we have received your request, our team of industry experts will quickly review and respond with a personalized quote in just 15 minutes or less.


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December 3, 2020
November 5, 2020

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