What Are Aircraft Airspeed Indicators?

In order to effectively and safely fly an aircraft, pilots must have a good understanding of where their aircraft is in the sky, where it is heading, how fast, etc. While some of this can be attained simply by looking out of the cockpit window, a pilot will only get a general estimation of conditions, assuming that it is light enough outside to see in the first place. As such, cockpit instruments are the most reliable tool for a pilot to use, ensuring accurate readings on a variety of flight conditions with instant updates. One of the instruments that is a staple of aviation is the airspeed indicator, and it allows a pilot to monitor just how fast the aircraft is traveling in relation to the outside air. As this instrument is used from the initial lift off procedure to landing, it is paramount that pilots have ample understanding of how an airspeed indicator functions.

When obtaining readings, the standard is for airspeed to be presented in knots, kilometers per hour, miles per hour, or other similar scales. Using this instrument, pilots can determine whether or not they are within an optimal speed range during each stage of a flight, ensuring that safety is upheld while following general rules. Most aircraft airspeed indicators measure speed through an indirect approach, utilizing air pressure measurements that are calculated by finding the difference between static and impact (pitot) air pressure. While static air pressure is simply the pressure of air based on the altitude that an aircraft is traveling at, impact pressure is the force of air acting against the aircraft as it moves forward.

To capture static air pressure, inlets known as static ports are situated in areas of the fuselage where air is relatively undisturbed. For redundancy in the case of ports becoming blocked, many aircraft may have more than one static port. Meanwhile, impact pressure is collected via a tube that is known as the pitot tube. As impact pressure is obtained from the force of air created by forward momentum, the pitot tube will be located in areas such as the front edge of a wing, the nose of the fuselage, or other similar spaces.

While other various cockpit instruments rely on pressure readings from these tubes and ports, airspeed indicators are the only instruments that utilize readings from both to make measurements. As static and pitot pressure are both collected, they will be routed through separate lines to reach the airspeed indicator case. While the static line runs directly into the case, the pitot line routes air into an internal pressure diaphragm that is contained within the case.

Based on the difference of pressures, the diaphragm will expand and contract in response. As this occurs, mechanical linkages will cause a needle on the instrument dial to move, with the needle pointing to various hash marks that indicate speed measurements. With this basic set of operations and through the comparisons of each pressure type, one can obtain accurate and reliable readings that correspond to airspeeds.

As a functional airspeed indicator, aircraft altimeter, or other related cockpit instruments are paramount for flight safety, it is important to keep them well functioning and reliable. Here at Expedited Quoting, we provide customers access to over 2 billion new, used, obsolete, and hard-to-find parts that have been sourced from top global manufacturers that we trust. As you explore our website, feel free to utilize our online RFQ form to request quotes on items of interest, and we guarantee a customized response within 15 minutes of reviewing your submission. Get started today and see how Expedited Quoting can serve as your strategic sourcing partner for all your operational needs!


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