What Is the Difference Between Pitot and Pitot-Static Tubes?
In the course of their journey through the air, it is crucial that pilots have timely, accurate information about various flight conditions with some of the most important being the speed and altitude of their aircraft. For this information, pilots generally rely on a grouping of pressure-sensing devices called the pitot-static system. These systems consist of a pitot tube and static tube, working in combination to tell the pilot valuable information about the airspeed, altitude, and vertical speed of their aircraft. For more information about this valuable system, read on as we discuss the inner workings and uses for pitot tubes and static tubes.
Pitot tubes are flow sensor instruments that may be used to measure the velocity of moving liquids or air. They consist of a tube that is bent perpendicularly, so that when fluid enters the inlet, it will stagnate as a result of there being no outlet present. The pressure caused by stagnating fluids is referred to as stagnation pressure, total pressure, or pitot pressure. When implemented on an aircraft, the pitot tube acts as a sensor that is used to measure ram air pressure, that is the pressure caused by air forcing its way into the inlet as the vehicle is in motion. The pitot tube is commonly placed on the wing of an aircraft or in the front section of the fuselage so that the opening is aligned with the flow of air. With such placement, there is less risk that obstructions will distort the measurements.
Pitot tubes are effective for giving a value of ram air pressure, but fail to account for the effect of altitude on normal air pressure around the aircraft. To solve this problem, pitot tubes often work in conjunction with a static tube that measures the pressure of the air at rest. By taking the differential between stagnation pressure and static pressure (h), you can find the airspeed. Pitot-static systems can also be used to calculate altitude and vertical speed of an aircraft. Often the pitot tube and static tube are separate components that can be placed in different areas in a fluid system. However, they may also be combined, as in a pitot-static tube. Pitot-static tubes have one inner opening for fluid to pass, along with a couple smaller outer openings. Whereas the inner opening serves as the stagnation tube which measures stagnation pressure, and the outer openings are the static tubes which measure static pressure. The inner tube is oriented so that it faces upstream, while the outer tube openings are directed perpendicular to the flow lines.
Pitot-static systems are incredibly valuable instruments on aircraft which display information such as airspeed, vertical speed, and altitude to the pilot. Using this information, the pilot can monitor their progress on a route and make informed decisions all throughout their flight. Though pitot tubes may come as a separate component to static tubes, they may also be combined in the form of a piston-static tube.
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