One of the systems that have been working since its creation in the aviation area is the pitot-static system, this is because thanks to it several instruments are fed receiving the necessary information for its operation, but what is it and how does the pitot-static system work?
The Pitot-Static System is a set of mechanisms that feed the basic instruments of the aircraft. These basic instruments are the ones needed for a flight, so there are rules and laws that make every aircraft must have them in order to have an airworthiness permit.
Although it is true that there are six (06) basic instruments that an aircraft must have, three of them are fed by this system. Whether it is a single-engine aircraft, a twin-engine aircraft, such as a Cessna 206, an Airbus 320, a Boeing 777 or a Bell 412, each one of them must have an altimeter, a vertical speed indicator and a speedometer. These can be digital or analogical but they will always have the same power supply, and they are mandatory to integrate the 6 basic instruments of the aircraft.
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What is the Pitot Static system?
It is a system that integrates several mechanisms sensitive to barometric pressure, which sends the information obtained to the different instruments that need it, which are the altimeter, the variometer, and the speedometer. However, this system is not so easy because there are several air pressures.
This is because in the atmosphere there are different pressures, for instance, if we cut vertically the atmosphere we will see some invisible layers that show us that the particles that are in more stuck to the ground are more compressed and are separated as they separate from the surface, so the chemical physicist Robert Boyle formulated one of the first laws which tells us that at a constant temperature the volume of mass is inversely proportional to the pressure that is exercised. For which to greater height smaller pressure and smaller temperature and thus vice versa.
Types of Pressures
- Static pressure, this is the pressure that air exerts on an object in the atmosphere, which is distributed uniformly around it and all the objects in it and will always be around it whether it is moving or not.
- Dynamic pressure, is the pressure that an object has when it moves through the air, that is to say, when it impacts the air at a certain speed, it will exert greater pressure on the object, so this pressure is exerted in the opposite direction to the direction of the object. And it varies depending on the speed and pressure of the air.
- Total pressure, is the sum of the static and dynamic pressure, that is, it is the sum of the pressure that has an object depending on its location in space and the speed with which it passes through the air. Therefore, if it is still, its pressure will be equal to the static pressure.
How does the static pitot system work?
Aircraft have a system called a pitot tube located under the wings in small aircraft and on larger aircraft at the sides of the cabin to receive the impact air, this sends the information received only to the speedometer and some static shots, which are located on the sides of the aircraft so that it only receives information on static pressure and this sends information to the variometer, altimeter and speedometer.
For all these reasons, the speedometer is the only instrument that receives the information of the impact air and the static shots, so it automatically calculates the speed that the aircraft has, this is because the static air controls the calibration of the height and the impact air moves the diaphragm showing the correct information of the speed of the aircraft.
The variometer measures the current pressure and the air pressure a few seconds before, making that variation be measured and indicated on the instrument which is calibrated in feet per minute, making the indicator needle go up or down depending on the pressure variation it suffers.
The altimeter, this instrument is calibrated depending on a pressure which is determined by the airfield or the standard height that pilots know is 29.92 inches of mercury or 1013 mb, this instrument receives the static pressure and varies quickly because the pressure quickly affects the aneroid capsule.
What do you think about this topic? Do you know how the pitot-static system works?
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