The Pitot-Static System
The pitot-static system is connected to the airplane's altimeter airspeed indicator and the vertical speed indicator. These instruments tell the pilothow high they are, how fast they are going, and how fast they climb or descend. These are determined by measuring the pressure of the atmosphere.
The pitot-static system gathers its pressure information from two sources, the pitot tube and the static ports, hence the name pitot-static. The pitot tube is designed to measure the pressure of the air as the airplane flies through it. In most smaller aircraft, this tube is located under the wing, so it can measure the flow of air without any interference. Finally, the pitot tube can also be heated. This is used to prevent ice from forming on the tube, which could potentially block the hole and prevent the system from functioning correctly. The counterpart of the pitot tube is the static port. The location of this port will vary with different aircraft designs, but should be in a location where it can measure the static pressure of the air unaffected by the dynamic airflow around the airplane.
The pitot tube and static port openings are connected to tubes that join into the pitot-static instruments. The pressure inside the instruments match the pressure of the outside atmosphere. All three pitot instruments connect to the static port, but only the airspeed indicator connects to the pitot tube.
The altimeter, displays the airplane's altitude. The instrument contains a set of wafers which expand and contract based on the pressure. The air inside the wafers is trapped, but the air and the rest of the case is able to change to match the pressure from the static port. As we increase altitude, the static pressure goes down. This means that the air inside the case will escape out the back and result in layer being less air pressure in the case compared to the wafers. Because of this, the wafers will expand until both pressures are equal.
The face of the altimeter contains three hands, the 10 thousand foot, 1 thousand foot, and 100 foot hands. These hands move clockwise and counterclockwise to display the appropriate altitude. Most altimeters in smaller aircraft will only work up to around 20 thousand feet, but those airplanes usually can't get that high anyway. Here's some examples of altitudes, 3 thousand feet, 8400 feet, 12 thousand feet, 5200 and 80 feet. It can be adjusted for the current atmospheric pressure. Because the pressure at any given point on the earth never stays, the same altimeters would always read incorrectly.
Another instrument that uses only the information from the static port is the vertical speed indicator, more commonly called the VSI. The VSI measures the vertical speed of the aircraft in terms of feet per minute. This is accomplished by comparing the current pressure of the air with the pressure of the air from a few seconds ago.
Inside the VSI is a diaphragm connected to some mechanical linkages that move the needles on the face of the instrument. The diaphragm has a direct connection to the static port, meaning that the pressure inside of it matches the current atmospheric pressure from the outside. The case of the instrument is also filled with static pressure, but the connection between the case and the static port is constricted by what is called a calibrated leak. This calibrated leak is nothing more than a tiny hole, which limits the rate at which the pressure of the case can change. When a plane climbs or descends the diaphragm pressure will change instantly, but the case pressure changes slowly. This results in two different pressures. The difference in pressure allows the instrument to display the vertical speed. Be aware, however, that it takes a few seconds to read accurately, so anticipate a slight amount of lag. Here's an example of how it works.
The airspeed indicator is the only pitot-static instrument that uses both input from the static port and the pitot tube. The pitot tube is used to measure what's called ram pressure. The faster the airplane travels, the greater the ramp pressure is.
The ram air entering the pitot tube gets sent to the airspeed indicator before goes into a diaphragm. The greater to the pressure, the more the diaphragm expands so the diaphragm will expand as the airspeed increases. The static port connects and fills the case surrounding the diaphragm with static air. This will subtract out the static air pressure that the pilot tube captured and only allow for the dynamic pressure to be read on the instrument. This keeps the airspeed indicator reading the correct values.
The face of the instrument displays color-coded speed ranges that the pilot should be aware of while they fly to avoid exceeding any limitations of the aircraft. For normal operations, the White Arc is where you're allowed to extend the flaps. The Yellow Arc is limited to flight in smooth air only, and the red line indicates the maximum allowed speed.
The pitot-static system gathers its pressure information from two sources, the pitot tube and the static ports, hence the name pitot-static. The pitot tube is designed to measure the pressure of the air as the airplane flies through it. In most smaller aircraft, this tube is located under the wing, so it can measure the flow of air without any interference. Finally, the pitot tube can also be heated. This is used to prevent ice from forming on the tube, which could potentially block the hole and prevent the system from functioning correctly. The counterpart of the pitot tube is the static port. The location of this port will vary with different aircraft designs, but should be in a location where it can measure the static pressure of the air unaffected by the dynamic airflow around the airplane.
The pitot tube and static port openings are connected to tubes that join into the pitot-static instruments. The pressure inside the instruments match the pressure of the outside atmosphere. All three pitot instruments connect to the static port, but only the airspeed indicator connects to the pitot tube.
The altimeter, displays the airplane's altitude. The instrument contains a set of wafers which expand and contract based on the pressure. The air inside the wafers is trapped, but the air and the rest of the case is able to change to match the pressure from the static port. As we increase altitude, the static pressure goes down. This means that the air inside the case will escape out the back and result in layer being less air pressure in the case compared to the wafers. Because of this, the wafers will expand until both pressures are equal.
The face of the altimeter contains three hands, the 10 thousand foot, 1 thousand foot, and 100 foot hands. These hands move clockwise and counterclockwise to display the appropriate altitude. Most altimeters in smaller aircraft will only work up to around 20 thousand feet, but those airplanes usually can't get that high anyway. Here's some examples of altitudes, 3 thousand feet, 8400 feet, 12 thousand feet, 5200 and 80 feet. It can be adjusted for the current atmospheric pressure. Because the pressure at any given point on the earth never stays, the same altimeters would always read incorrectly.
Another instrument that uses only the information from the static port is the vertical speed indicator, more commonly called the VSI. The VSI measures the vertical speed of the aircraft in terms of feet per minute. This is accomplished by comparing the current pressure of the air with the pressure of the air from a few seconds ago.
Inside the VSI is a diaphragm connected to some mechanical linkages that move the needles on the face of the instrument. The diaphragm has a direct connection to the static port, meaning that the pressure inside of it matches the current atmospheric pressure from the outside. The case of the instrument is also filled with static pressure, but the connection between the case and the static port is constricted by what is called a calibrated leak. This calibrated leak is nothing more than a tiny hole, which limits the rate at which the pressure of the case can change. When a plane climbs or descends the diaphragm pressure will change instantly, but the case pressure changes slowly. This results in two different pressures. The difference in pressure allows the instrument to display the vertical speed. Be aware, however, that it takes a few seconds to read accurately, so anticipate a slight amount of lag. Here's an example of how it works.
The airspeed indicator is the only pitot-static instrument that uses both input from the static port and the pitot tube. The pitot tube is used to measure what's called ram pressure. The faster the airplane travels, the greater the ramp pressure is.
The ram air entering the pitot tube gets sent to the airspeed indicator before goes into a diaphragm. The greater to the pressure, the more the diaphragm expands so the diaphragm will expand as the airspeed increases. The static port connects and fills the case surrounding the diaphragm with static air. This will subtract out the static air pressure that the pilot tube captured and only allow for the dynamic pressure to be read on the instrument. This keeps the airspeed indicator reading the correct values.
The face of the instrument displays color-coded speed ranges that the pilot should be aware of while they fly to avoid exceeding any limitations of the aircraft. For normal operations, the White Arc is where you're allowed to extend the flaps. The Yellow Arc is limited to flight in smooth air only, and the red line indicates the maximum allowed speed.