Total Pressure System:
1. Pitot Tube: There are one or more small cylindrical tubes called Pitot tubes mounted outside the aircraft, facing directly forward.
2. Static Ports: In addition to the Pitot tubes, there are static ports located on the side of the aircraft. These ports measure the static air pressure, which is the same pressure surrounding the aircraft.
3. Total Pressure Line: The Pitot tube opening connects to a total pressure line that runs inside the aircraft.
4. Static Pressure Line: Similarly, the static ports connect to a static pressure line that runs alongside the total pressure line.
Airspeed Indicator:
Inside the aircraft, the total pressure line and the static pressure line are connected to an airspeed indicator instrument. This instrument consists of several important components:
1. Diaphragm: There's a flexible diaphragm within the airspeed indicator that separates two sealed chambers: the total pressure chamber and the static pressure chamber.
2. Pressure Reference: The total pressure line connects to the total pressure chamber, while the static pressure line connects to the static pressure chamber.
3. Pointer Mechanism: The diaphragm is mechanically linked to a pointer that moves across a calibrated airspeed dial.
Measuring Airspeed:
As the aircraft moves forward:
1. Dynamic Pressure: The Pitot tube faces the oncoming air, which creates dynamic pressure. This dynamic pressure is higher than the static pressure surrounding the aircraft.
2. Pressure Difference: The total pressure line transmits this dynamic pressure to the total pressure chamber within the airspeed indicator.
3. Diaphragm Movement: The diaphragm deflects in response to the pressure difference between the total pressure chamber and the static pressure chamber.
4. Pointer Movement: As the diaphragm moves, it is linked to the pointer mechanism, which moves the pointer across the airspeed dial.
5. Airspeed Indication: The pointer's position on the dial indicates the airspeed of the aircraft in reference to the surrounding air.
The speedometer, or airspeed indicator, plays a crucial role in monitoring the aircraft's speed and ensuring safe flight operations, as it provides pilots with the necessary information to maintain appropriate speed for various flight conditions and maneuvers.
