Fueling Up
After learning about how the engine works, we remember that there are two things that are mixed together for combustion, fuel and air. Let's learn some things about the fuel system. The fuel system is designed to bring fuel from the fuel tanks to the engine. In general aviation airplanes, fuel systems can be broken down into two subsystems, gravity systems and fuel pump systems.
High wing airplanes such as the Cessna 100 and 72 are normally designed to be gravity systems. Because the fuel tank is inside the wing, which is located above the engine, gravity can naturally pull the fuel from the tank to the engine. Although in normal operation a fuel pump is not required. Many high-wing airplanes are still equipped with some sort of fuel pump either an engine- driven, electrically powered, or both as a backup for emergency operations.
In low-wing airplanes such as the Piper Arrow, a fuel pump is required to send the fuel from the tanks to the engine. Since the fuel is located below the engine, it is simply impossible for gravity to send the fuel upwards. For this reason, low-wing airplanes are designed with a fuel pump system. Normally, there are two fuel pumps. One of the fuel pumps is engine- driven and the backup is electrically driven. Some airplanes are equipped with the fuel primer. The fuel primer allows fuel to be injected straight into the cylinder prior to engine start. Fuel priming is especially useful during cold operations. While some airplanes are equipped with a fuel primer, others like the Cessna 100 and 72 are not.
Fuel is stored in fuel tanks which are usually located inside of the wings. These tanks are filled from the top. There is a cap on the top that is easily twisted off and gas is pumped into that tank until it is visually full. This cap is usually vented to allow outside air pressure to enter the fuel tank in order to prevent a vacuum from being created inside of the fuel tank.
If the fuel tank did not have a vent, fuel would initially flow from the tank, but as it empties there would be nothing to replace that space which would create a vacuum and eventually stop fuel flow to the engine. Therefore, manufacturers vent the tanks to allow air to replace the fuel that is leaving the tank to the engine.
Some airplanes not only have vented fuel caps, but they also have fuel vents that protrude from the wing. As the airplane flies through the air, air enters this vent and is pushed into the fuel tank.
Also inside the fuel tanks are fuel sensors. These fuel sensors send information to the fuel gauge which shows the pilot the amount of fuel in the tank. These sensors work in many different ways depending on the manufacturer of the airplane. It is absolutely critical to visually verify the amount of fuel in the tank, never entirely trust the fuel gauges.
Most general aviation airplanes utilize 100 lowered fuel, which is blue in color. Therefore, not only should the pilot check for impurities, the color of the fuel should also be inspected to ensure that the proper fuel was pumped into the tank.
A fuel shutoff valve is instead used to shut off the fuel supply. This valve is located just above the fuel selector and can be activated by pulling on the knob.
High wing airplanes such as the Cessna 100 and 72 are normally designed to be gravity systems. Because the fuel tank is inside the wing, which is located above the engine, gravity can naturally pull the fuel from the tank to the engine. Although in normal operation a fuel pump is not required. Many high-wing airplanes are still equipped with some sort of fuel pump either an engine- driven, electrically powered, or both as a backup for emergency operations.
In low-wing airplanes such as the Piper Arrow, a fuel pump is required to send the fuel from the tanks to the engine. Since the fuel is located below the engine, it is simply impossible for gravity to send the fuel upwards. For this reason, low-wing airplanes are designed with a fuel pump system. Normally, there are two fuel pumps. One of the fuel pumps is engine- driven and the backup is electrically driven. Some airplanes are equipped with the fuel primer. The fuel primer allows fuel to be injected straight into the cylinder prior to engine start. Fuel priming is especially useful during cold operations. While some airplanes are equipped with a fuel primer, others like the Cessna 100 and 72 are not.
Fuel is stored in fuel tanks which are usually located inside of the wings. These tanks are filled from the top. There is a cap on the top that is easily twisted off and gas is pumped into that tank until it is visually full. This cap is usually vented to allow outside air pressure to enter the fuel tank in order to prevent a vacuum from being created inside of the fuel tank.
If the fuel tank did not have a vent, fuel would initially flow from the tank, but as it empties there would be nothing to replace that space which would create a vacuum and eventually stop fuel flow to the engine. Therefore, manufacturers vent the tanks to allow air to replace the fuel that is leaving the tank to the engine.
Some airplanes not only have vented fuel caps, but they also have fuel vents that protrude from the wing. As the airplane flies through the air, air enters this vent and is pushed into the fuel tank.
Also inside the fuel tanks are fuel sensors. These fuel sensors send information to the fuel gauge which shows the pilot the amount of fuel in the tank. These sensors work in many different ways depending on the manufacturer of the airplane. It is absolutely critical to visually verify the amount of fuel in the tank, never entirely trust the fuel gauges.
Most general aviation airplanes utilize 100 lowered fuel, which is blue in color. Therefore, not only should the pilot check for impurities, the color of the fuel should also be inspected to ensure that the proper fuel was pumped into the tank.
A fuel shutoff valve is instead used to shut off the fuel supply. This valve is located just above the fuel selector and can be activated by pulling on the knob.