Navigating the Engine
We've just learned about the basic parts of an airplane and how it is controlled, but it's equally as important for us to understand how the power is generated to move the airplane through the air. An airplane has an engine which is commonly referred to as a power plant. While most airlines and corporate airplanes use turbine-powered airplanes, general aviation and training aircraft are equipped with reciprocating engines.
Reciprocating engines have several cylinders. Inside of those cylinders, fuel and air are mixed, compressed, and then ignited. As this fuel air mixture is ignited, its explosive force moves the piston inward. These pistons are connected to a crankshaft, and when the pistons move in and out that causes the crankshaft to rotate. The propeller is connected to the crankshaft. So as the crankshaft rotates, so does the propeller.
The cylinders undergo a continuous four stroke cycle. The four strokes are called intake, compression, power and exhaust.
On a typical four-cylinder engine, each one of the cylinders is in the middle of a different stroke. That way, one cylinder is always in the power stroke and the engine is able to keep the crankshaft rotating, thereby allowing the remaining cylinders to go through their respective stroke.
We get the fuel and air into the cylinders with the induction system. Inside of the cockpit of most general aviation aircraft, there are the throttle and mixture controls. The throttle controls the amount of fuel and air that go into the cylinders while the mixture controls how much fuel is mixed with the air. In simple terms, the mixture controls the ratio between fuel and air. The throttle, on the other hand, controls how much of that ratio is let into the cylinders. The more the throttle is open, the more fuel and air enter the cylinders, and therefore the more powerful the combustion will be, making the engine run faster.
The air that is part of the fuel air mixture enters the system at the air filter usually found in the front of the airplane. Once the air passes through the filter, it is metered and sent on its way to the cylinders.
The fuel on the other hand is housed on board the plane, typically inside of the wings, just like the air it is metered and then sent to the cylinders.
There are two different potential systems used that can control the fuel air mixture, the carburetor system and the fuel injection system. Fuel arrives at the carburetor and sits in the float chamber. Waiting to be used to the side of the float chamber is the venture which is where the air passes through. As the air passes through the venture, its velocity increases which causes the pressure to decrease. Towards the bottom of the venture we find a fuel discharge nozzle which is located near the area of low pressure. This draws the fuel out from the float chamber through the nozzle and mixes it with the air. Just past the venture is the throttle valve. This controls how much of the fuel air mixture is being sent to the cylinders.
We get that mixture to ignite through the ignition system is what provides the spark to the mixture. The major components of the ignition system include the magnets, the spark plugs wires, and the ignition switch.
Just as its name implies, a magneto consists of a rotating magnet that generates sparks of electricity. The spark plugs then release that energy, which ignites the fuel air mixture, creating power to turn the propeller. In the cylinders the spark plugs ignite the fuel air mixture, moving the piston in the power stroke.
The last step in the four stroke cycle is the exhaust. The exhaust system has a dual purpose in most general aviation airplanes. As expected, the exhaust system does allow the hot exhaust gases in the cylinder to escape the engine in a quiet manner. Additionally, the exhaust system also provides heat to the cabin.
What creates the thrust for the airplane to fly?
Remember that as the combustion occurs in the cylinder, the pistons rotate the crankshaft which directly drives the propeller. The propeller, when closely examined, is actually twisted. This is simply to create equal thrust along the propeller blade.
Reciprocating engines have several cylinders. Inside of those cylinders, fuel and air are mixed, compressed, and then ignited. As this fuel air mixture is ignited, its explosive force moves the piston inward. These pistons are connected to a crankshaft, and when the pistons move in and out that causes the crankshaft to rotate. The propeller is connected to the crankshaft. So as the crankshaft rotates, so does the propeller.
The cylinders undergo a continuous four stroke cycle. The four strokes are called intake, compression, power and exhaust.
On a typical four-cylinder engine, each one of the cylinders is in the middle of a different stroke. That way, one cylinder is always in the power stroke and the engine is able to keep the crankshaft rotating, thereby allowing the remaining cylinders to go through their respective stroke.
We get the fuel and air into the cylinders with the induction system. Inside of the cockpit of most general aviation aircraft, there are the throttle and mixture controls. The throttle controls the amount of fuel and air that go into the cylinders while the mixture controls how much fuel is mixed with the air. In simple terms, the mixture controls the ratio between fuel and air. The throttle, on the other hand, controls how much of that ratio is let into the cylinders. The more the throttle is open, the more fuel and air enter the cylinders, and therefore the more powerful the combustion will be, making the engine run faster.
The air that is part of the fuel air mixture enters the system at the air filter usually found in the front of the airplane. Once the air passes through the filter, it is metered and sent on its way to the cylinders.
The fuel on the other hand is housed on board the plane, typically inside of the wings, just like the air it is metered and then sent to the cylinders.
There are two different potential systems used that can control the fuel air mixture, the carburetor system and the fuel injection system. Fuel arrives at the carburetor and sits in the float chamber. Waiting to be used to the side of the float chamber is the venture which is where the air passes through. As the air passes through the venture, its velocity increases which causes the pressure to decrease. Towards the bottom of the venture we find a fuel discharge nozzle which is located near the area of low pressure. This draws the fuel out from the float chamber through the nozzle and mixes it with the air. Just past the venture is the throttle valve. This controls how much of the fuel air mixture is being sent to the cylinders.
We get that mixture to ignite through the ignition system is what provides the spark to the mixture. The major components of the ignition system include the magnets, the spark plugs wires, and the ignition switch.
Just as its name implies, a magneto consists of a rotating magnet that generates sparks of electricity. The spark plugs then release that energy, which ignites the fuel air mixture, creating power to turn the propeller. In the cylinders the spark plugs ignite the fuel air mixture, moving the piston in the power stroke.
The last step in the four stroke cycle is the exhaust. The exhaust system has a dual purpose in most general aviation airplanes. As expected, the exhaust system does allow the hot exhaust gases in the cylinder to escape the engine in a quiet manner. Additionally, the exhaust system also provides heat to the cabin.
What creates the thrust for the airplane to fly?
Remember that as the combustion occurs in the cylinder, the pistons rotate the crankshaft which directly drives the propeller. The propeller, when closely examined, is actually twisted. This is simply to create equal thrust along the propeller blade.