Notes

Parts of the airplane

The basic components of any airplane are the fuselage, the wings, the empennage, the landing gear, and the powerplant.

Flight Controls

Aircraft flight controls are broken into two systems: primary and secondary flight controls. The three primary flight controls are the ailerons, elevator, and rudder. The two secondary flight controls are the flaps and trim. In most general aviation airplanes, as the pilot moves the controls, he or she is moving steel cables or push rods, connected through other linkages that physically move those controls. As the control surface is deflected, the airflow is changed, which results in an aerodynamic force, changing the airplane’s path through the air.

The ailerons are located on the back end of the wings, out towards the tip, and control the aircraft’s roll or bank. The elevator is attached to the back end of the horizontal stabilizer and controls the airplane’s pitch, which allows the airplane to climb or descend. The rudder, is attached to the back end of the vertical stabilizer, which makes the airplane yaw.

The Powerplant and Propeller

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. The 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. 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.

The major components of the ignition system include the magnetos, the spark plugs, wires, and the ignition switch. As 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.

The Landing Gear

The landing gear system provides the ground support to the airplane for taxi, takeoff, and landing. With tricycle landing gear systems like those the Cessna 172, as the pilot pushes on the rudder pedals, the nose wheel rotates, allowing the pilot to steer the airplane. Differential braking can also be used on tricycle gear systems to aid the pilot in making tighter turns.

An airplane’s landing gear system is also classified in two other categories: fixed or retractable. A fixed landing gear system is one in which the landing gear is permanently extended. The benefit of having a retractable landing gear system is that it increases performance by streamlining the airplane.

The Fuel, Oil, and Hydraulic Systems

In general aviation airplanes, fuel systems can be broken down into two subsystems: gravity fed systems and fuel pump systems. High-wing airplanes, such as the Cessna 172, are normally designed to be gravity-fed systems. In low-wing airplanes, such as the Piper Arrow, a fuel pump is required to send fuel from the tanks to the engine. Since the fuel is located below the engine, it is simply impossible for gravity to send fuel upwards. 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. Most general aviation airplanes utilize 100 Low-Lead fuel, which is blue in color.

Oil cools the engine, lubricates the moving parts of the engine, provides a protective coating to prevent corrosion, and removes dirt and other particles from the engine. There are two types of oil systems: a wet-sump system and a dry-sump system. A wet-sump system, like that of a Cessna 172, is a system in which the oil is located in a tank at the base of the engine. A dry-sump system has a separate oil tank, which separates the oil system from the engine. It’s important to regularly check oil pressure and oil temperature. Anything outside of the normal range, which is usually designated by a green arc, may potentially lead to major problems, including engine failure.

In smaller airplanes, the hydraulic system powers the brakes to stop the airplane, extend and retract the landing gear, and change the blade angle on some constant-speed propellers. As the pilot presses on the brakes, a piston drives fluid from the brake actuator on the pedal, through hydraulic lines, and then to the actuator near the wheels. The fluid pushes a piston which then mechanically squeezes the brake pads against the brake disk, causing the airplane to slow down.

The Electrical System

The electrical system is usually comprised of a 14 volt or 28 volt direct current or DC system, made up of some basic components. These consist of: an alternator, a battery, switches, circuit breakers or fuses, relays, a voltage regulator, an ammeter or loadmeter, and the electrical wiring which connects it all.

The alternator is driven by the engine through an alternator belt, which generates electricity for the entire system. A circuit breaker pops when there is excessive voltage, which results in high heat in the electrical wire. An ammeter shows the performance of the electrical system. If the alternator is providing sufficient power to the electrical system and is charging the battery, then the ammeter will show a charge. A load meter shows the load that is being placed on the alternator.

The Environmental System

The environmental system of the airplane provides fresh air and heat to the cabin. The cabin heat valve allows outside air to pass over the exhaust muffler shroud, which heats the air. This heated air is then ducted into the cabin.