Principle Structural Units of the Aircraft

Airplanes can be monoplanes and biplanes. Monoplanes are planes with one wing. Biplanes are planes which have two sets of wings, one above the other. According to the arrangement of the wing as to the fuselage there are 3 types of monoplanes: the high-wing, the mid-wing and the low-wing. According to their use airplanes can be passenger, cargo (freight) and special mission.

The aircraft consists of five principle structural units, namely, the power plant, the fuselage, the wings, the tail unit and the landing gear.

The power plant is a source of power. The function of the power plant is to provide power for flight and to propel the aircraft. The main part of the power plant is the engine or engines. There are two main types of engines: piston and jet engines. Modern airplanes have different kinds of jet engines. The power plant also includes some systems, namely, the fuel system, the lubrication (oil) system, the fire-prevention (fire extinguishing) system, the engine cooling system and the engine control system. Each system has its function. The function of the fuel system is to provide the engine with fuel.

The fuselage is the body of the airplane to which the other sections are attached. It extends the fuselage from the nose to the tail of the machine. The size of the fuselage varies with the purpose of the plane but the main structure is the same for any of them. The fuselage can contain the flight compartment (cockpit), the passenger cabins, the galley, the baggage compartment, the cargo compartment, the toilets, the wardrobe (coat room), and the technical compartment. The flight compartment is normally in the forward (front) section of the fuselage. There is a window at the front of the flight compartment. It is called a windshield. On the port and starboard sides of the fuselage there are windows (portholes). The very front part of the fuselage is the nose. The very rear part of the fuselage is the tail unit (empennage). It consists of a fin and a horizontal stabilizer. The rudder is hinged to the fin and the elevator is hinged to the horizontal stabilizer. There is a tail wheel at the rear part of the fuselage on some aircraft.

The fuselage is the central body of the aircraft. It houses all passengers, crew, cargo, equipment and supports the tail unit, the wings and sometimes engines. The fuselage of modern aircraft are of all metal construction. The fuselage must be strong enough to withstand loads acting on it and have streamlined shape.

The most complicated section is the wing section. The wings are mostly metal structures which extend out on each side of the body of the aircraft. The wing may carry engines and fuel tanks. The wings are attached to the central panel. The function of the wings is to create lift and support the aircraft in flight (in the air). There are movable parts in the wing. They are ailerons and flaps. The design of the wing depends on the size, weight and use of the airplane. Modern aircraft use various types of wings: a box-type, a multispar type and a sandwich type.

The tail unit provides directional stability and control of the aircraft in flight. The vertical surface or fin serves to support the rudder. The rudder is attached to the fin and controls the direction of flight in the horizontal plane. The horizontal surface or “stabilizer” supports elevators. The elevators control climb and descent of the airplane. The rudder and elevator are the movable parts of the tail unit. On big aircraft, there is the main landing gear, the nose landing gear (nose wheel), and or the tail wheel. The function of the landing gear is to support the aircraft on the ground, to taxi the airplane and to absorb the energy of landing. Also its function is to reduce shocks during taxiing, take-off and landing. The landing gear consists of the main and auxiliary units. The main landing gear forms the principle support of the aircraft, when it is on the ground. The auxiliary unit forms the auxiliary support. Most modern aircraft use the tricycle landing gear, that is the landing gear with a nose wheel. The undercarriage can be fixed or retractable. The retractable landing gear is retracted during take-off and is lowered during landing. When the aircraft is safely airborne the pilot brakes the wheels and retracts the undercarriage. If the undercarriage is left in its extended position it reduces the rate of climb considerably. In case of an emergency landing it is possible to land the aircraft with the undercarriage retracted. This is called a “belly landing” or “wheels up landing”.