Aircraft

An aircraft is a vehicle or machine that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines. Common examples of aircraft include airplanes, helicopters, airships, gliders, and hot air balloons.

The human activity that surrounds aircraft is called aviation. The science of aviation, including designing and building aircraft, is called aeronautics.

Crewed aircraft are flown by an onboard pilot, but unmanned aircraft may be remotely controlled or self-controlled by onboard computers. Aircraft may be classified by different criteria, such as lift type, aircraft propulsion, usage, and others.

Methods of lift
  • Lighter than air Aircraft - use buoyancy to float in the air in much the same way that ships float on the water.
  • Heavier than air Aircraft - find some way to push air or gas downwards so that a reaction occurs (by Newton's laws of motion) to push the aircraft upwards.
    • Fixed-wing aircraft
    • Rotary-wing aircraft
Fixed-wing Aircraft
A fixed-wing aircraft is a heavier-than-air flying machine, such as an airplane, which is capable of flight using wings that generate lift caused by the aircraft's forward airspeed and the shape of the wings. Fixed-wing aircraft are in general characterized by their wing configuration. The most important wing characteristics are:
  • Number of wings - monoplane, biplane, etc.
  • Wing support - Braced or cantilever, rigid or flexible.
  • Wing planform - including aspect ratio, angle of sweep, and any variations along the span (including the important class of delta wings).
  • Location of the horizontal stabilizer, if any.
  • Dihedral angle - positive, zero, or negative (anhedral).
A variable geometry aircraft can change its wing configuration during flight.

Rotary-wing Aircraft
Rotorcraft, or rotary-wing aircraft, use a spinning rotor with aerofoil cross-section blades (a rotary wing) to provide lift. This include helicopters.
Helicopters have a rotor turned by an engine-driven shaft. The rotor pushes air downward to create lift. By tilting the rotor forward, the downward flow is tilted backward, producing thrust for forward flight. Some helicopters have more than one rotor. Some have a tail rotor to counteract the rotation of the main rotor, and to aid directional control.

Aircraft Propulsion

Aircraft propulsion refers to the mechanism or system responsible for generating the necessary thrust to propel an aircraft through the air. It is the means by which an aircraft overcomes the forces of drag and gravity to achieve and maintain controlled flight.

There are several types of aircraft propulsion systems, each with its own characteristics and applications:

Jet Engines: Jet engines are commonly used in commercial airliners, military aircraft, and some private jets. They work on the principle of jet propulsion, where air is drawn into the engine, compressed, mixed with fuel, ignited, and expelled at high velocity through a nozzle at the rear of the engine. This expelling of hot, high-speed gases produces thrust that propels the aircraft forward. Jet engines can be further classified into turbojet, turbofan, turboprop, and turboshaft engines, each with variations in their design and purpose.

Piston Engines: Piston engines, also known as reciprocating engines, are typically used in smaller general aviation aircraft and some helicopters. They work by converting the reciprocating motion of pistons to rotational motion, which drives a propeller to generate thrust. Piston engines can be powered by gasoline (avgas) or diesel fuel and are generally simpler in design compared to jet engines.

Electric Propulsion: Electric propulsion systems are a newer development in aircraft propulsion. They utilize electric motors powered by batteries or fuel cells to drive the aircraft's propellers or fans. Electric propulsion is more environmentally friendly and offers potential benefits in terms of reduced noise, improved efficiency, and lower emissions. While still in the experimental and early adoption stages, electric propulsion shows promise for smaller aircraft and unmanned aerial vehicles (UAVs).

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