An aircraft is a vehicle that is able to fly through the Earth’s atmosphere. The human factor in the activity surrounding aircraft is called aviation. An aircraft is only a vehicle that flies through and is supported by air. Therefore, a rocket that is traveling through space is not considered an aircraft. There are two broad categories of aircraft – lighter-than-air or heavier-than-air. Let’s explore the differences between the two.
A lighter-than-air vehicle is, as the definition implies, a vehicle that is lighter than air. These types of aircraft come commonly in the form of hot air balloons, which capture rising hot air to lift the craft, or dirigibles, which are large, gas-filled craft that can be steered, like the Goodyear Blimp. Dirigibles are also known as airships or blimps. The gas in dirigibles, helium, is lighter than air and is not flammable, as the Hindenburg disaster proved that airships and flammable gases are not a good idea.
Heavier-than-air vehicles consist of airplanes, helicopters, or any other type of craft that uses a wing to create lift. These are the most common aircraft because they can be built to any size, travel very quickly, and can be customized for special tasks. Heavier-than-air vehicles use wings to become airborne. While it may not seem like helicopters or rotorcraft, use wings to fly, the rotor blades of the helicopter are actually long, spinning wings.
The cross-section of a wing is taller on top and relatively flat on the bottom. When air passes over a wing, it speeds up so that it stays in line with the air below the wing. This creates lower pressure above the wing, and the air pressure below the wing lifts the aircraft skywards. A wing has four basic forces: lift, weight, thrust, and drag. If the lift is greater than the weight, the aircraft rises. If the weight is greater than the lift, the aircraft will fall. When thrust is more than drag, the plane accelerates, and conversely, when the drag is more than the thrust, the plane will decelerate.