Heavier-than-air craft: What are they and how do they fly?
A heavier-than-air craft is a type of aircraft that relies on a power source to provide the thrust and lift necessary to overcome gravity and stay aloft. Unlike lighter-than-air craft, such as balloons and airships, which float in the air by displacing a volume of gas that is less dense than the surrounding air, heavier-than-air craft must generate a force that pushes air or gas downwards, creating a reaction force that pushes the aircraft upwards. This is according to Newton’s third law of motion, which states that for every action there is an equal and opposite reaction .
The term heavier-than-air craft covers a wide range of flying machines, from kites and gliders to airplanes and helicopters. The common feature of these aircraft is that they have a defined aerodynamic shape that interacts with the airflow to produce lift. Lift is the force that acts perpendicular to the direction of motion and opposes the weight of the aircraft. The amount of lift depends on several factors, such as the shape, size, angle, and speed of the wing or rotor. The faster the air flows over the wing or rotor, the lower the pressure above it, creating a pressure difference that lifts the aircraft .
Heavier-than-air craft also need a source of propulsion to move forward and maintain lift. This can be achieved by various means, such as propellers, jet engines, rockets, or even human power. The thrust generated by the propulsion system must overcome the drag, which is the force that acts opposite to the direction of motion and resists the movement of the aircraft through the air. The amount of drag depends on several factors, such as the shape, size, surface texture, and speed of the aircraft. The more streamlined and smooth the aircraft is, the less drag it experiences .
Heavier-than-air craft have revolutionized transportation, exploration, warfare, and recreation. They have enabled humans to travel faster and farther than ever before, to reach remote and inaccessible places, to observe and study the Earth and beyond, to fight and defend their interests, and to enjoy the thrill and beauty of flying. Heavier-than-air craft are also constantly evolving and improving, as new technologies and designs are developed to enhance their performance, efficiency, safety, and environmental impact.
Types of heavier-than-air craft
Heavier-than-air craft can be classified into different types based on their design, function, and propulsion. Some of the main types are:
- Kites: These are unpowered, tethered craft that are flown by the wind. They have a flat or slightly curved surface, often with a tail for stability, and are attached to a string that is held by the operator. Kites can be used for recreation, scientific experiments, or communication.
- Gliders: These are unpowered, free-flying craft that are launched from a high point and glide through the air by using the lift generated by their wings. They have a fuselage, a wing, and a tail, and are controlled by the pilot using movable surfaces on the wing and tail. Gliders can be used for flight training, sport, or research.
- Sailplanes: These are sophisticated gliders that have a high aspect ratio wing (a long wing span in proportion to wing width) and a streamlined fuselage. They can fly long distances and reach high altitudes by using rising air currents (thermals) to gain lift. Some sailplanes have a small, retractable engine to assist in takeoff or extend flight.
- Airplanes: These are powered, fixed-wing craft that use propellers or jet engines to provide thrust and lift. They have a fuselage, a wing, a tail, and a landing gear, and are controlled by the pilot using movable surfaces on the wing and tail. Airplanes can vary in size, shape, speed, and function, and are used for transportation, military, recreation, or exploration .
- Helicopters: These are powered, rotary-wing craft that use one or more rotors to provide lift and thrust. They have a fuselage, a main rotor, a tail rotor, and a landing gear, and are controlled by the pilot using pedals and levers to change the pitch and speed of the rotors. Helicopters can hover, fly backwards or sideways, and take off and land vertically. They are used for rescue, surveillance, transport, or combat .
- Unmanned aerial vehicles (UAVs): These are remotely controlled or autonomous aircraft that can carry cameras, sensors, weapons, or other payloads. They have various designs and sizes depending on their purpose and mission. They are used for scientific, military, or commercial applications .
These are some of the most common types of heavier-than-air craft. There are also other types that are less conventional or experimental, such as rockets, jetpacks, ornithopters (flapping-wing craft), or flying cars.