Introduction to Airplanes
Introduction to Aerodynamics
The Study of Air in Motion
Aerodynamics is the study of how air moves around objects. When you stick your hand out of a moving car window, you're experimenting with aerodynamics. The way the air pushes against your hand changes depending on how you angle it. This same science explains how a 300-ton airplane can soar through the sky.
aerodynamics
noun
The study of the properties of moving air and the interaction between the air and solid bodies moving through it.
Understanding flight starts with understanding the forces at play. For any object to fly, it must manage its relationship with the air around it. This relationship is defined by four fundamental forces.
The Four Forces of Flight
An aircraft in flight is constantly affected by four primary forces: lift, weight, thrust, and drag.
These four forces are constantly battling each other. They can be thought of as two opposing pairs. For an airplane to fly straight and level at a constant speed, these forces must be in balance.
Let's break them down.
| Force | Description | Opposing Force |
|---|---|---|
| Weight | The force of gravity pulling the airplane down toward the Earth. | Lift |
| Lift | The upward force created by the wings as air flows over them. | Weight |
| Thrust | The forward force generated by the engines, pushing the airplane through the air. | Drag |
| Drag | The backward force of air resistance that opposes the airplane's motion. | Thrust |
To take off, lift must be greater than weight. To accelerate, thrust must be greater than drag. Once cruising, the pilot balances these forces to maintain a steady altitude and speed. To land, the pilot reduces thrust and manages lift to allow weight and drag to bring the plane down safely.
How Wings Create Lift
The magic of flight happens at the wings. A wing's curved shape, called an airfoil, is specially designed to manipulate the air flowing past it.
The top surface of a wing is more curved than the bottom surface. As the airplane moves forward, the wing splits the oncoming air. The air that goes over the top has a longer path to travel than the air that goes underneath. To meet up with the bottom air at the back of the wing, the top air has to move faster.
This difference in speed creates a difference in pressure. A key principle in fluid dynamics states that faster-moving air exerts less pressure. Because the air on top of the wing is moving faster, it creates a region of lower pressure. The slower-moving air below the wing creates a region of higher pressure.
This pressure difference results in a net upward force. The high pressure below the wing pushes up more than the low pressure above pushes down. That upward push is lift. By generating enough lift to overcome its weight, an airplane can climb into the sky and stay there.
For an airplane to accelerate forward while climbing, which two conditions must be met?
According to the principles of aerodynamics, how does a wing's shape (an airfoil) generate lift?
This balance of four forces and the clever design of the wing are the foundational concepts of flight. Every maneuver a pilot makes is about adjusting these forces to direct the aircraft through the air.