Forces in Aeronautics

Weight is a force that you are probably already familiar with. When you step on a scale, you are checking your weight. What you are actually doing is measuring the pull of Earth's gravity on your body. An airplane has a weight force, too. Even as an airplane flies thousands of feet above the Earth, its weight force is pulling it toward the ground. The lift force is generated by the airflow around an airplane's wings. When the lift force is greater than the airplane’s weight force, the airplane will be able to fly. A large 747 jetliner needs to generate a great amount of lift in order to fly. The Wright Brothers’ 1903 Flyer did not need to create as much lift because it weighed only 605 pounds. For the jetliner to get enough lift for takeoff, its wings will need to be pushed through the air at a high rate of speed. This is done with powerful jet engines. The force created by the engines is called the thrust force. Working opposite the thrust force (and slowing its speed) is drag. As an airplane flies, it pushes aside all those molecules in the air. Some of the molecules flow over the top of the airplane and its wings, while others flow underneath. The air molecules resist this separation. They rub against the airplane as it passes through them. This resistance is called drag. The thrust force must be stronger than the drag force in order for an airplane to be able to move forward.

These aeronautical forces work in opposition to each other. That means, lift pulls opposite to weight and drag pulls opposite to thrust. All four of these forces are hard at work when an airplane is flying. Although they work in opposite directions from each other, they all work together to make an airplane fly.