The way an airplane flies depends on four forces: gravity, lift, drag and thrust. When the four forces are equal and balanced, the airplane flies level. When one of the forces is greater than the other, the airplane goes up or down.
The first force an airplane uses to create lift is thrust. This force comes from the engine, whether it’s a jet or propeller. Thrust is a result of the action-reaction relationship described by Newton’s third law, which predicts that for every action there will be an equal and opposite reaction.
This law is important to understand as a pilot, and it’s crucial for students to grasp. This is because it’s at work every single time an airplane flies.
In fact, this force is the most essential element of flight, and it’s the reason why an airplane has to be able to overcome the weight of the air around it.
There are three primary ways an airplane can generate thrust: with a jet, a propeller, or with a rocket. However, all engines are similar and work on the same basic principle.
They all push air backwards (thrust) and cause the airplane to move forwards (lift). The movement of the thrust is matched by the movement of the wings that create the lift.
It’s very important for a pilot to understand how these forces act on an airplane, because they can be used in many different situations. If a plane’s flight isn’t going as smoothly as it could be, the pilot may need to change the thrust in order to get things back on track.
For example, when turning, the pilot will need to increase thrust so that the airplane can maintain its speed in a turn. The extra thrust will also push the airplane up, which will cause it to gain altitude.
But this additional thrust will have to be overcome by the airplane’s drag, which will make it slow down, unless the pilot can counteract the extra drag with more thrust.
This is why aircraft engines have to be designed in a way that will maximize their efficiency. The best way to do this is by designing an engine that will produce as much thrust as possible without generating excess drag.
Another key thing to know about how an airplane flies is that there are a few things that can influence how it flies, which you can learn about in the lessons on the next section of this book:
The Shape of an Airplane Wing
A wing generates lift by changing the pressure differences between the air above and below its surface. The airfoil’s shape, the angle of attack, and the ambient flow conditions affect the amount of lift that it produces.
As a result, an aircraft designer will determine the correct airfoil shape for each wing of an airplane. Then, he will apply Bernoulli’s equation, shown above, to find the coefficient of lift for the wing.
Generally speaking, the higher the airspeed and the lower the density of the air, the more lift that a wing will provide. This is why aircraft designers often create a variety of different airfoils for a single airplane, in order to get the most lift from each one.