Like so many of your fellow air passengers, wondering how an airplane flies, wouldn’t you want to know the answer?
There you are, sitting in this huge metal-bird, weighing several tons. How is it possible that this heavy thing can soar up in the air?
The 4 basic principles of flight
Airplanes can fly because of the four basic principles, which you’ll learn from the easy to understand explanation here:
- Thrust moves you forward.
- Drag opposes thrust and works to oppose the thrust force.
- Lift keeps you flying in the air.
- Weight (Gravity) opposes lift and it wants to pull you to the ground.
The engines are used to create thrust, which is the motion which moves you forward.
Scientist Isaac Newton discovered that for every action (force in nature) there is an equal and opposite reaction. This is called Newton’s Third Law of Motion.
So, since thrust is a force that moves you forward there must be an opposite reaction working on slowing you down at the same time. Newton was right.
That opposing force of thrust is called drag.
What is airplane drag?
Drag is anything that creates friction on the airplane as it moves through the air. Air molecules and airplane skin friction, and the body of the airplane itself are just a few of the many things causing drag.
The engines move the airplane forward at high speed. The speed creates wind (called relative wind), that hits the front (leading edge) of the airplane wings.
- Once the wind molecules hit the leading edge of the wing the air splits. Some air goes over the top of the wing. The rest goes under the wing.
Next, something interesting happens. Because of the shape, or curvature of a wing:
2A) The air flowing on TOP of the wing:
The air flowing on top of the wing passes across the wing at a faster speed, but at a LOWER PRESSURE than the pressure existing below the wing. Air that moves fast creates low air pressure.
2B) The pressure passing below the wing passes across the wing at a slower speed, but at a HIGHER PRESSURE than the pressure created on top of the wing.
Because of this HIGHER pressure BELOW the wing, the plane can be kept up in the air.
3) The back of the wing is called the trailing edge. The air coming from above and below the wing surface accelerates down. That creates a downward force of air, further helping the wing stay in the air.
Airplane wing science and the Lift it produces
Long before airplanes were invented an Italian scientist, Daniel Bernoulli discovered his Bernoulli’s Principle.
He discovered that an increase in the speed of fluid (as it also applies to the air at the top of the curved wing) occurs at the same time that a decrease in pressure occurs. The decrease in pressure also coincides with a decrease in the fluid’s potential energy.
Thus the solution to how to make a wing fly was born.
The specialty field that deals with the mechanics of flight is called “aerodynamics”. Aerodynamics is heavily covered in military pilot training, and covered well in civilian pilot training too.
Weight (Gravity) explained
Do your recall Newton’s Third Law of Motion, telling us that for every action there is an equal but opposite reaction?
The force that works opposite of lift is called weight (gravity). Gravity is what keeps us earthlings on earth.
Gravity is defined as a force pulling two objects toward each other. Anything which has mass (earth) has a gravitational pull.
When you take off or climb lift must overcome (be greater than) weight. We achieve that with engine power by advancing the throttles.
At cruise, lift and weight are in a state of equilibrium.
During the descent to landing, weight must overcome (be greater than) lift.
Do you have any questions about this?
Of course, there is more to how an airplane flies than what you just read here.
But now you can consider yourself one of the few airline passengers with some knowledge of the subject when you board your next flight.
Let me know your thoughts or questions here.