If you have ever heard the explanation of how a wing works, I'm sure it was an explanation using Bernoulli's Principle. While Bernoulli's Principle itself is not flawed in its teachings, the way it was used to explain wing operation was ultimately incorrect.
Bernoulli's Principle:
Bernoulli's Principle states that as a fluid's velocity increases its internal pressure decreases. While it remains plausible in the physics of aircraft flight, the effect is merely a byproduct of the lifting effect. In this theory, commonly called the Hump Theory1, the air flowing over the curved top of the wing must travel faster to catch up to the air moving on the straight bottom of the wing. A depressurization is created on the top of the wing, therefore, lifting the aircraft upwards. While it is a seemingly effective explanation, it does not explain inverted flight, or the use of an airfoil that has equal upper and lower quarters.
Newton's 3rd Law:
While flight mechanics are still developing, we now know that lift is cause by Newton's third law. Newton's third law states that for every action there is an equal and opposite reaction. As an airplane flies it keeps its wing angled slightly above level. This angle is known as the angle of attack. As the angle of the wings forces air towards the ground, lift is created by the reaction of the air pushing the wings upward. As the angle of attack increases so does lift, until the angle of attack is so steep that it disrupts the airflow on the top of the wing. This is called a stall. The curved airfoil is used only to guide the air smoothly across the surface of the wing. Bernoulli's Principle is true in that the pressure on the top of the wing is lower than the pressure on the bottom. This is only an effect of lift and not its cause.
