How Wing Lift Really Works

There are a few lessons in grade school that really make me cringe. Blatant falsehoods that are widely known to be untrue, often contradictory, yet are fed to our children in ignorance. Take Christopher Columbus, who did not discover America; it was already occupied by, well, the Native Americans, which are also acknowledged and often taught about in the same course. Then there is the discussion on how an airplane wing works.

Please don't get me wrong - there are complex details that are the intense course of study for aerodynamicists and rocket scientists; but the basic framework is not so overly complicated that teachers are forced to explain it utterly wrong. The most common explanation is the two-particle, longer path problem. It states that a pair of air particles encountering the wing will separate, one taking the path over the wing, the other under. They will then join again, together as they were before they separated, after they pass the wing. Since the particle that went over the wing took a longer path, it creates a lower pressure, and the wing is 'sucked up', thus producing lift.

There are more than a couple things wrong with this. Firstly, the particles that get separated in the first place often will not join up after passing the wing. Secondly, while the faster moving air over then wing does produce an area of negative pressure, it is nowhere near strong enough to sustain flight (although it does contribute to a very small percentage of overall lift). Thirdly, there is no mention of any air being deflected downward. It is simple physics - if a thousand pounds of air isn't pushed down, how is a thousand pound airplane pushed up?

The second more technical explanation, which is not completely wrong, but rather only a partial explanation, is that lift is generated by the angle at which the wing encounters oncoming air. By this theory, air strikes the lower surface and is "reflected" downward, pushing the wing upwards (creating lift). While this is indeed the way a wing produces the majority of it's lift, it fails to acknowledge that most wings produce lift even when the 'angle of attack', as it is referred to in the aviation industry, is zero. This is achieved through the adherence of the oncoming stream to the profile of the airfoil. Any airfoil that produces lift at a zero or negative angle of attack will prove this, as the average slope of the top and bottom surfaces must give a net deflection downward, thusly deflecting air downward and producing lift.

For any explanation to be called correct, it would have to explain that lift is produced by a combination of two dynamic forces. The major constituent is the deflection of air downward, which by Newton's third law of motion deflects the wing upwards. The second, minor contributor to lift is the creation of a negative region of pressure on the upper surface of the wing. This gives rise to a pressure differential, exerting a force on the high-pressure underside that is not completely counteracted by the low-pressure on top of the wing. Through these two dynamic processes, the phenomenon of lift is exercised.

Hopefully this has been an enlightening passage, one that inspires to inquire. It is through understanding our world in the best possible way that we can truly advance ourselves.