There's a serious problem with the organization of the article. Early on, he tells the story of being scolded in school for noticing that his teacher's explanation for how planes work cannot be right, because if you turned the plane upside down, the Bernoulli force would be toward the ground.
He then goes on to talk about the Coanda effect, and how that combined with the shape of the wing makes the wing direct air toward the ground, and thus provides lift.
Suppose back in sixth grade, his teacher had taught that explanation instead of the incorrect Bernoulli effect explanation. He'd still have the same problem! Turn a wing upside down and the Coanda effect and shape are now deflecting air toward the sky, and the lift is toward the ground.
He should have had a little section at the end covering how planes actually fly upside down.
There are at least four ways to force air downward in order to help provide lift. There's the Bernoulli effect, which he points out doesn't provide very much lift. There's the Coanda effect, which he covers. Then there's simple brute force--point whatever you are using to provide thrust so that the thrust vector aims up somewhat instead of level. Finally, put something in the air flow at an angle so that it directly deflects the airflow down.
The first two work in the wrong direction when upside down, so it is the later two that are responsible for upside down flight. Note that both of these come with significant cost. If you are pointing your thrust vector up, you lose some forward thrust, so it is going to take longer and cost more in fuel to get where you are going. If you stick some flat surface in the air flow to just directly direct air downward, you are also introducing considerable drag, again making your trip take longer and use a lot more fuel.
He then goes on to talk about the Coanda effect, and how that combined with the shape of the wing makes the wing direct air toward the ground, and thus provides lift.
Suppose back in sixth grade, his teacher had taught that explanation instead of the incorrect Bernoulli effect explanation. He'd still have the same problem! Turn a wing upside down and the Coanda effect and shape are now deflecting air toward the sky, and the lift is toward the ground.
He should have had a little section at the end covering how planes actually fly upside down.
There are at least four ways to force air downward in order to help provide lift. There's the Bernoulli effect, which he points out doesn't provide very much lift. There's the Coanda effect, which he covers. Then there's simple brute force--point whatever you are using to provide thrust so that the thrust vector aims up somewhat instead of level. Finally, put something in the air flow at an angle so that it directly deflects the airflow down.
The first two work in the wrong direction when upside down, so it is the later two that are responsible for upside down flight. Note that both of these come with significant cost. If you are pointing your thrust vector up, you lose some forward thrust, so it is going to take longer and cost more in fuel to get where you are going. If you stick some flat surface in the air flow to just directly direct air downward, you are also introducing considerable drag, again making your trip take longer and use a lot more fuel.