Continuing with negative models…
Some myths persist for centuries, like the earth being the center of the universe. Some for only a century, like ‘lift’, which supposedly keeps airplanes in the air. Let us look at this carefully, and also trust both our senses, and our minds.
Some theoreticians have created an abstract notion called ‘lift’. I consider it bogus, and here’s why. By the way, I’ll also show why it’s safe to fly.
Let’s look at a few of their definitions:
Lift: The lift force, lifting force or simply lift is a mechanical force generated by a solid object moving through a fluid.
The first red flag: It seems to me that a moving object doesn’t generate force; rather a force is need to make the object move.
The second red flag, air is a gas not a fluid!
Gases compress rather easily, and when compressed try to decompress, liquids or fluids, except under some extreme conditions do not.
Do try this at home:
Blow up a balloon. The tension of the balloon skin, compresses the air, keeping it from decompressing. Stick a pin in the balloon. The compressed air, given an opportunity decompresses very rapidly!
Here’s some help, I found. which is as clear as mud:
Sometimes the term dynamic lift or dynamic lifting force is used for the perpendicular force resulting from motion of the body in the fluid, as in an aerodyne, in contrast to the static lifting force resulting from buoyancy, as in an aerostat.
Again, air is a gas not a fluid!
Much of the supposed ‘lift’ of an aerodynamically shaped wing is attributed to Bernoulli’s principle which states: that in fluid flow, an increase
in velocity occurs simultaneously with decrease in pressure.
Yet again, air is a gas not a fluid!
They’ve even created wind tunnels where they blow air, with big fans past a stationary wing to determine its aerodynamic behavior. But that’s not what happens when you fly a plane. The air is sitting there rather happy, and undisturbed, and all of a sudden, you come along with your plane’s wing and try to penetrate the air. If you’re going slowly, say less than 60 mph, the air simply gets out of your way since it’s a rather flexible gas, almost fluid. But when you go faster than say 70+ mph, the air can’t get out of the way quick enough, so it compresses! Now it doesn’t take much compression for the air to get very firm, perhaps spongy is a better word. A mere 30 lbs. of pressure, can keep a 3000 lb. car off the ground.
So as a pilot, you look for air that you can ‘push against’. You compress it with your wing using speed, and as it tries to de-compress it pushes you up. Just like the dense cold air pushing the lighter hot air upwards. There is no mysterious force called ‘lift’, with a motor or batteries of it’s own that ’sucks’ you upward.
Regardless of the ‘aerodynamic shape’ of a wing, you can flip a plane upside down and continue to fly quite normally! acrobatic planes do it all the time. Indeed the shape of their wings is symmetric (same on top and bottom), not the popular ‘aerodynamic’ wing.
To see a diagram of an aerodynamic wing see:
Diagram of an aerodynamic wing
Newton on hot air
Another explanation, with fantastic pictures is at:
Naturally, if I ever have to take an FAA exam to get some sort of flying certificate, I’ll swear allegiance to the lie of lift, to get my license. But when caught in a micro burst, or spiraling to where my plane does not behave like a plane, but more like a rock, I’ll look for some air to ‘push against’!
As I promised…
Flying is safe, or at least far safer than driving. The most dangerous part of any flight is driving to the airport, you can get yourself killed on the highway. But if lift is a myth, and the aircraft industry relies on it, why is it safe to fly? Mathematically, the same forces exist in the real world, regardless of how you describe them. Just as with hot air rising, whether the ‘lift’ sucks the plane upward or pushes it upwards, the same forces are at play, just the explanations are different, one easy and natural, one abstract and difficult.
Please DO try this at home:
When you’re driving in a car down a highway, put your hand out of the window. First, put it out flat, with your thumb facing the wind. Then turn it slightly, raising your thumb, and feel what you experience. I feel a compression of air on the underside, which tries to push my hand upwards. I do not feel any suction from above pulling the skin on the back of my hand upwards. But that is only my experience, you try it, and decide for yourself.
Does the same or a similar principle apply for water when skipping a stone across it! Why for the first 2-3 skips does the water not allow the stone to penetrate it, but by the 4-5 skip it does allow it to penetrate the surface of the water and sink to the bottom?