Danger Zone: Physics and Flight
I Hate to Let You Down
I hate to let you down, but airplanes aren’t magically held up like the spaceships in the movies. Flight is a derivative of pure physics - at its finest. Ever watch a bird fly? I mean really watch it, closely. If you’ve ever watched a seagull or hawk, you’d see their feathers moving as they soar; a result of the air currents flowing around their little bird-bodies. More importantly, you will see a great many of micro-corrections as the bird cuts through the sky. These corrections happen in milliseconds. This function - a God given gift to the birds - is essential to flight. We humans - subconsciously - make similar millisecond corrections, just to stand upright (not nearly as cool as flying). Drunk/impaired people don't count, they’re horrible standers. But physics doesn’t play favorites; drunk birds fly about as well as drunk humans stand.
It's For the Birds
Daniel Bernoulli was watching birds before it was cool - back in the 1700's. He noticed that bird wing-shape played an important role in flight. This led to his discovery of fluid dynamics, and his principle of stationary flow - 165 years before the Wright brothers were able to build an airplane that flew under its own power. So, what is stationary flow? Consider the air around our earth (atmosphere) is a fluid. Though be it gaseous, it is technically a fluid. We can visually see its effects; what we call wind. Wind is simply this: fluid mass movement in relation to the earth.
The Wing: Natural Enemy of Air
Air and fluids naturally want to remain the way they are (stubborn). How can we use this to our advantage? Let's look at a basic wing. Flat on the bottom; possibly a slight inward curve; and a larger curvature on the top, with the highest point (of the curvature) about one-third of the way back from the front (leading edge), and tapering at the back (trailing edge). Just like a bird’s wing, imagine that! Draw a line through the wing from the leading edge to the trailing edge (the chord), and we find that the shape is not symmetrical. The distance on the top is longer than the distance on the bottom. Pull this shape through the air and here is what happens: because air naturally wants to remain the way it is, we force the air going over the wing to go a longer distance than the air going below the wing. So, it has to accelerate to catch up with the air below. It accelerates, therefore, a lower pressure is made on the top of the wing, which pulls up on the top surface of the wing. The air below doesn't have as far to go, so it has a higher pressure. Air wants to be the same pressure, it needs it. Voila! You have lift! Clear as mud?
Birds: Beefcakes in the Sky
Humans are basically land bound, but we have made a lot of progress with flight in a relatively short period of time. However, our bodies are designed for almost anything but flying. For our mass, we ourselves, are heavy and solid-boned - and as for me, hard headed too! Birds have, very thin hollow bones; small organs; a large heart, and huge chest muscles to propel their wings (they think they’re so cool). Their senses are much better than ours; their depth perception is impeccable, and their ugh, rear end (ass) muscles/feathers control their flight perfectly. We’re pretty good at other stuff, but birds are the only perfect flying "machines".
Give a Little, Take a Little
For humans, flying is always a compromise. Yeah, we got rocket engines and Falkor, but flying will always be a compromise. We cannot manipulate wings like birds (we aren't even born with them); weight is always an issue; then there is that evil "drag" word. NO, not that kind! The drag I'm referring to is what happens when we take - these broken wings - and drag them through the air. As said before, air doesn't like being messed with. It resists anything being pulled through it. Wanna prove it? Stick your hand out the window next time you going down the road in your car.
Okay, so far, we have discussed lift, weight, and evil drag. But wait there is more! Because air doesn't like anything being pulled through it, we need to find something that isn't afraid of air. Thrust. Thrust is critical for flight; it's the flux capacitor to the DeLorean. Birds (they think they’re so tough) do it with the massive chest muscles - pictured above. It is similar to the way a fish propels itself through water. Ahh ha! There's that fluid thing again. Aircraft have to use some sort of engine for propulsion. We will call it thrust; it sounds cool, and it's accurate. Now we have four things, lift, weight, evil drag and thrust. Oh and by the way, weight is evil too.
To satisfy physics (so we can fly), thrust must overcome drag, and lift must overcome weight. Every time you gaze up and see a plane fly over, you can safely assume it has met the aforementioned requirements. One very interesting note: when any plane is flying straight and level at a steady speed, thrust is equal to drag, and lift is equal to weight. Physics at it's finest, dear friend.
Now for some unnecessary fears
Flying is unsafe.
I can understand why some feel this way. They may not understand the physics of it, and it can harass your senses; remember, we are land creatures. Unsafe you say? Don't break any laws of physics, and your flight will be quite pleasurable. Personally, my heart rate is much higher when driving my truck among the texting, distracted public than when flying. For me, flying equals low heart rate and a smile that just will not go away.
We hit an air pocket and fell a hundred feet.
Really? What You experienced was turbulence. Our atmosphere can be turbulent because of temperature changes. It usually occurs at lower altitudes. You probably didn't fall 5 feet, much less, 100 feet. How did you measure that anyway?
What about those crazy videos with airplanes flying crooked and barely making it on the runway?
Once an airplane or bird begins flying, it becomes a part of the mass of air it is in, and no longer a part of the earth. Making the transition from the mass of air to the earth (landing) can be appear daunting. The mass of air around the earth is in constant motion in relation to the earth. Watch your local weather and see.
Big planes are safer.
Nope! All airplanes and birds fly by the exact same principles. The r/c planes in my shop, my plane at the airport, a f-16 fighter (Warren’s) and a Boeing 747, fly exactly the same, and are at the mercy of the same physics. Now, you might experience more turbulence on smaller planes simply because they normally are used for short flights, and don't go to the higher altitudes that larger, cross country aircraft will. The higher altitudes usually have less turbulence. So you see, it has absolutely nothing to do with the plane being smaller.
What if we stall?
Stall? Where did you hear that from? The news? Oh, a pilot mentioned that to you. Well, a wing can only stall when reaches its critical angle of attack. Angle of attack is the angle that a wing is in relation to the air it is flowing through (relative wind). When a wing is stalled it no longer can produce lift, however, the other three forces mentioned earlier are still present. We pilots practice stalls often, and know how to recognize one actually before it happens.
Buy the Ticket, Take the Ride
Now that you understand everything about the physics of flight, you can say yes when your neighbor - who builds his own planes in the garage - asks, “Wanna fly to California for a couple hours?”. Don't pass up the chance. You can see the world from an amazing perspective and experience physics at its finest. As for me, I was 12 years old when I first took to the skies. To this day - when I am not flying - I'm gazing up to see who is, and marvel at the physics of it all.
You can check out Tim's airplane here.
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