Flight
Flight is the act of moving through the air using wings and is facilitated by key forces that include weight, lift, thrust, and drag. Various creatures, such as birds and insects, as well as human-made vehicles like airplanes, helicopters, and spacecraft, are capable of flight, each employing unique adaptations or technologies. Birds, for instance, exhibit specialized features such as feathers, hollow bones, and efficient respiratory systems, which enable them to achieve and sustain flight. They take off and maneuver in various ways depending on their species, with distinct flying patterns and techniques.
Insects utilize either direct or indirect flight mechanisms, with the indirect method being more energy-efficient. Aircraft operate on similar principles to birds, relying on wing design for lift and engines for thrust, while needing to manage the balance of all forces involved for successful takeoff, flight, and landing. Spacecraft, in contrast, do not contend with atmospheric forces like lift and drag, but still require thrust to maneuver through space. Understanding these principles of flight reveals the intricate balance of forces that allow various forms of life and technology to soar through the skies.
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Flight
Flight is the act of passing through the air using wings. Flight involves certain forces, including weight, lift, thrust, and drag, that enable objects to fly. Birds, insects, and aircraft, such as airplanes, helicopters, and spacecraft, are able to fly. Birds have special adaptations that enable them to fly, while insects use one of two flight mechanisms to fly. Aircraft must employ the correct relationship among the forces of flight to be able to fly.
Forces of Flight
To achieve flight, several forces must be present. The forces of flight are weight, lift, thrust, and drag. Weight is the gravitational force on an object. Weight pushes down on an object. Lift is the force that acts on an object in a perpendicular direction. Thrust is the force that drives an object forward. Drag is a force that opposes an object's flight. An object must contend with these forces to be able to fly.
Birds
Birds are known for their ability to fly. They have several adaptations that make them light enough to glide through the air. These adaptations include feathers, hollow bones, short tail and wing bones, efficient lungs and digestion, and the lack of a bladder, nose, and teeth. A bird's feathers, hollow bones, and short tail and wing bones are essential to making it lightweight. A bird's lungs are very efficient at using oxygen. They do not have to fill up with much air, which keeps the bird from getting weighed down by air. A bird eats small amounts of food and maximizes the food's calories. This enables birds to quickly digest food and dispose of useless weight. Because birds do not have a bladder, they are able to quickly urinate, which also allows them to dispose of additional heft. A bird's lack of a nose and teeth also keeps them lightweight. Even though these structures are not very heavy, they can add weight to a bird.
A bird must first take off before engaging in actual flight. Different species of birds take off in a multitude of ways. Some birds jump up while flapping their wings, as cranes and songbirds do. Other birds, such as loons, run into the wind, causing the air to lift them. Some birds, including puffins, leap from a high perch.
Different species of birds also fly differently from one another. For example, swallows zigzag through the air, while crows fly perfectly straight. Other birds, including albatrosses, soar through the air with their wings outstretched. Albatrosses can remain in the air for hours without ever flapping their wings. Conversely, hummingbirds never stop flapping their wings while in flight.
Insects
Insects fly using either a direct or an indirect flight mechanism. The direct flight mechanism involves two sets of muscles on the insect's wing. Both sets of flight muscles are located near the base of the wing—one inside the base and one outside the base. One set contracts and moves the wing upward, while the other contracts and moves the wing downward. Both sets of flight muscles work together to move the wings.
The indirect flight mechanism is more complex than the direct flight mechanism. In this flight mechanism, the insect's flight muscles change the shape of the insect's thorax, or midsection. The dorsal, or backside, surface of the thorax contains muscles that contract and pull down the tergum, or back part of the insect. The movement of the tergum brings down the wing bases. As the wing bases move down, the wings lift up. Then a second set of muscles on the thorax contracts, distorting the thorax again. The tergum lifts up, which brings down the wings. Of the two flight mechanisms, the indirect flight mechanism uses less energy.
Aircraft
Aircraft have the ability to fly like birds and insects do, but they achieve flight in a different way. The forces of flight are present when an airplane flies. The airplane's wings provide lift. Enough lift is needed to overcome the weight of the airplane. This means heavy airplanes need larger wings. The airplane's engine provides thrust. As with the relationship between lift and weight, enough thrust is needed to overcome drag. Furthermore, a correlation exists among these forces. If more lift is needed, then drag would increase, and more thrust would be needed as well. For an airplane to take off and rise high in the air, the lift and thrust must be greater than the weight and drag, respectively. On the other hand, for an airplane to land, the lift and thrust must be less than the weight and drag, respectively. For an airplane to fly straight and level, it must achieve a balance between lift and weight and between thrust and drag.
Flight for spacecraft is a little different. When a spacecraft navigates through space, it does not have to contend with the forces of lift and drag. This is because little gravity exists in space compared to Earth's atmosphere. However, a spacecraft must still employ thrust to reach space.
Bibliography
Hadley, Debbie. “How Insects Fly.” Thought Company, 3 July 2019, http://insects.about.com/od/insects101/qt/How-Insects-Fly.htm. Accessed 15 Nov. 2024.
“Forces of Flight.” How Things Fly. Smithsonian National Air and Space Museum. Web. 10 Dec. 2014. https://howthingsfly.si.edu/forces-flight. Accessed 15 Nov. 2024.
Merrett, Craig. "How Do Airplanes Fly? An Aerospace Engineer Explains the Physics of Flight." Discover, 25 Mar. 2024, www.discovermagazine.com/technology/how-do-airplanes-fly-an-aerospace-engineer-explains-the-physics-of-flight. Accessed 15 Nov. 2024.
“Forces of Flight.” Smithsonian National Air and Space Museum, howthingsfly.si.edu/forces-flight. Accessed 15 Nov. 2024.