An aircraft adheres to similar principles of flight that birds do — it must overcome gravitational forces to achieve lift. In its simplest definition, the wings of an airplane curve the flow of air around them in order to generate lift.
Isaac Newton created three laws of motion that are applicable to all moving objects — even aircraft. The first law states that objects remain at rest or uniform motion unless they are compelled to change by an external force. The second law states that force is equal to the change in momentum per the change in time (F=ma). The last law states that for every action, there is an equal and opposite reaction. These scientific laws are important in understanding how and why aircraft can fly.
Lift is created mostly around the wings because the air flows over the top of the wing and directs the air downwards. This is why wings are designed to tilt from the horizontal plane of the aircraft. This is commonly referred to as the path of flight. Once an airplane is going fast enough, the downward air-flow starts produces enough pressure or force to overcome the weight and gravity that is holding the airplane to the ground. An airplane can achieve flight when enough force is produced to overcome weight and gravity.
The most important variable in generating lift is the tilt angle, or angle of attack. A pilot adjusts the angle of attack to control lift: too high of an angle of attack will stall the airplane— this is called the critical angle of attack. It is the difference between pitch angle and flight path angle when the flight path angle is referenced to the atmosphere. An airplane can reach a high angle of attack even with the nose below the horizon, when the flight path angle is a steep descent.
Another famous contributor to the laws of aerodynamics was Bernoulli; he stated that pressure is reduced as air increases in velocity. As air flow comes into contact with the leading
edge of a wing, it splits into two, flowing along the upper and lower surfaces. Because a typical aircraft has a cambered wing, the air will flow faster over the top and slower on the bottom; this means that there is higher pressure on the bottom surface of the wing. As the airplane gathers speed, the amount of lift increases.
Another important component of wing design is
aircraft ailerons. This structure is a hinged section close to the trailing edge of the wing that allows pilots to bank the aircraft left or right. They work in opposition with one another; as moves upward, the other moves down. This creates an unbalanced side force component which causes the aircraft’s flight path to curve. With greater downward deflection of the airflow, the lift will increase upward.
One last important force is drag, the aerodynamic force that creates resistance against the forward motion of a plane. Thrust is generated by the engines to overcome drag and is supplemented by the aerodynamic shape of an aircraft. It’s important to remember that an aircraft is designed to balance out contradictory forces. All components contribute to the flight cycle— whether it be the engines, the wings, the empennage, etc. The next time you see an aircraft, take a moment to admire the brilliance of its wings.
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