Flight can be divided into three basic groups:

 

 

 

When a plane is flying slower than the speed of sound, subsonic aerodynamics describes the two primary forces that slow it down as Form Drag and Induced Drag. Form drag is caused by turbulence as air flows over the plane, and is minimized by long, tapering trailing edges on each shape of the hull to keep air flowing smoothly along it. Wherever air encounters an angle too sharp to flow smoothly over (just as in airfoil stalls described above), excessive turbulence and drag results. The faster an object is moving, the vastly greater it's induced drag is! Objects in free fall eventually reach an equilibrium between gravity speeding them up and drag slowing them down, and this is described as their terminal velocity.

 

Induced drag is related to the redirection of airflow to generate lift - and since planes have to redirect airflow most to stay aloft at low speeds, induced drag decreases as an airplane's speed increases. An aircraft's maximum efficiency is obtained at the speed where induced and form drag are equal. When an airplane is rotated on it's yaw axis so that it points to the side of it's direction of travel, it's form drag is increased and the condition is described as a side slip. Aircraft are equipped with tail rudders to counteract this problem and aid in various maneuvers.

 

 

Dihedral angle describes the upward sweep of an aircraft's wings. When the wings of an airplane form a slight "V" shape when viewed along it's length, the lower wing generates extra lift when the aircraft begins to roll and automatically stabilizes it. If your paper airplane tends to dive left or right when flying, it definitely needs more dihedral!

 

Control surfaces such as ailerons, elevators, and rudders allow an aircraft to modify the shape (and therefore performance) of it's airfoils in flight to control it's attitude. You can add control surfaces to the trailing edges of the wings on your paper airplanes to stabilize their own flight: A curve to the left or right can be cured with an upward flap on the opposite wing, and nosedives or stalls can often be corrected by adjusting the "flaps" on both wings up or down.

 

Spin Stabilization is employed from frisbees to rockets for a simple stability solution - but where rapid rotations aren't an option, Fly by Wire systems feed sensor inputs into a computer to calculate the exact control deflections necessary to keep high performance aircraft (even RC ones!) in the sky.

 

 

• The Glider: AubreyFalconer.com/view-96
• The Starfighter: AubreyFalconer.com/view-51
• 10 Paper Airplanes: 10PaperAirplanes.com
• Alex's Paper Airplanes: PaperAirplanes.co.uk/planes.php
• The Paperang: Paperang.com
• Origami meets Rocket Science!

 

• What is a "wind tunnel", and for what are they used?
• How can an airplane pilot recover from a stall, or a helicopter pilot land when their engine dies?
• What does the term "terminal velocity" refer to?
• Why do "stealth" fighter jets look so angular? (Hint: this answer has very little to do with aerodynamics)
• Why are helicopters so much slower than airplanes? (Hint: visualize the relative airspeed of each side of the main rotor as the helicopter soars through the sky)