# Discovery Science: Technology – Airplanes: Propulsion

## Physics and Technology – Technology – Airplanes: Propulsion

The dream of flying finally became a reality with the first airplane built by Orville and Wilbur Wright in 1903.

Since then, the significance of flight has increased rapidly due to advances in technology and the need to transport goods and travelers worldwide.

Since airplanes are heavier than air, forces that are greater than the weight of the plane must act on the aircraft for flight to become possible.

Liftoff

Four forces act on an airplane during flight: weight, lift, thrust, and drag. These forces counteract each other to provide optimal conditions for a plane to take off and fly. To overcome the weight of the plane, aircrafts generate lift. The airflow that is produced while a plane
moves forward on the runway is split by its curved wings.

The upper airflow travels over the top curved part of the wing, and the lower airflow passes under the flatter underside of the wing. Airflow velocity above the wing is greater than velocity on the lower side of the wing, causing pressure below the wing to be greater.

The resulting lift is explained by Bernoulli’s principle, which states that an increase in velocity occurs with a decrease in pressure. The magnitude of lift depends on the speed of airflow and the shape of the wing. The force of air resistance opposing the motion of the plane is called drag.

To over-come drag, the airplane produces thrust, or propulsion, from a force such as an engine. The plane requires an appropriate amount of thrust to counteract drag and remain in flight.

Piloting

In an action similar to steering, the plane is piloted with the help of a rudder, elevators, and ailerons. The pilot controls these devices through the control stick, column, wheel, or side stick, and pedals for the rudder. Movement around the longitudinal axis of the airplane, which is called rolling, is regulated by the ailerons.

They are the flaps located on the farthest point of the wings and can be moved upward or downward independently of each other, causing the lift of the wings to change. The plane rolls toward the direction of the wing that has the aileron tilted upward.

The pilot’s control stick or column operates the ailerons. Airplane movement to the left and right around the vertical axis is controlled by the rudder. Similar to the structure of a boat, the airplane rudder is attached to the tail and lies perpendicular to the plane.

It is used during the landing approach and balances out the undesired yaw, which is a side to side movement caused by the ailerons. The control pedals for the rudder also steer the wheels of the plane on the ground.

Elevators are part of the horizontal tail of the air-plane and rotate the airplane around its lateral axis; that is, elevators control the pitch of the plane. The control stick or wheel operates the elevators.

### TURBOFANS

A turbofan functions according to the recoil principle. Air flowing into the fan is compressed in several stages and heated up to nearly 1112°F (600°C). The airstream is mixed with fuel in a combustion chamber and ignited.

During the burn, the gases stream through a turbine. This generates the energy for the compressors. The gases are released through a nozzle, and the plane is pushed by the force of expulsion.

### BASICS

AILERONS, RUDDERS, AND ELEVA TORS enable a plane to rotate around Its three axes.

AIR TRANSPORT will triple by the year 2015, according to estimates.

AIR TRAFFIC CONTROL (ATC) regulates aircraft flying throughout the majority of airspace.