RE Museum - THE FORCES OF FLIGHT

For a plane to fly, it has to overcome its weight and drag (air resistance) with lift and thrust.
When an aerofoil moves through the air, different pressures develop in the airstreams over and under it.

Air over the curved top of the wing goes faster. The result is that its pressure drops and the wing begins to lift.
The faster the speed, the less the pressure. A plane lifts when pressure below the wing exceeds that above it.

A jumbo takes off To become airborne, a plane has to travel at speed along the ground, getting faster and faster until the lift developed by its wings becomes greater than its own weight. A heavily loaded Boeing 747 has to reach a speed of about 180mph (290km/h) before it can take off.

On the wings, the main control surfaces are the ailerons - one on each wing, often near the wing tip. Moving the control column to the right raises the right-hand aileron and lowers the left-hand one. This makes the right-hand wing dip and the left-hand wing rise, a manoeuvre called banking. Moving the control column to the left makes the plane bank to the left.

To turn the plane's nose left or right, the pilot moves the rudder, a hinged surface on the vertical tail fin, by using foot pedals. Pressing the left-hand pedal swings the rudder left, so the nose swings left. Pressing the right-hand pedal swings the rudder and thus the nose to the right.

Use of the rudder alone does not make the aeroplane turn. It simply changes the position, or attitude, of the plane in the air - because of its considerable tendency to keep straight, the plane side-slips, or `skids'. To turn without side-slipping, the pilot uses a combination of ailerons and rudder, a manoeuvre known as bank and turn.

To move the plane's nose up or down, the pilot operates the control surfaces on the tailplane, which are called the elevators.

Pulling on the plane's control column makes the elevators hinge up, causing the nose to rise. Pushing on the column makes the elevators hinge down and the nose dip. But to make the plane climb or descend, the engine throttle must be operated as well. To climb, the pilot opens the throttle to admit more fuel to the engine and increase speed, and at the same time raises the elevators. Greater speed means greater lift, so with its nose pointing upwards the plane climbs. To descend, the elevators are lowered while the throttle is eased back. Lower speed means less lift, so the plane loses height.

Read More: RE Museum - Power-assisted controls