Education

How do planes fly?

For millennia, would-be aviators knew bird flight had something
to do with wing structure, but were clueless regarding the
details. As it turns out, the shape of a wing is optimised to
generate lift, an upward force caused by manipulating airflow. A wing
has a rounded leading edge with a slight upward tilt, a curved topside,
and a tapered trailing edge pointing downward. This shape alters
the flow of air molecules into a downward trajectory. This results
in – as Newton put it in his Third Law of Motion – “an equal and
opposite reaction.” When the wing pushes the air molecules down, the
molecules push the wing up with equal force. The airflow also creates
a lower pressure area above the wing, which sucks the wing up.
Constructing wings is the easy part. To fly, you need to generate
enough forward force – or thrust – to produce the necessary lift to
counteract gravity. The Wright Brothers accomplished this by linking
a piston engine to twin propellers. A plane propeller is simply a group
of rotating wings shifted 90 degrees, so the direction of lift is forwards
rather than upwards. In 1944, engineers upgraded to jet engines,
which produce much greater thrust by igniting a mixture of air and
fuel, and expelling hot gasses backward.
A pilot controls a plane by adjusting movable surfaces on the
main wings, as well as smaller surfaces and a wing-like rudder on
the tail. By changing the shape and position of these structures, the
pilot varies the lift force, acting on the different ends of the plane to
essentially pivot the plane along three axes: its pitch (up or down tilt of
the nose), roll (side to side rotation), and yaw (turn to the left or right).
Engineers keep planes as light and aerodynamic as possible. Modern
fighter jets are manufactured from super-strong, lightweight composite
material, applied in layers to form precise, aerodynamic shapes.

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