The ability of an airplane to fly is a result of a delicate balance between four fundamental forces: lift, weight, thrust, and drag. Understanding how these forces interact is key to grasping the principles of flight. Lift and weight oppose each other, with lift acting upwards and weight pulling the aircraft towards the earth’s centre. Similarly, thrust pushes the airplane forward while drag acts to slow it down.

How Airplanes Fly

Lift, the force that allows an airplane to take off and stay in the air, is primarily generated by the wings. According to Bernoulli’s Principle, as air flows over the curved upper surface of a wing, its velocity increases, and its pressure decreases. This creates a pressure difference between the top and bottom of the wing, resulting in an upward force. This lift force acts at a 90° angle to the relative airflow. Other parts of the plane, such as the horizontal stabilizer and fuselage, can also contribute to lift.

Weight, a force that is relatively straightforward to understand, is directly related to the mass of the aircraft. The heavier the aircraft and its contents, the greater the weight. Weight acts through the centre of gravity, always pointing towards the Earth’s centre. It’s crucial that an aircraft’s centre of gravity remains within a specific range; otherwise, it can lead to handling issues and potential crashes.

Thrust is generated by the airplane’s engine and propels the aircraft forward. Increasing thrust makes the aircraft move faster. The thrust vector generally acts in the forward direction, though this can change during climbs.

Drag, which opposes the aircraft’s motion, is a combination of factors, including the shape of the aircraft and the amount of lift being produced. Understanding these factors is important for designing efficient aircraft.

Turning in the Air: A Detailed Explanation

Turning an airplane isn’t as simple as steering a car. It involves a complex interplay of several flight controls, including the ailerons, spoilers, elevator, and rudder.

  • Ailerons: Located at the back of the wings, ailerons cause the airplane to roll around its longitudinal axis. Moving the sidestick or control column left or right adjusts the ailerons, increasing lift on one wing and decreasing lift on the other. This roll tilts the lift of the wings, causing the aircraft to change direction.
  • Spoilers: These devices on top of the wings act as speed brakes, slowing the airplane down and “spoiling” the lift. Spoilers also assist with turns by automatically adjusting to counter the extra drag created by a turning wing.
  • Elevator: Located at the back of the horizontal tail, the elevator makes the airplane go up or down. It is controlled by pulling or pushing the sidestick or control column. When turning, a pilot may pull the stick back a bit to deflect the elevator upwards, to prevent the airplane from slipping into the roll and losing altitude.
  • Rudder: This is the back part of the vertical tail that causes the airplane to “yaw”, moving the nose left or right. While the rudder is not used much during turns for big jets, it can be used for shallower turns and to keep the airplane straight during taxi. The rudder is important for keeping the airplane straight on take-off and landing.

When an airplane rolls to turn, the lift force tilts, causing the aircraft to change direction. When the airplane enters the roll, additional forces come into play. The wing generating more lift also experiences more drag, which must be compensated for by the spoilers or rudder. On larger jets, spoilers typically manage this process. To maintain altitude during a turn, pilots often need to increase power and lift.

During landing, after touchdown, the rudder is again used to keep the aircraft straight. At lower speeds the tiller is used to steer.

Understanding the interplay of these forces and flight controls is essential for comprehending how airplanes fly and turn.

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