Being in an airplane window seat can be quite engaging, particularly if you’re sitting near or at the rear part of the plane. This spot offers an excellent view of the wing’s trailing edge, where you can observe various moving components. One such moving part is the flap. Flaps serve as high-lift devices designed to lower the stalling speed of an aircraft wing for a specific weight. There are also different types of flaps.
Flaps are typically found on the trailing edges of a fixed-wing aircraft’s wings. They help shorten both the takeoff and landing distances, and they also create extra drag, so they’re pulled back into the wing when they’re not needed.
How Flaps Work and Their Deployment
Flaps are deployed using a lever, usually located to the right of the throttle. They generate lift but also create drag. On small aircraft, flaps typically have simple settings like ‘up,’ ‘takeoff,’ and ‘landing.’ In Boeing aircraft, the flap settings are based on degrees of deployment, such as 1°, 5°, 10°, 30°, or 40°. Airbus aircraft have flap settings referred to as 1, 2, 3, and full.
Common Types of Flaps
Plain Flaps
Plain flaps are simple hinged surfaces that extend downward from the wing when deployed. They increase the wing’s camber, which enhances lift generation at lower speeds. These flaps are easy to design and maintain, making them common on light aircraft.
Slotted Flaps
Slotted flaps are a more advanced design that creates a slot-like gap between the flap and the wing when deployed. This design allows high-pressure air from below the wing to flow over the top, delaying the stall and re-energizing the airflow. Most complex aircraft flaps include slots to manipulate the airflow and increase lift.
Split Flaps
Split flaps move downward and backward away from the wing when deployed. They do provide an increase in lift but introduce a substantial amount of drag, making them less efficient than other flap types. These were commonly used in older aircraft designs.
Fowler Flaps
Fowler flaps not only move downward but also slide backward, significantly increasing the wing’s area. This design provides higher lift coefficients and increased lift at lower speeds compared to other types of flaps. Fowler flaps are usually found on larger commercial aircraft.
Special Types of Flaps
Krueger Flaps and Slats
Krueger flaps are found on the leading edge of the wing and extend forward from the wing’s leading edge. Slats are movable surfaces that slide forward to improve lift at low speeds and high angles of attack. These leading-edge devices also improve lift performance during takeoff and landing.
Flaperons
Flaperons combine the functions of flaps and ailerons. They are located at the trailing edge of the wing and move up and down. Flaperons are usually found on large swept-wing aircraft and provide additional roll control during flight.
The type of flap used depends on the aircraft design and the desired performance characteristics for takeoff, landing, and other phases of flight. Modern aircraft often incorporate multiple flap types or even use innovative systems to improve overall aerodynamic performance and handling.
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