Flaps and Slats (2024)

The amount of lift generated by a wing depends on the shapeof the airfoil, the wing area, and theaircraft velocity.

During takeoff and landing the airplane's velocity is relativelylow. To keep the lift high (to avoid objects on the ground!),airplane designers try to increase the wing area and change theairfoil shape by putting some moving parts on the wings' leading andtrailing edges. The part on the leading edge is called a slat,while the part on the trailing edge is called a flap. Theflaps and slats move along metal tracks built into the wings. Movingthe flaps aft (toward the tail) and the slats forwardincreases the wing area. Pivoting the leading edge of the slat andthe trailing edge of the flap downward increases theeffective camber of the airfoil, whichincreases the lift. In addition, the large aft-projected area of theflap increases the drag of the aircraft.This helps the airplane slow down for landing.

Let's investigate how the flaps and slats work by using a Javasimulator.

You can deploy the flaps and slats by using the slider at the bottom.

You can download your own copy of this simulator for use off line. The programis provided as Flaps.zip. You must save this file on your hard driveand "Extract" the necessary files from Flaps.zip. Click on "Flapview.html"to launch your browser and load the program.

The next time you fly in an airliner, watch the wings duringtakeoff and landing. On takeoff, we want high lift and low drag, sothe flaps will be set downward at a moderate setting. During landingwe want high lift and high drag, so the flaps and slats will be fullydeployed. When the wheels touch down, we want to decrease the lift(to keep the plane on the ground!), so you will often see spoilersdeployed on the top of the wing to kill the lift. Spoilers createadditional drag to slow down the plane.