Leading-edge slats

Slats ( engl. = slat bar, board or slot = slot, see below) are small, attached to the front edge of the deck, aerodynamically active surfaces. The extension of the slats allows the aircraft to fly with a larger angle of attack. Since the lift is a product of angle of attack and speed ( squared), this allows the airplane specially when landing or other maneuvers close to the stall margin even slower to fly than with flaps. This makes it possible, for example, the required takeoff and landing distance shorten the start and runway. During the flight, the slats are retracted to reduce drag.

There are several types of slats:

• Fixed slats are constantly extended or simply slots into the wing leading edge, they are mostly used for special aircraft that are designed for slow flight, as this significantly reduces the speed of an airplane ( see, for example, the Polish towing aircraft PZL -104 Wilga ).
• Automatic slats are flush with the front edge of the leaf and are extended by springs forward, as soon as the dynamic pressure decreases due to lower airspeed. ( see, for example Morane -Saulnier Rallye 880, 892a, 893 ).
• Powered slats can be extended by the pilot. This type is common in commercial aircraft. They are electrically or hydraulically driven.

Making the slats usually made of only a few percent of the total chord. Enlarge the chord either over the entire leaf width or only at the outer third of the wing.

By the extension of the slat, a portion of the airflow from beneath the slat is accelerated by a tapered slot and is directed above the support surface. The boundary layer on the main wing surface is blown and stabilized so that a stall at lower flight speeds and higher angles of attack will be moved by it. At the same time enables a slat generated by the higher buoyancy to transport heavier loads, in conjunction with other high -lift devices, taking off and landing.

Some birds spread on landing some feathers of Alula forwards. Help you achieve an effect similar to a slat.

History of the slats

1918 was Gustav Lachmann the slats for a patent, which was rejected by the German Patent Office. For Handley - Page in England, he developed the first solid slats. This design is specifically used for aircraft that had to do with a short take-off and landing strip, for example on the German Fieseler Fi 156 Storch also called (picture below right). The stork sufficed to start 45m runway length for landing even only 18m.

During the Second World War, the first automatic slats were developed. The reason was that the air friction of the wings had to be reduced in order to achieve higher top speeds. Nevertheless, during takeoff and landing enough buoyancy must be present for which ensure the slats.

In the postwar period the slats have been greatly developed. They were now hydraulically or electrically powered and thus allowed a more variable use.