1) Aircraft control 
A deceleron, or split aileron, was developed in the late 1940s by Northrop originally for use on the F-89 Scorpion fighter aircraft. It is a two-part aileron that can be deflected as a unit to provide roll control, or split open to act as an air brake. Decelerons are also used on the Fairchild Republic A-10 Thunderbolt II, the A-6 Intruder and the...
an aileron that acts as a brake.