construction may be too heavy to allow this system to work without an excessive increase in the weight of the aileron. In this case, the weight may be added to a lever arm to move the weight well out in front to the aileron body. These balance weights are tear drop shaped (to reduce drag), which make them appear quite different from spades, although both project forward and below the aileron. In addition to reducing the risk of flutter, mass balances also reduce the stick forces required to move the control surface in maneuvers. Aileron fences Some aileron designs, particularly when fitted on swept wings, include fences like wing fences flush with their inboard plane, in order to suppress some of the spanwise component of the airflow running on the top of the wing, which tends to disrupt the laminar flow above the aileron, when deflected downwards. Types of ailerons Single acting ailerons Used during aviation's pre-war "pioneer era" and into the early years of the First World War, these ailerons were each controlled by a single cable, which pulled the aileron up. When the aircraft was at rest, the ailerons hung vertically down. This type of aileron was used on the Farman III biplane 1909 and the Short 166. A "reverse" version of this, utilizing wing-warping, existed on the later version of the Santos-Dumont Demoiselle, which only warped the wingtips "downward". One of the disadvantages of this setup was a greater tendency to yaw than even with basic interconnected ailerons. During the 1930s a number of light aircraft used single acting controls but used springs to return the ailerons to their neutral positions when the stick was released. Wingtip ailerons Used on the first-ever airframe to have the combination of "joystick/rudder-bar" controls that directly led to the modern flight control system, the Blériot VIII in 1908, some designs of early aircraft used "wingtip" ailerons, where the entire wingtip was rotated to achieve roll control as a separate, pivoting roll-control surface—the AEA June Bug used a form of these, with both the experimental German Fokker V.1 of 1916 and the earlier versions of the Junkers J 7 all-duralumin metal demonstrator monoplane using them—the J 7 led directly to the Junkers D.I all-duralumin metal German fighter design of 1918, which had conventionally hinged ailerons. The main problem with this type of aileron is the dangerous tendency to stall if used aggressively,