Aileron Tabs Improve Stability
Engineers at Lehigh University have come up with a relatively simple device that allows pilots to custom-tailor the lateral stability of their aircraft in flight. According to PhysOrg.com, Prof. Joachim Grenestedt designed "canted tabs" that attach to ailerons. The tabs rotate around an aluminum tube inserted in the aileron. The pilot can adjust them as much as 30 degrees in flight and the effect on lateral stability is significant. The tabs were installed on an Aermacchi AM-3 Bosbok and rendered it laterally stable. "We took an unstable aircraft, fitted it with the canted tabs and made it stable. When the plane started to side slip, the tabs applied force to the ailerons, causing the plane to bank, or roll, and regain lateral stability," Grenestedt said. The innovation could help aircraft designers solve an important aerodynamic problem in creating marketable aircraft. According to Grenestedt, civilian aircraft must be able to be rolled upright using rudder alone in case the aileron controls fail. The AM-3 doesn't have that ability and therefore can't be sold commercially. However, with the tabs installed, test pilots at the National Test Pilot School in Mojave were able to roll the plane with rudder alone. "The canted tabs actually made the plane handle properly," said test pilot Russ Stewart. Grenestedt said the tabs could be an easy fix for existing airplanes with stability problems. "The largest benefit of the canted tabs may be to serve as a cure for lateral stability deficiencies in existing aircraft, reducing the need for extensive airframe modifications," he said.
http://www.avweb.com/eletter/archive.../399-full.html
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