December 17, 2003
The airplane controls evolution has made a spiral turn to return to the old, almost forgotten technical solution.
Controls of an ordinary airplane are movable planes “cut out” of its wing and tail unit and hinged to carrying surfaces. Such attachment enables the control planes to deviate through a certain angle in accordance with the pilot's commands thereby changing the airplane position. As the same time, this type of attachment leads to that the plane deviation (and they should be regularly deviated in flight) violates the wing contour smoothness thereby impairing the wing flow-around by an air stream.
According to the technical systems evolution trends, it would be natural to expect a transfer from a hinged attachment to an elastic wing construction.
Such a wing has been developed and a so-called transformable supersonic airplane F/A-18 equipped with elastic wings (system AAW, Active Aeroelastic Wing) is now being tested at the NASA test center in California. The wing bending is controlled by a drive hidden inside the wing. As a result, in flight the bow and the tail unit of the wing may be deviated practically without violating the wing contour smoothness.
The decision to give up usual ailerons, slats and other wing mechanization methods considerably enhanced the aerodynamic properties of the wing, the airplane manoeuvrability and control reliability. A seamless smooth wing devoid of auxiliary mechanical surfaces has a reduced aerodynamic resistance; the elastic wing control drive is simplified and made lighter. In addition, the elastic wing is easy to make adaptable, capable of automatically changing its shape depending on the flight conditions. All these factors enhance the effectiveness and comfortableness of passenger airplanes and make war-planes less perceptible by radars.
It is interesting, that the elastic wing airplane is tested on the eve of the centenary of the first flight of the Wright borthers' airplane. That airplane was controlled by bending the carrying surfaces. This was causes by a desire to reach a maximum design simplicity in combination with resource possibilities of very limp and weakly loaded wings having a linen skin. The increased speed and carrying capacity of the planes required a transfer to comparatively rigid wooden and then metal structures. Control of the carrying surfaces that was an advanced solution for those times had to be replaced with a hinged attachment of rudders and airlerons. The airplane controls evolution has made a spiral turn to return to the old, almost forgotten technical solution.
The next wing dynamization step may be a system providing a change in the wing area, span, sweep angle and other parameters.