Abstract:
Individually operable ailerons pivotable to extend a forward end below a bottom wing surface and a rearward end above a top wing surface. The extended aileron forward end increases drag and subsumes the rudder function in the turn, while the aileron rear end produces drag and airflow redirection to reduce lift on the wing. The advantage of the safety ailerons is that habitual or instinctive pilot inputs to the yoke will recover from a dropped-wing stall at low speed and altitude, while conventional ailerons require counter-intuitive pilot actions to avoid crashing in such conditions.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional patent application 61/978,566 filed Apr. 11, 2014 to the same inventor, the contents of which are included herein by reference. 
    
    
     FIELD OF ART 
     The present invention relates to an aileron system that causes an aircraft to safely respond to a pilot&#39;s habitual actions in situations where the pilot&#39;s habitual actions would normally be hazardous. The present invention relates to an aileron system that uses unsynchronized ailerons to simultaneously cause yaw and roll and which can recover an aircraft from a dropped-wing stall by intuitive or habitual use of the yoke. 
     BACKGROUND OF THE INVENTION 
     Conventional aircraft execute turns using ailerons, which are aerodynamic devices that work as a synchronized opposing pair along the trailing edges of opposing wings. A first aileron rotates upward to give a first wing a downward aerodynamic force and the second aileron simultaneously rotates downward to give the second wing an upward force to roll the aircraft, thereby rotating the lift vector and so creating a horizontal component of lift that moves the aircraft horizontally to execute the turn. Synchronized ailerons produce differential profile drag, producing a reverse yaw effect that must be compensated for with a rudder. 
     Many crashes with loss of life have resulted from low speed stalls on final approach to landing, because only a highly-skilled pilot can resist the normal reaction to a wing dropping. The normal reaction is to turn the yoke in the direction opposite the low wing, which would normally (at higher speeds and altitudes) be the correct response. In response to the reaction, the low wing gains additional lift from the increase in camber caused by the drooping aileron, and the raised aileron on the opposite wing reduces lift on that wing. These combined forces cause the wings to become level. However, when the aircraft has slowed to minimum approach speed, and a wing drops, the normal reaction of turning the yoke in the opposite direction increases the camber of the low, slow wing and so increases drag on that wing, which is likely to cause the wing to stall and induce a tailspin from which even a skilled pilot could not recover at final-approach altitude. The correct procedure in this case is to lower the nose and increase power to avoid the stall. The skilled pilot must recognize that only increasing speed will allow the aircraft to maintain level flight and normal glide path to escape a low-altitude dropped wing stall using conventional ailerons. 
     Thus, there is a need for an aileron system that will cause the aircraft to avoid a low-speed dropped-wing stall in response to the intuitive reaction of a relatively unskilled pilot rather than require the reasoned reaction of a skilled pilot. 
     SUMMARY OF THE INVENTION 
     The present invention provides an aileron system that causes the aircraft to avoid a low-speed dropped-wing stall in response to the intuitive reaction of a relatively unskilled pilot. With the safety aileron system of the present invention, only one aileron operates at any time. The safety aileron pivots further back than conventional ailerons and so never droops like a conventional aileron. Rather the safety aileron rotates to position its leading edge below the bottom surface of the wing and position the trailing edge of the aileron above the surface of the wing. Turning the yoke in the intuitive direction (opposite the turn) works without inducing a stall, since the aileron on the low side doesn&#39;t move at all. The opposite (high side) safety aileron activates, reducing the lift of that wing to level the aircraft, instead of increasing lift (and drag) on the low side and risking a stall. The safety aileron on the high side lowers its leading edge below the wing, causing drag that produces a yawing moment toward that wing. This also increases the speed of the low wing, creating more lift and assisting in leveling the aircraft. 
     In addition to the low-speed safety features described herein, the safety aileron system is also superior to conventional ailerons at cruising speeds. First, because the safety aileron system provides both roll and yaw inputs in the same direction to effect a change in the aircraft&#39;s heading, little or no rudder input is required for normal turns. Rudder input will continue to be necessary for aerobatic maneuvers and cross-wind landings, in the same manner as the rudder is used in conjunction with conventional ailerons. Second, the safety aileron system is of particular benefit in canard, flying-wing and other unconventional aircraft configurations where a rudder is not effective. Third, because the safety aileron system reduces overall drag, a fuel savings is also realized 
     The safety aileron system has been successfully tested with unmanned aerial vehicles (UAVs) of both conventional and canard layouts. 
    
    
     
       DESCRIPTION OF THE FIGURES OF THE DRAWINGS 
       The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, the hundreds digits of reference numerals indicate the drawing number in which the feature is first referenced, and 
         FIG. 1  is a side cross-sectional view illustrating an exemplary embodiment of the safety aileron system in a wings level flight configuration, according to a preferred embodiment of the present invention; 
         FIG. 2  is a side cross-sectional view illustrating the exemplary embodiment of the safety aileron system of  FIG. 1  in a turning flight configuration, according to a preferred embodiment of the present invention; 
         FIG. 3  is a photographic view illustrating an exemplary embodiment of the safety aileron system of  FIG. 1  in a left turn configuration, according to a preferred embodiment of the present invention; 
         FIG. 4  is a photographic close-up view illustrating the exemplary embodiment of the safety aileron system of  FIG. 3 , according to a preferred embodiment of the present invention; 
         FIG. 5  is a photographic view illustrating an exemplary embodiment of the safety aileron system of  FIG. 1  in a right turn configuration, according to a preferred embodiment of the present invention; 
         FIG. 6  is a photographic close-up view illustrating the exemplary embodiment of the safety aileron system of  FIG. 5 , according to a preferred embodiment of the present invention; 
         FIG. 7  is a second photographic view illustrating an exemplary embodiment of the safety aileron system of  FIG. 1  in a right turn configuration of  FIG. 5 , according to a preferred embodiment of the present invention; and 
         FIG. 8  is a photographic close-up view illustrating the exemplary embodiment of the safety aileron system of  FIG. 7 , according to a preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a side cross-sectional view illustrating an exemplary embodiment of the safety aileron system  100  in a wings level flight configuration, according to a preferred embodiment of the present invention. Wing section  104  is pivotably connected to safety aileron  102  by means known in the art for installing ailerons. However, the pivot axis  106  for the safety aileron is positioned further aft than with conventional ailerons. Likewise, the safety aileron  102  is larger, for a given aircraft  302  (see  FIG. 3 ), than conventional ailerons. In some embodiments, particularly for high-speed aircraft, the pivot axis  106  may be moveable, in the manner of pivots for flaps, as is known in the art. 
     Wing section  104  has top surface  122 , a bottom surface  120 , and a rear surface  124 . The shape of the safety aileron  102  preferably completes the shape of the wing section  104  for the airfoil type of the particular wing. Gap  116  between rear surface  124  and safety aileron  102  should be sized to permit operational rotation of the safety aileron  102  about pivot axis  106 . Safety aileron  102  has a front portion  110  that is forward of the pivot axis  106  and a rear portion  108  that is aft of the pivot axis  106 . Safety aileron  102  forms part of the trailing edge of the wing  104  during wings level flight, as shown in relation to forward direction  118 . In some particular embodiments, gap covers  114  and  112  may be used to make continuous the top surface  122  and the bottom surface  120  of the wing, respectively, during wings level flight. Gap covers  114  and  112  may be flexible and resilient gap covers  114  and  112  such as, for non-limiting example, rubber gap covers  114  and  112 . In a high speed aircraft, gap covers  114  and  112  may be more rigid retractable devices that are extendable from wing section  104 . 
       FIG. 2  is a side cross-sectional view illustrating the exemplary embodiment of the safety aileron system  100  of  FIG. 1  in a turning flight configuration, according to a preferred embodiment of the present invention. Safety aileron  102  is shown pivoted by pivot angle α into an operational position. Front portion  110  extends below the bottom surface  120  of the wing  104 , thereby creating drag that induces yaw in the desired turning direction. The rear portion  108  extends above the top surface of the wing  104  to reduce lift on the wing  104 , causing the wing  104  to lower in further execution of the turn. In normal operation, the turning direction wing will have the configuration of  FIG. 2  and the other wing will concurrently have the configuration of  FIG. 1 . Only one wing&#39;s safety aileron  102  rotates at any given time. Pivot angle α is preferably controllably variable for varying rates of turn. 
     Gap  116  opens into slot  216  with safety aileron  102  rotated into active position. In various embodiments, slot  216  may be open to channel air flow or may be closed with further extended gap covers  114  and  112 . In a particular embodiment, gap covers  114  and  112  may incompletely cover slot  216 . 
     In dropping-wing stall avoidance operation, the safety aileron  102  is activated on the high wing  104  in response to intuitive or habitual yoke inputs to level the aircraft. The drag-induced yaw increases lift on the low wing, while the lift reduction on the high wing  104  assists in bringing the aircraft  302  (see  FIG. 3 ) level and so avoids the stall. 
       FIG. 3  is a photographic view illustrating an exemplary embodiment of the safety aileron system  100  of  FIG. 1  in a left turn configuration, according to a preferred embodiment of the present invention. Unmanned Aerial Vehicle (UAV) test aircraft  302  has two safety ailerons  102  with actuators  304 . The type of actuators  304  is not a limitation of the invention. The safety aileron  102  on the left wing  104  is shown in a left turn configuration for normal flight and in a configuration to avoid a right-dropped-wing stall in a dropped-wing stall avoidance flight regime. Right-wing safety aileron  102  is not activated in either case. 
     Safety aileron system  100  includes controls, actuators, and associated hardware and, in some embodiments, software. The actuators  304  are illustrated as a screw-type electro-mechanical actuator, but this is not a limitation of the invention. Actuators may include, for non-limiting examples, direct mechanical linkages from the yoke (manual operation), electro-mechanical (solenoid), hydraulic torsion, and pneumatic torsion actuators. Likewise, control systems may be, for non-limiting examples, analog mechanical, electrical (ON/OFF), electronic, and computer-controlled (fly-by-wire or wireless). Similarly, aircraft  302  may be any type of aircraft, including, for non-limiting examples, conventional two-winged aircraft, canard aircraft, and flying-wing aircraft. 
       FIG. 4  is a photographic close-up view illustrating the exemplary embodiment of the safety aileron system  100  of  FIG. 3 , according to a preferred embodiment of the present invention. The rear portion  108  of safety aileron  102  can be seen positioned above the top surface  122  of wing  104 . This reduces the lift on the wing  104 , thereby assisting in turning the aircraft. If the aircraft  302  were in a dropped-wing stall, safety aileron  102  would turn the aircraft  302  to the left, increasing the wind speed over the right wing to cause the right wing to rise, while the drag and the air flow pattern change from the safety aileron  102  on the left wing will cause that wing to drop. Thus, the aircraft  302  can be brought back from a dropped wing stall at low altitude. 
       FIG. 5  is a photographic view illustrating an exemplary embodiment of the safety aileron system  100  of  FIG. 1  in a right turn configuration, according to a preferred embodiment of the present invention. UAV test aircraft  302  has two safety ailerons  102  with actuators  304 . The safety aileron  102  on the right wing  104  is shown in a right turn configuration for normal flight and in a configuration to avoid a left-dropped-wing stall in a dropped-wing stall avoidance flight regime. Left-wing safety aileron  102  is not activated. If the aircraft  302  were in a dropped-wing stall, safety aileron  102  would turn the aircraft  302  to the right, increasing the wind speed over the dropped left wing to cause the left wing to rise, while the drag and the air flow pattern change from the safety aileron  102  on the right wing will cause that wing to drop. Thus, the aircraft  302  can be brought back from a dropped wing stall at low altitude. 
       FIG. 6  is a photographic close-up view illustrating the exemplary embodiment of the safety aileron system  100  of  FIG. 5 , according to a preferred embodiment of the present invention. The rear portion  108  of safety aileron  102  can be seen positioned above the top surface  122  of wing  104 . The forward portion  110  of safety aileron  102  extends below the bottom surface  120  (see  FIG. 2 ) 
       FIG. 7  is a second photographic view illustrating an exemplary embodiment of the safety aileron system  100  of  FIG. 1  in a right turn configuration of  FIG. 5 , according to a preferred embodiment of the present invention. The forward portion  110  of safety aileron  102  can be seen positioned below the wing  104  to induce drag to generate yaw to assist with turning the aircraft  302 . The rear portion  108  of safety aileron  102  is positioned above the wing  104  to reduce lift and so bank the turn in normal operation or correct a dropped-wing stall condition using the normal pilot responsive movement of the yoke. 
       FIG. 8  is a photographic close-up view illustrating the exemplary embodiment of the safety aileron system  100  of  FIG. 7 , according to a preferred embodiment of the present invention. Forward portion  110  is below the bottom surface  120  of the wing  104 . 
     Safety aileron system  100  will meet FAA Part 23 regulations for stall resistant aircraft and aircraft equipped with safety aileron system  100  will not require special training for dealing with low altitude stall warnings, as the habitual or intuitive pilot response will be the correct response. 
     Location of the pivot axis  106  and the best pivot angle α must be determined for each aircraft design and can be accomplished by a person of ordinary skill in that art (an aerospace engineer with aircraft design experience) without undue experimentation.