Aeronautics and astronautics – Aircraft control
Reexamination Certificate
1999-05-05
2001-05-08
Price, Thomas (Department: 3644)
Aeronautics and astronautics
Aircraft control
Reexamination Certificate
active
06227487
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to aerodynamic control apparatus and, more particularly, such apparatus used in combination with a wing of an aircraft and, even more particularly, to the wing tip for producing yaw and drag forces.
2. Description of the Prior Art
Over the years, there have been numerous advances in the state of the art relating to aircraft control devices positioned at outboard ends of the wings. A number of patents can be referred to which are generally representative of such advances. For example, an early improvement is provided by U.S. Pat. No. 1,989,291 to Prewitt which discloses an airplane with floating ailerons for roll control encompassing the entire tips of the wings. U.S. Pat. No. 2,210,642 to Thompson discloses a flying wing with fixed stabilizing and control surfaces arranged at the opposite extremities of the wing structure to minimize the possibility of stalling. U.S. Pat. No. 2,846,165 to Axelson discloses an aircraft control system with vertically disposed airfoils at the tip ends of the wings and mounted to pivot about a vertical axis to affect roll and lift control and guard against aileron reversal at high speeds. U.S. Pat. No. 3,067,971 to Dew discloses peripherally disposed drag flaps of unconventional design at the rear of an aircraft or missile to decelerate the vehicle from very high velocities, as upon reentry from space. U.S. Pat. No. 4,247,063 to Jenkins discloses retractable wing-tip mounted vanes for providing both roll control and direct lift control. U.S. Pat. No. 4,382,569 to Boppe et al. discloses a capture device at the tip of a fluid foil such that when provided with relative motion with respect to the fluid in which it is immersed, it intercepts a quantity of the crossflow which is generated by the difference in pressure on the lower surface relative to the upper surface so that lift-induced drag is thereby reduced. U.S. Pat. No. 4,545,552 to Welles discloses an aircraft which utilizes controllable winglets to generate pitching, yawing and rolling moments in flying wing or tailless airframe configurations which are preferably of a swept forward style. U.S. Pat. No. 4,598,885 to Waitzman discloses an aircraft airframe having wings connected to the fuselage by spars of smaller cross section than the wings. Movable winglets may be provided at the outboard ends of the wings.
It was with knowledge of the foregoing state of the technology that the present invention has been conceived and is now reduced to practice.
SUMMARY OF THE INVENTION
The present invention relates to aerodynamic control apparatus for the wing of an aircraft comprising a drag flap mechanism including a control surface member pivotally mounted for coupled movement about mutually perpendicular axes parallel to roll and yaw axes between a fully feathered position presenting minimal resistance to the airstream and a fully operative position presenting maximum resistance to the airstream. There can be a second control surface for the underside of the wing, or two such control surfaces back to back can extend beyond the wing tip. In the last embodiment, the control surfaces are contiguous and opposed when the mechanism is in the feathered position and define between them an obtuse angle at the common axis when in the operative position. The control surface is constrained so as to move out into the airstream in such a way that the very drag force it produces assists the force to move it there. The constraint is by a pivoting hinge plate which holds the control surface on one edge and a transfer strut which goes between the wing and the control surface. An actuator may be provided for moving the control surface members between the feathered and operative positions. The drag flap mechanism may include a single control surface which is actuated by a pivoting hinge plate and transfer strut buried in the wing structure beneath the control surface. In another implementation a cantilevered bracket member fixed to the wing and extending beyond a tip end thereof and a hinge plate pivotally mounted on the bracket member at a location spaced from the tip end of the wing, the first and second control surface members being mutually hinged to the hinge plate for pivotal movement about the common axis. Also, the transfer struts are mounted to the wing at a location distant from the bracket member and each of the transfer struts is mounted to its associated control surface at a location spaced from the common axis.
In short, this invention is effective for creating drag anywhere on an aircraft but most usefully at the wing tips. In the low drag configuration, an airfoil embodying the invention is flat, or horizontal, and in the high drag configuration is upright and in the airstream. The unique idea here is the mechanism for moving between low and high drag.
As noted above, the transfer struts are pivotally mounted to, and extend between, the wing and an associated control surface member in such a manner that the control surface member is movable primarily about the first axis when in the fully feathered position and simultaneously about the first and second axes when the control surface is intermediate the feathered position and the fully operative position. Thus, the mechanism of the invention is moved from the low drag, closed position to the opened position. The transfer struts allow the force of the airstream that is opening the control surface to augment an actuator, if available, in pushing the control surfaces ever more into the airstream. With this construction, only a relatively small controlling force is required to actuate a large drag force. The key to the mechanism of the invention is the coupling of the force that wedges the control surface members open to push the surface out into the airstream. The transfer strut is located on the outside of the control surface member in the figures to show how it works. In practical application of this invention it would be located on the inside of, or between the opposed control surface members. This has the further advantage that the transfer strut would be in tension instead of compression, when the drag forces are great. What is critical is that the hinge force be balanced against the pivot force for as much of the motion as possible. By proper placement of the components of the invention, namely, the transfer struts, hinges, front pivot and control surface members, the forces can be balanced to any amount of augmentation including self opening, that is, where the relaxed state of the aerodynamic control apparatus is the fully deployed position and a control force must be exerted to close it.
In one of the embodiments of this invention, the augmented drag flap is deployed at the wing tips and actuated on one side or the other to effect a yaw force. If the wings are swept back, as in the B-2 bomber, for example, the resultant force vector is more orthogonal to the moment arm from the center of gravity of the vehicle. Two advantages are thereby effected. First, increased torque results from the same applied force. Second, and more significantly, the augmenting force diminishes as the direction of the airstream comes more in line with the aircraft. Since the side load component of the force diminishes automatically, less overshoot occurs when the correcting force is applied for too long a time.
If the force to open the control surface member and the force to swing it out across the airstream are sufficiently balanced, the mere presence of a skewed airstream is enough to open it. This is a passive mechanism which works in the correcting sense. That is, the side slip angle of the airstream opens the control surface member automatically thereby creating drag in the direction that will move the wing back to its original orientation. As the wing becomes more and more into alignment with its original orientation, the control surface member closes until it becomes completely closed when the wing returns to its original orientation. This automatically operating mechanism dupli
Anderson Terry J.
Hoch, Jr. Karl J.
Northrop Grumman Corporation
Price Thomas
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