Abstract: A wing flap structure includes a wing, a flap, and a hinge mechanism connecting the wing and the flap. The hinge mechanism includes first and second hinge links connected between the wing and the flap. The pivot points for the hinge links are oriented so that as the flap moves away from the wing, the flap moves in a circular arc path relative to the wing. The first hinge link includes a first elongate link having a first end rotatably connected to the wing. The second hinge link includes a second elongate link having a first end rotatably connected to the second end of the first link, and having a second end rotatably connected to the flap. The rotatable connections have axes of rotation that meet at a point below the wing to define an axis of rotation for the circular arc of the flap. The hinge mechanism is contained substantially along the circular arc of the flap as the flap is extended and retracted. A drive mechanism is connected to the wing and to the flap for moving the flap through a circular arc.

Abstract: The application of active noise control to influence the fan-noise components in engine ducts. The fan is used as a source of counter noise by introducing flow distortions upstream or downstream of the fan. Microphone arrays sense the noise and produce a control output signal for controlling a distortion producer. The control output signal for the distortion producer comes from a control algorithm utilizing the output of the microphone signals sampled at a defined rate based on the fan blade passing frequency.

Abstract: The yaw control in an air vehicle having counter rotating rotors is provided by selectively and controllably applying a frictional drag or braking force to drive gears for the two rotors. Each of the drive gears includes a friction surface. Friction pads are located adjacent to and are releasably engagable with the friction surfaces of the drive gears. The friction pads are supported by a control mechanism for selectively moving each of the friction pads into engagement with the respective drive gear to provide a frictional drag on the drive gear and to a disengaged position spaced from the respective drive gear. The frictional forces created by engagement of the friction pads with the drive gear friction surfaces cause net torques on the air vehicle frame to rotate the air vehicle in the desired directions. Normally, the torque developed the counter rotating rotors is canceled, maintaining the air vehicle in the desired yaw orientation.