What Is a Rotation Flap?

Deformed flaps are flaps that can continuously change shape under a certain drive, unlike traditional rigid flaps that are attached to the fixed trailing edge of the wing. Deformation flaps are mainly composed of three components, including flexible upper and lower skins with reinforced stringers, curved beam driving mechanism with twisted discs, and the connection structure between twisted discs and twisted stringers.

Deformed flaps are flaps that can continuously change shape under a certain drive, different from

As a longitudinal member of the fuselage structure, the long beam is mainly used to bear the axial force caused by the bending of the fuselage. In addition, the long truss has a supporting effect on the skin. It increases the skin's compression and shear instability critical stress. Secondly, it bears the aerodynamic force acting on the fuselage skin and transmits it to the bulkhead. Long girders are similar ^[1]

The structural function of the fuselage skin is to form the aerodynamic shape of the fuselage, and to keep the surface smooth, so it bears local aerodynamic forces. The skin in the pressurized and sealed cockpit will bear the internal pressure load, and the skin will transfer it Fuselage skeleton.

Skin plays an important role in the overall load of the fuselage. It withstands shear forces and torques in two planes, vertical and horizontal; at the same time, it forms a wall plate with a long truss, etc. to withstand axial forces caused by bending moments in both vertical and horizontal planes ^[1]

A flap refers to a wing-shaped movable device on the edge of a modern wing. The flap can be installed at the trailing or leading edge of the wing, and can be deflected downward or (and) slid backward (forward). Its basic utility is to increase lift in flight. The flaps can be divided into trailing edge flaps and leading edge flaps according to the installed parts and specific functions ^[2]

The design of the deformed structure has great challenges due to some conflicting requirements. For example, from a structural point of view, the deformable flap should have great flexibility to change the shape of the skin, but at the same time need to have sufficient rigidity to withstand aerodynamic loads.

(1) Curved beam concept

The concept consists of a curved beam and disc driven horizontally on the trailing edge of the flap and driven by a rotary actuator. Since the curved beam is connected to the upper and lower skins of the flap through the disc, its rotation will cause the flap skin to deform.

This concept may seem very simple, but the difficulty of this concept is how to make it move normally. Because of the relative movement of the disc and the deformed skin, the point where the flap skin contacts when the curved beam is rotated is always the vertical limit point of the disc. In the process of rotation, the vertical limit point on the disc has horizontal movement in addition to vertical movement.

(2) Twisted Disk Concept

The design of the deformed structure allows the disc to twist and keep the disc perpendicular to the stringer axis so that the disc can move with the stringer at any time. The design challenge was to find the correct shape of the twisted disk ^[1]

Based on the structural characteristics of traditional propellers, the local curvature of the propeller was changed by adding deformable flaps along the edge. This is the local geometric reconstruction technology. Based on this technology, a "deformable propeller based on deformable flap structure" was proposed. "the concept of. This concept is inspired by the deflection flaps of fixed-wing aircraft. When a fixed-wing aircraft takes off, the flaps can be deflected downwards to increase the lift of the aircraft, thereby greatly reducing the take-off time and take-off distance of the aircraft. When deformable flaps are added to the helicopter rotor, the vibration and noise level of the helicopter propeller can be significantly reduced through proper control ^[2] .