US Patent 10343763 Lifting surfaces and associated method

An arrangement of lifting surfaces including a primary lifting surface having a flexural axis extending in the spanwise direction of the lifting surface, a root, and a tip. A first tip device is attached to the tip and has a first lifting surface. A second tip device is attached to the tip and has a second lifting surface. A control system is coupled to the first and second tip devices for moving the first and second lifting surfaces relative to the tip or for actively controlling circulation of the first and second lifting surfaces. The control system is operable to change a value of torque effective at the primary lifting surface about the flexural axis.