The triangular slit flap is to make the plane have better vulgar performance, but why does Boeing 787 use simple flaps?

The lift effect of simple flaps is not very high, so they are generally used in low-speed aircraft, and high-speed aircraft are rarely used alone. If three-slit and multi-slit flaps are used, the lift effect will be better, but the structure is complex, so at present, small and medium-sized aircraft mostly use double-slit flaps. However, in order to greatly improve aircraft performance and reduce operating costs, Boeing 787 Dreamliner adopts advanced aerodynamic technology, including smooth wing technology. That is to say, a simple crankshaft trailing edge flap is adopted, and its flap guide fairing is much smaller than that of a traditional aircraft. Thanks to this feature, Boeing 787 has achieved high lift-drag ratio performance and reduced fuel consumption cost. In addition, the simple trailing edge of the crankshaft requires fewer parts and reduces maintenance, but the advantages of this lighter and simpler high-lift system are not affected at all. During cruising, the variable curvature control of the trailing edge device optimizes the wing shape during cruising. In order to minimize fuel consumption, this variable curvature control technology can be realized on the basis of crankshaft trailing edge device and drooping spoiler technology. During cruise flight, the trailing edge of the wing is adjusted up and down to continuously optimize the airfoil and efficiency.