Preliminary Studies with Active Flaps

Abstract

There are primarily two types of flaps that are suitable to be mounted on helicopter blades: plain flaps and servo-flaps. The servo-flap design consists of auxiliary airfoil sections that are located aft of the trailing edge of the main blades, thereby resulting in high drag due to the exposure of hinges and supporting structure. In comparison, plain flaps are aerodynamically efficient since the flap is integrated into the blade structure, but are located closer to the blade elastic axis and their capability to generate pitching moments is correspondingly reduced. The plain flap configuration is used in this book. In this chapter, a simple aerodynamic model of the trailing-edge flap is used to obtain an idea about the advantages of 1, 2, and 4 trailing-edge flaps. Section 3.1 gives a brief description of the trailing-edge flap aerodynamic model and the flap control law. Section 3.2 explains formulation of optimization problem. Section 3.3 gives the numerical results. Section 3.4 gives the summary of this chapter.