Effects of Trailing Edge Flaps on The Aerodynamics and Performance Characteristics of Rotor Blades

Abstract

In the present study, helicopter rotor blades with trailing edge flaps are studied to analyze their aerodynamic and performance characteristics for hover conditions. The effect of different characteristics of trailing edge flaps, i.e. flap cord, flap span, the radial location of the flap along the blade and flap deflection angle are inspected. Preliminary calculations are conducted using the properties of BO105 rotor. In order to examine the parameters of the rotor blade, an in-house aerodynamic code is developed by applying the Blade Element Momentum Theory formulations with tip loss effects and XFoil program is used to find 2-D airfoil characteristics. Consequently, effects of several parameters of trailing edge flap concept are demonstrated in several figures where variation of the Flap authority (FA) and the figure of merit authority (FMA) are examined. Flap authority is more affected by the change of Sp, Cr, Md, δ parameters in cases where the thrust coefficient is low. It is directly proportional to the change of each of the flap parameters with the change of the FA value. The FMA increases in low-loaded blades when the flaps approach the root, while it decreases when the flaps are positioned towards the blade tip.

Keywords

• blade element momentum theory
• flap authority
• figure of merit authority
• helicopter performance