Aerodynamics of multifunctional transport aircraft devices

Steep approach is identified to be a feasible operational measure for transport aircraft to reduce perceived noise disturbing airport neighbors. Therefore, the steep approach performance of multifunctional aileron devices compared to a conventional spoiler configuration is investigated here. Additionally, the feasibility of the concepts to maintain the roll control function of a conventional aileron is investigated. The multifunctional aileron devices comprise a horizontally segmented aileron, designated as deceleron, and a laterally segmented aileron, designated as split aileron. These cover the same dimensions as a conventional aileron. A detailed wind tunnel half model of a transport aircraft in high lift configuration is used. The aerodynamic coefficients of lift, drag, and rolling and pitching moment are obtained for various angles of attack. The tests are conducted in a low-speed wind tunnel facility at TU München with a Reynolds number of 1.0 × 10⁶ based on wing mean aerodynamic chord. Aileron deflection and differential aileron deflection angles are varied. Most relevant parameters, regarding steep approach performance, are minimum approach velocity, maximum descent velocity and maximum approach angle. The corresponding values are theoretically derived. Therewith, the relative performances of the configurations are comparably shown. Regarding the objective to maximize approach angle, all multifunctional ailerons turn out to be inferior to conventional spoilers. However, the multifunctional ailerons do not have the penalty of a higher approach speed for steep approach being superior in this manner to the conventional spoiler. The roll control ability is maintained by the new ailerons for moderate differential deflections.