Aerodynamics of multifunctional transport aircraft devices

The steep-approach method is identified to be an operational measure for transport aircraft to reduce perceived noise. The steep-approach performance of multifunctional aileron devices compared to a conventional spoiler configuration was investigated, and the feasibility of the concepts to maintain roll control of a conventional aileron was evaluated. Multifunctional aileron devices comprise a horizontally segmented aileron, designated as a deceleron, and a laterally segmented aileron, designated as a split aileron. These aileron devices cover the same dimensions as a conventional aileron. A detailed wind-tunnel half-model in a high-lift configuration was used and the aerodynamic coefficients were obtained for various angles of attack. The tests were conducted in a low-speed wind-tunnel facility with a Reynolds number of 10 ⁶. Aileron deflection and differential aileron deflection angles were varied. The most relevant parameters were the minimum approach velocity, maximum descent velocity, and maximum approach angle. Regarding the objective to maximize the approach angle, it was found that none of the multifunctional ailerons were superior 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 was maintained by the new ailerons for moderate differential deflections.