Most simple ailerons produce adverse yaw. However, with proper aileron placement and wing twist, an aileron can produce proverse or neutral yaw, eliminating the need for aileron-rudder mixing, differential aileron deflection or Frise ailerons. The relationship between wing planform, aileron placement and lift distribution is studied here for a special class of optimal lift distributions that minimise induced drag for a variety of design constraints. It is shown that a wing employing the elliptic lift distribution will always produce adverse yaw, independent of aileron design or operating condition. However, for wings employing other optimal lift distributions, the ailerons can be placed to produce proverse or neutral yaw. A numerical lifting-line algorithm is used to explore the impact of aileron design on a wide range of wing planforms and lift distributions. Results can be used in the early stages of design to correctly place ailerons with respect to desired roll-yaw coupling.

In an aircraft design, optimisation has become a common practice, especially when structural and aerodynamics interactions are considered. Performance measures often used in an industrial setting include structural weight, drag, lift to drag ratio, fuel burn or maximum range. It is a common practice to evaluate such performance indicators only on a handful of sample points. To achieve a truly economical aircraft design it is necessary to include a fully integrated mission analysis during a multidisciplinary structural optimisation, as there is a strong coupling between a flight behaviour and actual operational conditions of an aircraft. This paper makes a case for a modular approach to a mission analysis implementation that could utilise a variety of physical models and their combinations, offsetting some of the computational demands related to a fully integrated mission analysis and allowing to focus resources where they are needed.

Most modern aircraft employ discrete ailerons for roll control. The induced drag, rolling moment, and yawing moment for an aircraft depend in part on the location and size of the ailerons. In the present study, lifting-line theory is used to formulate theoretical relationships between aileron design and the resulting forces and moments. The theory predicts that the optimum aileron geometry is independent of prescribed lift and rolling moment. A numerical potential flow algorithm is used to evaluate the optimum size and location of ailerons for a wide range of planforms with varying aspect ratio and taper ratio. Results show that the optimum aileron design to minimise induced drag always extends to the wing tip. Impacts to induced drag and yawing moment are also considered, and results can be used to inform initial design and placement of ailerons on future aircraft. Results of this optimisation study are also compared to theoretical optimum results that could be obtained from morphing-wing technology. Results of this comparison can be used to evaluate the potential benefits of using morphing-wing technology rather than traditional discrete ailerons.