Vee-tail conceptual design criteria for commercial transport aeroplanes

Vee-tail configuration is an unconventional tail configuration for commercial transport aviation, the use of which could suppose reductions on CO2 emissions. The conceptual design criteria have been selected inspired on the certification requirements established by the aviation regulation in force. They are static stability in cruise, control after Critical Engine Failure (CEF), control in crosswind landing, and trim in these three conditions. The study is carried out through a combination of semi-empirical techniques and Vortex-Lattice Methods (VLM) and thus this analyses the consequences of applying these criteria to a reference aeroplane substituting its conventional tail by a parametrised Vee-tail configuration. The Vee-tail is defined by four parameters: span, root chord, taper ratio and dihedral angle. The results of the study establish a relation between the parameters in order to accomplish the proposed conceptual design criteria. To sum up, minimum and maximum limits are obtained for dihedral angle depending on the combination of the rest of parameters. In addition, a design restriction to the yawing trailing-edge tail control is reached when the results are analysed, demonstrating that its minimum size must be between 60% and 80% of the half-span of the tail, depending on the Vee-tail geometry.