Proposal of a Crosswind-Tolerant Small Airplane with All Inherent Subsiding Modes by Adjusting Dihedral Angle and Vertical Tail Volume

Abstract

A small airplane is strongly affected by crosswind in take-off and landing phases, because the flight velocity and gravitational force acting on it are not much larger than the crosswind velocity and aerodynamic force due to crosswind, respectively. A vertical tail volume can be decreased dramatically for a smaller airplane for the stability of lateral/directional motions. The NDD (Neutral Dihedral effect and Directional stability) airplane defined as Cl_β = Cn_β = 0 was conceived so that it has a tolerance to crosswind. An airplane without a dihedral effect and directional stability is not accepted in the current regulation for airplane design. Then, an airplane with small values of Cl_β and Cn_β has been newly proposed. All of the modes in the lateral/directional motions can converge without oscillating in the proposed airplane, named ``QNDD'' airplane, which is not observed in the NDD airplane.