Minimal safe speed of the asymmetrically loaded combat airplane

The purpose of this paper is to present a method for determining the safe flight boundaries of the asymmetrically loaded airplane in the terminal flight phases. The method is applicable to both, the inherent airplane asymmetries and those asymmetries resulting from the airplane use irregularities, asymmetric stores under the wing being one of the examples. The method is aimed to be used in the airplane design and combat airplane service life support.

The analysis method is based on the comparison of demanded and structurally available flight control displacements. Control surface aerodynamic properties, structurally available flight control displacements and dynamic pressure define control surface authority as the capability of control surfaces to generate the forces and moments needed by the airplane to perform required maneuvers. Demanded flight control displacements are those related to the maneuvering requirements and to those needed to compensate lateral wind and any type of the asymmetric airplane load.

The method results are given in the form of the speed and lateral wind component and are a subset of the total set of airplane safe flight boundaries. The key objective is the improvement of flight safety of the asymmetrically loaded airplane.

The method supplements the safe flight boundaries of the symmetrically loaded airplane, the minimal landing speed being the dominant limitation. This boundary positions method analysis in the domain of linear lift coefficient variation, as the function of the angle of attack permits the addition of control surface displacements required to perform the maneuvers and compensate the asymmetrical loads.

The method combines a simple roll dynamics model, stationary equations of the airplane lateral-directional motion and several numeric analysis procedures to obtain the results. This new combination possesses synergy properties and is implemented as the computer program.