Mass distribution management & dynamic balancing of aircraft mass

Abstract

A new methodology has been proposed to control the distribution of mass in an aircraft during the design and development process. Having estimated the total mass, the aircraft is considered to be composed of different segments each with an unknown mass and the equations of motion are derived based on this discritized mass model. A suitable mass distribution is then found based on the desired dynamic and static stability criterion. Using this methodology the aircraft static margin can be controlled by changing the external shape (X_ac) as well as mass distribution (X_cg). By relating all applicable mass moments of inertia to the frequencies and damping ratios of longitudinal and lateral-directional dynamic modes, the chance of designing a well dynamically balanced aircraft in a variety of flight phases is increased. The mathematical procedure can explicitly be derived only for rigid airplanes where two-dimensional approximations are valid. However, numerical algorithms must be used for elastic and/or rigid aircraft with coupled equations of motion. The proposed methodology has been used to find suitable mass distributions for a B-747-100 in a cruising flight while satisfying the Level-I flying quality requirements.