This
paper addresses the use of centre of gravity (CG) of the aircraft by moving
fuel to and fro the trim tank: this CG movement is exploited as an additional
pitch control redundancy. In the high speed region of the flight envelope. the
full utilization of the flight controls is not possible due to load factor
limitations, so this redundancy can be used as a compensation system. Control
allocation in aircraft is the distribution of settings for various control surfaces to achieve virtual control
demands (i.e. pitch, roll and yaw moments. and forces). To achieve a control
demand there are two or more surfaces that can be utilized. In this paper a
control law was designed as a multi-variable proportional integral controller:
the output of it (i.e, virtual control demands) is sent to a control allocation
module, which distributes the demand among the control surfaces by solving a
sequential least squares problem using the active set method. The control
system (i.e. control law and control allocation) is applied to the non-linear model
of the Boeing 747-200. The s)stem was also tested on a non-linear model with
changes in longitudinal aerodynamics coefficients due to the wing damage. which
is based on the damage that arose on EL AL Flight 1862 accident Schiphol
airport near Amsterdam. The reduced efectivcncss of longitudinal control
surfaces due to a loss of hydraulics in this crash is also realized in the
control allocation.