This article presents basic methodology and some algorithms for estimating attitude and heading angles of an unmanned or optionally piloted aircraft in the event of a partial failure of the on-board measurement systems. The aim of the research is to develop effective estimation algorithms of non-measurable aircraft state variables. Correlation between quantities describing kinematics of the aircraft's movement in space were used. Properties of the estimation algorithms are illustrated by

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... ry calculations using real data recorded during test flights of the optionally controlled MP-02A Czajka airplane. Quality of the estimated signals allows to continue flight in case of a non-catastrophic failure of the measurement systems. Developed algorithms are used in control systems designed at the Department of Avionics and Control of the Rzeszów University of Technology, dedicated to unmanned and optionally controlled light aircraft.