Analysis of the Aircraft Motion at the Overcritical Angles of Attack: Errors of On-Board Measurements and Simulation of the Deviated Thrust Vector

Abstract

The article deals with the problems of the flight test data analysis concerning the flights at higher then critical angles of attack in order to improve the mathematical model of an aircraft's motion. The paper presents a technique for validation and correction of the on-board measurements for this type of motion. Regarding the use of the vector control during such maneuvers, the article considers the mathematical model of the forces and torques generated by the thrust vectoring. Examples of the data processing of the modern maneuverable aircraft's flight tests are presented to confirm the efficiency of the proposed models and methods. The validation of the on-board measurements, above all, the aerometric measurements, is based on the equations of the aircraft spatial motion. It is assumed that the correct values of the motion parameters must satisfy the system of the nonlinear differential equations known from the flight dynamics. This approach has already proved its efficiency in the analysis of the flight data in the operational range of the angles of attack. The signals obtained through the simulation are used to correct the measurements in case of errors. The article presents examples of detection and correction of errors in the measurement channels for a true airspeed and angle of attack. This paper also proposes two versions of the model capable of calculation the projections of the forces and torques on the aircraft principal axes. The first version is derived from the evident geometrical considerations, the second one is based on Rodrigues' vector rotation formula known in the theoretical mechanics. A numerical comparison confirmed correctness of both obtained models. These models were also verified by processing of the flight tests data.