Pilot-Induced Oscillation Prevention During the Aircraft Landing

The paper focuses on a manned aircraft landing control system. It is known that actuator level and rate limitations can cause pilot-induced oscillations. This phenomenon occurs during intensive pilot control in a closed-loop system under certain initiating conditions associated with both the influence of the external environment and changes in the system dynamics. Oscillations appear unintentionally and unexpectedly for the pilot, which jeopardizes flight safety. The study shows the possibility of preventing aircraft oscillations using the method of nonlinear correction of systems by sequential introduction of a pseudo-linear correcting device into the control loop, the phase-frequency characteristic of the device not depending on the amplitude of the input signal. The airplane-pilot closed-loop system for various parameters of the input signal is analyzed by calculating the generalized function of sensitivity and the excitation index. The results of the study are presented in the form of angle and the pitch rate time processes, and landing trajectories.

Nonlinear Correction to Intensity of Dipole Radiation of Uncharged Drop Oscillating in External Electrostatic Field

An asymptotic calculation of a dipole electromagnetic radiation of an uncharged conductive drop oscillating with a finite amplitude in an external electrostatic field to within the second order of smallness inclusive on the relation of the amplitude of oscillations to the radius of an initial drop is carried out. It is shown that the first mode of oscillations is excited in the calculation of the second order of smallness. As a result, the centers of the induced charges with different signs will synchronously oscillate, and the drop will radiate electromagnetic waves of dipolar type, forming the nonlinear correction to intensity of dipole radiation of the first order of smallness. An assessment of the intensity of electromagnetic radiation of this correction and of the width of a strip of frequencies depending on the size of a drop and the strength of an external electrostatic field is carried out.