Accuracy of determining the landing trajectory of aircrafts using a baro-inertial information and computing complex evaluation

Аuthors

Tran Q. D.

Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia

e-mail: tranduc@mail.ru

Abstract

This paper examines the problem of evaluating the accuracy in determining aircraft trajectories using a baro-inertial information and computing complex. The solution to the above-mentioned problem is proposed on the basis of application of complex mathematical modeling. Simulation of the motion of an aircraft during the landing flight phase on a glide path was carried out and the aircraft’s altitude estimation errors were obtained.

The algorithm implements simulation of an aircraft’s motion in a non-inertial coordinate system in accordance with the flight plan, the state of the medium of motion (with atmospheric variations), using general nonlinear models of aircraft performance, control system, comprising of aircraft optimal control algorithms for identifying required trajectories and control laws, aircraft stabilization and balance algorithms, measuring and computing complex based on a gyro-inertial block, barometric altimeter and onboard digital computing machine.

The novelty of this study consists in that the air data system (ADS) is simulated as accurately as possible in describing the aerometric part of the information and computing complex by using developed mathematical models of flow around an aircraft and airflow in pipelines of ADS based on numerical solutions of the Navier-Stokes equations.

The algorithm of the inertial block comprises of an algorithm that calculates the orientation angles and an algorithm calculating the velocity and coordinates. Determination of flight altitude based on the readings of the inertial systems is an unstable computing process. In order to ensure accurate determination of flight altitude, a method is used based on the co-processing measurements of the inertial system and air data computer. The study of the influence of aerometric characteristic parameters of the ADS (pitot-static system installation site, the diameter of the hole of the pipelines, pipe lengths, installation angle of the pitot-static system, and so forth) on flight altitude measuring errors (static and dynamic) is reflected in this paper.

The mathematical model of turbulence under development presented in this paper allows simulation of flow around the aircraft and airflow in the pipelines of the ADS.

The implementation of the developed model presented in the paper allows for solution of the above-mentioned problem, namely, for determining the installation site of the pitot-static system, for optimization of the pitot-static system, as well as for the calculation of the measurement errors of the pitot-static system. The calculated values of the errors Δ1Pst, Δ2Pst and dynamic distortions allow the prediction of errors in Pst in the ADC software in the ADC’s onboard computer in oder to implement distortion compensation.

The results obtained from this study allow estimation of characteristic parameters of the ADC impact on flight altitude measurement errors. It is shown that the dynamic distortion has little effect on measurement errors. The distortion on the flow angle of the pitot-static system and interference of the airframe and pitot-static system greatly affect the measurement error. For the accuracy in determining the flight altitude, it is necessary to utilize a co-processing of measurements of the strap down inertial navigation system and ADC.

Keywords:

time scale, aircraft landing, baro-inertial system, information and computing complex, pitot-static system

References

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