Energy-Saving Algorithm of Automatic Control of Compulsory Passenger Carrier Landing. Part 1

The task was to develop an automatic landing system (ALS) for a passenger carrier that can be externally activated and excludes the possibility of the crew’s interference into the landing process, for example, when a carrier alters its nominal course or there is no contact with the crew. The air crush history saw a lot of cases that could have been prevented if the planes had had an ALS system and airports had had possibilities to activate that system and suspend the crew from flight control. One of such unforgettable examples is the New-York tragedy of September 11, 2001. State-of-the-art technology allows solving the problem of automatic carrier landing. The most remarkable example demonstrating solution of this problem is the automatic landing of the Buran orbiter 30 years ago on November 15, 1988. The article consists of two sections. The first section of the article deals with conditions of effective solution of autoland problem. It describes in short, the flight modes during automatic landing control. To solve the problem of automatic longitudinal control in the most crucial final landing mode, the author proposes an energy-saving control algorithm that provides control in the mode of negative feedback. The system status vector comprises six parameters: range, altitude, pitch angle, and their first-order derivatives. The control algorithm is developed for the Tupolev TU-154M airliner. In development of the algorithm, the following assumptions were used: a) a linear model of dependence of aerodynamic data on the angle of attack; b) a linear model of programmed switch of engine thrust to the idle mode on the interval of 3 seconds from the beginning of the flareout; c) a pitch angular acceleration, occurring at elevator rate reversal, as a control signal; d) the frequency of the control algorithm operation equal to 200 Hz. The second section further analyzes characteristics of the energy-saving algorithm of automatic control of compulsory passenger carrier landing during the final landing phase, which was developed in the first section. The author developed a model program of control and mathematically modeled the carrier landing phases. When switching from one phase to another, the motion parameters were concatenated so that the final motion parameters of the previous phase became the initial motion parameters of the next phase. The author also studied the influence of errors in aerodynamic data on the landing conditions. The modeling revealed that if a pitch deflection direction is used for the determination of phases, then in a general case, the landing mode consists not of two traditionally determined phases, but of the following three: pitch angle increase (flareout), pitch angle decrease (float), and again, pitch angle increase (this phase is called ‘maintenance’). The necessity to introduce the third phase is determined by the presence of errors in the aerodynamic data of the airplane. On the whole, it is confirmed that the energy saving control algorithm provides successful solution of the problem of automatic landing of a passenger carrier at its final flight phase. At that, it is determined that the landing mode does not exceed 5s.