Jet Engine Starting With Variable Time Base

Abstract

Nowadays, jet engine starting systems on majority of aircrafts are working with constant time base, the fact that ignores the conditions of the started engine and feeding sources. We mean by constant time base starting of engine'that,a certain time mechanism, which operates independently, controls the process of starting cycle intervals. It means that at certain prescribed intervals of times, this mechanism pushes the starter motor to operate, then raises its speed, then lets aggregates (fuel pumps, ignition system,...) to take part in the process, ... and so on. Starting by this way is unsuitable from points of view of engine efficiency, reliability, and even the longer starting time. The using of solid state starting devices, allows to make a variable time base according to real parameters of started jet engine, and so to optimise the whole starting process. Main parameters of engine are its speed and temperature of gases in front of turbine plades (T3*). This work deals ' convential starting panels with constant time base, their advantages and disadvantages, and gives a praliminary solid state circuit that fulfills the variable time base starting process of an aircraft jet engine. The later configuration is very convenient from points of view of efficiency, reliability, weight and size, radio interference, and starting period. Besides, such concept may be found suitable with respect to starter motor efficiency. The designed circuit was applied practically to starter motor CT-2-48B in laboratory, and proved its applicability for such use. This circuit was designed to be suitable for use on ground and also during flight.