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The following article describes the low frequency vibration analysis of aircraft piston engine Rotax 912 ULS. The results are based on the vibration signal made by the engine in the frequency range up to 400 Hz measured on the engine block in three axes. The aim of the research was to determine the method of detecting the misfire of individual cylinders based on the power spectrum of the selected frequencies analysis. Frequencies resulting from the periodicity of engine operation related to the frequency of the work cycle, rotational speed and ignition frequency were considered for the analysis. The tests were carried out in one point of operation. The highest levels of changes were recorded in the Y axis - the axis of piston movement. It was shown that the vibration level changes after switching off one of the cylinders.

The ignition method significantly affects the combustion process in piston aircraft engines. This paper presents the results of bench tests of two variants of the radial piston aircraft engine: equipped with a standard magneto system and an electronic dual ignition system. The engine was tested in steady states for operating points defined by rotational speed and load. Their values corresponded to a load ranging from 50% of nominal power to take-off power. The ignition advance angle was constant for the engine equipped with ignition magnetos, while for the second engine variant it was determined by the developed algorithm introduced to the electronic ignition system control unit. The analysis of the combustion process was based on pressure measurements in one cylinder.