This publication describes the aim and essence of testing transient states of direct current electric power systems in relation to normative characteristics of a transient state. The above diagnostic tests of the given direct current nodes of the aircraft enable to quickly and efficiently...

Rolling-element bearings have been used in the engineering practice since the very beginning of the XIX century. The scientific literature on the subject is therefore rich. As rotational speeds of bearing shafts were getting higher, new problems appeared. Quite a new challenge to be faced were turbine engines with very high rotational speeds that considerably augmented both the scope of problems and the demand for fast and reliable diagnostic methods. The FDM-A diagnostic method (FM frequency modulation, D direct current, C - the level of the methods advancement) has been based on measurements of frequency modulation of the component of pulsation whereas the FAM-C method (FM frequency modulation, C alternating current, C - the level of the methods advancement, i.e. applications in the form of an automatic tester are in use) has been based on measurements of the alternating-current frequency. Both the methods have been developed at ITWL (Air Force Institute of Technology), Warsaw, Poland. Accuracy of these methods essentially results from the natural synchronization of the sampling signal with the angular velocity of kinematic links under examination. The methods enable abrasive wear of a given subassembly to be determined and localised in the course of the power plants regular operation. Possible is determination of numerous parameters of the bearings themselves, the bearing nodes, and the rotating (compressor-turbine) assembly, just to mention the degree of the rolling friction for any of the bearings, the smoothness of motion of the bearing cage, sizes of radial clearances, the level of abrasive wear of contact surfaces of both the bearing cage and the rolling element. A diagnostic unit is fitted to any item, e.g. an electrical joint, supplied with DC or AC voltage. What has been presented in the paper is findings from the performance testing of the aircraft turbine engine: the role of the generator observer has been played by a DC generator and a three-phase tachogenerator.

The paper outlines selected operational problems associated with electric fuel pumps that are indispensable to build-up positive pressure upstream the plunger pump of turbojet engines. Any failure of that electric pump may lead to suction of air into the plunger pump and eventually the engine flameout. Comparison is made between two electric drives for fuel pumps: a three phase 115/208 VG, 400 Hz AC drive and a 26V DC drive. Attention is paid to serviceability of pumps and capacities of the AFIT to diagnose and monitor technical status of electric fuel pumps.

The article presents the use of ground power sources for aircraft ground support. Both military and civil aircraft (A/C) require high-performance and reliable Ground Power Units (GPUs) to ensure safe operation in diverse environmental conditions. The power quality provided by these GPUs plays a crucial role in determining the reliability, cost efficiency and operational safety of the aircraft. The main objective of the article is to signal and propose a solution to the problems associated with the operation of GPUs in the Polish Armed Forces (PAF), resulting from the diversity of the equipment used (type, duration of operation, defects occurrence, etc.). Currently, the PAF utilize various types of GPUs to provide electrical power to aircraft while they are on the ground. Many of those devices have already been in service for many years. The presented statistics of defects registered in the airworthiness management system showed several dozen A/C failures or defects related to the operation of GPU. The authors highlight the importance and feasibility of diagnosing these ground-based power sources. The presented sample test results confirm that, following the methodology outlined in the article, it is possible to conduct comprehensive diagnostic assessment of the GPU systems currently in use by the PAF, as well as evaluate the quality of the electrical power they deliver in both steady and transient states.