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Evaluation of Steering Disks in Mi-17 and Mi-24 Helicopters by Means of the Fam-C Method

Abstract The paper deals with selected issues related to operation of steering disks designed for helicopters that are currently in operation of the Air Force of the Republic of Poland. The attempt is made to present a prediction of hazards to the transmission gear of that helicopter where the forecast is based on a theoretical analysis of mechanical phenomena as well as the statistical and diagnostic analyses. The major attention is paid to the opportunity to diagnose hazardous locations of the helicopter steering disk with use of a non-destructive FAM-C method originally developed by ITWL. The method is based on tracking of frequency modulation parameters generated by the on-board AC generator. The examination does not require the installation of any additional sensor since the transmission is subjected to neither additional load nor distortions of the rotation speed occur. The authors of this study disclosed the initial results from diagnostic measurements as well as snapshots taken during the disassembling of steering disks from Mi-24 and Mi-17 helicopters that were operated under heavy duty conditions of military missions in Iraq and Afghanistan. They also suggested an easy and cheap method for field checking of the steering disk bearing by photogrammetric measurements. It is also demonstrated that the method of diagnostic investigations can be also spread onto other helicopter makes and types.