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Failures of avionic generators and contactors operated under harsh ambient conditions

Gębura A., Radoń T.

Prace Naukowe Instytutu Technicznego Wojsk Lotniczych

2012

nr 30

153-176

The paper outlines failures of selected avionic electric power devices operated onboard of combat helicopters in Iraq and Afghanistan. While the authors were examining the electric power system of aircrafts in order to prolong their operation life they paid attention to numerous symptoms of wear demonstrated by some units of aircrafts. It was peculiar that such symptoms have never appeared during similar examinations of aircrafts operated in our country. By all accounts, the weird wear of components results from high intensity of flights and specific features of operating missions, but harsh climatic conditions seem to be the crucial factor. The authors believe that many of spotted failures experienced by electric power equipment may also happen to aircrafts operated in Poland but obviously, due to much lower intensity of operation and mild impact of environmental factors, such failures shall occur much later. The authors focused their attention on two groups of electric devices and associated destructive factors: 1. Air-cooled electric rotary machines. Fine-grained sand sucked together with air leads to very quick abrasion of protective paint coatings inside the machines. Not frequent but intense rainfalls are the reason for appearance of corrosion pits that lead to such effects as increase of pole shoe volumes. This, in turn, results in shearing of winding insulations with breakdowns (shorts) to ground and, as a final consequence, considerable drop of power demonstrated by an electric machine. 2. Contactors and electromagnets, which are allegedly tight. However, dust penetrates anyway via microfissures and disables operation of moving parts.