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.
Estimation of undrained shear strength of fine grained soils from cone penetration resistance
