A Rigorous Test for Extreme Icing Conditions

Issue

A major airframe manufacturer was having problems with the performance of pressure switches on certain types of flights that involved high humidity, coupled with extreme low temperature and high altitude. Fuel low pressure switches in certain locations of the aircraft can accumulate enough moisture which over the course of several flights can freeze, resulting in switch malfunction. The pressure switches being supplied from an existing manufacturer were struggling with these extreme conditions and exhibited in-flight failure levels that were unacceptable. The Tier 1 fuel system manufacturer serving the airframer turned to Hydra-Electric with the challenge of designing a pressure switch that could survive the challenging icing conditions resulting from high humidity, alternating altitude and fluctuating temperature.

Solution

Hydra-Electric designed a pressure switch (Series 12H/G) that was specially developed to excel under these extreme conditions. The switch that Hydra created incorporated a unique venting scheme that allows the switch to breathe while preventing the unit from freezing under extreme icing conditions. A series of tests designed to validate these features involved subjecting the switch to rigorous qualification testing, as mandated by the airframer, including a 200-cycle icing test which consisted of a series of ascending and descending altitudes, extreme humidity and fluctuating ambient temperatures. This extensive testing was required to simulate the extreme icing conditions during flight that were causing the failure of the existing switches. Hydra-Electric’s switch was able to meet these requirements without failure.