MIL-C-25478B – Military Specification: Coolers, Lubricating Oil, Aircraft General Specification

April 11, 2018

“The MIL-C-25478B specification is the general specification for aircraft engine lubricating oil coolers that provide oil temperature regulation for aircraft gas turbine engines using high temperature synthetic base lubricating oil, and aircraft piston engines, turbo propeller gear boxes, and helicopter transmission gear boxes using petroleum based oil.”

This standard calls out a number of test methods including:

  • Static Pressure test – oil cooler is subjected to hydrostatic pressure for leak testing
  • Decongealing characteristics and oil pressure drop with air – demonstrates that the oil cooler shall decongeal so that the pressure drop through the cooler shall be compatible with the maximum engine scavenging system.
  • Oil pressure drop without airflow – oil pressure drop throughout the cooler assembly
  • Oil flow pressure resistance – Maintain outlet pressure without leakage or distortion
  • Vibration – with unit under pressure, triaxial vibration for 35 hours or biaxial vibration for 50 hours
  • Pressure Cycling – 50,000 cycles 2 to 2.5 seconds each
  • Fluid resistance
  • High temperature test to 350°F with cycling
  • Low Temperature test to -65° with cycling

NTS conducts all of these test methods and many more at our facility in Santa Clarita, CA. We have the ability to design complex multi-system tests, including low and/or pressure testing at temperature to include ramp rates of 5°C/min while unit is undergoing vibration or environmental testing. We are also the only lab in Southern California to conduct fuel icing testing in accordance with MIL-F-8615D and SAE ARP 1401 and to provide NAS Class V fuel cleanliness.

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