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High Temperature, High Performance Wire Insulation



TECHNOLOGY AREA(S): Air Platform, Electronics, Materials/Processes

ACQUISITION PROGRAM: PMA-299, H-60 Helicopter Program

OBJECTIVE: Develop a high temperature, insulated wire construction for use in a flexible harness for engine applications, able to withstand the severe environment of an engine bay.

DESCRIPTION: Unique operating environments and conditions expose our systems and their components to extreme temperatures, moisture/humidity, altitude, fluids, vibration, and various other challenges. Unlike a majority of electrical/wiring applications that require harnesses and cables able to withstand temperatures up to 260C, a small number of Navy applications require flexible engine wiring harnesses to operate in continuous, high-temperature conditions exceeding 425C. While many options exist for high-performance wire insulations that can withstand up to 260C temperatures, currently no suitable insulations exist that can withstand continuous temperatures up to 425C while still maintaining the following Key Performance Parameters (KPPs) listed in order of importance.

• Temperature operating range of -55C to 425C


• Mandrel wrap bend test; insulation may not show evidence of visible cracks when wrapped around a six-inch mandrel, while under tension of two-pound weight after high-temperature endurance (MIL-DTL-25028J, para 4.6.4.a and para 4.6.5). Fluid immersion limited to sodium chloride-water solution, omit 4.6.4.b and c.


• Wet dielectric; meet minimum requirement of voltage and withstand insulation integrity test at 500 Volts RMS, 60 Hz after high-temperature endurance (MIL-DTL-25038J, para 4.6.4 and 4.6.6). Fluid immersion limited to sodium chloride-water solution for eight hours, omit 4.6.6.b and c.


• Insulation resistance; meet minimum requirement of 100 Megohms at 500V DC, per SAE AS4373 Method 504 after high-temperature endurance (MIL-DTL-25038J, para 4.6.6).


• Insulation outer diameter not to exceed MIL-DTL-25038/1 requirement of 0.125” ±25% (including conductor)


• Concentricity of wire insulation over the conductor, may be no less than 70% (MIL-DTL-25038J, para and 4.6.2)


• 20-gauge conductor of K, of KP type (thermocouple ASTM E230), using 19 strand construction


• Needle abrasion of 1500 cycles at ambient temperature per SAE AS4373 Method 301 after high-temperature endurance at 425C (MIL-DTL-25038, para 4.6.4).

Several different insulations exist today that satisfy some of the KPPs listed above; however the requirement for this effort is focused on development of innovative materials and processes able to meet all KPPs listed above.

Wiring insulation will need to pass a 50-hour temperature endurance test (at two temperature extremes of -55C and +425C), a 500-hour temperature endurance test (at two temperature extremes of -55C and +425C) and ultimately endure a 5000-hour temperature endurance test meeting all five of the KPPs outlined above and in accordance with the MIL-STDs listed in the References section of this topic.

PHASE I: Design, develop and demonstrate the feasibility of a new, innovative insulated wire construction which meets all the KPPs listed in the Description.

PHASE II: Further develop and produce a prototype wire insulation capable of meeting all the KPPs. Demonstrate the prototype by performing a 50-hour temperature endurance test (at two temperature extremes of -55C and +425C). Further modify and refine the insulated wire construction based on the results of the 50-hour test. Perform a 500-hour temperature endurance test (at two temperature extremes of -55C and +425C, with the goal of meeting all KPPs requirements outlined in the description.

PHASE III DUAL USE APPLICATIONS: Perform a full 5000-hour temperature endurance test meeting KPPs outlined in description. Additionally, all requirements in MIL-DTL-25038J (whichever is greater) must be met. Develop a commercialization plan to integrate the new insulation as necessary. Private Sector Commercial Potential: There is a current need for this type of insulation within the commercial engine application as well. This capability will allow for the use of high-temperature, flexible harnesses in current and future military and commercial engine applications.


  • MIL-DTL-25038J, 10 January 2012. Wire, Electrical, High Temperature, Fire Resistant and Flight Critical
  • MIL-DTL-25038/1E, 01 December 2000. Wire, Electrical, High Temperature, Fire Resistant and Flight Critical, Normal Weight
  • SAE AS4373E, 03 February 2012. Test Methods for Insulated Electric Wire

KEYWORDS: Material; Insulation; Wiring; Electrical; Cable; Wire

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