This technical description details a custom-engineered high-resistance wire designed for use in repair patches for aircraft heated leading edges, specifically addressing damage caused by lightning strikes. This wire solution is tailored to provide reliable and consistent heating performance in demanding aerospace environments.
Conductor Design and Properties:
The conductor is a 29 AWG, 7/37 stranded construction (7 strands, each comprised of 37 individual wires). This multi-stranded configuration enhances the wire’s flexibility and resistance to fatigue, crucial for applications involving potential flexing and vibration during flight. The conductor material is a specialized high-resistance alloy, designated “Alloy 60,” chosen for its specific electrical resistivity and temperature coefficient of resistance. This alloy enables precise control of the heating element’s power output and temperature profile. The conductor has a diameter of 0.0135 inches. The 29 AWG size provides a balance between resistance, flexibility, and physical size, making it suitable for integration into thin, flexible repair patches.
Insulation Material and Properties:
The conductor is insulated with a 0.004-inch thick layer of polyimide tape wrap. Polyimide is a high-performance polymer known for its exceptional thermal stability, dielectric strength, and resistance to radiation and chemicals. This thin tape wrap insulation provides a reliable electrical barrier while minimizing the overall thickness of the wire, essential for maintaining the patch’s aerodynamic profile. The polyimide tape is selected for its ability to withstand the extreme temperature fluctuations and environmental conditions encountered in aerospace applications.
Finished Dimensions and Construction:
The nominal finished diameter of the insulated wire is 0.0215 inches. This precise diameter is critical for ensuring proper integration within the woven cloth mat that forms the heating element of the repair patch. The construction of the wire, combining the stranded conductor and polyimide tape insulation, is optimized for flexibility, durability, and consistent performance in demanding aerospace environments.
Application and Performance:
This high-resistance wire is designed for use in repair patches for aircraft heated leading edges, specifically to address damage caused by lightning strikes. The wire is woven into a cloth mat, which is then laminated in fiberglass with a vinyl ester epoxy resin. This composite structure forms a durable and effective repair patch that can restore the heated leading edge’s functionality. The high-resistance alloy enables precise control of the patch’s heating profile, ensuring uniform heating and preventing ice buildup. The polyimide tape insulation provides robust protection against electrical shorts and environmental factors, ensuring the longevity and safety of the repair patch.
Technical Considerations:
- Resistance Tolerance: The resistance of the wire is critical for controlling the patch’s heating output. The alloy’s properties and wire dimensions are precisely controlled to achieve the desired resistance.
- Temperature Coefficient of Resistance (TCR): The TCR of the alloy is a critical parameter, as it determines how the resistance changes with temperature.
- Dielectric Strength: The polyimide tape insulation provides high dielectric strength, ensuring electrical isolation even under high voltage conditions.
- Thermal Stability: The polyimide tape and high-resistance alloy are chosen for their ability to withstand extreme temperature fluctuations and maintain their properties over time.
- Flex Life: The stranded conductor design enhances the wire’s flex life, making it suitable for applications involving potential flexing and vibration.
- Chemical Resistance: The polyimide tape and vinyl ester epoxy resin provide excellent resistance to chemicals and fluids commonly encountered in aerospace applications.
- Dimensional Tolerances: Precise dimensional tolerances are essential for ensuring proper integration within the woven cloth mat and laminated patch.
- Aerodynamic Profile: The thin wire and insulation minimize the patch’s thickness, ensuring a smooth aerodynamic profile.
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