The cockpit window heading systems on jet transports use laminated glass with a middle layer of which material?

• A. Electrically conductive metal
• B. Polycarbonate
• C. PVB interlayer
• D. Aluminum foil

Answer: (A)

The window is heated to prevent ice and fogging in flight, especially at high altitude. This is done by running electrical current through a thin conductive layer that's sandwiched between the glass panes. That middle layer is electrically conductive, providing resistance heat across the windshield when powered by the aircraft’s electrical system.

Why the other materials aren’t used: a polycarbonate middle layer won’t provide the needed high-temperature resistance or optical quality for a primary cockpit window; a nonconductive PVB interlayer doesn’t generate heat; aluminum foil wouldn’t be practical as a stable, transparent, and durable heating layer in a laminated aircraft windshield.