Description of metal-sprayed heaters
Introduction
A metal-sprayed heater is an electric heater mat most commonly used to warm aircraft surfaces and prevent or melt ice. A pattern of sprayed-metal heating elements is embedded between insulating layers. Heaters can be applied directly to a surface or produced in prefabricated form and bonded to a component. They are strong, light, thin, and can be designed for a wide range of power loadings, voltages, and heating patterns.
Heater elements
Granular metallic electrical-resistance paths are sprayed under controlled conditions onto base insulation. Element width and thickness are engineered for the required heating intensity. Resistance is checked locally and adjusted before the outer insulation is applied.
Terminals
Electrical-supply and control-system terminals are normally bonded to the inside of the component. The terminal post projects through the base insulation so the heater element can be sprayed directly to it.
Insulation
A base-insulation layer separates the heater element from the component structure. A tough, heat-resistant thermosetting plastic with glass-cloth reinforcement forms the outer protective insulation.
Erosion protection
An EROCOAT application normally protects the outer insulation against severe rain erosion, foreign-object impact, and static-electricity damage. For extreme conditions, a metallic sheath may be installed, such as on helicopter rotor-blade leading edges.
Installations
Metal-sprayed systems withstand severe impact, normal abrasion, weather, and aircraft environments. They are used on engine intakes, airfoil sections, tail units, auxiliary air scoops, propeller spinners, helicopter rotor blades, and other components needing protection from ice or very low temperatures in flight.