Probe/Window Heat Switch
DESCRIPTION - The pitot probes, static ports, angle of attack probes, and total air temperature probes are electrically heated. Three independent probe heat computers automatically control the ground/flight modes and provide overheat protection and fault indications. The probes are automatically heated in flight, and on the ground when at least one engine is running. They can be operated manually prior to engine start by placing the PROBE/WINDOW HEAT switch ON. The TAT probes are not heated on the ground. Probe heat operates at low power on the ground, and automatically switches to normal power in flight.
AUTO - The AUTO selection (no lights) provides automatic heating of probes and windows in flight. On the ground if one engine is running windows and probes are automatically heated except for TAT probes.
ON - When the probe/window heat switch is selected to ON all probes and windows are electrically heated. The ON light also illuminates blue.