How are the avionics cooled?

• A. Ambient underfloor air
• B. Avionics exhaust fan
• C. External air
• D. Ambient underfloor air or by the avionics exhaust fan

Answer: (D)

Avionics cooling relies on moving ambient air through the avionics bay to carry away heat from the equipment. This air can come from the ambient ram air gathered in the underfloor plenum, supplying cooling air to the racks. If ram air isn’t enough, an avionics exhaust fan actively pulls air through the equipment and vents it overboard, maintaining a steady flow. Some aircraft use either source, or both, to keep temperatures within limits during different phases of flight and ground operations. External air alone isn’t a complete cooling solution because it requires a defined flow path and a means to move and expel the air; the system is designed to use ambient underfloor air or the avionics exhaust fan to provide that flow. So the avionics are cooled by ambient underfloor air or by the avionics exhaust fan.