What provides cooling air for hydraulic systems 1 and 2 during ground operations?

• A. Ram air from the ram air scoop passing over the heat exchanger, with an electric fan providing air during ground ops
• B. Ram air scoop alone
• C. Pack air only
• D. No cooling on the ground

Answer: (A)

Cooling of hydraulic systems relies on air flowing through heat exchangers to remove heat from the pumps. When the aircraft is moving, ram air from the ram air scoop naturally flows through these exchangers. On the ground, there’s little to no ram air, so an electric fan is used to push air across the heat exchangers. The combination of ram air through the heat exchanger with the electric fan active during ground ops provides the necessary cooling for hydraulic systems 1 and 2. Ram air alone wouldn’t supply enough cooling on the ground, pack air is for the environmental control system and not hydraulic cooling, and having no cooling would lead to overheating.