Ram Air System
The ram air system provides cooling air for the heat exchangers. Operation of the system is
automatically controlled by the packs through operation of ram air inlet
doors. On the ground, or during slow flight with the flaps not fully retracted, the ram air inlet
doors move to the full open position for maximum cooling. In normal cruise, the doors
modulate between open and closed. A RAM DOOR FULL OPEN light illuminates whenever
a ram door is fully open.
Deflector doors are installed forward of the ram air inlet doors to prevent slush
ingestion prior to liftoff and after touchdown. Deflector doors extend when
activated electrically by the air–ground safety sensor.
Cooling Cycle
The flow through the cooling cycle starts with bleed air passing through a heat
exchanger for cooling. The air then flows to an air cycle machine for refrigeration
and to a water separator which removes moisture. The processed cold air is then
combined with hot air. The conditioned air flows into the mix manifold and
distribution system.
Overheat protection is provided by temperature sensors located in the cooling
cycle. An overheat condition causes the pack valve to close and the PACK TRIP
OFF light to illuminate.
