Air-conditioning system for below-deck areas of a passenger aircraft

Abstract

An aircraft air-conditioning system provides ventilation, air-conditioning and fire protection for a below-deck stairwell and cargo hold that may be equipped with passenger sleeping compartment containers. An air mixing unit mixes fresh air and recycled air to supply mixed air through a first supply air main line (,) and a supply air unit (,) into the freight hold (,), and through a second supply air main line (,) into the stairwell (,). A trimming air unit (,A) provides hot bleed air from the aircraft engines into the mixed air supplied through the first and second supply air main lines (,). An exhaust air line (,) extracts exhaust air from the freight hold (,), while an exhaust air supplemental line (,) extracts exhaust air from the stairwell (,), both of which are connected to an exhaust air main line with an exhaust air ventilator (,) that blows the exhaust air overboard. A bypass line (,) provides bypass air if needed for the demands of the ventilator (,). Regulating valves and non-return flap valves in the supply air line and in the exhaust air line regulate the flow of air and prevent back-flow. Temperature sensors are connected to a controller that regulates the temperature of the mixed supply air to achieve a comfortable temperature in the freight hold and in the stairwell. In the event of fire, the air valves are closed, to seal-off the freight hold (,) and prevent the spread of smoke into the stairwell or other ventilated areas.