737 MAX Flight Crew Operations Manual
Air Systems -
Air Conditioning System
Description
MN-FLT-OH-201
2.30.7
There is also a dual purpose valve behind the rudder pedal of each pilot. These
valves provide air for warming the pilots' feet and for defogging the inside of the
No. 1 windows. Each valve is controlled by knobs located on the Captain's and
First Officer's panels.
Passenger Cabin
The passenger cabin air supply distribution system consists of the mix manifold,
sidewall risers, and an overhead distribution duct.
Sidewall risers go up the right and left walls of the passenger cabin to supply air
to the overhead distribution duct. The overhead distribution duct routes
conditioned air to the passenger cabin. It extends from the forward to the aft end
of the ceiling along the airplane centerline and also supplies the sidewall diffusers.
Recirculation Fans
The recirculation fan system reduces the air conditioning system pack load and the
engine bleed air demand. Air from the passenger cabin and electrical equipment
bay is drawn to the forward cargo bay where it is filtered and recirculated to the
mix manifold. The fans are driven by AC motors. Each recirculation fan operates
only if the respective RECIRC FAN Switch is selected to AUTO. In flight, the left
recirculation fan operates if both packs are operating unless either PACK switch
is in HIGH. The right recirculation fan operates in flight if both packs are
operating unless both PACK switches are in HIGH. On the ground, the left
recirculation fan operates unless both PACK switches are in HIGH and the right
recirculation fan operates even if both PACK switches are in HIGH.
Equipment Cooling
The equipment cooling system cools electronic equipment in the flight deck and
the E & E bay.
The equipment cooling system consists of a supply duct and an exhaust duct. Each
duct has a normal fan and an alternate fan. The supply duct supplies cool air to the
flight deck displays and electronic equipment in the E & E bay. The exhaust duct
collects and discards warm air from the flight deck displays, the overhead and aft
electronic panels, circuit breaker panels in the flight deck, and electronic
equipment in the E & E bay. Two smoke detectors are installed downstream of the
fans. The EQUIP SMOKE, MASTER CAUTION, and OVERHEAD System
Annunciator lights will illuminate if smoke is detected. When smoke is detected
the system will automatically set the packs to high flow, turn the E/E Cooling
Supply Fan(s) OFF for approximately 5 minutes, overboard exhaust valve opens
to the smoke position and the recirculation fans turn off. The E/E Cooling Supply
Fans return to normal operations 5 minutes after the first detection of smoke. If
smoke is re-detected, the Supply Fans turn OFF for another 5 minutes. The OFF
light for the supply fan does not illuminate during this automatic shut off.
March 1, 2021
