Air Systems -Air Conditioning System Description
737 Flight Crew Operations Manual
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.
Loss of airflow due to failure of an equipment cooling fan results in illumination of the related equipment cooling OFF light. Selecting the alternate fan should restore airflow and extinguish the OFF light within approximately 5 seconds.
If an overtemperature occurs on the ground, alerting is provided through the crew call horn in the nose wheel well.
Forward Cargo Compartment
The recirculation fan system circulates air from the passenger cabin around the lining of the forward cargo compartment. When the overboard exhaust valve is closed, exhaust air from the equipment cooling system is also diffused to the lining of the forward cargo compartment for additional inflight heating.
Conditioned Air Source Connection
A ground air conditioning source may be connected to the mix manifold to distribute preconditioned air throughout the airplane.
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June 1, 2005 2.30.5
Air Systems -Air Conditioning System Description 737 Flight Crew Operations Manual
Air Conditioning Distribution Schematic
YA721 - YA809
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2.30.6 June 1, 2003
Air Systems -Air Conditioning System Description
737 Flight Crew Operations Manual
YA613 - YA687
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Air Systems -Air Conditioning System Description 737 Flight Crew Operations Manual
Intentionally
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2.30.8 June 1, 2003
737 Flight Crew Operations Manual
This Section Applies to YC153 - YK104
Introduction
Conditioned air for the cabin comes from either the airplane air conditioning system or a preconditioned ground source. Air from the preconditioned ground source enters the air conditioning system through the mix manifold.
The air conditioning system provides temperature controlled air by processing bleed air from the engines, APU, or a ground air source in air conditioning packs. Conditioned air from the left pack, upstream of the mix manifold, flows directly to the flight deck. Excess air from the left pack, air from the right pack, and air from the recirculation system is combined in the mix manifold. The mixed air is then distributed through the left and right sidewall risers to the passenger cabin.
Air Conditioning Pack
The flow of bleed air from the main bleed air duct through each air conditioning pack is controlled by the respective pack valve. Normally, the left pack uses bleed air from engine No. 1 and the right pack uses bleed air from engine No. 2. A single pack is capable of maintaining pressurization and acceptable temperatures throughout the airplane up to the maximum certified ceiling.
The APU is capable of supplying bleed air for two packs on the ground, or one pack in flight. Most external air carts are capable of supplying adequate bleed air for two pack operation. Do not operate more than one pack from one engine at any time.
Airflow Control
With both air conditioning pack switches in AUTO and both packs operating, the packs provide “normal air flow”. However, with one pack not operating, the other pack automatically switches to “high air flow” in order to maintain the necessary ventilation rate. This automatic switching is inhibited when the airplane is on the ground, or inflight with the flaps extended, to insure adequate engine power for single engine operation. Automatic switching to “high air flow” occurs if both engine bleed air switches are OFF and the APU bleed air switch is ON, regardless of flap position, air/ground status or number of packs operating.
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