B737 Air Systems

Front 1

Which stage of the compressor does the air system get it's bleed air?

Back 1

5th and 9th stage

Front 2

Which stage of the compressor is normal bleed air from?

Back 2

5th stage. 9th stage supplies bleed air through the high stage modulation valve if 5th stage air is not sufficient

Front 3

Describe the Engine Bleed Air Valves

Back 3

They are pressure regulating and shutoff valves. When bleed air is ON, they are DC activated and pressure operated

Front 4

What do the bleed trip sensors do?

Back 4

When bleed air temperature and pressure exceed a certain limit it closes the engine bleed valve and illuminates a BLEED TRIP OFF light

Front 5

What does the Isolation Valve do?

Back 5

For normal operations it is closed and isolates the left and right bleed air ducts

Front 6

What powers the Isolation Valve?

Back 6

AC power

Front 7

When will the Isolation Valve open when the switch is in the AUTO position?

Back 7

Either bleed air switch or air conditioning pack switch is OFF

Front 8

Is the Isolation Valve position affected by the APU bleed switch position?

Back 8

No

Front 9

What controls and operates the APU bleed air valve?

Back 9

It is DC operated and pressure controlled

Front 10

What does the DUAL BLEED light indicate?

Back 10

APU bleed valve is open and position of engine bleed valves and isolation valve would permit possible backpressure of the APU

Front 11

What does a WING-BODY OVERHEAT light indicate?

Back 11

A left light means a bleed air duct leak has been sensed by one of 5 sensors on the left side. A right light means a bleed air duct leak has been sensed by one of 3 sensors on the right side

Front 12

Can a single pack provide adequate pressurization?

Back 12

Yes, a single pack in high mode can maintain pressurization and temperatures up to the maximum certified ceiling

Front 13

How many packs can the APU bleed air supply?

Back 13

Two on the ground and one in flight

Front 14

Is it acceptable to operate more than one pack from one engine?

Back 14

No

Front 15

What happens of both pack switches are in the AUTO position and one pack fails?

Back 15

The operating pack automatically switches from "normal" air flow to "high" air flow

Front 16

When is the automatic switching to high mode inhibited?

Back 16

In order to provide more engine thrust for single engine operation it is inhibited in flight with flaps extended or on the ground

Front 17

In the AUTO position, do the packs operate using normal or high flow if the APU is the bleed source and the engine bleeds are OFF?

Back 17

High no matter the condition

Front 18

What does the Ram Air System do? What controls it?

Back 18

The system provides cooling air for the heat exchangers. It is controlled by the packs

Front 19

Describe the path of the cooling cycle

Back 19

Heat exchanger, air cycle machine, water separator, mix manifold, then distribution

Front 20

What does a PACK light illumination indicate?

Back 20

An overheat condition has occurred in the cooling cycle. The associated pack valve will automatically close

Front 21

What happens if a primary pack controller fails?

Back 21

The opposite system standby controller will then control it. During Recall, a PACK, MASTER CAUTION, and AIR COND lights will illuminate.

Front 22

What happens if both the primary and secondary pack controllers fail?

Back 22

A PACK, MASTER CAUTION, and AIR COND lights will illuminate. The pack will continue to operate uncontrolled unless excessive temperatures trip the pack off

Front 23

How many temperature control zones are there?

Back 23

3: flight deck, forward cabin and aft cabin

Front 24

What is the temperature range of the selectors?

Back 24

18C to 30C (65F to 85F)

Front 25

How do the packs regulate the temperature in each zone?

Back 25

The packs satisfy the zone requesting the coolest temperature. Then trim air is used to regulate the zones

Front 26

How does the pack regulate the zone temperature with only one pack operating?

Back 26

With TRIM AIR on, same as two pack operation. With TRIM AIR off, the pack produces an average temperature of the demands of the zones

Front 27

What happens if a zone duct supply overheats?

Back 27

An amber ZONE TEMP will illuminate above the zone temperature selector and the associated modulating valve will close

Front 28

Can the modulating valve reopen after a ZONE TEMP overheat?

Back 28

Yes, after it cools by pressing the TRIP RESET switch

Front 29

What temperature control zones does the left electronic controller control?

Back 29

Aft Cabin and as a backup to the flight deck

Front 30

What temperature control zones does the right electronic controller control?

Back 30

Forward Cabin and primary for flight deck

Front 31

What happens to the pack control if trim air supply is lost?

Back 31

Then temperature control system will control both packs independently. Left pack will control the flight deck and right pack will control the cabin

Front 32

What happens if zone controls and primary pack controls all fail?

Back 32

The standby pack control will command the packs to satisfy average temperature demand of the two cabin zones

Front 33

What happens if all temperature controllers are selected off?

Back 33

Left pack will maintain 24C and the right will maintain 18C.

Front 34

What is the function of the recirculation fan system?

Back 34

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

Front 35

What is the operating logic of the recirculation fans for ground and flight?

Back 35

Left fan: On ground it operates unless both pack switches are in HIGH. In flight it operates when both packs are operating unless either pack switch is in HIGH. Right fan: On ground it operates even if both pack switches are in HIGH. In flight it operates when both packs are operating unless both pack switches are in HIGH.

Front 36

What does the equipment cooling system do?

Back 36

It cools electronic equipment in the flight deck and the E & E bay.

Front 37

What does the equipment cooling system consist of?

Back 37

A supply duct an an exhaust duct. Each duct has a normal fan and alternate fan

Front 38

What does the supply duct do?

Back 38

It supplies cool air to the flight deck displays and electronic equipment in the E & E bay

Front 39

What does the exhaust duct do?

Back 39

It 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

Front 40

What does the illumination of the related equipment cooling OFF light mean?

Back 40

Loss of airflow due to failure of an equipment cooling fan. Selecting the alternate fan should restore airflow and extinguish the OFF light within approximately 5 seconds

Front 41

What if an overtemperature occurs in the equipment cooling system on the ground?

Back 41

There is an alert provided through the crew call horn in the nose wheel well.

Front 42

How does the forward cargo compartment get air?

Back 42

Through the recirculation fan, and if the outboard exhaust valve is closed, additional air through the equipment cooling system

Front 43

What are the different modes of the cabin pressure control system?

Back 43

There are two identical automatic modes (AUTO and ALTN) and a manual (MAN) pilot controlled mode

Front 44

How many pressure relief valves are there?

Back 44

3, two positive pressure relief at 9.1 PSI and one negative pressure relief

Front 45

What other systems send information to the automatic controllers?

Back 45

-The ADIRU's send pressure, altitude, and calibrated airspeed, -the stall management system sends throttle position, and -the air ground sensors send air ground info.

Front 46

What controls cabin air outflow?

Back 46

2 valves, outflow and overboard exhaust

Front 47

Describe the outflow valve

Back 47

It is controlled by 3 DC motors, one for each mode. It is the exhaust exit for the majority of the cabin air. Air exiting the cabin flows around the aft cargo compartment for heating and then through the outflow valve

Front 48

What scenarios would cause the overboard exhaust valve to open?

Back 48

-On the ground and in flight with low differential pressure to discharge warm air from the E & E bay, -In flight with either pack in HIGH and the right recirculation fan is off to allow for increased ventilation in the smoke removal configuration.

Front 49

Where does the air go when the overboard exhaust valve is closed?

Back 49

It is diffused to the lining of the forward cargo compartment

Front 50

Which of the two identical automatic pressurization controllers is the primary controller?

Back 50

Each controller alternately sequences as the primary controller for each flight

Front 51

What two altitudes are preset into the pressurization controller?

Back 51

Cruise altitude and landing altitude

Front 52

What does an amber OFF SCHED DESCENT indicate?

Back 52

A descent has been started before reaching the preset cruise altitude

Front 53

If the OFF SCHED DESCENT light illuminates, what does the controller do?

Back 53

It will automatically sets the departure elevation as the landing elevation

Front 54

When would the controllers automatic abort to the takeoff elevation be lost?

Back 54

If the FLT ALT indicator is changed

Front 55

What is cruise mode and when is it activated?

Back 55

In cruise mode the controller maintains the lowest possible cabin altitude. It is activated within .25 psi of the selected FLT ALT

Front 56

What is descent mode and when is it activated?

Back 56

Descent mode is a proportional descent from cruise altitude to just below landing altitude. It starts when the airplane descends below .25 psi of the cruise altitude

Front 57

When would an amber AUTO FAIL light illuminate?

Back 57

•Loss of DC power, •Controller fault, •Outflow valve control fault, •Excessive differential pressure (> 8.75 psi), •Excessive rate of cabin pressure change (±2000 sea level feet/minute), •High cabin altitude (above 15,800 feet)

Front 58

What do the controllers do when the AUTO FAIL light illuminates?

Back 58

The pressure control automatically transfers to the other auto controller (ALTN mode).

Front 59

What lights will you see if you move the mode selector to ALTN after an AUTO FAIL?

Back 59

It will extinguish the AUTO FAIL light and the ALTN light will remain illuminated to indicate single channel operation

Front 60

How is manual mode operation accomplished?

Back 60

The outflow valve position switch is used to control outflow air valve position and consequently cabin altitude

Front 61

What does the DUAL BLEED light indicate?

Back 61

APU bleed valve open and engine no. 1 bleed switch ON, or APU bleed valve open and engine no. 2 bleed switch on and isolation valve open

Front 62

What does the left WING BODY OVERHEAT light indicate?

Back 62

Overheat from bleed leak in left engine strut, left inboard wing leading edge, left air conditioning bay, keel beam, or APU bleed air duct

Front 63

What does the right WING BODY OVERHEAT light indicate?

Back 63

Overheat from bleed leak in right engine strut, right inboard wing leading edge, or right air conditioning bay

Front 64

What does the engine BLEED air switch do?

Back 64

OFF: closes engine bleed air valve. ON: opens engine bleed air valve when engines are operating

Front 65

What does the APU BLEED air switch do?

Back 65

OFF: closes APU bleed air valve. ON: opens APU bleed air valve when APU is operating

Front 66

What does the OVHT TEST switch do?

Back 66

-Tests the WING BODY OVERHEAT detector circuits, -Illuminates both WING BODY OVERHEAT lights

Front 67

What does the BLEED TRIP OFF light indicate?

Back 67

Excessive bleed air temperature or pressure

Front 68

What does pressing the TRIP RESET switch do?

Back 68

If fault is corrected, -Resets BLEED TRIP OFF, PACK, or ZONE TEMP lights, -related engine bleed air, pack, or trim air modulating valve opens

Front 69

What does an illuminated ZONE TEMP light indicate?

Back 69

-Indicates duct temperature overheat, -and/or for CONT CAB indicates failure of flight deck primary and standby temperature controller

Front 70

What does a ZONE TEMP light indicate during master caution recall?

Back 70

-CONT CAB: failure of flight deck primary or standby temperature controller. -FWD CAB or AFT CAB: failure of the associated zone temperature controller

Front 71

What does placing the temperature selector in OFF do?

Back 71

Closes the associated trim air modulating valve

Front 72

With engine bleed source(s), what does the AUTO position of the air conditioning PACK switch do?

Back 72

-Both packs operating, each pack regulates to low (normal) flow. -One pack operating regulates to high flow when in flight with flaps up.

Front 73

With APU bleed source, what does the AUTO position of the air conditioning PACK switch do?

Back 73

Regulates to normal flow. Regulates to high flow if both engine bleeds are switched OFF regardless of flap position, air/ground status, or number of packs operating.

Front 74

What does the HIGH position of the air conditioning PACK switch do?

Back 74

Regulates to high flow. On ground with APU bleed switch ON provides "APU high air flow".

Front 75

What does the TRIM AIR switch do?

Back 75

It signals the trim air pressure regulating and shutoff valve open (ON) or closed (OFF)

Front 76

What does placing the left recirculation fan switch in AUTO do?

Back 76

-On Ground: operates unless both PACK switches are in HIGH. -In Flight: operates if both packs are operating unless either PACK switch is in HIGH.

Front 77

What does placing the right recirculation fan switch in AUTO do?

Back 77

-On Ground: operates even if both PACK switches are in HIGH. -In Flight: operates if both packs are operating unless both PACK switches are in HIGH.

Front 78

What does an illuminated PACK light indicate?

Back 78

-Pack trip off, or -Failure of both primary and standby pack controls.

Front 79

What does a PACK light indicate during master caution recall?

Back 79

Failure of either primary or standby pack control.

Front 80

What are the possible sources for the bleed air system?

Back 80

Engines, APU, External Air

Front 81

What systems use bleed air?

Back 81

-Air conditioning and pressurization, -Engine and wing anti ice, -Engine starter, -Hydraulic reservoir pressurization, -Potable water tank pressurization

Front 82

What happens to the APU bleed air valve when the APU is shut down?

Back 82

APU bleed air valve automatically closes

Front 83

Where does the air exiting the left pack go?

Back 83

Directly to the flight deck and leftover air to the mix manifold.

Front 84

Where does air exiting the right pack go?

Back 84

Into the mix manifold.

Front 85

What air is fed into the mix manifold?

Back 85

Pre conditioned air, OR air from the right pack, leftover air from the left pack, and air from the recirculating fans.

Front 86

Where does air exiting the mix manifold go?

Back 86

Directly to the forward and aft passenger cabin sidewall risers.

Front 87

Can you operate both packs from an external air cart?

Back 87

Yes, most air carts supply adequate air for two pack operation.

Front 88

When will the ram air doors be fully open?

Back 88

On the ground or slow flight with the flaps extended. It will modulate between open and closed during normal cruise.

Front 89

What are the Deflector Doors?

Back 89

They are forward of the ram air inlets and prevent slush ingestion prior to liftoff and after touchdown.

Front 90

What controls the Deflector Doors? When are they extended?

Back 90

They are controlled electrically from the air/ground sensor.

Front 91

What does the left pack electronic controller control?

Back 91

It controls the left primary pack temperature control valve, the right standby pack temperature control valve, the backup flight deck zone temperature control, and the aft cabin zone temperature control

Front 92

What does the right pack electronic controller control?

Back 92

It controls the right primary pack temperature control valve, the left standby pack temperature control valve, the primary flight deck zone temperature control, and the forward cabin zone temperature control

Front 93

Under normal conditions, what temperature are the packs trying to produce?

Back 93

The temperature of the zone that requires the most cooling.

Front 94

How is the temperature of the individual zones controlled?

Back 94

The zone supply duct is given the proper amount of trim air regulated from the individual trim air modulating valve.

Front 95

How is zone temperature control affected during single pack operation?

Back 95

Trim Air ON: same as two pack operation. Trim Air OFF: The pack attempts to produce a temperature of the average demand of all three zones.

Front 96

How is zone temperature control affected if the forward or aft cabin zone temperature control fails?

Back 96

The temperature selectors will operate normally, however the two temperature selector settings will be averaged.

Front 97

What happens to dual pack operation if one of the passenger zone trim air or all of the trim air supplies fail?

Back 97

Packs go to independent operation. The right pack will output the average temperature of the forward and aft temperature selectors, left pack will output selected temperature of the flight deck temperature selector.

Front 98

What happens to dual pack operation if the flight deck trim air fails?

Back 98

Packs go to independent operation. The right pack will output the forward or aft zone requiring the most cooling, the left pack will output selected temperature of the flight deck temperature selector.

Front 99

What happens if an individual zone temperature selector is placed to OFF?

Back 99

The associated trim air modulating valve closes and the the selector is ignored by the temperature control system.

Front 100

What happens if all zone controls and primary pack controls fail?

Back 100

The standby pack controls command the packs to produce air temperatures that will satisfy the average demand of the two cabin zones. The flight deck temperature selector will have no affect.

Front 101

What happens if all temperature selectors are placed in OFF?

Back 101

The left pack will produce a temperature of 24C and the right pack will produce 18C.

Front 102

Describe the route the air takes via the recirculation fans.

Back 102

Air from the passenger cabin and electrical equipment bay is drawn into the forward cargo bay where it is filtered and recirculated to the mix manifold.

Front 103

What happens to the equipment cooling exhaust fan if there is a forward cargo fire warning?

Back 103

The fan is shut off and the OFF light is inhibited.

Front 104

When does the altitude warning horn sound?

Back 104

When cabin altitude exceeds 10,000 feet.

Front 105

What does the ALT HORN CUTOUT switch do?

Back 105

It cuts out the intermittent cabin altitude warning horn.

Front 106

What does the AUTO FAIL light indicate?

Back 106

Dual auto controller failure if illuminated alone, or single auto controller failure if ALTN light illuminated also.

Front 107

What action should be taken if "88888", dashes, non numbers, or blank is displayed in either the FLT or LAND ALT indicators?

Back 107

Automatic control may or may not be affected. Monitor the pressurization system, especially during climb and descent.

Front 108

What does an illuminated green ALTN light indicate?

Back 108

Pressurization system operating in the alternate automatic mode.

Front 109

What does an illuminated green MANUAL light indicate?

Back 109

Pressurization system operating in the manual mode.