Air Systems

Question 1

What are the three sources of bleed air?

Answer 1

Engines, APU, external air cart / source.

Ref: FRM 2.2.1

Question 2

What are some systems that rely on bleed air?

Answer 2

• Air conditioning / pressurization
• Wing and engine thermal anti-icing
• Engine Starting
• Hydraulic reservoirs pressurization
• Water tank pressurization
• Nitrogen generation system
• Aspirated TAT probe

Ref: FRM2.2.1

Question 3

On the NG, what does a BLEED TRIP OF light mean, what happens, and can it be reset?

Answer 3

-Illuminates when engine bleed air temperatures or pressure exceed a predetermined limit.

-The engine bleed valve closes automatically.

• IF temperature and / or pressure have returned to a normal range, it can be reset with the TRIP RESET button.

Ref: FRM B737NG2.1.1 2.2.2.2

Question 4

What is the purpose of the WING-BODY OVERHEAT light?

Answer 4

Indicates overheat from bleed duct leak.

Ref: FRM 2.1.1 FRM B737NG 2.2.2.9 FRM B737MAX 2.2.2.11

Question 5

Where does the WIng-Body Overheat system monitor for both the Left and Right side?

Answer 5

• Left / Right engine strut
• Left / Right inboard wing leading edge
• Left / Right hand air conditioning bay

Ref: FRM 2.1.1 FRM B737NG 2.2.2.9 FRM B737MAX 2.2.2.11

Question 6

What two unique areas does the Left side Wing-Body Overheat system monitor?

Answer 6

-Keel beam
-Bleed duct from APU

Reference: FRM 2.1.1, FRM B737NG 2.2.2.9, FRM B737MAX 2.2.2.11

Question 7

Q.2.7. What is the purpose of the TRIP RESET switch?

Answer 7

-700: Resets BLEED TRIP OFF, PACK TRIP OFF, and DUCT OVERHEAT lights
- 800: Resets BLEED TRIP OFF, PACK, and ZONE TEMP lights
- MAX: Resets BLEED, PACK, or ZONE TEMP lights

Reference: FRM B737 -700/-800 2.1.1, 2.1.2, FRM MAX 2.1.2

Question 8

Q.2.8. With the Isolation Valve switch in AUTO, when will the valve automatically go from closed to open?

Answer 8

Opens automatically if either engine BLEED air or air conditioning PACK switch is positioned OFF.

Reference: FRM 2.1.1, 2.1.2

Question 9

Q.2.9. In the -700, what would cause the PACK TRIP OFF light to illuminate? What happens?

Answer 9

Indicates pack temperature has exceeded limits. Related pack valve automatically closes and mix valves drive full cold.

Reference: FRM B737NG 2.1.2

Question 10

Q.2.10. In the -800, what would cause a PACK light to illuminate? What about on recall?

Answer 10

-Pack trip off (over temperature) or
-Failure of both primary and standby pack controls or
-Failed closed Smart Ram Air Door Actuators (SRADA) system fault (as installed)

Recall
-Failure of either primary or standby pack control or
-Smart Ram Air Door Actuator (SRADA) system fault (as installed)

Reference: FRM B737NG 2.1.2, 2.4.7

Question 11

Q.2.11. If an amber caution light illuminates only on MASTER CAUTION recall but goes out when the MASTER CAUTION is reset, is running the associated QRH required?

Answer 11

No.

Reference: AOM 5.1.1.2

Question 12

Q.2.12. In the MAX, what would cause both PACK lights to illuminate?

Answer 12

Incorrect pack configuration after takeoff or go-around 45 seconds after flap retraction.

Reference: FRM B737MAX 2.1.2, 2.3, MAX QRH 2.22

Question 13

Q.2.13. What does a DUAL BLEED light mean?

Answer 13

APU bleed air valve open and engine No. 1 BLEED air switch ON, or engine No. 2 BLEED air switch ON, APU bleed air valve and isolation valve open.

Reference: FRM 2.1.1, FRM B737NG 2.2.2.7, FRM B737MAX 2.2.2.9, B737NG QRH 2.12, B737MAX QRH 2.17

Question 14

Q.2.14. In the -700, what would cause the DUCT OVERHEAT lights to illuminate and what happens?

Answer 14

Distribution air temperature in related duct exceeds limit. Air mix valves drive full cold.

Reference: FRM B737NG 2.1

Question 15

Q.2.15. In the -800, what would cause the ZONE TEMP lights to illuminate? During recall?

Answer 15

Illuminates
CONT CAB indicates a duct temperature overheat or failure of the flight deck primary and standby temperature control.

FWD CAB or AFT CAB indicates duct temperature overheat.

Illuminates during recall
CONT CAB - indicates failure of the flight deck primary or standby temperature controller.
Either FWD CAB or AFT CAB indicates failure of the associated zone temperature control.

Reference: FRM B737NG 2.1.2, 2.4.9

Question 16

Q.2.16. In the MAX, what causes the ZONE TEMP light(s) to illuminate?

Answer 16

-CONT CAB indicates a duct temperature overheat or failure of the flight deck primary and standby temperature control.

• FWD CAB or AFT CAB indicates duct temperature overheat.

Reference: FRM B737MAX 2.1.2

Question 17

Q.2.17. How many fans are in the Equipment Cooling system?

Answer 17

Four. A normal and alternate fan for both the supply and exhaust system.

Reference: FRM B737NG 2.3.3.5, 2.4.13.4, FRM B737MAX 2.3.4.4

Question 18

Q.2.18. What would cause the equipment cooling OFF light to illuminate?

Answer 18

Loss of airflow due to failure of an equipment cooling fan.

Reference: FRM B737NG 2.1.3, 2.3.3.5, 2.4.13.4, FRM B737MAX 2.3.4.4, B737NG QRH 2.13, B737MAX QRH 2.18

Question 19

Q.2.19. What are the effects of a forward cargo fire warning on the equipment cooling system?

Answer 19

-800 (-700 as installed) and MAX, the equipment cooling exhaust fan is shutoff and the equipment cooling exhaust OFF light is inhibited.

Reference: FRM B737NG 2.3.3.5.1, 2.4.13.4.1, FRM B737MAX 2.3.4.4

Question 20

Q.2.20. The MAX has an additional light on the equipment cooling panel, EQUIP SMOKE, what causes this light to illuminate?

Answer 20

Smoke is detected in the equipment cooling system. Light extinguishes 30 seconds after smoke is no longer detected.

Reference: FRM B737MAX 2.1.3, FRM B737MAX 2.3.4.4

Question 21

Q.2.21. What does the CABIN ALTITUDE WARNING indicate, can it be silenced?

Answer 21

It Indicates the cabin altitude has exceeded 10,000 ft. It can be silenced by pressing the ALT HORN CUTOUT Switch.

Reference: FRM 2.1.4

Question 22

Q.2.22. What is our policy/guidance on silencing aural alert and resetting the MASTER CAUTION System?

Answer 22

Flight Deck Crew should silence any aural alert and reset the MASTER CAUTION System as soon as the cause of the alert is recognized.

Reference: AOM 5.1.1.2

Question 23

Q.2.23. What causes an OFF SCHED DESCENT light to illuminate?

Answer 23

An amber OFF SCHED DESCENT light illuminates if the aircraft begins to descend without having reached the preset cruise altitude in the FLT ALT indicator.

Reference: FRM 2.1.5, FRM B737NG 2.5.5, FRM B737MAX 2.4.5

Question 24

Q.2.24. What is the pressurization controller scheduling for the landing altitude after receiving an OFF SCHED DESCENT light?

Answer 24

The controller programs the cabin to land at the takeoff field elevation (unless the Crew resets the FLT ALT setting).

Reference: FRM B737NG 2.5.5, FRM B737MAX 2.4.5

Question 25

Q.2.25. How many pressure relief valves are on the aircraft?

Answer 25

2 positive pressure relief valves, and 1 negative pressure relief valve

Reference: FRM B737NG 2.5.2, FRM B737MAX 2.4.2

Question 26

Q.2.26. Why is there a CAUTION associated with using manual pressurization?

Answer 26

The manual motor operates at higher rate than AUTO or ALTN motor.
A small movement of the outflow valve can cause a large change in cabin rate of climb rate or descent. Manual actuation of the outflow valve can produce large, rapid changes in cabin pressure which could result in passenger and crew discomfort and/or injury.

Reference: FRM B737NG 2.5.2, FRM B737MAX 2.4.2