737 Systems: Pneumatics

Question 1

What sources supply air to the Bleed Air System?

Answer 1

Engines, APU, or ground cart (LP or HP)

Question 2

What causes the engine bleed valve to automatically close? Which lights indicate this has occurred?

Answer 2

High Temperature or High Pressure

Will cause the BLEED TRIP OFF light, AIR COND annunciator, and MASTER CAUTION to illuminate

Question 3

Which conditions will the TRIP RESET switch reset?

Answer 3

The BLEED TRIP OFF, ZONE TEMP, or PACK lights, if the exceedances no longer exist

Question 4

What will cause the automatic closure of the APU Bleed valve?

Answer 4

When the APU is shut down regardless of switch position

Question 5

Normally, what is the position of the Isolation Valve with the Isolation Valve switch in AUTO?

Answer 5

Closed

Question 6

What will cause the Isolation Valve to open automatically with the Isolation Valve switch in AUTO?

Answer 6

Placing the Engine BLEED Air or AC PACK switches to OFF

Question 7

What does a DUAL BLEED light indicate?

Answer 7

When the APU Bleed Air Valve is OPEN and:
-ENG 1 Bleed Switch ON

And/or

-ENG 2 Bleed Switch ON with the Isolation Valve OPEN

Question 8

What is the primary source of conditioned air in the Flight Deck?

Answer 8

Left PACK

Question 9

A single PACK in High Flow mode can maintain pressurization up to what altitude?

Answer 9

Up to the Maximum Certified Ceiling

Question 10

What conditions would cause a PACK to change from Normal to High Flow with both PACK switches in AUTO?

Answer 10

If Airborne, with Flaps UP, both PACK switches in AUTO, and ENG Bleed Switches to ON, if on PACK fails, an engine fails, or a PACK switch selected OFF, the remaining PACK switches to high air flow.

Question 11

What is indicated by the amber PACK light on the Bleed Air Panel?

Answer 11

Indicates a failure of the primary and standby pack controls for the same pack.

Question 12

What provides cooling air for the heat exchangers in the PACK system?

Answer 12

Ram Air

Question 13

What is indicated by a bright blue RAM DOOR FULL OPEN light?

Answer 13

Whenever a Ram Air Door is fully open

Question 14

What is the purpose of the recirculating fans?

Answer 14

To reduce:

-Bleed Air Load (efficiency)
-Engine Bleed Air (increase relative humidity)
-Airborne participles and micro-organisms (higher circulation in HEPA filters)

Question 15

What does the illumination of the ZONE TEMP light indicate?

Answer 15

An associated overheat of the supply duct and the closing of that associated Trim Air Valve

(CONT included a failure of BOTH the primary and standby temperature controls)

Question 16

What limitations, if any, are there when using external conditioned air?

Answer 16

PACK switches should be positioned off

Question 17

What is the purpose of the Equipment Cooling System?

Answer 17

To cool the electronic equipment in the Flight Deck and the E/E Bay

Question 18

Which, if any, of the Cargo Compartments are heated by the Equipment Cooling System exhaust fans?

Answer 18

The FWD Bay

Question 19

What does the Equip Cooling OFF light indicate?

Answer 19

Loss of airflow due to the failure of the respective Equipment Cooling Fan

Question 20

How is the alternate Cabin Pressurization Controller selected?

Answer 20

By positioning the Pressurization Mode Selector to ALTN

Question 21

What are the indications that an active Cabin Pressurization Controller has failed?

Answer 21

AUTO FAIL amber light and ALTN green light. Ascended of the ALTN light indicates a DUAL Cabin Pressure controller failure

Question 22

What causes the illumination of the OFF SCHED DESCENT light?

Answer 22

If the aircraft appears to descend without having reached the present cruise altitude selected in the FLT ALT window

Question 23

At approximately what altitude will the CABIN ALTITUDE light and the Cabin Altitude Warning Horn activate? Can the horn be silenced?

Answer 23

Either Cabin Altitude Pressure switches sense the Cabin. Altitude exceeds 10,000ft +/- 1000ft

Yes you can silence it with the ALT HORN CUTOUT button on the Cabin Altitude Panel