Air Systems

Question 1

Max differential pressure?

Answer 1

9.1 PSI (relief valves)

Question 2

With main deck cargo air flow rate set to high what is the cruise fuel burn increase?

When would we use High flow mode?

Answer 2

0.2% - 0.5%

Intended for carrying live animals and perishable cargo

Question 3

Max differential pressure for takeoff and landing?

Answer 3

0.11 PSI

Question 4

How many relief valves/vents are there?

Answer 4

2 positive pressure relief valves (left side only fwd of wing)

4 negative pressure relief vents (2 left, 2 right fwd of wing)

Question 5

How many packs and recirculating fans?

Answer 5

2 packs and 2 recirculating fans

Question 6

Max cabin altitude?

Answer 6

8,000’ cabin altitude at max operating altitude 43,100’ MSL

Question 7

What supplies O2 to the supernumerary O2 system?

Where is the bottle located?

Answer 7

Bottled gaseous oxygen

In the forward Electrical and Electronic (E & E) Compartment

Question 8

What is the purpose of the Alternate Ventilation System?

Answer 8

Provides airflow to flight deck and sprn cabin when both packs are inoperative.

Question 9

How many seconds does it take to move the outflow valve from full open to close in manual?

Answer 9

30 seconds

Question 10

How many outflow valves?

Answer 10

2, one fwd and one aft. 80% goes through aft

Question 11

When does the PAX/SPN oxygen system deploy automatically?

Answer 11

system activates when cabin altitude reaches approximately 13,500 feet.

Question 12

When will the passenger signs come on automatically regardless of switch position/ what about in the auto position?

Answer 12

In Auto
• landing gear not up and locked, or 
• flap lever not up, or
• airplane altitude below 10,000, or 
• cabin altitude above 10,000 feet, or

Off:
• SPN O2 is on

Question 13

What is an easy way to eliminate unwanted galley odors quickly?

Answer 13

Turn off the recirc fans.

Question 14

What causes a pack to enter the standby cooling mode?

Answer 14

For certain internal malfunctions, pack control automatically uses standby cooling mode as a backup to normal mode. In standby cooling mode, the EICAS advisory message PACK MODE (L, R) is displayed, and STBY COOLING is displayed in amber on the AIR synoptic.

Question 15

What does the trim air do?

Answer 15

Hot trim air from the bleed air system is added through trim air valves in the conditioned air supply ducts. The CACTCS (cabin air conditioning and temperature control system) modulates the zone trim air valves to achieve the target temperature of the conditioned air in each zone.

Trim air from the left engine bleed is added to conditioned air ducts for the flight deck, supernumerary cabin, forward main deck cargo, and lower aft cargo compartments. Trim air from the right engine is added to the conditioned air ducts for the aft main deck cargo and lower forward cargo compartments, and the flight deck equipment cooling during flight.

Question 16

Can cabin zone temperatures be maintained with the loss of trim air?

Answer 16

If the left or right trim air system is off, the CACTCS attempts to maintain all zones at the average selected temperature. Flight deck temperature will be maintained between 65°F and 85°F (18°C and 29°C).

The flight deck may become uncomfortably warm or cool. Setting the FWD or AFT MAIN DECK CARGO TEMP selector to a cooler or warmer temperature may achieve a cooler or warmer flight deck temperature.

Question 17

What is the purpose of the bleed isolation valves?

Answer 17

If a duct leak is detected, the system automatically isolates the leak. The EICAS caution message BLEED LEAK is displayed.

The automatic isolation logic may include one, two, or three sequential steps. During isolation, the ENGINE and/or APU bleed switch OFF lights and the ISOLATION switch CLOSED lights illuminate and extinguish as the respective valves close and open.

When the temperature in the affected duct area cools, the BLEED LEAK EICAS message is no longer displayed. The valves isolating the leak remain closed and the appropriate EICAS message BLEED LOSS is displayed. The switch OFF or CLOSED lights are illuminated for the respective valves which remain closed to isolate the affected duct area.

Question 18

What causes the APU bleed valve to open automatically?

Answer 18

It’s pressure activated at altitudes below 22000’ with the APU bleed switch in the auto position.

Question 19

What do you see on the EICAS when an outflow valve is selected to manual?

Answer 19

Outflow valve position is displayed on the EICAS display.

If the outflow valve position is not available on EICAS, holding the respective OUTFLOW VALVE MANUAL switch in the desired position for 30 seconds will move the valve from full open or close to the selected position.

Question 20

What is the best way to manually control the pressurization?

Answer 20

Only use the aft outflow valve. One second = 100fpm.

Question 21

Explain pack standby cooling mode with one or both packs in standby mode.

Answer 21

If one pack is in standby mode and the other is operative the one in stby shuts down at low altitude and high outside temp.

With both packs in stby mode (or 1 pack inop and other pack in stby) the pack/packs operate continuously to maintain cabin pressure

Pack cooling capacity is less than in normal mode and may result in warm flight deck at lower altitudes

Question 22

What are the sources of bleed air?

Answer 22

Engines, APU, External Air

Question 23

What is bleed air used for?

Answer 23

• Air Conditioning
• Pressurization
• Wing and engine anti-ice
• APU and engine start
• Air driven hydraulic pumps
• Hydraulic reservoir pressurization
• Potable water tank pressurization
• TAT probe aspiration
• Aft cargo heat

Question 24

How does the automatic function of the pressurization system work?

Is there a backup?

Answer 24

Cabin pressurization is controlled by regulating the discharge of conditioned cabin air through the forward and aft outflow valves.

Manual mode is the backup