CRJ7/9 - Air Conditioning/Pressurization/Pneumatic

Question 1

LIM: Maximum Positive Differential Pressure

Answer 1

8.7 psi

Question 2

LIM: Maximum Negative Differential Pressure

Answer 2

-0.5 psi

Question 3

LIM: Maximum Differential Pressure During Taxi and Takeoff

Answer 3

0.1 psi

Question 4

LIM: Maximum Differential Pressure During Landing

Answer 4

1.0 psi

Question 5

LIM: Cabin Pressure Limit Prior to Opening Doors

Answer 5

Cabin must be depressurized

Question 6

LIM: Maximum Altitude for Single-Engine Pack Operation

Answer 6

• 700: 31,000 feet
• 900: 31,000 feet with 82 or fewer cabin occupants, 25,000 feet with more than 82 cabin occupants

(cabin occupants counts FAs, extra FAs, passengers, and infants, but does not count FD jumpseaters)

Question 7

LIM: Maximum Altitude to Use EMER DEPRESS

Answer 7

15,000 feet

Question 8

What are the Power Sources for the ACSCs?

Answer 8

ACSC1 Channel A: DC Battery Bus
ACSC1 Channel B: DC Bus 2

ACSC2 Channel A: DC Bus 1
ACSC2 Channel B: DC Essential Bus

Question 9

When does the ACSC switch channels?

Answer 9

Daily, or automatically in the event of a failure

Question 10

Which ACSC controls the L PACK?

Answer 10

ACSC1 only

Question 11

Which ACSC controls the R PACK?

Answer 11

ACSC2 only

Question 12

Which flight deck switches control the Flow Control Valves (pack valves)?

Answer 12

L and R PACK switches

Question 13

What is the difference between the -700 and -900 packs?

Answer 13

• 700: Uses a Hot Air Shutoff Valve to allow some hot air to bypass the precooler to be mixed back in after the precooler, raising the temperature of the precooler air output for pack pull-up mode.
• 900: Uses a Ram Air Regulating Valve to reduce the amount of ram air passing over the precooler to raise the temperature of the precooler air output for pack pull-up mode.

Question 14

The Flow Control Valves (pack valves) are downstream of ____ and upstream of _____?

Answer 14

Downstream of the Precooler and upstream of either the Primary Heat Exchanger or Temperature Control Valve

Question 15

What is the function of the Temperature Control Valve?

Answer 15

Allows some air from the Precooler to bypass the rest of the pack before being mixed in again, enabling the pack output temperature to be regulated.

Question 16

What flight deck switch(es) control the Temperature Control Valve?

Answer 16

The CKPT or CABIN temperature knobs (via the respective ACSC), or the respective HOT/COLD switches (directly) when in Manual mode.

Question 17

When will the ACSC command pack pull-up or pull-down?

Answer 17

On the ground when a difference of >10 C between selected and actual temperature is sensed

Question 18

In manual mode, when will the L(R) PACK TEMP message be displayed?

Answer 18

If the pack discharge temperature is less than or equal to 5 degrees C, or greater than or equal to 85 degrees C.

Question 19

Why is there no L(R) PACK TEMP message for an undertemperature condition in auto mode while there is in manual mode?

Answer 19

In auto mode, if pack discharge temperature is too low, the ACSC will open the Temperature Control Valve to mix hot air into the pack output. In manual mode, the flight crew must manipulate the valve themselves.

Question 20

What drives the fan in the ram air duct?

Answer 20

The Air Cycle Machine.