Pressurisation

Question 1

Auto System Components Are?

Answer 1

Cabin pressure controller on avionics rack
2 electro pneumatic normal outflow valves (1 on the 100)
Associated controls and indicators in flight deck

Question 2

Cabin Pressure Controller

Answer 2

Digital computer
Pre programmed pressure schedule from takeoff to touch down
Commands metering valve to adjust outflow
Fault detection programmed

Question 3

Which is master outflow valve?

Answer 3

RHS is master, LHS is slaved to follow

Question 4

Ejector details?

Answer 4

18 PSI air from de-ice system.
Creates suction at outflow valves.
Electronically positions from flight deck cabin pressure controller settings.
To master outflow valve.

Question 5

Manual system components?

Answer 5

Manual metering valve and flight deck control knob.
Safety outflow valve in forward pressure bulkhead (similar to normal outflow valves, suction created by vent in slipstream).
Needs no electric power or pneumatic pressure.

Question 6

Pressure Relief Valves

Answer 6

Both normal and safety outflow valves have relief valves.
Vent excess pressure if Cab Difference exceeds 5.8 +/- PSI.
Max settable Cab Diff is 5.5 +/_ PSI. (approx 8k ft at 25k ft).

Question 7

Negative Pressure Relief Valves.

Answer 7

Both normal and safety valves open is cabin suction >0.1 PSI.

Question 8

4 Cab Altitude Modes?

Answer 8

Auto, Semi Auto, Manual, Dump

Question 9

“Fault” light?

Answer 9

Internal failure of pressure computer.

Question 10

“Cabin Pressure” warning light

Answer 10

> 10,000 ft cabin pressure.

Question 11

Automatic Pressure Control:
When active?
Self check?
Crew input?

Answer 11

Cab Press controller active when Left Main Bus pwr available, and switch is in AUTO.
Self checks on startup (2s fault light)
Crew input is destination elevation on cab alt indicator, and Local QNH (reset to desti QNH @ TOD).

Question 12

Auto Pressure Operation on Ground

Answer 12

Cabin pressure controller in ground mode when power levers are idle.
Normal outflow valve open to prevent pressurisation.
When power levers advance to 15.5 degrees slight pressurisation occurs.
Normal outflow valves start modulating.

Question 13

Auto Pressure Operation on Landing

Answer 13

If Cab Alt is set higher than Desti alt, plane lands unpressurised.
If Cab Alt is set lower than Desti alt, plane lands pressuried.
1 min after landing, the normal outflow valves open.

Question 14

Semi Automatic Operation

Answer 14

Switch set to “CAB SET”
Desired cruise cabin alt set on CAB ALT indicator.
Prior TOD, CAB ALT indicator set to desti ALT.

Question 15

Rate knob

Answer 15

Centred : 500 fpm up, 300 fpm down
Full CW: 2500 +/-150 fpm up, 1500 +/- fpm down.
Full CCW: 150 +/- 50 fpm up, 90 +/- 50 fpm down

Question 16

Bleed air setting for T/O and Landing

Answer 16

OFF

Question 17

Max Cabin Alt

Answer 17

8,000 ft

Question 18

Max Cabin Diff for taxi, takeoff and landing

Answer 18

0.5 PSI

Question 19

Max Cabin Diff

Answer 19

5.95 PSI (relief valves open at 5.8 +/- .15 PSI

Question 20

Normal Cabin Diff

Answer 20

5.5 PSI

Question 21

What do rear outflow valves need to operate?

Answer 21

18 PSI pressure from De-Ice, and power to the pressure controller (comes from left man DC bus).
(On essential power, the rear outflow valves will close and pressure difference can rise quickly)

Question 22

Forward Outflow Valves

Answer 22

Similar to rear outflow valves.
No power required.
Normally closed, used for abnormal ops.
Operated using with on FO side panel, or Man Control Knob on pressure controller.

Question 23

Manual Mode?

Answer 23

Used if Elec Power Lost, or if Auto Mode malfunctions.

Can allow smoke removal without depressurising plane.