Cabin conditioning and pressurisation

Question 1

How is warm air provided in a SEP?

Answer 1

Atmospheric air passed over a heat exchanger around the exhaust

Question 2

Large aircraft have air conditioning and pressurisation systems to provide:

Answer 2

Ventilation
Temperature
Cabin pressure

Question 3

The pressurisation system comprises:

Answer 3

Air from the conditioning packs
outflow valve
actuator
pressure controller

Question 4

Outflow control valve is located?

Answer 4

Rear of the fuselage

Question 5

What valve controls the pressure?

Answer 5

outflow control valve

Question 6

If the outflow control valve is open then pressure in the cabin would….

Answer 6

decrease

Question 7

If the outflow control valve is closed then the pressure in the cabin would…

Answer 7

build or maintain

Question 8

How is excess pressure guarded against? (2)

Answer 8

Excessive differential pressure-release valve

and

Differential pressure between

Question 9

Cabin pressure is indicated as cabin altitude. What is the maximum allowed for CS-25

Answer 9

8000ft

Question 10

Describe cabin vertical speed

Answer 10

rate of change of the cabin altitude

Question 11

What determines the maximum altitude for an aircraft?

Answer 11

Pressure differential between cabin and ambient.

Question 12

What is the max differential pressure between cabin and ambient?

Answer 12

8 or 9 psi

Question 13

What is the purpose of ground pressurisation?

Answer 13

Even out fluctuations during take-off.
Eases the initial pressurisation.

Question 14

What controls do the crew have when it comes to presurisation?

Answer 14

Auto
landing altitude
Manual

Question 15

What controls the outflow valve?

Answer 15

Pressurisation controller, adjusts the position of the outflow valve.

Question 16

What can be done if the pressurisation controller fails?

Answer 16

The outflow valve can be manually controlled

Question 17

Cabin conditioning is achieved with an air conditioning pack. How many are there and what can they be driven with.

Answer 17

2 or 3
bleed air or electrics

Question 18

Before bleed air enters the cabin it goes through packs. What do the packs do?
(2)

Answer 18

Cools
Control humidity
HEPA filter

Question 19

What does HEPA stand for

Answer 19

High-efficiency particulate air

Question 20

The packs are very good at cooling the air, but the temperature needs regulating. How is this done?

Answer 20

The system is calibrated to the lowest demanded cabin temperature.
‘Trim air’ is then used to fine tune the zones.

Question 21

How much air would we expect to re-circulate?

Answer 21

50%

Question 22

On the ground there may not be enough ram air. What is done about this?

Answer 22

A motor (possibly driven from the turbine/compressor in the pack) will suck air through the ram air duct.

Question 23

Where are the pack’s located?

Answer 23

Outside the pressure hull by the wing root.

Question 24

What are the other names for the ‘packs’ (3)

Answer 24

Cold air unit
Aircycle machine
bootstrapping

Question 25

A pack can have two heat exchangers. Which is larger and provides a greater temperature drop?

Answer 25

Second

Question 26

What is the mandated airflow for each passenger?

Answer 26

1 lb. / passenger / minute
(halved if you have a failure)