Cabin conditioning and pressurisation Flashcards
How is warm air provided in a SEP?
Atmospheric air passed over a heat exchanger around the exhaust
Large aircraft have air conditioning and pressurisation systems to provide:
Ventilation
Temperature
Cabin pressure
The pressurisation system comprises:
Air from the conditioning packs
outflow valve
actuator
pressure controller
Outflow control valve is located?
Rear of the fuselage
What valve controls the pressure?
outflow control valve
If the outflow control valve is open then pressure in the cabin would….
decrease
If the outflow control valve is closed then the pressure in the cabin would…
build or maintain
How is excess pressure guarded against? (2)
Excessive differential pressure-release valve
and
Differential pressure between
Cabin pressure is indicated as cabin altitude. What is the maximum allowed for CS-25
8000ft
Describe cabin vertical speed
rate of change of the cabin altitude
What determines the maximum altitude for an aircraft?
Pressure differential between cabin and ambient.
What is the max differential pressure between cabin and ambient?
8 or 9 psi
What is the purpose of ground pressurisation?
Even out fluctuations during take-off.
Eases the initial pressurisation.
What controls do the crew have when it comes to presurisation?
Auto
landing altitude
Manual
What controls the outflow valve?
Pressurisation controller, adjusts the position of the outflow valve.
What can be done if the pressurisation controller fails?
The outflow valve can be manually controlled
Cabin conditioning is achieved with an air conditioning pack. How many are there and what can they be driven with.
2 or 3
bleed air or electrics
Before bleed air enters the cabin it goes through packs. What do the packs do?
(2)
Cools
Control humidity
HEPA filter
What does HEPA stand for
High-efficiency particulate air
The packs are very good at cooling the air, but the temperature needs regulating. How is this done?
The system is calibrated to the lowest demanded cabin temperature.
‘Trim air’ is then used to fine tune the zones.
How much air would we expect to re-circulate?
50%
On the ground there may not be enough ram air. What is done about this?
A motor (possibly driven from the turbine/compressor in the pack) will suck air through the ram air duct.
Where are the pack’s located?
Outside the pressure hull by the wing root.
What are the other names for the ‘packs’ (3)
Cold air unit
Aircycle machine
bootstrapping
A pack can have two heat exchangers. Which is larger and provides a greater temperature drop?
Second
What is the mandated airflow for each passenger?
1 lb. / passenger / minute
(halved if you have a failure)
