11.4 Pressurisation Systems

Question 1

At what altitude are aircraft normally pressurised to

Answer 1

8000ft above sea level

Question 2

At what cabin altitude must crew be on oxygen

Answer 2

10000ft

Question 3

At what cabin altitude must passengers be on oxygen

Answer 3

15000ft

Question 4

What is cabin altitude

Answer 4

The equivalent altitude of the cabin pressure relative to sea level

Question 5

What is the max cabin altitude of commercial aircraft

Answer 5

8000ft

Question 6

Why aren’t aircraft pressurised to sea level for maximum comfort

Answer 6

Structural stress on the aircraft structure would be too great

Question 7

What is the unit for cabin pressure

Answer 7

Psi

Question 8

What is differential pressure

Answer 8

Outside pressure - cabin pressure

Question 9

How much does temperature decrease by when altitude increases by 1000ft

Answer 9

2°C

Question 10

Temperature of upper boundary of tropopause (cruise altitude)

Answer 10

-57°C

Question 11

What happens to temperature as altitude increases in the stratosphere

Answer 11

Temperature slightly increases before decreasing again in mesosphere

Question 12

What is cabin rate of climb

Answer 12

Rate of change of pressure inside cabin, expressed in feet per minute

Question 13

Where is pressurised on an aircraft

Answer 13

Cockpit, Fwd/Aft cabins, Fwd/aft cargo holds

Question 14

Where is unpressurised on an aircraft

Answer 14

Radomes, Nose U/C bay, Centre section torque box, Main U/C bay, Tail cone

Question 15

What are the 3 pressurisation modes

Answer 15

Isobaric, differential, manual (emergency)

Question 16

What is differential cabin mode

Answer 16

System works to maintain cabin pressure to a constant pressure difference between inside and outside of cabin regardless of aircraft altitude changes

Question 17

What is manual mode with regard to cabin pressurisation

Answer 17

Allows cabin isobaric control and rate of change of control to be turned off if operation is faulty. Also used for trouble shooting

Question 18

What is isobaric mode in regard to cabin pressurisation

Answer 18

Pressurisation system maintains the cabin altitude selected by flight crew. This is done in normal operation

Question 19

What is the normal cabin vertical speed

Answer 19

500fpm ascend 300fpm descend