11.4

Question 1

Whats the 3 thing which provide the aircraft with pressurised air ?

Answer 1

Engines
APU
Ground source

Question 2

What part of the engine takes in air to pressurise the cabin ?

Answer 2

Compressor

Question 3

Whats the three types of compressors ?

Answer 3

Positive displacement compressor
Centrifugal compressor
Turbo compressor

Question 4

How is air pressure adjusted ?

Answer 4

Pressure regulating valve or
Bleed air valve

Question 5

When is low pressure air used ?

Answer 5

During take-off climb and cruise.
( high pressure bleed air is used at low engine RPM speeds during decent )

Question 6

What lowers the hot air which is bled from the engine ?

Answer 6

Pneumatic system

Question 7

What happens to the engines power when air is bled from the compressor ?

Answer 7

Power will drop
( this decreases the engine efficiency as the compressor is resulted to work harder )
- individual cabin compressors are designed to minimise the disadvantages which follow from bleeding the air from the engines compressor )

Question 8

Explain a positive displacement blower ?

Answer 8

Two rotors rotate at the same speed in which air travels around the outside of the case and is deposited.

Question 9

Explain centrifugal cabin compressor ?

Answer 9

Takes air from atmosphere into a supercharger, where it is compressed by the high-speed impeller and delivered to a distribution

Question 10

What does the supercharger have in a centrifugal cabin compressor which produces optimal airflow regardless of the engine speed ?

Answer 10

Variable - ratio drive

Question 11

How does the turbo compressor work ?

Answer 11

Bleed air from engine drives a turbine, which directly drives a compressor. Hot air produced is blended with cooled decompressed bleed air.

Question 12

What is the cabin air compressor powered by ?

Answer 12

Three-phase motor

Question 13

What does the APU compressor supply ?

Answer 13

Bleed air to a load compressor

Question 14

If the APU is designed to provide bleed air extraction in flight, what altitude is the bleed air extraction normally limited to ?

Answer 14

22,000 ft

Question 15

Whats the two APU outputs ?

Answer 15

Electrical
Pneumatic ( compressed air )

Question 16

What does a ground cart air supply consist of to supply air ?

Answer 16

Small jet engine inside soundproof steel unit which carry’s conditioned air through ducks from the pack where it is required on the aircraft.

Question 17

Whats the two types of air conditioning systems used on aircraft ?

Answer 17

Air cycle machine - used on large aircraft
Vapour cycle machine - used on small aircraft

Question 18

Whats the two types of air conditioning systems used on aircraft ?

Answer 18

Air cycle machine
Vapour cycle machine

Question 19

Whats the range that an air conditioning system is capable of maintaining ?

Answer 19

21 - 27 degrees

Question 20

Whats the use of a pack ?

Answer 20

To drop air down to around 0 degrees

Question 21

What two things are found in an air con pack ?

Answer 21

Heat exchanges
Air cycle machine

Question 22

How is conditioned air distributed to the cabin ?

Answer 22

Trough ducts
( conditioned exits through ceiling vents where it circulates )

Question 23

What are distribution ducts constructed of?

Answer 23

Light fibreglass coated to prevent moisture damage
( ducts must be able to expand and shrink without loss of the pressure tight properties )

Question 24

Where are temperature monitoring valves located ?

Answer 24

Electronics compartment

Question 25

Whats a thermistor ?

Answer 25

Resistor that changes with its exposure to heat and has a shut off control. ( its not a on/off switch. It’s resistant changes as temperature changes )

Question 26

What do on board humidifiers do ?

Answer 26

Help passengers stay hydrated

Question 27

How much of the cabin air is filtered and recirculated ?

Answer 27

50% ( this means engines only need to supply the other 50% of cabin air which saves fuel )

Question 28

When the air is supplied to cabin and circulates around, how is it discharged out of the cabin ?

Answer 28

Through air grilles located on the sidewalls near the floor.

Question 29

*Cannot mix r12 And r134a

Question 30

Whats a gaspo fan ?

Answer 30

Air conditioning outlet in the cabin

Question 31

What fan is found in packs ?

Answer 31

ACU fans

Question 32

Above what altitude does there be a lack of oxygen and cabin pressurisation be needed ?

Answer 32

Above 10,000 ft

Question 33

What happens to the outside pressure as the altitude increases ?

Answer 33

It decreases

Question 34

What high is the cabin pressure when at cruise ?

Answer 34

8,000 ft

Question 35

How much is 1 atm in psi and Hecto pascal ?

Answer 35

14.7 psi 1013.2 hPa

Question 36

In the terms of passenger comfort, why do we pressurise the cabin ?

Answer 36

Depressurised cabin would make it have for passengers to breathe

Question 37

Whats hypoxia ?

Answer 37

Becoming unconscious due to a depressurised cabin.

Question 38

Whats the airframe subjected to when the aircraft’s being pressurised in a high altitude ?

Answer 38

Differential pressure Calculation- (cabin psi - outside psi)

Question 39

Whats the maximum anticipated loads called ?

Answer 39

Limit load ( limit load x safety factor = ultimate load )

Question 40

Whats cabin altitude ?

Answer 40

Cabin pressure inside of aircraft in terms of altitude above sea level. ( Normally maintained around 8,000 ft )

Question 41

How is the cabin pressurisation controlled in light ?

Answer 41

Through an outflow valve which regulates the amount of air that flows out of the cabin. This is controlled from the flight deck.

Question 42

If cabin altitude increases, what happens to the cabin pressure ?

Answer 42

It decreases.

Question 43

If you want to increase cabin pressure, should the outflow valve be open or closed ?

Answer 43

Closed.

Question 44

Whats the three pressurisation mode ?

Answer 44

Isobaric mode - maintains cabin altitude no matter the altitude change. Differential mode. - maintains cabin pressure Manual mode ( emergency ) - used if isobaric control is faulty so it controls cabin pressure manually.

Question 45

Explain a positive safety valve ?

Answer 45

Outwards pressure relief valve fitted to relive positive pressure in cabin when maximum pressure differential is exceeded. ( if its exceeded by 8 - 10 psi )

Question 46

Explain a negative safety valve

Answer 46

Inwards relief valve which is fitted to prevent excessive negative differential pressure which will open if pressure outside the aircraft exceeds that inside the aircraft by 0.5 - 1 psi. ( allows air to enter cabin ) - to much air entering can cause difficulties opening the cabin door or structural damage.

Question 47

Explain the leak detector methods for air conditioning ?

Answer 47

1. Held close to component with a hose connection and an audible and visual alarm will signal. 2. Apply soapy solution to fittings and inspect for bubbles. 3. Injecting special leak detection dyes.

Question 48

How do you find cabin differential pressure ?

Answer 48

Inside cabin pressure - outside ( ambient ) pressure

Question 49

Explain he difference between a positive and negative negative safety pressure valve ?

Answer 49

Positive - opens outwards - let’s excessive differential pressure out of Cabin. Negative - opens inwards - allows ambient air to enter cabin

Question 50

Whats a dump valve used for ?

Answer 50

Quickly remove air from the cabin and operates automatically or by a switch in the flight deck.

Question 51

What is used to allow the flight crew to warn about a bleed air leak or monitor the systems function ?

Answer 51

Flight deck gauges Overheat detectors Bleed air monitoring systems