Jeppesen Oral- Chapter 14 (Cabin Atmosphere Control Systems )

Question 1

What are the two main gasses that make up our atmosphere?

Answer 1

Nitrogen and oxygen

Question 2

Why are the cabins of most turbine powered aircraft pressurized?

Answer 2

These aircraft fly at such high altitudes that supplemental oxygen would be needed for the occupants if the cabins were not pressurized.

Question 3

Where does the pressurizing air come from on most turbine-powered aircraft?

Answer 3

From the engine turbocharger.

Question 4

What determines the amount of pressurization that an aircraft can use?

Answer 4

The structural strength of the aircraft cabin.

Question 5

How is cabin pressure controlled in a pressurized aircraft?

Answer 5

More pressure than is needed is pumped into the aircraft cabin, and the pressure controller modulates the outflow valve to maintain the correct pressure in the cabin.

Question 6

What is meant by the isobaric mode of cabin pressurization?

Answer 6

The isobaric mode of cabin pressurization is the mode that keeps the cabin altitude constant as the aircraft changes its flight altitude.

Question 7

What is meant by the constant differential mode of cabin pressurization?

Answer 7

After the pressure in the aircraft reaches maximum value that is allowed by structural considerations, the constant differential mode of operation is the mode that holds the pressure inside the cabin a constant amount above the outside air pressure.

Question 8

What is the function of the cabin outflow valve on a pressurized aircraft?

Answer 8

The cabin outflow valve, which is controlled by the pressure controller, maintains the correct amount of pressure inside the cabin.

Question 9

What is the function of the cabin pressure safety valve on a pressurized aircraft?

Answer 9

The cabin pressure safety valve prevents cabin pressure exceeding the maximum allowable differential pressure.

Question 10

Why must pressurized aircraft ave a negative pressure relief valve?

Answer 10

The structure of an aircraft cabin is not designed in such a way that it can tolerate the inside pressure being lower than the outside pressure.

Question 11

What keeps the cabin of a pressurized aircraft from being pressurized when the aircraft is on the ground?

Answer 11

A squat switch on the landing gear holds the safety valve open when the aircraft is on the ground.

Question 12

What are two types of air conditioning systems that may be installed on an aircraft?

Answer 12

Air-cycle systems and vapor-cycle systems.

Question 13

Where does the warm air come from that is used to heat the cabin of a large jet transport aircraft?

Answer 13

Warm compressor bleed air is used.

Question 14

Where does the warm air come from that is used to heat the cabin of most small single-engine reciprocating-engine-powered aircraft?

Answer 14

From a shroud around the engine muffler.

Question 15

Where does the fuel come from that is used in an aircraft combustion heater?

Answer 15

From the aircraft fuel tanks

Question 16

What happens to a combustion heater if the flow of ventilating air is restricted?

Answer 16

If the ventilating air is restricted and the temperature reaches a preset value, the limit switch will cause the fuel to be shut off to the heater.

Question 17

How is the heat removed from an aircraft cabin with a vapor-cycle air conditioning system?

Answer 17

The cabin heat is absorbed by the refrigerant in the evaporator, and it is carried outside the aircraft where it is given up to the outside air in the condenser.

Question 18

What produces the cool air in the air-cycle air conditioning system?

Answer 18

Warm air is blown across the evaporator where its heat is transferred into the refrigerant. The air that leaves the evaporator is cool.

Question 19

Why must air-cycle air conditioning systems incorporate a water separator?

Answer 19

The rapid cooling of the air in the expansion turbine causes moisture to condense in the form of fog. The moisture is trapped in the moisture separator before the air is released into the cabin.

Question 20

What is used as the refrigerant in a vapor-cycle air conditioning system?

Answer 20

A Freon-type liquid refrigerant known as Refrigerant 12

Question 21

What are three ways supplemental oxygen can be carried in an aircraft?

Answer 21

As a high-pressure gas, in its liquid form, and as a solid in the form of a candle.

Question 22

What kind of gaseous oxygen must be used to service an aircraft oxygen system?

Answer 22

Only aviators breathing oxygen. Hospital oxygen and welding oxygen contain too much moisture to be used.

Question 23

What is used to check an oxygen system for leaks?

Answer 23

A special leak detector liquid that is a form of nonoily soap.

Question 24

What is a continuous flow oxygen system?

Answer 24

An oxygen system that continuously flows a metered amount of oxygen into the mask.

Question 25

What is a pressure-demand oxygen system?

Answer 25

An oxygen system that flows oxygen to the mask only when the wearer of the mask inhales. Above a specified altitude, the regulator meters oxygen under pressure into the mask when the wearer inhales.

Question 26

What identification must be stamped on an oxygen bottle that is carried in an aircraft?

Answer 26

The identification DOT 3AA or DOT 3HT, the date of manufacture, and the date of all of the hydrostatic tests.

Question 27

Is there a special requirement as to the type of oxygen used in aircraft systems, and if so, what is it?

Answer 27

Only aviator’s breathing oxygen should be used.

Question 28

Describe the operating principle of a continuous-flow oxygen system.

Answer 28

High-pressure oxygen flows from the storage cylinder to a pressure regulator where it is reduced and then to the mask outlets whenever the system is turned on.

Question 29

Describe the operating principle of a pressure-demand oxygen system.

Answer 29

Demand systems allow oxygen to flow from the cylinder to the regulator and them to the mask only when the user inhales. Pressure-demand systems provide oxygen to the mask at higher than atmospheric pressure when used at extremely high altitudes, forcing oxygen into the user’s lungs.

Question 30

Why should be used to purge an oxygen system of moisture?

Answer 30

Oxygen, dry air, or dry nitrogen.

Question 31

What action must be taken when an oxygen system has been open to the atmosphere?

Answer 31

The system must be purged of any moisture.

Question 32

Describe the safety precautions that should be observed when servicing oxygen systems.

Answer 32

Avoid all contact with petroleum based oil or grease, don’t smoke, keep everything very clean, service systems outdoors if at all possible, and keep the caps on the bottles to protect the valves.

Question 33

What is a Roots blower?

Answer 33

A type of engine-driven compresor

Question 34

Name two different types of independent cabin air compressors.

Answer 34

Positive-displacement and centrifugal

Question 35

What is the source of pressurization air in most jet aircraft?

Answer 35

bleed air

Question 36

What device provides the principle means of controlling cabin pressure?

Answer 36

outflow valve

Question 37

What unit regulates the position of an outflow valve?

Answer 37

The cabin pressure controller

Question 38

Name several methods used on reciprocating-engine aircraft for providing heated cabin air.

Answer 38

Exhaust shroud heat exchangers, combustion heaters, and electric heaters.

Question 39

What is the function of the ventilating air in a combustion heater?

Answer 39

Ventilating air transports the heat from the heater into the cabin and prevents combustion gasses from entering the cabin if the combustion chamber develops a crack

Question 40

What are the sources of ventilating air in a combustion heater?

Answer 40

Ram air in flight, a blower on the ground, or possibly a compressor if the airplane is pressurized.

Question 41

Name the basic components of an air-cycle cooling system.

Answer 41

The compressor and expansion turbine, heat exchangers, and various valves.

Question 42

Describe the basic operating principles that allow an air-cycle system to produce cool air.

Answer 42

Hot engine bleed air is cooled in the primary heat exchanger, compressed, then cooled again in the secondary heat exchanger. This air is expanded across the turbine where energy is extracted and the pressure is reduced. This produces a large temperature drop.

Question 43

Describe the basic operating principles of a water separator.

Answer 43

Cool, moist air is swirled so that water droplets are separated by centrifugal force, captured by a sock, and drained.

Question 44

Name the principle components of a vapor-cycle system.

Answer 44

A compressor, condenser, expansion valve, and an evaporator.

Question 45

In what significant way is a vapor-cycle cooling system different from an air-cycle system?

Answer 45

Vapor-cycle systems use refrigerant liquid, usually Freon.

Question 46

Why is oil added to the refrigerant in a vapor-cycle air conditioning system?

Answer 46

To lubricate the compressor.