11.4 Flashcards by Lewis Young

What stage of the engine is bleed air usually taken from

Compressor

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What two stages is air usually bled from the compressor

Which of these is low pressure and which is high pressure

5th (lp) (low stage bleed port) and 9th(hp) (high stage bleed port)

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when’s low pressure air bleed air used

During takeoff climb and cruise

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When’s hp air used

At low engine RPM during descent or anytime LP air is inadequate

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Can the LP and HP bleed ports be opened at the same time.

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What regulates the air pressure from the bleed ports

What do these also acts as

Pressure regulating valve and bleed air valve

Shut off valves through cockpit signals or auto by pneumatic controller

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What happens to the efficiency of the turbine engine when air is bled

Reduced efficiency as it means there’s less air for combustion

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What was made as a result of the disadvantages caused by bleeding air from the turbine engines

Independent cabin compressor (to prevent an increase in fuel consumption)

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What powers the CAC

Three phase motor

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How many CACs are on 787

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Where do bleed loads place there largely demand

APU

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Where does the apu compressor supply air to before being using for heating, anti ice and engine starting

Load compressor

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What 3 methods does the apu use to supply air for air conditioning and cabin pressurisation

Bleed air extracted from the compressor section.
Bleed air extracted from a separate load compressor driven by the turbine power section.
Bleed air extraction from the compressor driven from the two-stage axial turbine.

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What altitude is bleed air extraction from the apu usually limited too

22,000ft

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What does the apu supply via to get to the air con packs

Bleed air duct

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What size hose is used to attach the ground cart air supply to the ac pneumatic system

4 inch

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What can the ground cart be used for

Pneumatic system troubleshooting

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What can the ground cart be used for

Pneumatic system troubleshooting

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What direction does the connection point for the ground cart air supply point

Away from ac

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What’s adiabatic mean

Temp change without additional or removal of heat

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What’s convection mean

Process in which heat is transferred by a large movement of fluid

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What’s super heat

Heat energy added to a gas after complete evaporation

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What’s latent heat

Heat that causes a change in state with no change in temp

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What temperature range can air con systems provide air

21-27 degrees

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What does the air con systems functions

Supply ventilation air Supply heated air Supply cooled air Cabin Pressurisation Equipment Cooling

What are the two types of air con systems

Air cycle machine (used in larger passenger ac) Vapour cycle machines

What temp at psi does the ac bleed air arrive at the primary heat exchanger What temp drop does the primary heat exchanger give

30-40psi 150 c 100 c

What happens to the air from the primary heat exchanger when it goes to the compressor

Increase in pressure and temp (usually +30-40 c)

Where does the air go after the compressor in an air con system and why

To the secondary heat exchanger to remove the added heat from the compressor

Where does the air go after the compressor and why

To the secondary heat exchanger to remove the added heat from the compressor (drops 60-70 c)

Wheres the water from the water extractors go after removed from air

To spray nozzles into the ram air duct to improve cooling efficiency

What speed does the shaft for the turbine wheel, wheels of compressor and the fan (in RPM)

40,000-50,000rpm

What speed does the shaft for the turbine wheel, wheels of compressor and the fan (in RPM)

40,000-50,000rpm

What does the pack valve/ flow control valve do

Valve that regulates bleed air from the pneumatic manifold into the air cycle air conditioning system

How are pack/ flow control valves operated and controlled

Electrically controlled Pneumatically operated

What are pack / flow control valves also referred to

Supply shut off valve

What type of valve is a pack valve

A Venturi type butterfly valve controlled by a solenoid

How are pack valves shut

Spring loaded to shut unless operated pneumatically

How are pack valves shut

Spring loaded to shut unless operated pneumatically

What’s in place as a fail safe for the pack valve if electrical supply is is broken

Opens

What does the manual override on the pack valve allow

For it to stay fixed in a closed position

What’s the main function of the pack valve

Control the airflow to the cabin

On the ground what’s the mass flow brought the pack valve What’s the mass flow at 8,000ft

1.1kg/s 0.86kg/s

How can ac aircraft conditioning systems save energy

By adjusting the amount of airflow t9 the amount of passengers on board

What % of airflow does the cabin receive when the pack flow selector is in the… Normal position High position Low position

Norm- 100% Hi- +100% Low- 80%

What happens to pressure and temp as the air reaches the turbine

Pressure and temp goes down

What are the two types of lubrication for the air cycle machine

Air lubrication Oil lubrication

What two functions does the condenser/reheated have

To heat the air so it’s given energy To cool the air before it goes through the water collector

What low temps can be reached in water separator

-50

What’s bypass airs function

To keep the air temp around 35 deg FAREMHEIT

What are trim air valves used for

Used in systems to Mix conditioned air and provide temp controlled air to cabin and flight deck

What does the mix chamber/manifold do

Collects the temp controlled clean conditioned air from the packs and distributes the warm or cold air to the flight compartments

What do the RAM air door/valves do

Control the quantity of outside ambient air that flows through the primary and secondary heat exchanger This RAM airs purpose is to remove some of the hear

When’s maximum ram air available through the ram air door/valve

Ground and take off

What do the ram air doors do during flight and why

Modulate to reduce drag and ram air

What type of ac used vapour cycle machines

Ones powered by reciprocating engines (piston) Only suitable for piston engines as they do t produce RAM air Sometimes turbine powered tooo

What principle does the vapour cycle machine work on

Thermodynamics

What’s heat energy

Energy transferred by a temp diff

What’s heat energy

Energy transferred by a temp diff

What’s important to remember about the way heat energy travels

One direction only

If the pressure in water increases by 20 psi what temp will it boil at

107.8 c

What’s the refrigeration process

Compression Condenser Receiver-dryer Expansion Evaporation Repeat

What’s the refrigeration process

Compression Condenser Receiver-dryer Expansion Evaporation Repeat

What two problems can water in the refrigerant of the vapour cycle machine cause

Water could cause ice and block the flow of the refrigerant around the system Water and refrigerant can cause acid

What does the thermostatic expansion valve do in the vapour cycle machine

Has an adjustable orffice that allows the correct amount of refrigerant through to obtain optimal cooling

What are evaporators made of

Copper or alluminium tubing coiled into a compact unit

What can reduce the efficiency of the heat exchange to the refrigerant

Ice on the evaporator

What two uses does the compressor isolation valve have

It permits servicing the system with refrigerant. It can isolate the compressor so the oil level can be checked and replenished without opening the entire system and losing the refrigerant charge

What two uses does the compressor isolation valve have (ac system)

It permits servicing the system with refrigerant. It can isolate the compressor so the oil level can be checked and replenished without opening the entire system and losing the refrigerant charge

What two uses does the compressor isolation valve have in refrigerator syst

It permits servicing the system with refrigerant. It can isolate the compressor so the oil level can be checked and replenished without opening the entire system and losing the refrigerant charge

What a distribution ducts made off

Light fibreglass material coated to prevent damage from moisture

What’s important to remember about the distribution ducts changing temperatures depending on the temp desired for cabin

They will expand and shrink but without losing the pressure tight seals of the ducts

What’s a percentage of cabin air is filtered and recirculated ans what’s a positive of this

50% Saves fuel as engines only provide the other 50% of the air

What’s a percentage of cabin air is filtered and recirculated ans what’s a positive of this

50% Saves fuel as engines only provide the other 50% of the air

What are airflow outlets designed to do to the airflow pattern

To make it circular and controlled

What mode is selected when at cruise

Isobaric

What’s the max permissible rate of change in cabin pressure

0.16 psi per min

When are ground tests of the pressure system required

Perform initial proof pressure test. When specified in the maintenance manual. After actual or suspected system malfunction. After repairs and modifications to the aircraft pressure hull.

How much refrigerant should a good leak detector be able to detect it losing in a year

Less than 1/2 ounce a year

How much refrigerant should a good leak detector be able to detect it losing in a year

Less than 1/2 ounce a year

What two other ways are there to detect leaks other than a electronic leak detector

Soapy water and inspect for bubbles Injecting leak detection dyes and observing where they force a leak

When was r12 refrigerant banned and why

1980 Harmful to earths ozone layee

What’s can be used to determine which pneumatic device is at fault in a pressurisation system

EICAS or ecam

What type of fire detector is using for pneumatic ducting

Continuous loop

When would a “overheat” warning for the pack be displayed in the flight deck

When it overheats (outlet temp more than 260 ) or when the outlet temp is more than 230 c (four times in one flight)

What do the colours mean on the central warning panel (r, a, g, w/b)

Red-systems I’m crit condit ans requires immediate temp Amber- requires timely attention or will do soon Green- system ready t9 be used White or blue- system is in use

What do the colours mean on the central warning panel (r, a, g, w/b)

Red-systems I’m crit condit ans requires immediate temp Amber- requires timely attention or will do soon Green- system ready t9 be used White or blue- system is in use

At what cabin altitude is does the central warning system aler the crew of high cabin alt

10,000ft

At what cabin altitude is does the central warning system aler the crew of high cabin alt

10,000ft

What will happen on the 737 if the cabin alt goes above 10,000ft How’s it kept below 8k feet

A warning horn Aural warning system (attention getter)

What alt did Boeing make some cabin alt in 2005

6,500ft

What alt did Boeing make some cabin alt in 2005

6,500ft