11.4 Flashcards
What stage of the engine is bleed air usually taken from
Compressor
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)
when’s low pressure air bleed air used
During takeoff climb and cruise
When’s hp air used
At low engine RPM during descent or anytime LP air is inadequate
Can the LP and HP bleed ports be opened at the same time.
No
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
What happens to the efficiency of the turbine engine when air is bled
Reduced efficiency as it means there’s less air for combustion
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)
What powers the CAC
Three phase motor
How many CACs are on 787
2
Where do bleed loads place there largely demand
APU
Where does the apu compressor supply air to before being using for heating, anti ice and engine starting
Load compressor
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.
What altitude is bleed air extraction from the apu usually limited too
22,000ft
What does the apu supply via to get to the air con packs
Bleed air duct
What size hose is used to attach the ground cart air supply to the ac pneumatic system
4 inch
What can the ground cart be used for
Pneumatic system troubleshooting
What can the ground cart be used for
Pneumatic system troubleshooting
What direction does the connection point for the ground cart air supply point
Away from ac
What’s adiabatic mean
Temp change without additional or removal of heat
What’s convection mean
Process in which heat is transferred by a large movement of fluid
What’s super heat
Heat energy added to a gas after complete evaporation
What’s latent heat
Heat that causes a change in state with no change in temp
What temperature range can air con systems provide air
21-27 degrees
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
