air conditioning systems Flashcards
the human body is not capable of withstanding the cold temperatures and lack of oxygen at these altitudes. if exposed to these conditions, a person would soon succumb to problems such as ________ and __________, eventually leading to unconsciousness and death
the human body is not capable of withstanding the cold temperatures and lack of oxygen at these altitudes. if exposed to these conditions, a person would soon succumb to problems such as HYPOXIA and HYPOTHERMIA, eventually leading to unconsciousness and death
air conditioning air supplies on commercial aircraft: (4)
- gas turbine compressors
- engine driven blowers
- APU compressors
- ambient ram air inlets
the major components of gas turbine beed air conditioning systems: (6)
- air selector valves from engine/APU
- isolation and non-return valves
- air conditioning packs
- mixer chambers
- distribution systems
- recirculation fans
air conditioning. the cooling packs are controlled by ________-pneumatic pack valves
the cooling packs are controlled by ELECTRO-pneumatic pack valves
air conditioning. the pack valves are opened initially or closed by switches on the pilots ________ panel
air conditioning. the pack valves are opened initially or closed by switches on the pilots OVERHEAD panel
air conditioning. each cooling pack supplies cold air to the main ____________ manifold
air conditioning. each cooling pack supplies cold air to the main DISTRIBUTION manifold
air conditioning. cold air is ducted through the _______ system
air conditioning. cold air is ducted through the GASPER system
air conditioning pack valves. they also meter the airflow to the pack. when the APU is supplying the air, the flow rate is _________
air conditioning pack valves. they also meter the airflow to the pack. when the APU is supplying the air, the flow rate is INCREASED
air conditioning pack valves. the valves are ___________ operated and _____________ controlled
air conditioning pack valves. the valves are PNEUMATICALLY operated and ELECTRICALLY controlled
when the engine low pressure stage cannot supply the required amount of air, the pneumatic system will automatically open the engine _____ pressure stage to satisfy the needs of the air conditioning system
when the engine low pressure stage cannot supply the required amount of air, the pneumatic system will automatically open the engine HIGH pressure stage to satisfy the needs of the air conditioning system
overheat protection. if the ACM (air cycle machine) compressor _________ overheat switch, or the ACM _______ inlet overheat switch are actuated, the pack valve will close. the air cycle machine will then stop.
overheat protection. if the ACM (air cycle machine) compressor DISCHARGE overheat switch, or the ACM TURBINE inlet overheat switch are actuated, the pack valve will close. the air cycle machine will then stop.
cold air units/air cycle machines. the hot air is cooled in the ________ heat exchanger and enters the cold air unit via the _____ inlet of the compressor and is compressed by the action of the compressor ________ and passes through the secondary heat exchanger which dissipates a large proportion of the heat produced by compression
cold air units/air cycle machines. the hot air is cooled in the PRIMARY heat exchanger and enters the cold air unit via the AXIAL inlet of the compressor and is compressed by the action of the compressor IMPELLER and passes through the secondary heat exchanger which dissipates a large proportion of the heat produced by compression
cold air units/air cycle machines. the air also _______ in passing through the turbine wheel; the pressure drop causing further _______ of the air.
the heat energy extracted is converted into __________ energy by the turbine
cold air units/air cycle machines. the air also EXPANDS in passing through the turbine wheel; the pressure drop causing further COOLING of the air.
the heat energy extracted is converted into MECHANICAL energy by the turbine
cabin humidity control. on relatively _____ flights at high altitude, the relative humidity in the cabin is maintained at a comfortable level by ___________ of moisture from furnishings, clothing, etc. and humidifiers are not normally provided.
however, aircraft which normally undertake long flights at high altitudes may be provided with humidifiers to maintain the relative humidity at about __%
cabin humidity control. on relatively SHORT flights at high altitude, the relative humidity in the cabin is maintained at a comfortable level by EVAPORATION of moisture from furnishings, clothing, etc. and humidifiers are not normally provided.
however, aircraft which normally undertake long flights at high altitudes may be provided with humidifiers to maintain the relative humidity at about 30%
cabin humidity control. when humidification is required, the water control is opened either manually or automatically, and the water jet impinges at _____ angles on the high pressure ___ jet which is also operating
cabin humidity control. when humidification is required, the water control is opened either manually or automatically, and the water jet impinges at RIGHT angles on the high pressure AIR jet which is also operating
operation of three wheel air cycle machine system. three wheel air cycle machines, or cold air units, incorporate a ___ which is used to induce airflow across the heat exchangers.
this allows what is basically a ________ cooling system to function of the ground when ram air cooling for the heat exchangers is not available
operation of three wheel air cycle machine system. three wheel air cycle machines, or cold air units, incorporate a FAN which is used to induce airflow across the heat exchangers.
this allows what is basically a BOOTSTRAP cooling system to function of the ground when ram air cooling for the heat exchangers is not available
operation of three wheel air cycle machine system. ____________ is a technique though which something is brought into the desired state through its own action. in the case of the air cycle machine, the hot air is cooled through its own action
operation of three wheel air cycle machine system. BOOTSTRAPPING is a technique though which something is brought into the desired state through its own action. in the case of the air cycle machine, the hot air is cooled through its own action
recirculation fan. the fan is an _____ vane type fan. it is fitted within the recirculation air ducting and draws used conditioned air from the cabin. it is placed downstream of the check valve.
the fan drives the cabin air to the mixer where it is mixed approximately __% fresh air to 40% recirculated cabin air, before returning to the cabin
recirculation fan. the fan is an AXIAL vane type fan. it is fitted within the recirculation air ducting and draws used conditioned air from the cabin. it is placed downstream of the check valve.
the fan drives the cabin air to the mixer where it is mixed approximately 60% fresh air to __% recirculated cabin air, before returning to the cabin
ozone converters. atmospheric ozone is separated out by passing through the ___________ stages of the engines, the air conditioning packs and the ozone converters
the ozone separates out further when in contact with air ducting within the aircraft, interior surfaces and the aircrafts recirculation system
the ozone converter separates out the ozone and by the ________ action of the substance contained within the converter (noble metals such as __________) converts the ozone to oxygen
a modern ozone converter is capable of converting up to __% of the ozone entering it to oxygen and has an average life of approximately _____ flying hours
ozone converters. atmospheric ozone is separated out by passing through the COMPRESSOR stages of the engines, the air conditioning packs and the ozone converters
the ozone separates out further when in contact with air ducting within the aircraft, interior surfaces and the aircrafts recirculation system
the ozone converter separates out the ozone and by the CATALYTIC action of the substance contained within the converter (noble metals such as PALLADIUM) converts the ozone to oxygen
a modern ozone converter is capable of converting up to 95% of the ozone entering it to oxygen and has an average life of approximately 12000 flying hours
description and operation of displacement blower system. provided the spill valves are selected to AUTO, a ___ ____ selection will _______ the mass flow controller, _____ the temperature control valve and bring the spill valves under control of the cold air duct pressure and temperature switches
description and operation of displacement blower system. provided the spill valves are selected to AUTO, a MAX COOL selection will ISOLATE the mass flow controller, CLOSE the temperature control valve and bring the spill valves under control of the cold air duct pressure and temperature switches
mass flow control and the spill valve. each blower is capable of maintaining air conditioning and pressurisation of the cabin at ________ altitude.
therefore when both blowers are operating normally, the excess air supplied must be _______ off.
excess air is spilled off by opening or closing a _____ valve
mass flow control and the spill valve. each blower is capable of maintaining air conditioning and pressurisation of the cabin at CRUISING altitude.
therefore when both blowers are operating normally, the excess air supplied must be SPILLED off.
excess air is spilled off by opening or closing a SPILL valve
mass flow control and the spill valve. the spill valves are __________ operated and may be controlled as follows:
- directly via ___ switches on a control panel in the control cabin
- automatically via the ____ ____ _________ which senses the mass flow through the cabin delivery duct
- automatically via _________ switches and a ___________ switch which senses pressure and temperature in the ducting
mass flow control and the spill valve. the spill valves are ELECTRICALLY operated and may be controlled as follows:
- directly via TWO switches on a control panel in the control cabin
- automatically via the MASS FLOW CONTROLLER which senses the mass flow through the cabin delivery duct
- automatically via PRESSURE switches and a TEMPERATURE switch which senses pressure and temperature in the ducting
mass flow controller. the mass flow controller contains a _________ which responds to ________ pressures. duct pressure is applied below the diaphragm and venturi throat pressure above it.
should the flow rate increase above a pre set value, the lower pressure in the venturi will cause the diaphragm to deflect _______ completing the electrical circuit to open the spill valve and ________ the flow
should the flow rate ________ below the pre set vale, the diaphragm will deflect __________, decreasing the amount of air being spilled
mass flow controller. the mass flow controller contains a DIAPHRAGM which responds to VENTURI pressures. duct pressure is applied below the diaphragm and venturi throat pressure above it.
should the flow rate increase above a pre set value, the lower pressure in the venturi will cause the diaphragm to deflect UPWARDS completing the electrical circuit to open the spill valve and DECREASE the flow
should the flow rate DECREASE below the pre set vale, the diaphragm will deflect DOWNWARDS, decreasing the amount of air being spilled
equipment cooling systems. equipment cooling occurs as long as _________ _____ is available
loss of airflow due to failure of an equipment cooling fan causes __________ heat to activate a thermal switch, illuminating the respective equipment cooling ___ light. selecting the _________ fan will restore airflow past the switch and extinguish the OFF light
equipment cooling systems. equipment cooling occurs as long as ELECTRICAL POWER is available
loss of airflow due to failure of an equipment cooling fan causes INCREASING heat to activate a thermal switch, illuminating the respective equipment cooling OFF light. selecting the ALTERNATE fan will restore airflow past the switch and extinguish the OFF light
basic vapour cycle cooling system. the principle of vapour cycle cooling is based on the ability of a ____________ to absorb heat in the process of changing from a liquid to a gas
after the gas has absorbed all its ______ heat of vaporisation, it can be compressed and condensed back into its liquid state
this is done by removing the heat of vaporisation and compression. in their liquid state, refrigerants are able to assume their former heat __________ ability
basic vapour cycle cooling system. the principle of vapour cycle cooling is based on the ability of a REFRIGERANT to absorb heat in the process of changing from a liquid to a gas
after the gas has absorbed all its LATENT heat of vaporisation, it can be compressed and condensed back into its liquid state
this is done by removing the heat of vaporisation and compression. in their liquid state, refrigerants are able to assume their former heat ABSORPTIVE ability
basic vapour cycle cooling system. the components of a basic vapour cycle system are:
- ________ dryer
- thermostatic _________ _____
- eva______
- com______
- con______
basic vapour cycle cooling system. the components of a basic vapour cycle system are:
- RECEIVER dryer
- thermostatic EXPANSION VALVE
- evaPORATOR
- comRESSOR
- conDENSER
compressor. the compressor is designed to raise the pressure of the __________ vapour from evaporator pressure to condensing pressure
it also supplies the refrigerant to the __________ at a pressure and temperature at which it can be easily condensed back into liquid
the compressor also lowers the ________ in the __________, assisting the evaporation of the refrigerant
compressor. the compressor is designed to raise the pressure of the REFRIGERANT vapour from evaporator pressure to condensing pressure
it also supplies the refrigerant to the CONDENSER at a pressure and temperature at which it can be easily condensed back into liquid
the compressor also lowers the PRESSURE in the EVAPORATOR, assisting the evaporation of the refrigerant
vapour cycling system servicing. charging hoses.
charging hoses used with ______ valves must have a pin to depress the valve.
these hoses are normally colour coded to quickly identify them
the high side hose is ___, the low side hose is ____ and the centre hose is usually ______
when not in use the hoses must be ______ to prevent moisture contaminating the valves
vapour cycling system servicing. charging hoses.
charging hoses used with SHRADER valves must have a pin to depress the valve.
these hoses are normally colour coded to quickly identify them
the high side hose is RED, the low side hose is BLUE and the centre hose is usually YELLOW
when not in use the hoses must be CAPPED to prevent moisture contaminating the valves
properties of a refrigerant.
refrigerants used in aircraft installations must have the following properties:
- non-_________
- non-_________
- non-_____, both in pure state and mixed with air
- the refrigerant must not react unfavourably with ___________ oils used within the system
- ideally the lubricating oil should be ________ with the refrigerant
- non-_________
aircraft refrigeration systems either use or are being modified to use refrigerant _-____ which is a new chlorine free refrigerant called tetrafluoroethane
properties of a refrigerant.
refrigerants used in aircraft installations must have the following properties:
- non-FLAMMABLE
- non-EXPLOSIVE
- non-TOXIC, both in pure state and mixed with air
- the refrigerant must not react unfavourably with LUBRICATING oils used within the system
- ideally the lubricating oil should be MISCIBLE with the refrigerant
- non-CORROSIVE
aircraft refrigeration systems either use or are being modified to use refrigerant R-134a which is a new chlorine free refrigerant called tetrafluoroethane
refrigerant handling precautions
- always wear _______ ________ when handling refrigerants. any liquid refrigerant which may accidentally escape is at an extremely ___ temperature. serious injury could result if refrigerant comes into contact with ____
- do not ___ the eyes. rinse the eyes with cold water to gradually get the temperature above the freezing point
- apply a protective film of __________ oil over the eyeball to reduce the possibility of infection
- consult a doctor immediately
- should the refrigerant come into contact with the skin, it should be treated as though the skin has been _____ ______ or ______
- do not release refrigerant into the __________
- if refrigerant vapour comes into contact with a naked flame, a _________ gas is produced. DO NOT SMOKE
refrigerant handling precautions
- always wear SAFETY GOGGLES when handling refrigerants. any liquid refrigerant which may accidentally escape is at an extremely LOW temperature. serious injury could result if refrigerant comes into contact with EYES
- do not RUB the eyes. rinse the eyes with cold water to gradually get the temperature above the freezing point
- apply a protective film of ANTISEPTIC oil over the eyeball to reduce the possibility of infection
- consult a doctor immediately
- should the refrigerant come into contact with the skin, it should be treated as though the skin has been FROST BITTEN or FROZEN
- do not release refrigerant into the ATMOSPHERE
- if refrigerant vapour comes into contact with a naked flame, a POISONOUS gas is produced. DO NOT SMOKE
combustion heaters
the combustion heaters are supplied with fuel from the aircraft ____ ____ _____, which is burnt in a combustion chamber kept at a positive pressure by a _______ ___
the combustion air enters the chamber at an angle to promote a ________ _____ combustion, which ensures even burning of the fuel and heating of the ________ walls
combustion heaters
the combustion heaters are supplied with fuel from the aircraft MAIN FUEL TANKS, which is burnt in a combustion chamber kept at a positive pressure by a BLOWER FAN
the combustion air enters the chamber at an angle to promote a WHIRLING FLAME combustion, which ensures even burning of the fuel and heating of the CHAMBER walls
combustion heater operation
by cycling on and off the heater maintains the reselected cabin temperature as set by the pilot on the heater control panel
should the heater temperature exceed a ground set temperature (usually about ___ degrees C), a __________ limit switch will close the fuel valve, opening it again once ________ condition is corrected
additionally, should the temperature continue to rise, possibly caused by a fault in the __________ and limit switch, then the overheat switch will shut the combustion heater down, and it cannot be _________ in flight
when the overheat switch operates, it will illuminate the overheat _____ on the flight deck heater control panel to advise the flight crew that the combustion heater is now ___________
combustion heater operation
by cycling on and off the heater maintains the reselected cabin temperature as set by the pilot on the heater control panel
should the heater temperature exceed a ground set temperature (usually about 100 degrees C), a TEMPERATURE limit switch will close the fuel valve, opening it again once OVERHEAT condition is corrected
additionally, should the temperature continue to rise, possibly caused by a fault in the THERMOSTAT and limit switch, then the overheat switch will shut the combustion heater down, and it cannot be RESTARTED in flight
when the overheat switch operates, it will illuminate the overheat LIGHT on the flight deck heater control panel to advise the flight crew that the combustion heater is now INOPERATIVE
carbon monoxide detector
the carbon monoxide detector consists of a small plastic card incorporating a ____ chemical spot
if CO is present, the spot will turn ____ or _____ within __ minutes, even slight darkening indicates dangerous CO concentration
when the air freshens, the spot may turn pink again and can be ______. the pink spot may darken gradually after about a _____ and should be replaced.
the CO detector usually has a shelf life of _____ years in an unopened pack
carbon monoxide detector
the carbon monoxide detector consists of a small plastic card incorporating a PINK chemical spot
if CO is present, the spot will turn GREY or BLACK within 15 minutes, even slight darkening indicates dangerous CO concentration
when the air freshens, the spot may turn pink again and can be REUSED. the pink spot may darken gradually after about a MONTH and should be replaced.
the CO detector usually has a shelf life of THREE years in an unopened pack
carbon monoxide
the maximum concentration of CO permitted in an aircraft cabin is __ parts per million by volume or _ part in 20000
carbon monoxide
the maximum concentration of CO permitted in an aircraft cabin is 50 parts per million by volume or 1 part in 20000
