M11.4 Flashcards
What are the two ways to separate water in the temperature control pack?
High-pressure loop or low-pressure loop
What is the function of the jet pump in the low-pressure system?
It sprays condensed water into the RAM air inlet duct to increase the cooling efficiency of the heat exchanger
What is a coalescer?
It is a strainer/gauze filter that combines water particles to make them into larger water droplets
When the differential pressure increases between the water separator inlet and outlet what does the pack controller assume is the fault and how does it counteract this?
It assumes that there is ice and counteracts this by opening the turbine bypass valve more
In a high-pressure loop what component could clog with ice?
The condenser
What is the minimum number of sensors you must have in a pack, and what are they?
Three; compressor discharge pressure temperature sensor, pack discharge temperature sensor and compressor overheat switch
If a pack controller fails, what protection is provided?
There is a backup pack controller
If the bypass valve fails in the open position what does the pack controller trigger and why?
Triggers the RAM air doors to open more, in order to keep the pack cool
What do the letters ECS stand for?
Environmental control system
On the ground, what position are the RAM air doors in?
They are fully open
What are the five things and air-conditioning system must provide?
Fresh, clean air, at a comfortable temperature and the correct humidity and pressure
What do regulations state about fresh air?
An acceptable limit of fresh air is 0.283 m³ per minute per person
What do we ensure about the cabin temperature?
That it ranges between 18 and 30°C
What does humidity of air depend on?
Air Temperature
Cabin pressurisation is a compromise between what?
Passenger comfort and structural design
Do you heat exchanges work using either: Conduction, convection or radiation?
Conduction
What is the function of the cooling pack?
It is to cool hot bleed air to a given value by the pack controller
What temperature and pressure is the bleed air at when it reaches the pack control valve?
200°C and 45 to 50 psi
What is the sequential process that the vapour cycle machine uses?
Evaporation, expansion, condensing and compression
What is the purpose of the ozone converter and what material is employed to do this?
To remove ozone by converting it to oxygen by using palladium
What is the purpose of the pack control valve?
It controls the amount of air that goes into the cabin
How is the pack control valve operated?
It is pneumatically operated and solenoid controlled
If the pack valve solenoid is energised and there is no flow, what position will the valve take and why?
Closed because of spring pressure
How does the air cycle machine cool air?
Hot air is cooled by the primary heat exchanger, then it is compressed which increases pressure and temperature, it then gets passed through the secondary/main heat exchanger is where temperature decreases and pressure stays the same and then the turbine expands the air reducing temperature and pressure and then cool air is produced.
If the compressor overheat sensor operates, what action will the pack controller attempt?
It will reduce flow through the pack control and open the RAM air doors more.
What does EBA stand for?
Engine bleed air
How many compressor stages are there for bleed air?
Two; intermediate pressure (IP) and high-pressure (HP)
Why is there a check valve fitted between intermediate and HP bleed off takes?
So that air that comes off the high-pressure line cannot bleed into the engine by the intermediate pressure line
How is pneumatic air distributed?
Via ducts
What are the three areas that are not pressurised?
Landing gear bays, tailcone and the radome
How do you calculate volumetric flow?
By dividing mass flow by density
When is all conditioned air not necessary on aircraft?
When the plane is not full of passengers
When the pack flow selector is in low position, what percentage airflow is supplied to the cabin?
80%
How many heat exchanges do modern packs have and what are they called?
Two, primary heat exchanger and the secondary or main heat exchanger
What are the air cycle machines main parts?
Compressor, turbine and fan
Regarding lavatories, do some aircraft have reserve extraction fans?
Yes
Are lavatories and galleys ventilated in the same way?
Yes
In the equipment cooling system, how many normal modes exist in automatic operation and what are they?
Two; inboard and outboard
If a low flow situation is detected in equipment cooling system, what’s the first thing to occur?
A signal will be sent to the equipment cooling system computer
What happens in the equipment cooling system if a component fails or if there is smoke detected?
The flight crew would get an indication from the controller and then would have to manually operate the cooling system
What are the two ways the cargo compartment can be heated?
Are using hot bleed air from the pneumatic system or by an electrical heater combined with blowers
Electrical heaters start heating the cargo compartment at around what temperature?
7°C
What is activated if a dramatic temperature increase occurs in the cargo compartment?
The overheat circuit
How is the cargo temperature adjusted and where from?
By a selector on the cabin temperature control panel
Through what tubes does the condition end of the cargo compartment and where are these tubes found?
Spray tubes in the cargo compartment ceiling
What are the two types of temperature sensors in the zone control system?
Duct temperature sensors and zone temperature sensors
How are the temperature sensors in the zone control system ventilated?
By the lavatory ventilation or the equipment cooling system or by an electrical fan
What indications are a typical air-conditioning system page?
Actual cabin temperature, actual duct temperature and the actual trim air valve position.
When talking about cargo ventilation what are the four different ventilation types for cargo compartments?
Nonventilated cargo compartments, ventilated and heated cargo compartment, ventilated and heated cargo compartments and air-conditioned cargo compartments
In a ventilated cargo compartment how can we increase airflow?
By the use of a blower fan or extractor fan
When there is a negative cabin rate does pressure increase or decrease?
Increase
True or false? The pressurised cabin get a constant airflow from the air conditioning system?
True
When cabin altitude increases above normal values what three things must happen?
At 10,000 feet the flight crew get a warning to put on their oxygen masks. At 14,000 feet the oxygen mask is automatically released from the passenger cabin ceiling. At 15,000 feet the outflow valve’s must close automatically and independently of the normal control signal
True or false? When the differential pressure increases the stress on the aircraft structure also increases.
True
What are the three modes of the cabin pressurisation system?
Automatic, semi automatic and manual
What is the mixing chamber also known as?
The plenum chamber
What are the two ways in which the cockpit is conditioned?
And directly from the pack before it goes to the mixing unit or air is taken from the mixing unit but because of the cockpits position it only gets freshly conditioned air
What system supports the packs in making conditioned cabin air thus reducing the packs workload?
The recirculation system
How is the gasper system supplied with air?
It is supplied by normal cabin air or an individual supply duct
The mixing unit mixes what to sources of air?
Cold air from the packs and discharged cabin pressure
What is the function of the emergency air RAM inlet?
It will supply ambient air to the mixing unit in case all the packs fail during flight
Name three parameters that can affect cabin temperature?
Ambient temperature, radiation from the sun, cabin insulation (Also; heat from equipment, heat from passengers and rate and temperature of the air supply to the cabin)
In regards to automatic control, what temperature ranges usually set on the cabin selector?
18 to 30°C
In regards to the trim air system, what is the purpose of a protection circuit?
To prevent the system from duct overheat
In the trim air system, how are the valves usually operated?
By an electrical stepper motor
What is the function of the ditch push button on the Control Panel?
Closes all the valves below the flotation line of the aircraft
What does pre-pressurisation mode prove and also prevent?
Proves that there are no leaks from the cabin and to prevent pressure fluctuations during aircraft rotation when the airflow hits open valves
What is internal climb mode also known as?
Proportional mode
In the external climate control of calculates what kind of cabin rate?
It calculate a smooth and constant cabin rate
During normal operation of the safety valve is kept closed by?
Spring pressure
During a pressure leakage test the cabin is pressurised to what pressure higher than the ambient pressure?
Four psi
Give an example of how you would protect the liquid tanks against pressure damage during a pressure test?
By filling them
Prior to performing a cabin leakage test what must you do?
Inform personal and put barriers in place
Before the cabin pressurisation leak test starts which lights must be switched on?
Aircraft beacon lights
In aircraft with two cabin pressure controllers the controller in command is changed when?
At touchdown
