ECS Flashcards
Need for ECS
Humans need protection for the effects that changes in environments cause.
Temperature, its effect
Low temp- Humans cant stand low temps for long as it causes lack in judgement and motor functions. eventually will cause death
high temp-High temps cause you to sweat, if this fails you become overheated leading to fall in mental state, fatigue and unconsciousness.
Humidity.
low moisture content of air causes cold sensation because dry air causes moisture to dry around the body. can be tolerated for a short time before discomfort and lack of efficiency
Cabin environment meaning
methods used are designed to over come injurious effects of the outside atmosphere may cause, provide complete protection for crew and aircrew
aspects of cabin environment
Temperature humidity Ventilation purity pressure
Temperature
maintain suitable temp inside cabin
control release of heat from equiptment and occupants
Humidity
Prevent misting by removing moisture
limit the rise in humidity above certain levels
prevents low humidity
ventilation
prevent CO2 levels from getting to high
stops smells
purity
stop gases from being introduced into cabin, my making air pure
removes fumes and dust that are harmfull to health and can damage systems
pressure
maintain pressure to prevent the harmful effects of high pressure
air conditioning
controls temp. provide air supply to satisfy ventilation and pressurisation requirements. make cockpit comfy
engine bleed air
air condition uses this air from the late compressor stage of the turbine engine.
compressor bleed air is used for deicing and anti ice, cabin pressurisation, heating and cooling systems
Auxillary power unit
a/c with apu can use the bleed air to condition the a/c when it its grounded.
ground trolley
ground vehicle thats used to supply air. when external source is connected, internal check valves open and pressurised air come through. external air/ground receptacle allows this
Ram air
intake ducts guide air into the cabin. forward movement pushes air into the air ducts causing a pressure build up
Air condition
Complete system, control both temp and humidity and heating and cooling if necessary
provide adequate movement of air through vents, cabin doors should come off.
Air cooling
hot compressor bleed air taken from engine , basic physics used to cool air then mix with hot bleed air to achieve desired temps.
heat exchangers
radiatior that has metal fins that catch the hot bleed air, uses cold ram air to cool the bleed air
fans
fans provide air flow to cool heat exchangers
Cold air unit (CAU)
turbine engine extracts energy from burning fuel to turn compressor. compressed air taken from engine bleed air fed into CAU where it turn the fans inside. large amount of its energy is used for this resulting in a pressure loss, resulting in lower temps
water extraction
Moisture from the CAU is fed into a fibreglass sock which catches the moisture, then slung into the sides of the container then carried overboard by the drain valve.
Cabin temp sensor
use in tandem with a/c air con, thermistor with a protective sleeve used to tell the difference.
Whats a thermistor
electrical resistor which resistance is reduced by heating
temperature control.
located in cabin to control temp. cooled air passes through mixer then the controller uses sense difference to determine how much of the mixed air to release, two mode automatic and manual
shut off
ac shutoff valve is used to control the flow of air. can either shut off the valve or modualte the flow of the air
cabin distrobution
Air vents near the feat and lower body parts , controlled by the user. cold air only on vents that are opened by used.
Ventilation
could be a window of little valve that deliver ram air. some fans to help airflow when a/c is grounded.
conditioning systems
hot air from engine compressors routed through primary and secondary heat exchanges and cold air unit.
to provide airstream at req temp, enters mixing chamber where its mixed with recycled cabin air and hot moist bypass air. any water is removed here.
operation of conditioning systems
bleed air enters primary heat exchangers and cooled by ram air before sent to on/off valve.
when off bleed air cannot flow into system
when on bleed air operates at a reduced temp and pressure to the CAU where the air is compressed again.
what happens when air is compressed in the CAU
temp is raised then ducted to secondary heat exchanges where temp is reduced again before flowing into CAU turbine inlet. during passage air is expanded and temp and press reduced. finally sent through water extractor.
what does fully cold mean.
fully cold- at temp control mixer will remain closed. all air is passed into cabin beofr entering both heat exchanges and CAU
what does intermediate temperature mean
air flow of pre cooled air skips secondary heat exchange/CAU, mixed with air from primary heat exchange before entering the cabin.
if temp valve is increase more by pilot it allows more of this air into the cabin
what does hot operation mean
Temperature control valve opened fully al hot air bypass Secondary heat exchanges and is entered into the cabin
cabin warning indicators
failure of these system can cause serious affects., warning system incorporated so that crew can see if one fails. some have individual warning devices but most are at the central warning panel
What is the sign for excessive cabing temp.
illumination of “Air T” on CWP, done by using a “high limit” thermostat which will remain lit until temps return to normal operating level.
