Chapter 11: Air Cycle Air Conditioning Flashcards
what does the pneumatic system provide high pressure air for?
aircon, wing anti icing, water pressurisation & engine starting
sources of air
1) engine
2) APU
3) ground cart
purpose of pack valve
regulates bleed air from pneumatic manifold into air cycle conditioning system
function of refrigeration bypass valve
bypasses warm air around ACM when opened
regulates temperature of ACM discharge air to prevent it from freezing in the water separator
function of water separator
condenses and coalesces the mist into large water droplets > swirls air & water inside separator > water is collected at the side & drained out, dry air sent to cabin
what does the cabin temperature controller control?
turbine bypass valve, low limit valve, ram air doors
how do airports provide conditioned air to the aircraft? and why?
air-handling unit
AHU uses electricity while APU uses fuel (more environment friendly)
advantages of using fixed points systems in airports
1) facilitates removal of service vehicles
2) units can be serviced independently (turnaround shortened)
3) increases safety & capacity, improved ground service
what % of air is recirculated in cabin?
50%
what are HEPA filters? and why is it needed?
high-efficiency particulate air
ensure cabin air quality, protection against dust, fibers, microbes
3 mechanisms in fine air filters
1) direct interception
2) inertial impaction
3) diffusional interception
what is direct interception in air filters?
removes particles bigger than filter pore size
what is inertial impaction
particles smaller than filter pore size, leaves streamline and captured by fibers in filter
what is diffusional interception
small particles below 0.2 microns (Brownian motion, random movements to stick to fiber and pore walls)
how is ozone control achieved?
2 valves control airflow > upper valve opens at altitudes up to 26k ft > lower valve opens above 26k ft > lower valve allows air to enter ozone converter before entering cabin
