11.4 Air Con & Cabin Air Supply Flashcards
what are the three ways an aircraft can recieve pressurised air?
- engine bleed air
- auxiliary power unit
- ground source (air cart)
what is used to control the amount of air releases out of the aircraft and keeps the cabin pressurised ?
outflow valves
what stages are bleed air taken from in a turbine engined aircraft?
5th and 9th stages
when tapping bleed air from a turbine engine, what pressure air is from the 5th stage and 9th stage ?
air tapped from the 5th stage is considered low pressure, and from the 9th stage is high pressure
when is low pressure bleed air used?
during take-off, climb and cruise conditions
when is high pressure bleed air used?
during low engine RPM speeds during descent
what is used to adjust air pressure ?
a pressure regulating valve or the bleed air valve
what is the main disadvantage of using bleed air as a power source ?
reduces engine efficiency
what can be used to reduce the need of bleed air as a pnuematic source ?
independent cabin compressors
what are the three catagories that compressors can be divided into ?
- positive displacement compressors ( roots-type blower)
- centrifugal compressors
- turbo compressors
what needs to be fitted with all positive displacement type pumps?
relief valves/ outflow valves
when is the centrifugal cabin compressor at it’s optimal function?
at high altitudes with a low engine RPM
although turbo compressors are very good at supplying air to the cabin, what is a major problem with them ?
they use engine bleed air to compress air, reducing engine efficiencey
where can the APU supply air to?
the load compressor for heating
anti ice
engine starting
where should the APU be used ?
usually on ground only
