36 Pneumatic

Question 1

what are two classifications of types of pneumatic systems

Answer 1

high pressure systems (~200bar)

low pressure systems (~3bar)

Question 2

what is a high pressure pneumatic system comparable to? what is the key difference?

Answer 2

hydraulic system

hydraulic-> non compressible fluid
hp pneumatic -> compressible gas
-no reservoir for hp pneumatic

Question 3

what are the advantages and disadvantages of hp pneumatic compared to hydraulics

Answer 3

+:

• air is readily available, nonaggressive, lightweight, clean
• no need for return lines
• :
• energy loss in compressing air
• very important to demoisturize air because freezing can be a real problem
• power is highly load dependent. Can be difficult to control exact actuator position even once it is reached.
• not as instant of responce

Question 4

how common are hp pneumatic systems?

Answer 4

highly uncommon

Question 5

what are the common lp pneumatic consumers

Answer 5

• air conditioning
• anti-icing (wing and engine nacelle)
• pressurizing hyraulic fluid resevoirs
• engine start
• presurize potable water tank
• air-driven hydraulic pumps

Question 6

what are possible sources of pressurized air? which is the most common?

Answer 6

ram air, supercharger, turbocharger, engine driven compressor, bleed air

most common: bleed air

Question 7

where is bleed air taken from? how is this controlled?

Answer 7

IP stages of the compressor (during cruise) of HP stages of the compressor (when I is not adequete such as circling, or ___ ie when the engine is in idle)

Question 8

what controls where the engine bleed air is taken from?

Answer 8

pressure control valve detects if IP is enough. THere is a valve to shut IP is HP is being taken to prevent airflow from HP to IP

Question 9

what are some typical system components of a bleed air system?

Answer 9

• HP bleed valve,
• IP bleed valve,
• pressure regulating valve
• precooler
• fan air valve
• isolation valve
• crossbleed valve
• check valves