13.18 Pneumatic/Vacuum Flashcards
(48 cards)
What are the advantages of pneumatic systems?
Lightweight
Safe
Reliable
Eco–friendly
Small (can be)
Unaffected by atmospheric changes
Inexpensive components
Pressure seals are usually problem free
Forces transmitted are easy to manage (within acceptable PSI limits)
What is caused by increasing the pressure of a volume of air, and what is therefore required in a compressor?
Increasing pressure causes an increase in temperature
Cooling fins on the compressor
How does a compressor increase the pressure of the air?
Volume of each successive stage is smaller than the preceding one
What stage of air is exhausted to atmosphere when the pressure regulator is open?
Third stage air
What encourages the air to spin in a oil and water trap?
Radial drillings
In a pneumatic system, what component is used to remove the last of the oil and water from the system?
Dehydrator
What is contained in the dehydrator which will remove oil and water from the air?
Dessicant – Activated alumina
What should be carried out if moisture is found in the air filter housing?
Oil and water trap should be examined for faults
What are commonly used as filters in the pneumatic system filters?
Paper gauze
Glass wool
Felt
Fine metal mesh
How are air storage cylinders usually mounted?
In the upright position
How is the operating pressure of a relief valve changed?
Adjustable by means of increasing or decreasing spring pressure
How does a pressure maintaining valve operate?
Allows pressure to primary/essential systems as well as secondary/non–essential systems
At a loss of pressure, shuts off pressure to secondary/non–essential
What might a pressure maintaining valve also be called?
Priority or pressure regulating valve
In a pneumatic actuator, how is damping achieved?
Forcing grease through an annular space between the inner wall of the piston rod and a stationary damper piston
What might air extracted from gas turbine engines also be known as?
Charge air
What might charge air be used for?
Cabin air conditioning and pressurisation
Anti–icing
Drinking water pressurisation
Hydraulic reservoir pressurisation
In an engine air bleed pneumatic system, what is the main supply of compressed air provided by?
Low pressure/intermediate stages of the engine compressor
In an engine air bleed pneumatic system, what happens under reduced power settings?
High stage valve will open to allow the high–pressure compressor to satisfy the demands of the user system
In an engine air bleed pneumatic system, what does the distribution system do?
Interconnects the engine bleeds and the bleed from the APU
Contains all the necessary valves to shut off bleed air at each engine and isolates various ducts
Where does some of the hot air from the low/intermediate stage compressor go?
Forward to the engine cowling anti–icing system if selected
When will a pressure relief valve open in the duct coming from the low/intermediate stage compressor?
If the duct pressure exceeds 100 lb/in²
In an engine air bleed pneumatic system, what are the four functions of the Pressure Regulator and Shut–off Valve?
Opens or closes in response to the control switch on the bleed air control panel in the crew compartment, or when temperature and pressure limits are exceeded (will also close when the engine fire handle is operated to arm the extinguisher circuit)
Prevents reverse flow when duct pressure exceeds engine supply pressure
Modulates to limit pressure in the pneumatic manifold to approximately 45 lb/in²
Limits temperature to 230 °C
In an engine air bleed pneumatic system, what is the pre–cooler also known as, and what temperature does it cool bleed air to?
200°C to 230 °C
In an engine air bleed pneumatic system, how does a pre–cooler cool the bleed air?
Uses cold air from the engine fan
