11.16 Pneumatic System Flashcards
What is aircraft pneumatic energy used for?
. Engine starting
. Cabin press and air conditioning
. Wing anti ice
. Water reservoir pressurisation
. Hydraulic pressurisation
What is the main source of air for pneumatic system?
Engine compressor or APU
When on ground what can supply external air?
HP ground connectors
What does the change in thrust cause?
Varying amount of air pressure
What is used to maintain the constant level of pressure and regulate bleed supply?
Bleed valve (pressure regulator)
What type of valve is a bleed valve?
Pneumatically operated Butterfly valve
What PSI is most common in pneumatic system?
45 PSI
What are the two compressor stages?
HP - high pressure
IP - intermediate pressure
Does an APU have a pressure regulator valve?
No, just a shut off valve
What is the purpose of a pre cooler?
Cools the engine bleed temperature
Where is the cooling air taken from?
Engine Fan duct
What 2 components does the temperature regulation consist of?
. Precooler
. Fan air valve
How is pneumatic air distributed?
Via ducts
What are the pneumatic ducts monitored by?
Leak detection system
What is the role of the pneumatic controller?
. Monitors pressure temperature
. Registers leaks
. Monitors operation of pneumatic controllers
How many pneumatic controllers are there for each engine bleed system?
One for each engine bleed air system
What are the two main features of bleed valves?
. Butterfly type
. Pneumatically operated
What are the 5 functions of bleed valve?
. Shut off function
. Pressure regulation function
. Check valve function
. Over temp control function
. A reverse flow function
What valve regulates pressure?
Bleed valve
When air pressure is great enough in open slide of actuator, what happens?
Overrides the spring force and moves piston
What happens when shut off function is performed?
Bleed valve closes and no pneumatic air from engine is available
What temperature does the precooler inlet air have to be?
160 degrees to 200 degrees
What is used to monitor temperature?
Thermostate
Where is the location of the thermostat in conjunction to the precooler?
Down stream of the precooler
Where is the bleed valve located in conjunction to the precooler?
Upstream of the precooler (before)
What is pressurised air used for in conjunction with the engines?
Start the APU by reverse flow function
When is reverse flow of air allowed through the bleed valve?
Only for engine starts
If failure of bleed valve happens, what is used to prevent over-pressurisation?
Over pressure valve
What PSI is the over pressure valve fully closed at?
85 PSI
What type of valve is an over pressure valve?
Pneumatically operated butterfly type valve that is spring loaded to open
What type of valve is a bleed valve?
Pneumatically operated electrically controlled spring loaded closed
What is the purpose of the pre cooler?
Cools engine bleed air system
(Air to air heat exchanger)
What is the cooling air regulated by?
Fan air valve
The temperature sensor measure the temp, if temp is high what happens?
Then More the fan air valve opens
The temperature sensor measure the temp, if temp is low what happens?
The more the fan air valve closes
What type of valve is HP?
Pneumatically operated butterfly valve, spring loaded to close
When would HP Valve open and IP close?
HP = opens at low engine RPM
IP = opens at High engine RPM
What are two other alternate ways of supplying pneumatic system?
. APU
. HP ground supply
For HP ground supply what size is the ground connector?
3 inches
How is APU bleed load valve controlled?
Switch in cockpit
What is purpose of cross bleed valve?
Connects or isolates the left/ right bleed air system
What is the cross bleed valve operated by?
Electric motor
If there is a leak in an air duct, it results in overheating, what is this monitored by?
Overheat detection sensors
Where are the main controls for bleed air system located?
Overhead bleed panel
When aircraft is supplied with air by external unit in ground what should you ensure?
At least one window of door is open to prevent accidental cabin pressurisation