11.16 Pnuematics Flashcards
What uses pneumatic energy? (4)
- engine starting
- cabin pressurisation and air conditioning
- wing anti ice
- water reservoir and hydraulic pressurisation
How can pneumatics be supplied? (3)
- engine
- apu
- high pressure ground connectors
What is required to maintain a constant level of pressure?
Pressure regulator
What are the different type of compressor stages? [2]
- intermediate pressure (IP)
- high pressure (HP)
When the HP stage is being used to supply pneumatics, what is used to protect the engine compressor from back flow?
Check valve
What is used as a shut off to the APU?
APU bleed valve
What is used to cool the engine bleed air?
Built in precooler
Where is the cooling air taken from to cool the engine bleed air?
Engine fan duct (fan air)
What is used to vary the amount of cool air entering the pre cooler?
Fan air valve
What are the names of the ducts that distribute pneumatics? (4)
- Pylon duct
- left and right wing ducts
- apu duct
- crossover duct (cross bleed manifold)
Where is the cross bleed manifold usually located? And what does it connect?
In the fuselage connecting the left and right wing ducts
What are the pneumatic ducts monitored by?
A leak detection system
What controls the pneumatics? [2]
- Pneumatic controller (automatically)
- Pneumatic controller panel in flight deck (manual)
How many pneumatic controllers are there?
One for each engine bleed air system
What is the role of the pneumatic controller? (3)
- monitor pressure and temperature,
- register leaks
- monitor operation if pneumatic components
Which valve usually regulates the pressure and shut off?
Bleed valve
If the pressure regulator and shut off valve were two separate components, by how much more PSI would the pressure regulator control the pressure?
20psi above
What is the usual pressure of the pneumatic system?
45 psi
What type of valve is the bleed valve?
Butterfly type and pneumatically operated
What functions does the bleed valve have? (5)
- Shut off function
- pressure regulation
- check valve function
- over temperature control function
- reverse flow function
How does a pneumatically operated butterfly valve operate?
Spring loaded and pressure will override the spring tension and move the piston upwards opening the valve
How does shut off function work on a butterfly valve?
The shut off switch energises a solenoid which opens a port to ambient releasing pressure and closing the valve
What is the purpose of the bleed valve check valve? [2]
- To prevent an imbalance of pressure between both sides of the valve,
- to protect the engine of a compressor stall (disturbed air flow)
What does the temperature of the pneumatic system need to between after going through the precooler?
160 and 200 degrees c
Where is the thermostat located?
Downstream of the precooler
What happens if an over temperature occurs after the precooler ?
It can open an ambient bleed port or close the bleed valve
When might the reverse flow function be used?
To start the engines
During an overpressure situation, at what psi will the valve be fully closed?
85psi
What 2 methods of over pressurisation protection is there?
- Pneumatically operated butterfly valve
- pressure switches connected to flight deck
What is usually used as a precooler?
An air to air heat exchanger
How does an air to air heat exchanger work?
Cools hot engine bleed air by cross flowing it with cold air
What type of valve is the fan air valve?
Pneumatically operated butterfly valve
What controls the amount of air the fan air valve allow passing through it?
Temperature sensor located down stream of the precooler
How big are the connections for the high pressure ground connectors?
3 inches
What is the result of a duct leak?
Overheat
What happens if an over heat condition occurs because of a leak?
The effected engine bleed air system is shut off automatically by the pneumatic controller or manually
