A pneumatic system carries power by employing compressed gas, generally air, as a fluid for transmitting energy from an energy-generating source to an energy-using point to accomplish useful work.
- Used for: Brakes, opening and closing doors, driving hydraulic pumps, alternators, starters, water injection pumps, operating emergency devices etc.
- Pneumatic Systems are light in weight.
- Operating elements are cheaper and easy to operate.
- Leakage is less and does not influence the systems. Moreover, leakage is not harmful.
- Exhaust air noise is unpleasant and silence has to be used.
Bleed air is extracted from the compressor of the engine or APU. The specific stage of the compressor from which the air is bled varies by engine type. In some engines, air may be taken from more than one location for different uses as the temperature and pressure of the air is variable dependant upon the compressor stage at which it is extracted. Bleed air typically has a temperature of 200 – 250 degrees c. and a pressure of approximately 40psi exiting the engine pylon.
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