What are the requirements for APU load control valve to open in-flight?
There are only three sources of air on ground.
External, APU and engine air. Airflow is supplied to aircraft systems through a bleed air manifold connected to both engines and the APU. The manifold also has a connection to allow an external cart to provide pressurized air for engine starting or air conditioning on the ground.
The APU can be operated on the ground, during takeoff, in flight and during landing. In flight it is an optional source of electrical power via the APU GEN instead of one or both engine-driven generators. The APU cannot be used to supply pressurization airflow in flight. The APU may be used for starter assisted main engine starts at and below _____ if required.
One function of the bleed air system is temperature regulation. To avoid high temperatures inside the aircraft, fan air is used as a cooling medium together with a bleed air precooler located in each pylon.
Air supplied by the engines is temperature and pressure regulated by Bleed Air Controllers (BACs) that monitor the air supply via sensors within the ductwork. The engine BACs draw air from either the 5th or the higher temperature 8th of the compressor sections of the engines, depending upon the engine power settings and bleed air demand. Can you give another name for the 5th and 8th stage air?
Air supplied by the APU or a ground cart is not regulated.
As long as the engine is operating, bleed air is always available for the TAI system, even when the respective bleed air system is selected OFF.
When the L ENG or R ENG switch (BLEED AIR panel, COP) is selected 'ON', the PRSOV opens and allows HP 8 bleed air to flow to the respective side ECS and to the air starter ducting. The Pressure Regulating and Shutoff Valves (PRSOV) controls the supply of bleed air to the Environmental Control System (ECS) from the engine.
When the L ENG or R ENG switch (BLEED AIR panel, COP) is selected 'ON', the PRSOV opens and allows HP 5 bleed air to flow to the respective side ECS and to the air starter ducting. When ECS system demand is greater than HP 5 supply, the HPSOV opens, allowing HP 8 air to supplement the bleed air system. The HPSOV is regulated by a sense line downstream of the servo pressure regulator / torque motor.
What are the aircraft systems that require a modulated pneumatic source?
What computers control operation of the bleed air system?
The BACs are installed on the aft side of the baggage compartment bulkhead. The units are digital, microprocessor-based and are designed to automatically regulate bleed air manifold supply pressure and temperature. They are capable of controlling bleed air for all systems utilizing bleed air within the capacity of the engine over the entire aircraft operating envelope.
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