Bleed Air Flashcards
3 Sources of bleed air:
Engines, APUs & External air
7 uses of Bleed Air:
Cabin pressurization Air-conditioning Cargo floor heat Engine starting Engine anti-icing Thrust Reversers ATM operation
The engine bleed air system regulates engine bleed pressures and temperatures produced by the _____ stage and _____ stage of the engine compressor to supply airplane pneumatic system requirements.
8th; 14th
The ________ is a combination pressure regulator and shutoff valve, which is capable of controlling airflow from the 14th stage compressor discharge bleed manifold into the 8th stage connection duct.
HPSOV (High Pressure Shut Off Valve)
The ________ regulates air downstream of the bleed ports from the engine’s mid and high-stage compressor which supply the bleed air to the airplane cross-ship manifold.
PRSOV (Pressure Regulator Shut Off Valve)
The _______ is a solenoid-controlled, spring-loaded-open, pneumatically actuated valve that provides the capability to shut off all bleed airflow from the engine into the cross-ship manifold
PSOV (Pylon Shut Off Valve)
The ________ control the engine bleed air system, Environmental Control System (ECS) valves, cabin temperature control and underfloor heat.
AMSC (Air Management System Controllers)
The AMSC controls which two valves to regulate bleed air from an engine?
High Pressure Shut Off Valve (HPSOV)
Pressure Regulator Shut Off Valve (PRSOV)
The _____________ ensures that an adequate supply of bleed air pressure is available to the operating ATMs when the output pressure of the APUs is marginal.
ATM Priority Valve
The _________ is comprised of a dual channel digital control unit and a series of temperature sensors that monitor the bleed airducting system for leaks.
BAOWS (Bleed Air Overheat and Warning System)
How many detection/protection zones compose the Bleed Air Overheat Warning System?
Seven. These zones are the left and right wings; engine pylons No. 1, No. 2, No. 3, and No. 4; and the cargo area. Each zone contains two independent sensor loops, with each loop containing a series of independent sensors.
During a left, right, or center duct overheat condition what overrides all valve closing signals generated by the overheat condition?
Engine start sequence
What valves close with L or R DUCT OVHT CWA?
7 valves PER side
ENG 1 & 2 or ENG 3 & 4 High Pressure Shut Off Valve (HPSOV)
ENG 1 & 2 or ENG 3 & 4 Pressure Regulator Shut Off Valve (PRSOV)
ENG 1 & 2 or ENG 3 & 4 Pylon Shut Off Valve (PSOV)
Left or Right Wing Isolation Valve
What valves close with a center bleed air overheat condition?
8 valves total APU Bleed Air Shutoff Valves (2) APU Isolation Valves (2) Floor heat Valves (2) Wing Isolation Valves (2)
Each refrigeration unit has a primary and secondary heat exchanger. Cooling air for the heat exchangers is provided by ram air during flight at airspeeds above __________ when the slats are retracted, and by a cooling fan for all other airspeeds, ground ops, and when the slats are extended.
Mach 0.3
During flight, to prevent one engine from supplying both packs and floor heat, a condition which could exceed precooler capacity under some conditions, the flight engineer will _________________.
Close one wing isolation valve
During normal operation, the ______ air-conditioning system provides air to the flight station, relief crew compartment, and the troop compartment, with a minimal flow of air going to the cargo compartment.
Left
During normal operation, the ______ air-conditioning system provides air to the cargo compartment.
Right
What must be functioning in order to maintain full pressurization?
Both Air Conditioning systems or one AC system and floor heat
How is pressurization maintained using bleed air from the engines?
Pressure is maintained by providing an inflow through the flow control valves and modulating the outflow through the outflow valve (composed of two units: the thrust-recovery valve and a butterfly valve)
The ______________ valve controls the overboard flow of cabin air during all normal flight conditions while the butterfly valve is closed.
thrust-recovery
The _____________ is opened with the thrust recovery valve during ground operations, unpressurized flight and during emergency depressurization.
butterfly valve
What system is in place to prevent over pressurization?
Two cabin safety valves open when the pressure gets too high. The valves open at 8.4 PSID and regulate the cabin pressure to no more than 8.7 PSID
What system is in place to prevent negative pressurization?
Two mechanical negative pressure relief valves in the aft troop. If ambient pressure is equal to or greater than cabin pressure, the negative pressure relief valves open allowing ambient pressure to enter the cabin.
What does the Emergency Depressurization Switch on the Engineer’s Panel do?
When placed to EMERG DEPRESS, it causes the outflow valves to open, closes the left and right air conditioning flow control and shutoff valves, and closes both floor heat temperature control valves. This will depressurize the aircraft from approximately 4,000’ to 30,000’ in 60 seconds.
When does the CABIN PRESS LOW CWA illuminate?
If the cabin altitude exceeds 10,000 feet
The CAB PRESS DIFF HIGH warning is displayed if the differential pressure exceeds safety valve limits of ____ PSID.
8.7
How does the ice detector work?
There is a mast that is mounted on the nose. When it ices up in icing conditions, it triggers a switch to turn on the ICING light and nacelle ANTI-ICE if the ice detector switch is in AUTO. A 60 second timer is then initiated and the mast is heated to melt the ice for 5 seconds. After 60 seconds, if ice still exists, the ICING light will remain illuminated and the ANTI-ICE will remain on. If there is no ice on the mast after 60 seconds, the ICING light will extinguish and the ANTI-ICE will be turned off.
How are the nacelles heated for anti-icing?
The nacelle anti-icing system provides hot air (11th stage compressor) to the nacelle inlet to prevent accumulation of ice on the inlet lip. The system activates when the Nacelle Anti-Ice switch on the nacelle anti-ice panel is ON, or when the Nacelle Anti-Ice switch is selected to AUTO and icing conditions are detected by the ice detector system.
How is Nacelle Anti-Ice system controlled?
The nacelle anti-ice valve is controlled by the EEC in response to a VIA/AIU provided input signal. The EEC defaults to nacelle anti-icing on when the ARINC communication between the VIA and EEC fails, or when the airplane is operating in backup mode.
How many Pitot Tubes are installed on the aircraft and how are they protected from icing?
Four (pilot – upper left, lower right; co-pilot – upper right, lower left), electrically heated
What is the COLD START switch used for with regards to windshield heat?
Used when windshields are cold soaked to below -40C to reduce thermal stress. The switch should be manually cycled 5 seconds on, 10 seconds off until the windshield reached -40C
What are the speeds associated with the windshield wipers?
Good rain clearing up to 150 KCAS, adequate to 175 KCAS
