Bleed Air

Question 1

3 Sources of bleed air:

Answer 1

Engines, APUs & External air

Question 2

7 uses of Bleed Air:

Answer 2

 Cabin pressurization
 Air-conditioning
 Cargo floor heat
 Engine starting
 Engine anti-icing
 Thrust Reversers
 ATM operation

Question 3

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.

Answer 3

8th; 14th

Question 4

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.

Answer 4

HPSOV (High Pressure Shut Off Valve)

Question 5

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.

Answer 5

PRSOV (Pressure Regulator Shut Off Valve)

Question 6

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

Answer 6

PSOV (Pylon Shut Off Valve)

Question 7

The ________ control the engine bleed air system, Environmental Control System (ECS) valves, cabin temperature control and underfloor heat.

Answer 7

AMSC (Air Management System Controllers)

Question 8

The AMSC controls which two valves to regulate bleed air from an engine?

Answer 8

 High Pressure Shut Off Valve (HPSOV)

 Pressure Regulator Shut Off Valve (PRSOV)

Question 9

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.

Answer 9

ATM Priority Valve

Question 10

The _________ is comprised of a dual channel digital control unit and a series of temperature sensors that monitor the bleed airducting system for leaks.

Answer 10

BAOWS (Bleed Air Overheat and Warning System)

Question 11

How many detection/protection zones compose the Bleed Air Overheat Warning System?

Answer 11

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.

Question 12

During a left, right, or center duct overheat condition what overrides all valve closing signals generated by the overheat condition?

Answer 12

Engine start sequence

Question 13

What valves close with L or R DUCT OVHT CWA?

Answer 13

 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

Question 14

What valves close with a center bleed air overheat condition?

Answer 14

 8 valves total
 APU Bleed Air Shutoff Valves (2)
 APU Isolation Valves (2)
 Floor heat Valves (2)
 Wing Isolation Valves (2)

Question 15

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.

Answer 15

Mach 0.3

Question 16

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 _________________.

Answer 16

Close one wing isolation valve

Question 17

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.

Answer 17

Left

Question 18

During normal operation, the ______ air-conditioning system provides air to the cargo compartment.

Answer 18

Right

Question 19

What must be functioning in order to maintain full pressurization?

Answer 19

Both Air Conditioning systems or one AC system and floor heat

Question 20

How is pressurization maintained using bleed air from the engines?

Answer 20

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)

Question 21

The ______________ valve controls the overboard flow of cabin air during all normal flight conditions while the butterfly valve is closed.

Answer 21

thrust-recovery

Question 22

The _____________ is opened with the thrust recovery valve during ground operations, unpressurized flight and during emergency depressurization.

Answer 22

butterfly valve

Question 23

What system is in place to prevent over pressurization?

Answer 23

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

Question 24

What system is in place to prevent negative pressurization?

Answer 24

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.

Question 25

What does the Emergency Depressurization Switch on the Engineer’s Panel do?

Answer 25

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.

Question 26

When does the CABIN PRESS LOW CWA illuminate?

Answer 26

If the cabin altitude exceeds 10,000 feet

Question 27

The CAB PRESS DIFF HIGH warning is displayed if the differential pressure exceeds safety valve limits of ____ PSID.

Answer 27

8.7

Question 28

How does the ice detector work?

Answer 28

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.

Question 29

How are the nacelles heated for anti-icing?

Answer 29

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.

Question 30

How is Nacelle Anti-Ice system controlled?

Answer 30

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.

Question 31

How many Pitot Tubes are installed on the aircraft and how are they protected from icing?

Answer 31

Four (pilot – upper left, lower right; co-pilot – upper right, lower left), electrically heated

Question 32

What is the COLD START switch used for with regards to windshield heat?

Answer 32

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

Question 33

What are the speeds associated with the windshield wipers?

Answer 33

Good rain clearing up to 150 KCAS, adequate to 175 KCAS