Bleed Air Sytem

Question 1

The bleed air system is divided into how many ducts?

Answer 1

Two ducts ( Left pneumatic duct & Right pneumatic duct)

Question 2

How are the ducts connected?

Answer 2

The two ducts can be connected through an isolation valve

Question 3

Which duct does the APU introduce bleed air into?

Answer 3

The left pneumatic duct

Question 4

Which duct does pressurized air from a ground source supply bleed air into?

Answer 4

The right pneumatic duct

Question 5

What is bleed air used for?

Answer 5

Engine starting
Engine anti-ice
Wing anti-ice
Air conditioning & pressurization
Water tank pressurization
Hydraulic reservoir pressurization
Used by NGS (Nitrogen Generation System)

Question 6

What is installed to monitor bleed air pressure and temperature?

Answer 6

Bleed trip sensors

Question 7

How is the pressure controlled?

Answer 7

Pressure is controlled by the engine bleed air valves which act as Pressure Regulator and Shutoff valves (PRSOV)

Question 8

During flight the engines normally supply bleed air for the pneumatic system. What stages within the engine compressor section is the air supplied from?

Answer 8

The 5th stage or low pressure stage ( Primary Source )
The 9th stage or high pressure stage ( Back-up Source )

Question 9

What happens when 5th stage air is insufficient for bleed air system requirements?

Answer 9

The 9th stage valve modulates open to maintain adequate pressure.

Question 10

How are the engine bleed air valves Controlled?

Answer 10

They are electrically (DC Power) by the engine bleed air switch.

Question 11

When do the bleed air valves open?

Answer 11

The valve is pneumatically operated and opens once sufficient pressure is available. After the engine is started, bleed air pressure from the engine opens the bleed air valve.

Question 12

What happens when the bleed air temperature is high as it passes through the bleed air valve?

Answer 12

The engine bleed air valve reduces bleed air outflow.

Question 13

What happens when the engine bleed air temperature or pressure exceeds a predetermined limit?

Answer 13

The BLEED TRIP OFF light illuminates. This causes the valve to automatically close.

Question 14

What are the three isolation valve switch positions?

Answer 14

Close
Auto
Open

Question 15

What causes the isolation valve to open?

Answer 15

1. Isolation valve switch in the open position
2. Isolation valve switch in the Auto position and placing any one of the PACK switches or ENGINE BLEED AIR switches to the off position.

Question 16

Is the isolation valve operated by AC or DC power source?

Answer 16

AC power source

Question 17

Which side of the system is the APU connected to and what is APU valve operated?

Answer 17

The APU is connected to the left side of the pneumatic system through a DC operated APU bleed air valve.

Question 18

If the isolation valve is open or closed, which ducts are supplied bleed air from the APU?

Answer 18

Isolation valve closed: left duct
Isolation valve open: both ducts

Question 19

How many packs can the APU supply bleed air for on the ground and in flight?

Answer 19

On the ground: two packs
In flight: one pack

Question 20

Up to what altitude is APU bleed air available?

Answer 20

17,000 feet

Question 21

What is the primary use for APU bleed air?

Answer 21

Ground pneumatic source for air conditioning pack operation
Engine starting

Question 22

What are the two circumstances that the DUAL BLEED light will illuminate?

Answer 22

1. The APU bleed air valve is open and the number 1 engine BLEED air switch is ON.
2. 1. The APU bleed air valve is open and the number 2 engine BLEED air switch is ON, and the isolation valve is open.

Question 23

What part of the system will prevent any back flow of engine bleed air to the APU during engine start?

Answer 23

A check valve located in the APU duct.

Question 24

Where are the overheat detectors installed?

Answer 24

Near the pneumatic ducts

Question 25

When does a hot element illuminate a WING-BODY OVERHEAT annunciator?

Answer 25

If a leak is detected.

Question 26

What detection does a left WING-BODY OVERHEAT annunciator provide?

Answer 26

Left engine strut Left inboard wing leading edge Left air conditioning bay Keel beam Bleed duct from the APU

Question 27

What detection does a right WING-BODY OVERHEAT annunciator provide?

Answer 27

Right engine strut Right inboard wing leading edge Right air conditioning bay

Question 28

Air conditioning pack switch positions?

Answer 28

Off Auto High

Question 29

When can you push the trip reset switch and what will it do?

Answer 29

Push only if the fault condition has been corrected. Resets : bleed trip off, pack trip off, and duct overheat lights

Question 30

Where does the external air connect into when on the ground to provide cabin air?

Answer 30

Into the Mix Manifold

Question 31

Ram air system: what does it do?

Answer 31

Provides cooling air for the heat exchangers.

Question 32

Ram air system: when does the RAM DOOR FULL OPEN lights illuminate?

Answer 32

Whenever the ram doors are in the full open position.

Question 33

When is it most common for the ram doors to be fully open?

Answer 33

On the ground, or In slow flight with the flaps not fully retracted

Question 34

Ram air system: what are the deflector doors?

Answer 34

Installed forward of ram air doors to prevent ingestion of slush on landing and takeoff. Operated electronically using air-ground safety sensor

Question 35

What the purpose of the recirc fan system?

Answer 35

Helps reduce the load on the AC system pack and the engine bleed air demand.

Question 36

With the recirc fan switch in the Auto position, when will it turn on automatically?

Answer 36

Usually on except when both packs operating with either pack switch in HIGH

Question 37

What does the recirc fan do?

Answer 37

Air from the pax cabin and electrical equip bay is drawn to the forward cargo bay where it is filtered and recirculated to the Mix Manifold