Bleed Air Sytem Flashcards
The bleed air system is divided into how many ducts?
Two ducts ( Left pneumatic duct & Right pneumatic duct)
How are the ducts connected?
The two ducts can be connected through an isolation valve
Which duct does the APU introduce bleed air into?
The left pneumatic duct
Which duct does pressurized air from a ground source supply bleed air into?
The right pneumatic duct
What is bleed air used for?
Engine starting
Engine anti-ice
Wing anti-ice
Air conditioning & pressurization
Water tank pressurization
Hydraulic reservoir pressurization
Used by NGS (Nitrogen Generation System)
What is installed to monitor bleed air pressure and temperature?
Bleed trip sensors
How is the pressure controlled?
Pressure is controlled by the engine bleed air valves which act as Pressure Regulator and Shutoff valves (PRSOV)
During flight the engines normally supply bleed air for the pneumatic system. What stages within the engine compressor section is the air supplied from?
The 5th stage or low pressure stage ( Primary Source )
The 9th stage or high pressure stage ( Back-up Source )
What happens when 5th stage air is insufficient for bleed air system requirements?
The 9th stage valve modulates open to maintain adequate pressure.
How are the engine bleed air valves Controlled?
They are electrically (DC Power) by the engine bleed air switch.
When do the bleed air valves open?
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.
What happens when the bleed air temperature is high as it passes through the bleed air valve?
The engine bleed air valve reduces bleed air outflow.
What happens when the engine bleed air temperature or pressure exceeds a predetermined limit?
The BLEED TRIP OFF light illuminates. This causes the valve to automatically close.
What are the three isolation valve switch positions?
Close
Auto
Open
What causes the isolation valve to open?
- Isolation valve switch in the open position
- Isolation valve switch in the Auto position and placing any one of the PACK switches or ENGINE BLEED AIR switches to the off position.
Is the isolation valve operated by AC or DC power source?
AC power source
Which side of the system is the APU connected to and what is APU valve operated?
The APU is connected to the left side of the pneumatic system through a DC operated APU bleed air valve.
If the isolation valve is open or closed, which ducts are supplied bleed air from the APU?
Isolation valve closed: left duct
Isolation valve open: both ducts
How many packs can the APU supply bleed air for on the ground and in flight?
On the ground: two packs
In flight: one pack
Up to what altitude is APU bleed air available?
17,000 feet
What is the primary use for APU bleed air?
Ground pneumatic source for air conditioning pack operation
Engine starting
What are the two circumstances that the DUAL BLEED light will illuminate?
- The APU bleed air valve is open and the number 1 engine BLEED air switch is ON.
- The APU bleed air valve is open and the number 2 engine BLEED air switch is ON, and the isolation valve is open.
What part of the system will prevent any back flow of engine bleed air to the APU during engine start?
A check valve located in the APU duct.
Where are the overheat detectors installed?
Near the pneumatic ducts
When does a hot element illuminate a WING-BODY OVERHEAT annunciator?
If a leak is detected.
What detection does a left WING-BODY OVERHEAT annunciator provide?
Left engine strut
Left inboard wing leading edge
Left air conditioning bay
Keel beam
Bleed duct from the APU
What detection does a right WING-BODY OVERHEAT annunciator provide?
Right engine strut
Right inboard wing leading edge
Right air conditioning bay
Air conditioning pack switch positions?
Off
Auto
High
When can you push the trip reset switch and what will it do?
Push only if the fault condition has been corrected.
Resets : bleed trip off, pack trip off, and duct overheat lights
Where does the external air connect into when on the ground to provide cabin air?
Into the Mix Manifold
Ram air system: what does it do?
Provides cooling air for the heat exchangers.
Ram air system: when does the RAM DOOR FULL OPEN lights illuminate?
Whenever the ram doors are in the full open position.
When is it most common for the ram doors to be fully open?
On the ground, or
In slow flight with the flaps not fully retracted
Ram air system: what are the deflector doors?
Installed forward of ram air doors to prevent ingestion of slush on landing and takeoff. Operated electronically using air-ground safety sensor
What the purpose of the recirc fan system?
Helps reduce the load on the AC system pack and the engine bleed air demand.
With the recirc fan switch in the Auto position, when will it turn on automatically?
Usually on except when both packs operating with either pack switch in HIGH
What does the recirc fan do?
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
