Air Systems Flashcards
DUAL BLEED (light)
Illuminated:
- APU bleed air valve open and engine NO.1 BLEED air switch ON or
- engine NO.2 BLEED air switch ON, APU bleed air valve and isolation valve open
illuminates when the APU Bleed Valve is open and a possibility exists that the engine bleed air could provide back pressure on the APU. So this light provides protection in the event the APU check valve should fail.
Note: The light monitors the position of the Engine Bleed Switch, (not the Engine Bleed valve). So if the APU Bleed Valve is open and the #1 Bleed Switch is ON, the DUAL BLEED light illuminates whether engine #1 is running or not.
Engines must remain in idle power when the DUAL BLEED light is on. And although the light indicates an abnormal condition, the DUAL BLEED light will be on during normal engine starting.
ISOLATION VALVE (switch)
Close = closes isolation valve
AUTO (this is the normal position):
- closes isolation valve if both BLEED air switches are ON and both air conditioning PACK switches are AUTO or high
- opens isolation valve automatically if either engine BLEED air or air conditioning PACK switch positioned OFF
Open = opens isolation valve
WING-BODY OVERHEAT light (Left or right)
illuminated:
LEFT light indicates overheat from bleed air duct leak in left engine strut, left inboard wing leading edge, left air conditioning bay, keel beam or APU bleed air duct
RIGHT light indicates overheat from bleed air duct leak in right engine strut, right inboard wind leading edge or right air conditioning bay
When one of these lights comes on, the MASTER CAUTION and AIR COND annunciator lights will illuminate.
Follow the WING BODY OVERHEAT Non-Normal checklist to correct this condition (Note: There is NO automatic bleed air shutoff for this system!)
BLEED TRIP OFF Light
illuminated: excessive engine bleed air temperature or pressure (protects the pneumatic system from overtemp or overpressure sensed downstream of the 9th stage bleed, but the pressure sensor is located Upstream of the Bleed Air Valve.)
- related engine bleed air valve closes automatically (a temperature sensor will close the Bleed Valve and activate the BLEED TRIP OFF light)
- When BLEED TRIP OFF occurs, the MASTER CAUTION lights and the AIR COND annunciator will illuminate.
- requires reset (see below or press the TRIP RESET switch)
how to reset = pilot may reset trip reset switch if fault condition is corrected (after cooling). Note: normally the fault will correct itself since closure of the Bleed Valve allows the temperature to decrease but the BLEED TRIP OFF must be reset. (follow the QRH).
PACK (switch)
OFF = pack signaled off
Auto:
- with both packs operating, each pack regulates low flow
- with one pack operating, operating pack regulates to high flow in flight with flaps up (Note: when on the ground or in flight with flaps EXTENDED, the automatic switching to High Flow is INHIBITED to ensure adequate engine power for single engine operation).
- when operating one pack from APU (both engine BLEED air switches OFF) regulates to high flow (regardless of flap position or in air/on ground)
- High Flow is provided from APU bleed supply as long as both engine BLEED switches are OFF. (This automatic switching to High flow (when APU is the supply) occurs for any operating pack (in AUTO) regardless of flap position or air/ground status.)
HIGH:
- pack regulates to high flow (Don’t select HIGH for takeoff or landing as the SE performance is based upon low flow)
- provides maximum flow rate on ground with APU BLEED air switch ON
PACK (light)
Illuminated:
- indicates pack trip off (see below) or failure of both primary and standby pack controls
- during master caution recall, indicates failure of either primary or standby pack control. extinguishes when master caution is reset
Below: An overheat detection will cause the pack valve to close and the PACK light will come on.
What systems rely on Bleed Air?
Air conditioning / pressurization wing and engine thermal anti-icing engine starting HYD reservoirs pressurization Water System Pessurization Aspirated TAT probe
With the engine bleed air switch ON, the valve is (BLANK) activated and (BLANK) operated?
DC (electrical power) / pressure (pneumatically)
The Duct pressure indicator is powered by what electrical?
AC
The isolation valve is powered by what electrical ?
AC
Does the isolation valve open or close if either bleed air switch or air con pack is switched to off?
it automatically opens. Thus, in AUTO, if any engine bleed or pack switch is off (the 4 corners), the Isolation Valve enables pneumatic users to receive air from either manifold.
With the isolation valve switch in AUTO, both bleed air switches ON, and both air conditioning pack switches AUTO or HIGH is the isolation valve open or closed?
Closed
Is a single pack capable of maintaining max pressurization and acceptable temperatures up to the certified ceiling?
YUP
But note: although possible to route bleed air from one engine to operate both packs, don’t because he single engine performance is NOT based on one engine operating 2 packs. Therefore: do NOT operate more than 1 pack from 1 engine.
Bleed switches control…
respective Bleed Valves
Which stage provides bleed air to the pneumatic system when an engine is operating?
What happens if this stage is not sufficient?
5th stage bleed air.
the 9th stage modulating valve begins to open.
What happens when the bleed switch is turned off?
What happens when the bleed switch is turned on?
the bleed valve closes and isolates engine bleed air from the manifold.
Depends on if the engine is running or not. If the engine is OFF, turning on the bleed switch (and no bleed air is available from the associated engine), the valve remains closed.
If the engine is ON, turning on the bleed switch (and bleed air pressure IS available from the associated engine), the valve opens.
What powers the pneumatic valves?
DC electrical power activates the bleed valve, but the valve is opened by bleed air pressure. Therefore, this type of valve is electrically controlled but pneumatically operated.
Each bleed valve functions as…?
a pressure regulator and a shutoff valve.
*Note: Engine Bleed Valves are NOT reverse flow check valves.
What happens when you press the TRIP RESET button?
resets the MASTER CAUTION, AIR COND annunciator, resets the Protective Circuits, and restores operation of the Bleed Air Valve.
Resets a BLEED TRIP OFF, the PACK lights, or the ZONE TEMP lights.
(the related engine bleed valve opens, or related pack valve opens, or related trim air modulating valve opens. But lights remain illuminated until reset.)
The APU Bleed Valve is controlled by
With the APU Bleed air switch ON, the valve is (BLANK) controlled by (BLANK) power and is (BLANK) operated?
The APU bleed air directly feeds the
the APU Bleed Switch
electrically, DC (28V DC power), pneumatically
left pneumatic manifold
With the APU operating and the engine and APU bleed valves open, there is a possibility of what?
So what must be done?
possibility of APU bleed air back-pressuring the 9th stage modulating and shutoff valve. (This would cause the 9th stage valve to close).
The APU Bleed Valve must be closed during use of engine anti-ice to ensure that sufficient bleed air is available for cowl anti-ice.
In order for the APU to supply bleed air for engine start, the APU must be operating at over (BLANK) RPM?
How long must you wait to turn on the APU Bleed air?
95%
1 minute
Why do we turn off both PACK Switches before engine start?
so that all APU air is available to start the engines. (Both Engine Bleed switches should be on as this is the normal position of these switches. Each Bleed Valve remains closed until engine is started (there’s no pneumatic pressure present yet)
Why would you use the APU to operate the left pack during takeoff?
How would this be set up?
to increase engine performance (“bleeds off takeoff”)
Pilot manually closes the Isolation Valve, (both packs in AUTO), turns both engine Bleed Switches off, and turns the APU Bleed ON. (Note: This configuration will operate only the LEFT Pack).
After T/O, once obstacles clearance is assured:
- Turn ON #2 engine Bleed switch (R pack operates)
- Verify cabin pressure is stable
- Turn OFF APU Bleed switch (wait for valve to close=left duct pressure drops to zero)
- Turn ON #1 engine Bleed switch
- Turn Isolation Valve switch to AUTO
(This procedure applies #1 engine bleed air to the left pack. Note: Care must be used after TO to turn OFF the APU air before turning on the #1 Bleed switch to avoid causing the DUAL BLEED light to come on at high power settings.)
How do we test the WING BODY OVERHEAT System?
press the OVHT TEST button (just to the right of the Duct Pressure gauge). This tests the wing-body overheat detector circuits.
When this button is pressed, both WING BODY OVERHEAT, MASTER CAUTION, and AIR COND annunciator lights will illuminate after a short pause. When released, both WING BODY OVERHEAT lights should extinguish.
Does the Pack Ram Air system provide cooling airflow for the pack heat exchangers when the aircraft is on the ground or in the air?
Both.
What do the Ram Inlet Doors do? How do they work?
The Ram inlet door position controls the amount of airflow that moves through the ram air system and therefore over the heat exchangers for the associated pack.
When are the Ram Inlet Doors fully open, and how would we know if they’re fully open?
When does the RAM DOOR FULL OPEN light illuminate?
When on the ground, or when inflight with flaps extended, or inflight when maximum cooling is necessary.
The RAM DOOR FULL OPEN light illuminates when they are full open, otherwise it’s extinguished.
When will the Ram Inlet Doors close, and how would we know?
What determines the position of the Ram Inlet Doors?
They begin to close after takeoff and during cruise flight.
The RAM DOOR FULL OPEN lights extinguish when the doors begin to close.
The compressor discharge temperature determines the position of the Ram Inlet Door. (The position of each Ram inlet door modulates to maintain the optimum compressor discharge temperature for the associated air cycle machine operation.)
