Air systems/Bleed Flashcards
What sources supply air to the bleed air (pneumatic) system?
Eng, APU, Ext.
What systems rely on bleed (pneumatic) air for operation?
Air Cond/Press, Wing/Engine Anti-Ice, Engine Starting, Hyd Res Press, Water Tank Press, NGS
What is the purpose of the Engine Bleed Air Valve, and how is it operated?
Pressure regulator and shutoff valve. DC-controlled, pressure-operated.
What is the purpose of the Precooler System?
Regulates (cools) the temp of the Eng bleed air down via an air to-air heat exchanger.
What causes Bleed Trip Sensors to automatically close the Engine Bleed Air Valve?
Excessively high engine bleed air temp, or pressures. Illuminates BLEED TRIP OFF light, AIR COND
annunciator, and MASTER CAUTION.
How is the bleed trip condition reset?
Push the TRIP RESET switch if Condition must no longer exist
What do the WING-BODY OVERHEAT, BLEED TRIP OFF, and DUAL BLEED amber lights on the Bleed Air Panel indicate?
a. WING-BODY OVERHEAT: a duct leak in a critical area
b. BLEED TRIP OFF - Sensors around the Bleed air Valve sense an over temp/pressure
c. DUAL BLEED – 2 sources on left duct, APU and Eng 1 bleed, or Eng 2 bleed and isolation valve open
What is the purpose of the APU Bleed Air Valve, and how is it operated?
APU bleed air to the left duct. DC-controlled, pneumatically operated. APU Bleed Switch
What is the purpose of the Isolation Valve?
Isolates the left and right bleed air ducts during normal ops
What do the Isolation Valve positions CLOSE, OPEN, and AUTO do?
a. CLOSE: remains closed
b. OPEN remains open
c. AUTO - Isolations valve will auto closes when Both engine bleed ON and Both PACKs AUTO/HIGH and
switching any to OFF. (four corner switches)
How do the Engine BLEED Air or Air Conditioning PACK switches impact operation of the Isolation Valve?
a. Turning any engine bleed air switch or pack switch OFF will OPEN the valve
Where is the external pneumatic air connection located?
e right side of the aircraft (immediately aft of the right landing light)
What is the path of conditioned air from an external (ground) source?
Directly into the mixing manifold
. When connected to external air, which position should the PACK switches be in?
off
What is the primary source of conditioned air to the Flight Deck?
Left pack
To the passenger cabin?
Right pack
How is the forward cargo compartment heated?
Exhaust air from the E/E bay via equipment cooling fans
The aft cargo compartment?
Aft cargo is unheated
What do the PACK amber lights on the Bleed Air Panel indicate?
Overheat or failure of a pack controllers
What causes these lights to illuminate?
Immediately for overheat or dual controller failure, during recall for single pack controller failure
. What happens with the Master Caution light during a failure of Primary pack control?
Nothing.
. Standby pack control?
Nothing. Single failure is only shown in recall
. A single pack in high flow mode can maintain pressurization and comfort up to what altitude?
41,000
Explain the auto logic for high airflow during normal operations and with a pack or engine failure.
In AUTO: Pack fails or engine fails? Automatically goes into HIGH with the flaps up
What controls pack temperature control?
Zone that needs the most cooling is what decides what the packs do, then the Trim Air System regulates the
other 2 zones
What is the purpose of the recirculation fans?
a. Reduction of bleed air demand and recirculates air
b. RIGHT recirc fan takes air from holes in floor and runs it to mix manifold
LEFT recirc fan takes in air from the air conditioning distribution compartment
What is the purpose of the Equipment Cooling System?
a. Cools electronic equipment in the Flight Deck and the E/E bay. Warms Fwd cargo bay, Smoke removal
What does the EQUIP COOLING OFF (amber) light indicate?
Low flow from Equipment Cooling Fan.
What causes the AUTO FAIL and OFF SCHED DESCENT amber lights to illuminate?
AUTO FAIL - one or both pressurization channels are INOP
b. OFF SCHED DESCENT - descent without reaching initial cruise altitude.
How does the primary heat exchanger lower the bleed air temperature?
Ram air flow augmented with an induction impeller driven by an extension of ACM shaft.
What is indicated by a bright blue RAM DOOR FULL OPEN light? Dim blue? Extinguished?
Bright Ram door is in the full open position
Dim=Never happens
Extinguished= closed or modulating
What do the ALTN (green) light and MANUAL (green) light on the Cabin Pressurization panel indicate?
a. ALTN - Alternate mode activated
b. MANUAL - manual mode
What causes these lights to illuminate?
a. ALTN- manually selected or main CPC unit has failed
b. MANUAL- mode selected to manual pressurization
What does the Pressurization Mode Selector do?
Selects either auto, alt, or man pressurization
Describe the 3 temperature control zones
Control cabin (cockpit), Forward cabin, Aft cabin
. What does an illuminated ZONE TEMP (amber) light indicate?
Overheat in associated ducting, or double controller failure
What happens with the Master Caution light when ZONE TEMP illuminates?
Master caution illuminates. Not inhibited
What is the purpose of the Mix Manifold?
Joins recirculated air with conditioned air from PACK, distributes to pax cabin
On the Cabin Pressurization Panel, what do the FLT ALT indicator and LAND ALT indicator display?
a. FLT ALT- scheduled cruise alt for pressurization
b. LAND ALT- Landing airport altitude (schedule)
What are indications and impact of a panel failure?
Display 8888888, if all is normal nothing is affected. If Display ———— controller failed, manual mode
What is indicated by the CABIN ALTITUDE (red) light and the Cabin Altitude Warning Horn? How can this horn be
silenced?
> 10000’ cabin alt. Alt horn cutout by cabin alt gauge silences.
What does AUTO FAIL light indicate?
Dual controller failure or Single controller fail if ALTN is on
