2. Air Systems Flashcards
(44 cards)
WING-BODY OVERHEAT Light
- Not resettable,
- Indicates overheat from bleed air duct leak,
- Monitors Engine Struts, Inboard Wing Leading Edges, Air Conditioning Bays,
- For L side also, Keel Beam or APU Bleed Air Duct
BLEED TRIP OFF Light
Indicates excessive Engine Bleed Air Temperature or Pressure
TRIP RESET Switch
Resets:
- BLEED TRIP OFF,
- PACK,
- ZONE TEMP lights
Related Bleed Air Valve / Pack Valve / Trim Air Modulating Valve opens
ZONE TEMP Lights
CONT CAB:
- Indicates duct overheat or failure of the both flight deck temperature controls,
- During RECALL indicates failure of primary or standby flight deck temperature contol
- Extinguishes when Master Caution is reset
FWD / AFT CAB:
- Indicates duct overheat,
- During RECALL indicates failure of the associated zone temperature control
- Extinguishes when Master Caution is reset
PACK Switches
AUTO:
- With both Packs operating, each Pack regulates to low flow,
- With one Pack operating, it regulates to high flow in flight with Flaps UP,
- When operating one Pack from APU (both BLEED switches OFF) regulates to high flow
HIGH:
- Provides maximum flow rate on the ground with APU BLEED ON
RECIRC FAN Switches
AUTO inflight:
- L operates if both Packs operating unless either PACK Switch is in HIGH,
- R operates if both Packs operating unless both PACK Switch is in HIGH,
AUTO on the ground:
- L operates unless both PACK Switch is in HIGH
- R operates even if both PACK Switch is in HIGH
PACK Light
- Indicates Pack Trip Off or failure of both primary and standby Pack Controls,
- During RECALL indicates failure of either primary or standby Pack Control,
- Extinguishes when Master Caution is reset
Systems Relying on Bleed Air
- Air conditioning/pressurization,
- Thermal Anti-icing,
- Engine Starting,
- Hydraulic reservoir pressurization,
- Water tank pressurization,
- Nitrogen Generation System
Engine Bleed System Supply
- Obtained from 5th and 9th stages of compressor section,
- When 5th stage low pressure is insufficient high stage valve modulates open
Engine and APU Bleed Air Valves
- Engines valves are Pressure Regulator and Shut-off Valves (PRSOV),
- All valves DC activated and pressure operated
Duct Pressure Transmitters
- Indicator is AC operated,
- As long as there is sufficient air for cabin pressurization, differences between L/R considered normal
Isolation Valve
- AC operated,
- AUTO: If any Engine Bleed or Pack Switch is OFF, valve is open. Otherwise it’s closed
Airconditioning Distribution
- Left PACK: Flows directly to Flight Deck, excess air flows to Mix Manifold,
- Right PACK: Flows directly to Mix Manifold,
- Recirculation System: Flows directly to Mix Manifold,
- Preconditioned Ground Air: Flows directly to Mix Manifold
PACK Air Sources
- APU is capable to supply 2 Packs on the ground and single Pack in flight,
- Do not operate more than one Pack from one Engine,
- Most External Air Carts are capable of supplying both Packs
Single Pack Operation
In High Flow, capable of maintaining pressurization and acceptable temperatures up to maximum certified ceiling
Automatic PACK High Flow Switch
For Engine Bleeds:
- Inflight with Flaps UP,
- Both PACK switches AUTO,
- Both Engine Bleed switches ON,
- If one Pack fails or selected OFF
For APU Bleed:
- When both Engine Bleed switches are OFF,
- Both PACK switches AUTO,
- Switches to High Flow regardless of air/gnd or Flap position,
- If one Pack fails
Ram Air System
- Provides cooling air for heat exchangers,
- Automatically controlled by Packs,
- On the ground or during slow flight with Flaps extended doors are full open,
- In normal cruise modulates between open and closed,
- Deflector doors extend electrically by air-ground safety sensor
- They prevent slush ingestion prior liftoff and after touchdown
Cooling Cycle
- Bleed Air passing through a heat exchanger for cooling,
- Then air flows to an air cycle machine for refrigeration,
- Processed cold air combined with hot air which bypassed air cycle machine,
- Mixed air passes through a high pressure water seperator which removes moisture
Pack Temperature Controls
- Electronic controllers command the Pack Temperature Control Valve toward open or closed,
- If primary Pack Control fails, the affected Pack is controlled by the Standby Pack Control in the opposite Controller,
- If both Controls fails for the same Pack, Pack will continue to operate until excessive temperatures cause a Pack to trip off
Zone Temperature Selector Range
18-30 degrees
Zone Temperature Control Basics
- Packs produce an air temperature that satisfies the zone which requires the most cooling,
- Zone temperature is controlled by introducing the proper amount of trim air to the zone ducts,
- Quantity of trim air is regulated by individual trim air modulating valves
Single Pack Operation and Trim Air
- If TRIM AIR switch is ON, it’s same as during 2 Packs operation,
- If TRIM AIR switch is OFF, Pack attempts to produce an air temperature to satisfy the average temperature demands of all 3 zones
Zone Temperature Control Modes
- Left Electronic Controller controls Aft Cabin Zone and provides backup for Flight Deck,
- Right Electronic Controller controls the FWD Cabin Zone and provides primary control for Flight Deck
FWD or AFT Cabin Temperature Control Failure
- Associated Trim Air Modulating Valve closes,
- Temperature Selectors operate normally but 2 cabin zone selections will be averaged
