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Uses engine bleed air at the proper temperature pressure & flow to provide air for:
-cabin temperature control
-electronic equipment cooling
- & various anti-icing systems.
Bomber Air Conditioning System
+is designed to provide conditioned air for cabin temperature control and aircraft pressurization.
Cabin Air Conditioning system
* TEMPERATURE, PRESSURE & FLOW depend on the ____________.*
is delivered at lower pressures & temps. than Air Supplies by Aircraft Engines.
Ground Service Bleed Air
used to provide cabin temperature control and pack anti-icing.
reduces the temperature of bleed air & provides cold air for cabin temperature control & electronic cooling.
consists of heat exchanger, pack turbine & fan assembly, water separator, & pack anti-icing system.
+ referred to as the ( AIR CONDITIONING PACK )
COLD AIR SECTION
Cabin temperature is maintained by mixing hot air w/ the ____ air & can be controlled automatically or ________.
-only 2 components used to the control the temp. of the air in the Cabin: Air-Conditioning Modulating Valve & the Temperature Control Selector.
- used to select the desired temperature & electrically controls the air conditioning modulating valve during manual temperature control.
Temperature Control Selector
- used to control cabin temperature by controlling the amount of hot air that flows into the cabin.
- controls the low of hot air into the cabin, & it will open or close in response to signals from the temperature control selector.
+ opened to increase temperature+ closed to decrease cabin temperature
+ can be controlled automatically or manually
+ actuated by a 115-VAC, 3 phase motor
Air Conditioning Modulating Valve
-Air-Conditioning Modulating Valve
-Cabin Temperature Regulator
-Cabin Temperature Sensing Element
-Duct Temperature Sensing Elements
- & Cabin Temperature Selector.
5-components in AUTO:
Cabin Temperature will be maintained at a pre-selected temperature. (By 5 Components)
- controls flow of bleed air into the system.
+ 1st component in the system
+ has no regulating functions
+ simply used to shutoff airflow when ac sys.
is not being used.
+ 115 VAC motor (controlled by the cabin pressure master sw.) actuates it.
Air Conditioning Shutoff Valve
- used to remove the contaminants from the air going into the system.
+ contains 2 types of replaceable filter elements: particulate element & catalytic element.
Air Conditioning System Filter
- used to remove any solid particles that may get into the bleed air system.
- used to remove any obnoxious odors or gases that may enter the system.
+ composed of a granular substance called hopcalite.
- has two active components, manganese and copper oxides.
- They cause a reaction between contaminates & oxygen & air.
- contaminates are oxidized & changed into water vapor or carbon dioxide.
- maintains even airflow throughout the system during air-conditioning system operation.
+ Regulates Airflow at a constant 140 PPM.
- Consists of: Venturi, a diaphragm operated control head, & a butterfly valve.
+ Differences in Pressures between the top & bottom of the diaphragm will cause it to move.
Pack Pressure Limiter
- is mechanically connected - to the control head diaphragm.
- Movement of the diaphragm will open or close to the butterfly valve to regulate airflow into air conditioning system at 140 PPM. (by pack pressure limiter)
- used to partially cool the bleed air prior to entering the turbine fan assembly.
+ includes a series of small tubes (coils) through which the bleed air is routed.
* Air to Air - (TYPE)
- 1ST STAGE OF COOLING IN THE AC SYS.
- An opening on the left wing leading edge, that allows the ambient air to flow across the heat exchanger for cooling of the bleed air.
Air Inlet Scoop
- used to super cool the air by a method known as rapid expansion.
Pac Turbine Fan Assembly
- compressing air & then shooting it into a large opening causes the compressed air molecules to quickly separate and reduce the temperature of the air to below freezing point.
- the driving force of the assembly & creates super-cooled air through a process knows as rapid expansion.
1) rapidly expands bleed air to DROP temp. VVV
2) changes HEAT ENERGY to MECHANICAL ENERGY ( spinning action )
- (2 purposes)
1: to place a workload on the turbine to prevent a turbine over speed condition.
2: to provide ram air for cooling the heat exchanger.
- The Vacuum Effect created by the fan: provides the means of cooling the heat exchanger while the aircraft is on the ground.
+ The turbine & fan are connected by a shaft: which must be lubricated to reduce friction & prevent damage to assembly.
- To reduce the amount of moisture in the air and prevent fogging & snowing.
+ will remove 70% to 80% of the moisture.
* When you COOL Bleed Air, there will be 10X moisture left over *
+ ADDITION COOLING FOR BLEED AIR
(Primary cooling - Ram Air for Heat Exchanger)
2 Sections: Condenser & Eliminator Section.
-consists of a cone-shaped louvered grid covered w/ a Dacron Fabric sleeve
Condenser Section ( Coalser )
- forms droplets when the water separator forces air to it to condense moisture.
- makes the air rotate in a cyclone type motion as it flows through the water separator.
- as air flows through it, the cyclone motion of the air throw the water droplets to the sides of the water separator.
- ensures sufficient airflow through to the cabin by opening when the water separator inlet pressure reaches a specified point.
+ incorporated into the water separator
+ located on the inlet side of the water separator
+ held by spring tension
- Moisture will NOT be removed whenever the bypass valve is OPEN. (full of moisture)
Water Separator Bypass Valve
- to provide additional cooling of the heat exchanger.
+ located in the ram air scoop inlet of the heat exchanger.
+ It sprays the water over the coils of the heat exchanger
+++ provides & increases the cool efficiency of the heat exchanger.
- used to control the temperature of the air entering the water separator.
+ It mixes hot air from the hot air manifold w/ the cold air @ at the expansion turbine outlet.
+ actuated by a 115-VAC motor
+ controlled by a pack temperature controller
Pack Anti-Ice Valve
- to maintain temperature at the water separator outlet at a set value of 38 degree F.
+(aka 38 degree pack anti-ice controller)
- Regulates POS of Anti-Ice Valve
+ uses electronic signals to control the position of the pack anti-ice valve.
+ Change in resistance in the sensing element causes IT to send a corresponding electrical signal to open or close the pack anti-ice valve.
Pack Temperature Controller
- senses water separator discharge temperature and sends a signal to the pack temperature controller for operation of the pack anti-ice valve.
+ Negative Coefficient
+ located at the water separator outlet.
+ The change in current flow through the sensing element is a signal for the pack temperature controller to either open or close the pack anti-ice valve.
Anti-Ice Sensing Element
- installed into the system to absorb valve noise that may be transmitted through the hot air ducts.
Hot Air Muffler
- prevents flow of air & protect components from being damaged.
* + prevents rapid depressurization of the cabin.
+ flapper type check valves - forced closed by a reverse flow of air.
If bleed air supply is lost, the pressurized cabin air will try to flow back through the air conditioning system ducts.
+ reverse flow of air will force the hot & cold air check valves to close & trap pressure inside the aircraft.
+ Air flows in one direction only
Hot & Cold Check Valves
is used to sense the temperature of the cabin air.
+ part of the automatic temperature control system.
+ located on the let side of the upper cabin
+ Negative Coefficient, variable resistor.
+ Venturi restricts amount of Air-Flow over sensor
+ Sends signal to Cabin Temp Regulator
Cabin Temperature Sensor
+ A ________ provides a restriction to limit the airflow.
An _____ ____ allows air passing over the aircraft’s outer surface to draw cabin airflow across the Cabin Temp. Sensor.
***As the temperature in the cabin changes, current flow through the sensor changes.***
*** Makes up one leg of a bridge circuit used for AUTOMATIC temperature control.***
- The sensing elements sense the temperature of the air in both the hot and cold ducts and send signals to the cabin temperature regulator for control of the air conditioning modulating valve.
+ contains 2 positive coefficient variable resistors (sensing elements)
+ makes up two legs of a bridge circuit - used for AUTOMATIC temperature control.
Duct Temperature Sensor
- used to control the temperature in the cabin automatically or manually.
+ located on the co-pilot’s side console.
+ variabel resistor w/ a positive coefficient.
+ makes up one led of a bridge circuit used for AUTOMATIC temperature control.
+ spring loaded to the off position : during normal operation.
+ must be held in ‘manual warm or manual cold pos. until the desired cabin temp. is achieved.
Temperature Control Selector
it is used to select a preset temperature value & sends a signal to the cabin temperature regulator.
automatic temperature control:
holding the temperature control selector in either the manual cold or manual warm position allows the aircraft co-pilot to adjust the cabin temperature.
manual operation:(temperature control)
The Air conditioning modulating valve, when signaled by the ________ ______ _____, will OPEN for manual warm and close for manual cold.
temperature control selector
- is the central control point for automatic temperature control.
: receives electrical input signals from:
- Temperature Control Selector
- Cabin Temperature Sensor
- & the Duct Temperature Sensor.
( ^^^ together they form a ‘bridge circuit’ )
+ will use the electrical signals to control the air-conditioning modulating valve.
Cabin Temperature Regulator
REQUIRES: 2 PWR SOURCES - for automatic temperature control: 28VDC & 115VAC.
*If either power source is lost, it will NOT function & automatic temperature control will be lost.*
* Controls Mod. Valve During Auto *
Cabin Temperature Regulator
+ functions to control the cabin temperature at a temperature pre-selected by the pilot or person operating the air conditioning system.
Consists of 5 Components:
- cabine temperature sensor
- duct temperature sensor
- air conditioning modulating valve
- cabin temperature regulator
- & cabin temperature selector.
Automatic Temperature Control Circuit
- provides ventilation of the aircraft cabin & cooling of electronic equipment during an emergency.
+ located on the left side of the aircraft fuselage
+ sits flush w/ the skin on the aircraft
+ actuated by 115- VAC motor
+ controlled by the cabin pressure master switch
+ Shuts off Whole AC Sys
* Dumps Pressure *
Emergency Retractable Ram Air scoop
*** extended/opened: when outside air required to ventilate the cabin. ***
*** retracted/closed : during normal operation of the air conditioning system. ***
- a four position switch used to turn the air conditioning system on or off.
4 POSITIONS: RAM - OFF - 7.45 (normal) - 4.50 (combat)
SW @ 7.45 or 4.50 :
*will open the body crossover manifold valve & ac shutoff valve to provide conditioned air to the aircraft cabin.
SW @ OFF : will stop airflow into the air conditioning shutoff valve.
SW @ RAM :
- will energize the open winding of the 115VAC-motor & open the valve.
- will also close the air conditioning shutoff valve, thus shuts down ac sys. down
- will energize a pressure dump control valve to dump cabin pressure.
* CABIN P-M SW PLACED TO ANY OTHER POS. : will energize the closed windings of the 115VAC motor & keep the valve closed.
Cabin Pressure Master Switch
+ The Air conditioning shutoff valve is regulated at
140 pounds per minute (PPM) by a pack pressure limiter.