Environmental Flashcards
Air conditioner
•Air-cycle machines
•Found on turbine aircraft
•Compressed air is bled from turbine and used to pressurize the cabin
•Vapor-cycle systems
•Used on light reciprocating engine aircraft
•Pressurized liquid refrigerant (Freon) evaporates, causing temperature reductio
Air cycle machine theory
•Uses pressurized air from turbine compressors
•Called “bleed air”
•System utilizes heat exchangers, an expansion Turbine, and electronic control valves to produce pressurized cabin air of selected temperatures
Air cycle machine components
Pack Valve – controls the supply of hot pressurized air. Closes when system overheats, or abnormal condition occurs
•Primary Heat Exchanger – warm bleed air is sent through a heat exchanger to cool. Outside ram air runs across the exchanger to cool the air inside
Air flows from Primary Heat Exchanger into a turbine
•The air is compressed (causes a temp rise)
•Goes through a Secondary Heat Exchanger and the Turbine
•Air then expands, losing energy and cooling down
Air is then ducted through a water separator to remove excess moisture
•The filtered water is injected into air flowing over heat exchangers to increase cooling
Bleed Air Bypass – to regulate temperature entering the cabin, bypass valve allows some bleed air to bypass the ACM and is used to regulate temperature of air entering the cabin
Controls-
•Auto
•Env. control system automatically controls bypass valves to regulate cabin temperature
•Manual
•Pack bypass valves are controlled manually to regulate cabin temp
Vapor cycle machine theory
•Closed system in which refrigerant is circulated through tubing and other components
•While circulating, the refrigerant changes state from liquid, to gas and back to liquid
•Similar to air conditioning systems found in homes and automobiles
Vapor cycle machine components
Expansion Valve – changes the high-pressure liquid into a low-pressure liquid with an orifice
•Evaporator – warm air from cabin flows over metal fins. Heat from cabin is absorbed by refrigerant
•The Low-Pressure liquid evaporates due to the heat
•Liquid in the system changes to a vapor due to evaporation
•Compressor – piston sucks in the low-pressure vapor, compresses it into a high-pressure vapor
Condenser Coil – Ambient air flows over fins to cool down the high-pressure vapor.
•As the vapor condenses it cools down and turns back into a liquid
•Receiver Dryer – acts as the reservoir and filter for the refrigerant
Air conditioner
•Not commonly found on low powered single or multi-engine light aircraft
•High initial purchase & operating costs
•System management adds to pilot workload
•Operation may cause a decrease in cruise speed & range
•Weight penalty lowers useful load
•Engine power required to run compressor decreases thrust output
•Must be turned OFF during takeoff & max performance operations
•Must be turned OFF prior to landing approach, for possible go-around
Exhaust manifold heater
Found on single engine airplanes
•Simple but effective system if properly installed, inspected, & maintained
Advantages
• No reduction in flight performance
• No consumption of fuel
• No reduction of engine power
• No decreased airspeed or range
Disadvantages
• Ineffective ground heater
• Poor windshield defrosting
• CO poisoning threat
Combustion heater
Three basic light airplane types
•Janitrol Combustion Heater and
•C&D Associates Combustion Heater
•Found on Piper multiengine aircraft
•Stewart Warner Southwind Heater
Disadvantages
• Reduced flight performance
• Consumes fuel
• Decreases range
• CO poisoning threat
Uses a separate source of heat that is not dependent on the aircrafts engine
•Instant heat without starting engine
•Found on most multiengine airplanes
•Located in forward fuselage nose cone
•Has it’s own Hobbs to monitor usage
•Requires routine overhaul (generally every 500 hours or 24 months)
Janitrol combustion heater
•Combustion Air – ambient air is scooped from the outside of the aircraft
•Blower – ensures the correct amount and pressure of air enter the chamber
•Spray nozzle - provides a regulated, atomized fuel/air mixture to heater “whirling flame” combustion chamber
Spark Plug – provides continuous ignition with a high voltage spark
•Outside Air – is ducted through different tubing around the combustion chamber
•Similar to the Exhaust Manifold System
•Ground Blower – is used to provide the system with outside air when the aircraft is not moving
•Requires a separate fuel pump
•Burns Avgas from aircraft fuel system
•Electric fuel pump draws fuel from tank
•Left tank @ ½ gallon per hour (Seminole)
•Up to 2 gals an hour depending on type
Janitoral combustion heater components
Combustion Air Pressure Switch
•Ensures adequate airflow for combustion
•Air Intake (duct) Switch
•Deactivates heater if there is insufficient airflow for cabin
•Overheat Limit Switch
•Safety device to deactivate the heater if a malfunction should occur
•HEATER OVER TEMP annunciator light
•Only MX can reset
•Temperature Cycling Switch
•Turns on/off FUEL to regulate temperature
•Nose Gear Up-limit witch
•Turns off the ventilation blower so that cabin air is circulated by ram air pressure
Heater switches
Overtemp Limit Switch
•Manual Reset = Janitrol
•Auto Reset = C&D
•Cycling Thermostat
Pressure Switch
•Detects crack in combustion chamber
•Nose gear up-limit switch
•Shuts off Vent Air/Heat Blower
Heater components
Controls
•Switches
▪Cabin Heat/Fan
▪Recirculation Blower
•Levers
▪Air Intake
▪Temperature
▪Defroster
•Hour Meter
•Janitrol Heater Only
Abnormal heater conditions
Heater Overtemp
•Thermal Switch
•300 - 400o F
•Heater Overtemp Light
•Action
▪Shut off heater/turn on fan
▪Open fresh air vent
▪Land as soon as practical
