AFS4-1
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Questions and Answers

What is the primary function of the shut-off valve?

  • To mix air and fuel in the engine
  • To regulate the temperature in the aircraft
  • To control the air flowing through to the flow control valve (correct)
  • To regulate air pressure in the cabin

    • What triggers the shut-off valve to open?

  • A pneumatic signal from the engine
  • An electrical signal from the air conditioning control panel (correct)
  • A manual override from the pilot
  • A mechanical signal from the air conditioning control panel

    • What is the function of the metering valve ball?

  • To regulate the air pressure in the system
  • To mix air and fuel in the engine
  • To regulate the temperature in the aircraft
  • To meter the air flow into the piston chamber (correct)

    • What is the purpose of the actuating piston?

    <p>To open the butterfly valve, allowing bleed air to flow through the system</p> Signup and view all the answers

    What is the function of the spring load on the piston?

    <p>To calibrated the metering valve to bleed air into the piston chamber</p> Signup and view all the answers

    What does the flow control valve maintain?

    <p>A pressure ratio between the bleed air pressure and the cabin air pressure</p> Signup and view all the answers

    What is the purpose of the pressure ratio limiting unit?

    <p>To maintain a pressure ratio between the bleed air pressure and the cabin air pressure</p> Signup and view all the answers

    What is the source of the bleed air that enters the air cycle system?

    <p>The aircraft's engines or auxiliary power unit</p> Signup and view all the answers

    What are the three difficulties that have been solved with the advent of aircraft environmental systems?

    <p>Effects of altitude, low temperature, and low humidity</p> Signup and view all the answers

    What is the primary function of air-conditioning in an aircraft?

    <p>To condition the air for human habitation</p> Signup and view all the answers

    What is the result of a decrease in partial pressure of oxygen in the lungs?

    <p>Decreased oxygen absorption</p> Signup and view all the answers

    What is the approximate oxygen pressure at sea level?

    <p>3 PSI</p> Signup and view all the answers

    What is the term for the lack of sufficient oxygen reaching the cells in the body?

    <p>Hypoxia</p> Signup and view all the answers

    What is the purpose of pressurisation in an aircraft?

    <p>To combat low oxygen pressure</p> Signup and view all the answers

    What percentage of the total air pressure is exerted by oxygen at any given altitude?

    <p>One-fifth</p> Signup and view all the answers

    What is the consequence of hypoxia?

    <p>Decreased oxygen in the blood</p> Signup and view all the answers

    What is the primary function of the temperature selector in the cabin temperature control panel?

    <p>To select a desired cabin temperature</p> Signup and view all the answers

    In automatic mode, what receives inputs from the temperature selector and temperature sensors?

    <p>The centralised environmental controller</p> Signup and view all the answers

    What happens when the mode selector is set to manual?

    <p>The mixing valves are electrically driven by the switch position</p> Signup and view all the answers

    What is the main cause of dehydration at high altitude?

    <p>Excess water loss through breathing</p> Signup and view all the answers

    What type of switch is used in the manual mode?

    <p>Spring-loaded to the centre position</p> Signup and view all the answers

    What is the ideal relative humidity for human comfort?

    <p>Between 30% and 70%</p> Signup and view all the answers

    What is recommended when using manual temperature control?

    <p>Make small changes to the temperature setting</p> Signup and view all the answers

    Why is it necessary to increase the moisture content of the conditioned air in an aircraft at high altitude?

    <p>To overcome physical discomfort arising from low humidity</p> Signup and view all the answers

    What type of aircraft typically has a simplified control panel?

    <p>Fighter aircraft</p> Signup and view all the answers

    What is the purpose of the indicators in the cabin temperature control system?

    <p>To advise the aircrew of system parameters</p> Signup and view all the answers

    What is the purpose of a heat exchanger in a pressurisation system?

    <p>To cool the pressurisation air</p> Signup and view all the answers

    What type of information may be displayed on the indicators in some larger aircraft?

    <p>The mixing valve positions and temperature gauges</p> Signup and view all the answers

    What is the ideal temperature range for human comfort?

    <p>Between 20°C and 30°C</p> Signup and view all the answers

    What is the effect of compression on air temperature?

    <p>It increases the temperature</p> Signup and view all the answers

    What is the primary factor that determines the source of air to pressurise an aircraft?

    <p>Engine type</p> Signup and view all the answers

    What happens when the mode selector is moved to 'manual'?

    <p>The centralised environmental controller is disabled</p> Signup and view all the answers

    What is the primary function of the air distribution system?

    <p>To divide conditioned air to the airplane zones</p> Signup and view all the answers

    What happens to the air in the cabin after it is released from ceiling vents?

    <p>It circulates and flows out floor-level vents</p> Signup and view all the answers

    Where is the ducting typically located in the aircraft?

    <p>Below the cabin floor and behind walls and ceiling panels</p> Signup and view all the answers

    What is the purpose of the air distribution system in relation to lavatories and galleys?

    <p>To remove offensive air from lavatories and galleys</p> Signup and view all the answers

    What is the result of the air flowing through the cabin and baggage compartments?

    <p>The air flows out of the pressure vessel through the outflow valve</p> Signup and view all the answers

    What should be done when using manual temperature control?

    <p>Make small changes to the temperature setting</p> Signup and view all the answers

    What is the characteristic of the air flow in the cabin?

    <p>It is nearly imperceptible</p> Signup and view all the answers

    Study Notes

    Shut-off Valve

    • The shut-off valve controls air flow to the flow control valve and its design varies depending on the type and application.
    • When bleed air is required, an electrical signal is sent to the solenoid, which moves the metering valve ball, allowing bleed air to flow.

    Flow Control Valve

    • The flow control valve maintains a pressure ratio between bleed air pressure and cabin air pressure.
    • It solves problems caused by altitude, low temperature, and low humidity.

    Effects of Altitude

    • Hypoxia occurs when the lungs do not absorb sufficient oxygen due to decreased oxygen pressure.
    • Oxygen pressure is approximately 1/5 of total air pressure, and at sea level, it is sufficient to saturate the blood.
    • At high altitude, oxygen pressure decreases, leading to hypoxia.

    Air Conditioning

    • Air conditioning conditions air for human habitation and combats low oxygen pressure.
    • Conditioned air is treated and circulated throughout the flight deck and cabin.

    Humidity and Comfort

    • At high altitude, air is dry, and humidity is low, leading to dehydration.
    • The comfort zone for humans is 20°C to 30°C with 30% to 70% relative humidity.

    Pressurisation Systems

    • Sources of pressurised air vary with engine type.
    • Air is cooled using heat exchangers or cold ambient air.

    Cabin Temperature Control

    • The control panel varies depending on the aircraft type.
    • In automatic mode, the system processes inputs from temperature sensors and sends drive signals to mixing valves.
    • In manual mode, the system is controlled by the temperature selector switch.

    Air Distribution System

    • The system distributes conditioned air to airplane zones, reduces engine bleed requirements, and removes offensive air from lavatories and galleys.
    • Air is ducted from the pressurisation source into and throughout the cabin.

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    Description

    Learn about the design and operation of shut-off valves in aviation technical systems, including their role in controlling air flow to flow control valves.

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