Engine Mixture Control and Fuel Economy Quiz
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Questions and Answers

What is the purpose of a cut-off valve in the slow running passage of a carburetor?

  • To increase throttle response during acceleration
  • To block the air intake into the cylinder
  • To improve fuel efficiency at high altitudes
  • To weaken the fuel mixture until combustion cannot be sustained (correct)
  • How does air density affect the fuel mixture in a carburetor as altitude increases?

  • Leads to a richer fuel mixture (correct)
  • Does not impact the fuel mixture
  • Causes an increase in air drawn into the cylinder
  • Results in a leaner fuel mixture
  • In a needle type mixture control, what does moving the lever up or down do?

  • Stops the flow of air into the engine
  • Changes the pressure in the float chamber
  • Determines the mixture strength by adjusting the needle valve (correct)
  • Adjusts the air intake to the cylinder
  • What is the main function of the fuel strainer in a carburetor system?

    <p>To prevent blockages in the fuel jet from dirt or debris</p> Signup and view all the answers

    What happens when a needle in a needle type mixture control is fully down?

    <p>Blocks fuel flow to the main jet</p> Signup and view all the answers

    Why is it important for carburetors to ensure a smooth transition between slow running and main systems?

    <p>To avoid flat spots and poor throttle response during acceleration</p> Signup and view all the answers

    What role does a cut-off valve play when operating an engine?

    <p>Shuts down the engine by weakening the mixture until combustion can't be sustained</p> Signup and view all the answers

    Why does altitude affect the air-fuel ratio in a carburetor system?

    <p>As altitude rises, there is a decrease in air density, leading to a richer fuel mixture</p> Signup and view all the answers

    What causes a richer fuel mixture at higher altitudes in relation to carburetors?

    <p>Air density decrease causes less reduction in fuel flow rate</p> Signup and view all the answers

    In a carburetor system, what is the function of a cut-off valve?

    <p>Blocks fuel flow for engine shutdown by weakening mixture until combustion can't be sustained</p> Signup and view all the answers

    Study Notes

    Fuel-Air Mixture and Engine Performance

    • A progressively richer fuel-air mixture can cause engine roughness and significant power loss.
    • Roughness is often a result of spark plug fouling due to excess carbon buildup.

    Mixture Control for Optimal Engine Function

    • Monitoring engine temperature is crucial for adjusting the fuel-air mixture appropriately.
    • An exhaust gas temperature (EGT) gauge aids in achieving proper mixture control and enhances fuel economy for fuel-injected engines.

    Reference Procedures for Mixture Adjustment

    • Mixture adjustment methods vary across aircraft models; always consult the Aircraft Flight Manual (AFM) or Pilot's Operating Handbook (POH) for specific guidelines.

    Air Bleed Mixture Control System

    • Air Bleed Mixture Control adjusts air pressure in the float chamber to regulate fuel flow.
    • A small air bleed between the float chamber and the Venturi lowers air pressure, directly affecting fuel flow.
    • A cockpit lever-operated valve manages the air flow into the float chamber, influencing mixture richness.

    Valve Functionality in Mixture Control

    • When the valve is fully open, maximum air pressure leads to a rich mixture; closing the valve decreases air pressure, weakening the mixture.
    • In 'idle cut-off' position, the cockpit control connects air pressure from the float chamber to stop fuel flow and engine operation.

    Power Enrichment Techniques

    • At power settings above cruising, a richer mixture is essential to prevent engine detonation.
    • Methods for achieving power enrichment include:
      • Additional Fuel Supply: Adding extra fuel to enrich mixture.
      • Carburetor Adjustment: Modifying the carburetor to ensure a rich mixture during high power settings.
      • Float Chamber Pressure Adjustment: Bleeding off pressure to reduce fuel flow for cruising.

    Economizer Jet Functionality

    • Some carburetors feature a power enrichment or economizer jet that includes an extra needle valve.
    • As throttle opens beyond a certain point, this needle valve gradually opens, fully engaging at full throttle to increase fuel supply.

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    Description

    Test your knowledge on engine mixture control and fuel economy measures. Learn about monitoring engine temperature, enriching the mixture, and using exhaust gas temperature gauges for better fuel economy.

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