Understanding Aircraft Fuel Systems and Carburetor Icing

1. The basic purpose of adjusting the fuel/air mixture at altitude is to...

Decrease the fuel flow in order to compensate for decreased air density.

Increase the fuel flow to account for increased air density.

Keep the fuel flow constant regardless of altitude.

Adjust the air intake only, without changing the fuel flow.

When flying at higher altitudes, the air density decreases, which means less oxygen is available for combustion. To maintain the correct fuel/air ratio, the fuel flow needs to be decreased to prevent a rich mixture.

Explanation

When flying at higher altitudes, the air density decreases, which means less oxygen is available for combustion. To maintain the correct fuel/air ratio, the fuel flow needs to be decreased to prevent a rich mixture.

2. While cruising at 9,500 feet MSL, the fuel/air mixture is properly adjusted. What will occur if a descent to 4,500 feet MSL is made without readjusting the mixture?

The fuel/air mixture may become excessively lean.

The fuel/air mixture may become excessively rich.

There will be no change in the fuel/air mixture.

The engine will stop running.

When descending without readjusting the fuel/air mixture, the decrease in altitude leads to an increase in air density. This increase can cause the mixture to become excessively lean, potentially resulting in engine roughness or performance issues.

Explanation

When descending without readjusting the fuel/air mixture, the decrease in altitude leads to an increase in air density. This increase can cause the mixture to become excessively lean, potentially resulting in engine roughness or performance issues.

3. What condition is most favorable to the development of carburetor icing?

Temperature below 10 degrees F and low humidity.

Precipitation and low humidity.

Temperatrue between 20 and 70 degrees F and high humidity

High temperature and low humidity.

Carburetor icing occurs when the temperature is between 20 and 70 degrees F and humidity is high, leading to ice formation in the carburetor. The incorrect answers do not align with the specific conditions required for carburetor icing to develop.

Explanation

Carburetor icing occurs when the temperature is between 20 and 70 degrees F and humidity is high, leading to ice formation in the carburetor. The incorrect answers do not align with the specific conditions required for carburetor icing to develop.

4. The possibility of carburetor icing exists even when the ambient air temperature is as high as 70 degrees F and the relative humidity is high.

High as 70 degrees F and the relative humidity is high.

Low as 70 degrees F and the relative humidity is low.

High as 90 degrees F and the relative humidity is low.

Low as 70 degrees F and the relative humidity is high.

Carburetor icing can occur at temperatures as high as 70 degrees F when the relative humidity is high due to the cooling effect of the fuel and air mixture as it enters the intake system.

Explanation

Carburetor icing can occur at temperatures as high as 70 degrees F when the relative humidity is high due to the cooling effect of the fuel and air mixture as it enters the intake system.

5. What change occurs in the fuel/air mixture when the carburetor heat is applied?

The fuel/air mixture becomes leaner.

The fuel/air mixture becomes colder.

The fuel/air mixture becomes richer.

The fuel/air mixture remains the same.

When carburetor heat is applied, it warms the air going into the engine, causing the fuel/air mixture to become richer.

Explanation

When carburetor heat is applied, it warms the air going into the engine, causing the fuel/air mixture to become richer.

6. What effect does the use of carburetor heat generally have on engine performance?

Decrease engine performance.

Improve engine performance.

Increase engine performance.

Have no effect on engine performance.

When carburetor heat is used, it warms the air entering the carburetor, which decreases its density and tends to decrease engine performance due to the reduced amount of oxygen available for combustion.

Explanation

When carburetor heat is used, it warms the air entering the carburetor, which decreases its density and tends to decrease engine performance due to the reduced amount of oxygen available for combustion.

7. With regard to carburetor ice, float type carburetor systems in comparison to fuel injection systems are generally considered to be...

Less susceptible to icing.

Not affected by icing.

More susceptible to icing.

Equally susceptible to icing.

Float type carburetor systems are more susceptible to icing due to the design of the carburetor and how it functions compared to fuel injection systems.

Explanation

Float type carburetor systems are more susceptible to icing due to the design of the carburetor and how it functions compared to fuel injection systems.

8. What operating principle are float-type carburetors based on?

Difference in air pressure at the venturi throat and the air inlet.

Temperature gradient within the carburetor.

Amount of fuel in the float chamber.

Speed of the engine's rotation.

Float-type carburetors rely on the difference in air pressure at the venturi throat and the air inlet to regulate the flow of fuel into the engine.

Explanation

Float-type carburetors rely on the difference in air pressure at the venturi throat and the air inlet to regulate the flow of fuel into the engine.

9. At what OAT and relative humidity can carburetor icing occur?

25 degrees C and high relative humidity.

20 degrees C and high relative humidity.

10 degrees C and low relative humidity.

15 degrees C and moderate relative humidity.

Carburetor icing can occur when the temperature is around 20 degrees C and there is high relative humidity, which creates condensation in the intake air.

Explanation

Carburetor icing can occur when the temperature is around 20 degrees C and there is high relative humidity, which creates condensation in the intake air.

10. Applying carburetor heat will...

Enrich the fuel/air mixture.

Increase engine rpm.

Improve fuel efficiency.

Lean out the fuel/air mixture.

Carburetor heat is applied to prevent ice formation in the carburetor by warming the incoming air. This process enriches the fuel/air mixture to compensate for the reduced air density caused by ice buildup potential, thereby preventing engine power loss or stall.

Explanation

Carburetor heat is applied to prevent ice formation in the carburetor by warming the incoming air. This process enriches the fuel/air mixture to compensate for the reduced air density caused by ice buildup potential, thereby preventing engine power loss or stall.