Module 5 Carburetors

Question 1

Main metering components

Answer 1

• Fuel regulator
• Main metering jet
• Throttle valve

Question 2

Functions of the Fuel regulator ?

Answer 2

Responsible for metering the appropriate amount of fuel

Question 3

Function of Main Metering jet?

Answer 3

calibrate orifice

Question 4

Function of throttle valve ?

Answer 4

Determines airflow through carburetor

Question 5

Primary purpose of carburetor is to:

Answer 5

Deliver the proper fuel/air ratio so it can combust

Question 6

What is the function of the Venturi in the carburetor?

Answer 6

To create pressure differential required to deliver fuel

Question 7

The pressure reduction created in the throat of a carburetor Venturi is due to ?

Answer 7

Velocity

Bernoulli’s principle

Question 8

Explain Bernoulli’s principle ?

Answer 8

As velocity increase pressure and temp decrease

Question 9

Main disadvantage of the carburetor

Answer 9

• Susceptible to icing
• Affect by maneuvers
• Incomplete vaporization of fuel

Question 10

Why are float type carburetors prone to icing

Answer 10

The main discharge nozzle deliver fuel to the throat of the carburetor where the greatest temperature reduction is

Question 11

Main factor contributing to carb icing?

Answer 11

Humidity

Question 12

When applying carb heat the engine will?

Answer 12

Experience loss power and immediately run rough due to rich mixture

Question 13

What is the most common method to prevent carb icing?

Answer 13

Pre heat the air before entering the carburetor by either Heat muff or engine compartment air

Question 14

What does updraft it downdraft refer to :

Answer 14

Direction of the air flow

Question 15

Main purpose of the throttle valve

Answer 15

Regulate the power output of the engine

Question 16

On a float type carburetor, where is the throttle plate located?

Answer 16

After the main discharge nozzle and Venturi

Question 17

What is the function of the float needle valve?

Answer 17

Controlled the amount of fuel stored in the float chamber

Question 18

The function of the carburetor jet (fixed orifice) is to:

Answer 18

Meter fuel - control and limit WF (fuel flow) at full throttle

Question 19

What is the function of the metering system ?

Answer 19

To supply fuel flow at all conditions above idle

Question 20

What is the source and purpose of the main air bleed in float-type carb:

Answer 20

Atmospheric air add to emulsify the fuel, refusing the surface tension assuring with better vaporization.

Question 21

Why is the idle system necessary in a carburetor?

Answer 21

At idle speeds the airflow through the Venturi is not sufficient to draw fuel out to the main discharge nozzle

Question 22

Where does idle systems discharge fuel ?

Answer 22

Through small ports adjacent to the throttle valve

Question 23

What is the function of the idle jet ?

Answer 23

Meters the fuel at idle speeds, and is an integral part of the emulation tube

Question 24

The adjustment of the idle mixture affects ?

Answer 24

Idle power only

Question 25

What is an indication of the idle mixture is to rich ?

Answer 25

RPM rise of 100, rough running with black smoke from the exhaust

Question 26

How does the Manual mixture control work on the pressure carburetor?

Answer 26

Variable air bleed between the chamber A-B

Question 27

How is the automatic mixture control (AMC) compensates for changes in air density?

Answer 27

Used brass bellows filled with helium to actuate a reverse tapered needle valve, to change the relationship between impact air and Venturi air.
As ambient pressure change the bellows expand and contracts, varying the size of the air bleed orifice between chamber A-B

Question 28

How does the accelerator in pressure carburetor work ?

Answer 28

Increase the MAP on the diaphragm pressurized fuel in the primary chamber

Question 29

What are the principle functions of the mixture control system?

Answer 29

• Prevent mixture becoming to rich at altitude

- To economize on fuel at Cruise

Question 30

The variable orifice mixture controls mixture by?

Answer 30

A valve which controls the amount of fuel flow to discharge nozzle

Question 31

The back suction mixture control, controls the amount of fuel to discharge nozzle by :

Answer 31

By position of the valve, controlling the differential pressure to the float chamber

Question 32

Improper use of the carburetor mixture control would probably cause ?

Answer 32

Leaning to much causing damage to the engine due to overheat-detonation

Question 33

Describe the difference between the idle mixture control and the manual mixture control ?

Answer 33

• Manual mix control operate from the flight deck and affect all power settings including idle
• Idle mixture control is set on the carburetor and effects idle mixture only

Question 34

The purpose of a power enrichment/economizer is ?

Answer 34

Provide richer fuel/air mixture at higher power setting

Question 35

A power enrichment system that increases fuel flow at higher RPM setting but allows for a leaner mixture cruise is sometimes refer to a?

Answer 35

The (Back suction) economizer system

Question 36

Where is the fuel nozzle placed in a pressure carburetor ?

Answer 36

Downstream of the Venturi, therefore less likely to have carb-icing conditions

Question 37

Differences between pressure carburetor and float type carburetor

Answer 37

The pressure carburetor supplies the fuel pressurized by a fuel pump

Question 38

Most carb includes 5 systems:

Answer 38

• Main metering
• Idling
• Mixture control
• Accelerating
• Power enrichment or economizer