FUEL METERING SYSTEM

95問 • 1年前

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If the main air bleed of a float-type carburetor becomes clogged, the engine will run

rich at rated power

One of the best ways to increase engine power and control detonation and preignition is to

use water injection

One purpose of an air bleed in a float-type carburetor is to

decrease fuel density and destroy surface tension.

An excessively lean fuel/air mixture may cause

an increase in cylinder head temperature.

When checking the idle mixture on a carburetor, the engine should be idling normally, then pull the mixture control toward the IDLE CUTOFF position. A correct idling mixture will be indicated by

an increase of 10 to 50 RPM before decreasing.

Detonation occurs when the fuel/air mixture

burns too fast

What component is used to ensure fuel delivery during periods of rapid engine acceleration?

Acceleration pump

In order to stabilize cams, springs, and linkages within the fuel control, manufacturers generally recommend that all final turbine engine trim adjustments be made in the

increase direction

If the idling jet becomes clogged in a float-type carburetor, the

engine will not idle

A carburetor is prevented from leaning out during quick acceleration by the

accelerating system

For what primary purpose is a turbine engine fuel control unit trimmed?

To obtain maximum thrust output when desired.

What is the relationship between the pressure existing within the throat of a venturi and the velocity of the air passing through the venturi?

The pressure is inversely proportional to the velocity.

The fuel metering force of a conventional float-type carburetor in its normal operating range is the difference between the pressure acting on the discharge nozzle located within the venturi and the pressure

acting on the fuel in the float chamber.

A major difference between the Teledyne-Continental and RSA (Precision Airmotive or Bendix) continuous flow fuel injection systems in fuel metering is that the

Continental system uses fuel pressure only as a metering force.

(1) The mixture used at rated power in air cooled reciprocating engines is richer than the mixture used through the normal cruising range. (2) The mixture used at idle in air cooled reciprocating engines is richer than the mixture used at rated power. Regarding the above statements,

both No. 1 and No. 2 are true

Generally, the practice when trimming an engine is to

turn all accessory bleed air off.

The device that controls the volume of the fuel/air mixture to the cylinders is called a

throttle valve

During engine operation, if carburetor heat is applied, it will

decrease the air density to the carburetor.

Anine-cylinder radial engine, using a multiple-point priming system with a central spider, will prime which cylinders?

One, two, three, eight, and nine.

What effect does high atmospheric humidity have on the operation of a jet engine?

Has little or no effect

The throttle valve of float-type aircraft carburetors is located

between the venturi and the engine.

On a float-type carburetor, the purpose of the economizer valve is to

provide a richer mixture and cooling at maximum power output.

In turbine engines that utilize a pressurization and dump valve, the dump portion of the valve

drains the engine manifold lines to prevent fuel boiling and subsequent deposits in the lines as a result of residual engine heat (at engine shutdown).

If a float-type carburetor becomes flooded, the condition is most likely caused by

a leaking needle valve and seat assembly.

Which of the following is NOT an input parameter for a turbine engine fuel control unit?

Ambient humidity

An aircraft should be facing into the wind when trimming an engine. However, if the velocity of the wind blowing into the intake is excessive, it is likely to cause a

false high compression and turbine discharge pressure, and a subsequent low trim.

When troubleshooting an engine for too rich a mixture to allow the engine to idle, what would be a possible cause?

Economizer valve not operating correctly.

An aircraft engine equipped with a pressure-type carburetor is started with the

primer while the mixture control is positioned at IDLE CUTOFF.

The back-suction mixture control system operates by

varying the pressure acting on the fuel in the float chamber.

On an engine equipped with a pressure-type carburetor, fuel supply in the idling range is ensured by the inclusion in the carburetor of

a spring in the unmetered fuel chamber to supplement the action of normal metering forces.

What should be checked/changed to ensure the validity of a turbine engine performance check if an alternate fuel is to be used?

Fuel specific gravity setting

The device that controls the ratio of the fuel/air mixture to the cylinders is called a

mixture control

Select the statement which is correct relating to a fuel level check of a float-type carburetor

Do not measure the level at the edge of the float chamber.

If an aircraft engine is equipped with a carburetor that is not compensated for altitude and temperature variations, the fuel/air mixture will become

richer as either the altitude or temperature increases.

An aircraft engine continuous cylinder fuel injection system normally discharges fuel during which stroke(s)?

All (continuously).

What carburetor component actually limits the desired maximum airflow to the engine at full throttle?

Venturi

The desired engine idle speed and mixture setting

is adjusted with engine warmed up and operating.

An indication that the optimum idle mixture has been obtained occurs when the mixture control is moved to IDLE CUTOFF and manifold pressure

decreases and RPM increases momentarily before the engine ceases to fire.

Which method is commonly used to adjust the level of a float in a float-type carburetor?

Add or remove shims under the needle-valve seat.

Under which of the following conditions will the trimming of a turbine engine be most accurate?

No wind and low moisture

What factor is not used in the operation of an aircraft gas turbine engine fuel control unit?

Mixture control position

Which statement is correct regarding a continuous-flow fuel injection system used on many reciprocating engines?

Fuel is injected at each cylinder intake port.

At what engine speed does the main metering jet actually function as a metering jet in a float-type carburetor?

All RPM’s above idle range.

.When a new carburetor is installed on an engine,

the engine is warmed up to normal temperatures, adjust the idle mixture, then the idle speed.

What carburetor component measures the amount of air delivered to the engine?

Venturi

What is the relationship between the accelerating pump and the enrichment valve in a pressure injection carburetor?

No relationship since they operate independently.

Which of the following is NOT a function

Regulates the idle system

.A full-authority electronic engine control (EEC) is a system that receives all the necessary data for engine operation and

develops the commands to various actuators to control engine parameters.

One of the things a metering orifice in a main air bleed helps to accomplish (at a given altitude) in a carburetor is

pressure in the float chamber to increase as airflow through the carburetor increases.

During the operation of an aircraft engine, the pressure drop in the carburetor venturi depends primarily upon the

air velocity

Which type of fuel control is used on most of today’s turbine engines?

Hydromechanical or electronic

When trimming a turbine engine, the fuel control is adjusted to

set idle RPM and maximum speed or EPR.

Ona carburetor without an automatic mixture control as you ascend to altitude, the mixture will

be enriched

What corrective action should be taken when a carburetor is found to be leaking fuel from the discharge nozzle?

Replace the needle valve and seat.

In a supervisory EEC system, any fault in the EEC that adversely affects engine operation

causes an immediate reversion to control by the hydromechanical fuel control unit.

Which of the following is least likely to occur during operation of an engine equipped with a direct cylinder fuel injection system?

Backfiring

If the volume of air passing through a carburetor venturi is reduced, the pressure at the venturi throat will

increase

The purpose of the back-suction mixture control in a float-type carburetor is to adjust the mixture by

regulating the pressure on the fuel in the float chamber.

The function of the altitude compensating, or aneroid valve used with the Teledyne-Continental fuel injection system on many turbocharged engines is to

prevent an overly rich mixture during sudden acceleration

How will the mixture of an engine be affected if the bellows of the automatic mixture control (AMC) in a pressure carburetor ruptures while the engine is operating at altitude?

It will become richer

A supervisory electronic engine control (EEC) is a system that receives engine operating information and

adjusts a standard hydromechanical fuel control unit to obtain the most effective engine operation.

Where is the throttle valve located on a float-type carburetor?

After the main discharge nozzle and venturi.

.The economizer system in a float-type carburetor

increases the fuel/air ratio at high power settings.

Under which of the following conditions would an engine run lean even though there is a normal amount of fuel present?

Incomplete fuel vaporization.

The active clearance control (ACC) portion of an EEC system aids turbine engine efficiency by

ensuring turbine blade to engine case clearances are kept to a minimum by controlling case temperatures.

What method is ordinarily used to make idle speed adjustments on a float-type carburetor?

An adjustable throttle stop or linkage.

Which of the following best describes the function of an altitude mixture control?

Regulates the richness of the fuel/air charge entering the engine.

What could cause a lean mixture and high cylinder head temperature at sea level or low altitudes?

Automatic mixture control stuck in the extended position.

A punctured float in a float-type carburetor will cause the fuel level to

rise, and enrich the mixture.

Which of the following causes a single diaphragm accelerator pump to discharge fuel?

An increase in manifold pressure that occurs when the throttle valve is opened.

During idle mixture adjustments, which of the following is normally observed to determine when the correct mixture has been achieved?

Changes in RPM or manifold pressure.

The generally acceptable way to obtain accurate on-site temperature prior to performing engine trimming is to

hang a thermometer in the shade of the nose wheel- well until the temperature reading stabilizes.

What are the positions of the pressurization valve and the dump valve in a jet engine fuel system when the engine is shut down?

Pressurization valve closed, dump valve open.

What is a function of the idling air bleed in a float-type carburetor?

It aids in emulsifying/vaporizing the fuel at idle speeds.

If an engine is equipped with a float-type carburetor and the engine runs excessively rich at full throttle, a possible cause of the trouble is a clogged

main air bleed

A mixture ratio of 11:1 normally refers to

1 part fuel to 11 parts air.

What will occur if the vapor vent float in a pressure carburetor loses its buoyancy?

The amount of fuel returning to the fuel tank from the carburetor will be increased.

The metered fuel pressure (chamber C) in an injection-type carburetor

is held constant throughout the entire engine operating range.

Why must a float-type carburetor supply a rich mixture during idle?

Because at idling speeds the engine may not have enough airflow around the cylinders to provide proper cooling.

If a float-type carburetor leaks fuel when the engine is stopped, a likely cause is that the

float needle valve is worn or otherwise not seated properly.

A reciprocating engine automatic mixture control responds to changes in air density caused by changes in

altitude or temperature

When air passes through the venturi of a carburetor, what three changes occur?

Velocity increases, temperature decreases, and pressure decreases.

Float-type carburetors which are equipped with economizers are normally set for

their leanest practical mixture delivery at cruising speeds and enriched by means of the economizer system at higher power settings.

What is the possible cause of an engine running rich at full throttle if it is equipped with a float-type carburetor?

Clogged main air bleed.

The use of less than normal throttle opening during starting will cause

a rich mixture

The primary purpose of the air bleed openings used with continuous flow fuel injector nozzles is to

aid in proper fuel vaporization.

The density of air is very important when mixing fuel and air to obtain a correct fuel-to-air ratio. Which of the following weighs the most?

100 parts of dry air.

Reciprocating engine power will be decreased at all altitudes if the

humidity is increased

Select the correct statement concerning the idle system of a conventional float-type carburetor.

The low pressure between the edges of the throttle valve and the throttle body pulls the fuel from the idle passage.

An aircraft carburetor is equipped with a mixture control in order to prevent the mixture from becoming too

rich at high altitudes

To determine the float level in a float-type carburetor, a measurement is usually made from the top of the fuel in the float chamber to the

parting surface of the carburetor

The economizer system of a float-type carburetor performs which c following functions?

It supplies and regulates the additional fuel required for all engine speeds abovecruising.

Fuel is discharged for idling speeds on a float-type carburetor

from the idle discharge nozzle

The fuel level within the float chamber of a properly adjusted float-type carburetor will be

slightly lower than the discharge nozzle outlet.

What is the purpose of the carburetor accelerating system?

Temporarily enrich the mixture when the throttle is suddenly opened.

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