Powerplant: I - Fuel Metering Systems

Front 1

Where does the fuel metering system of a turbine engine discharge its fuel?

Back 1

The fuel is discharged through spray nozzles into the combustion chambers.

Front 2

What is adjusted when the fuel control unit of a turbine engine is trimmed?

Back 2

The idle speed and the maximum–thrust speed.

Front 3

What are two locations water may be injected into a turbine engine?

Back 3

At the compressor inlet and at the inlet to the diffuser section.

Front 4

What is meant by a duplex nozzle in a turbine engine fuel metering system?

Back 4

A duplex fuel nozzle is one that has two fuel discharge passages. A flow divider sends fuel for low–pressure operation through one discharge passage, and when the engine demands more fuel, it is sprayed out through the second discharge passage. The spray pattern keeps the flame centered in the burner for all operating conditions.

Front 5

Does the fuel–air mixture provided by a float carburetor become richer or leaner as the aircraft goes up in altitude?

Back 5

If the mixture is not adjusted, it will become richer as the aircraft gains in altitude.

Front 6

Does the fuel–air mixture provided by a float carburetor become richer or leaner when carburetor heat is applied?

Back 6

The mixture becomes richer when carburetor heat is applied.

Front 7

What would happen to the fuel–air mixture ratio in a float carburetor if the main air bleed were to become plugged?

Back 7

The mixture would become excessively rich.

Front 8

How does the automatic mixture control in a pressure carburetor keep the fuel–air mixture constant as the aircraft changes altitude?

Back 8

It automatically, and progressively, bleeds the air between the two sides of the air diaphragm and decreases the air metering force. This leans the mixture as the aircraft goes up in altitude.

Front 9

What are two purposes of the manifold valve (or flow divider) in the fuel injection system of a horizontally opposed aircraft engine?

Back 9

It provides a constant discharge fuel pressure for idling, and it provides a positive shutoff for the fuel when the engine is shut down.

Front 10

How does the mixture control change the fuel–air mixture ratio on the Teledyne–Continental fuel injection system?

Back 10

When the mixture control is in its Full Rich position, all fuel goes to the manifold valve. When it is in the Idle Cutoff position, all fuel is returned to the pump inlet. Intermediate positions vary the amount of fuel that goes to the engine.

Front 11

Why must the diaphragms of a pressure carburetor be soaked before the carburetor is ready for flight?

Back 11

Soaking the diaphragms of a pressure carburetor restores them to the condition of flexibility that they had when the carburetor was calibrated.

Front 12

What are two basic types of fuel controls for aircraft turbine engines?

Back 12

Hydropneumatic and electro–hydromechanical.

Front 13

How does the exhaust gas temperature of a reciprocating engine tell anything about the fuel–air mixture being burned by the engine?

Back 13

A stoichiometric mixture (a mixture in which all of the constituents of the fuel–air mixture are burned) produces the highest exhaust gas temperature. The mixture is adjusted to get the highest EGT, and then it is enriched to place it on the rich side of stoichiometric.

Front 14

What two things are adjusted when adjusting the idling of a reciprocating engine?

Back 14

The throttle stop, to get the proper idling RPM, and the idle mixture control, to get the smoothest operation.

Front 15

What is controlled by the adjustment of the orifice in the fuel pump of a Teledyne–Continental fuel injection system?

Back 15

The high unmetered fuel pressure.

Front 16

What is the significance of the letters that are stamped on the flats of a fuel injection nozzle?

Back 16

These letters designate the relative size of the orifice in the injector nozzle. The lower the letter in the alphabet, the smaller the amount of fuel the nozzle will flow.

Front 17

What is the function of the derichment valve in a pressure carburetor used on an aircraft engine with an antidetonation injection system?

Back 17

The derichment valve automatically closes to lean the fuel–air mixture when ADI fluid is flowing. As soon as the ADI fluid stops flowing, the derichment valve opens and the mixture returns to its rich condition.

Front 18

What is the function of the economizer system in an aircraft engine carburetor?

Back 18

The economizer (or power enrichment) system allows the engine to operate with an economically lean mixture for all conditions other than full power. When the throttle is opened for full power, the power enrichment system automatically enriches the mixture to remove some of the heat that is developed during this type of operation.

Front 19

In what position is the mixture control placed for starting an engine that is equipped with a pressure carburetor?

Back 19

In the Idle Cutoff position. The engine is started with fuel from the primer system.

Front 20

In what position is the carburetor heat control placed when starting an aircraft engine?

Back 20

In the Cold position.

Front 21

Why is an aircraft reciprocating engine killed by placing the mixture control in the Cutoff position, rather than by using the magneto switch?

Back 21

By shutting off the fuel to the cylinders, the combustion chambers are left full of air with no fuel. This makes the engine less likely to fire if the propeller is pulled through with the ignition switch accidentally on.

Front 22

Where is the fuel from a continuous–flow fuel injection system discharged?

Back 22

It is discharged through injector nozzles screwed into the cylinder heads near the intake valves.

Front 23

In which direction relative to the wind should a turbine–powered aircraft be positioned when the fuel control is being trimmed?

Back 23

If the wind velocity is less than 10 miles per hour, it can be faced in any direction. If the wind velocity is between 10 and 25 MPH, it should be trimmed facing into the wind. The engine should not be trimmed when the wind velocity is more than 25 MPH.

Front 24

What engine parameters are sensed by the fuel control unit of a turbine engine?

Back 24

Engine RPM, inlet air pressure, compressor discharge pressure, burner can pressure, and inlet air temperature.

Front 25

When does the acceleration system operate on an aircraft carburetor?

Back 25

When the throttle is suddenly opened.

Front 26

What parameters are normally sensed by a turbine engine fuel control?

Back 26

Power lever angle
Compressor inlet total temp
Compressor RPM
Burner pressure

Front 27

What is meant by trimming a turbine engine?

Back 27

Adjusting the fuel control for the proper specific gravity of the fuel and for the proper idle and full throttle RPM

Front 28

What are two types of electronic fuel controls for turbine engines?

Back 28

Supervisory Electronic Engine Control and Full–Authority Digital Electronic Control

Front 29

What is a FADEC?

Back 29

Full–Authority Digital Electronic Control is a high–precision digital electronic fuel control that functions during all engine operations.

Front 30

Does a turbine engine controlled by a FADEC require manual trimming?

Back 30

No, this is done by the FADEC

Front 31

When should a turbine engine be retrimmed?

Back 31

Any time there is a decrease in engine thrust, and after any maintenance that the manufacture specifies as requiring retrimming

Front 32

Are the instruments installed in a aircraft suitable for use when trimming a turbine engine?

Back 32

No, a special analyzer/trimmer such as a JetCal should be used

Front 33

What specifications are used to trim a turbine engine?

Back 33

The data plate spec for the specific engine. This data was obtained when the engine was calibrated in the manufacturer's test cell

Front 34

Where should ambient temp be measured when trimming?

Back 34

In a shaded area as near the engine inlet as is practical