Fuel Metering Systems

Question 1

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

Answer 1

The fuel is discharged through spray nozzles into the combustion chambers

Question 2

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

Answer 2

The idle speed and the maximum thrust speed

Question 3

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

Answer 3

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

Question 4

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

Answer 4

A duplex fuel nozzle is one that has two fuel discharge passages.
Flow divider sends fuel for low pressure op. through one discharge passage, and through the other when the engine demands more fuel.
Spray pattern keeps the flame centered in burner for all op. conditions

Question 5

What is the function of a float carburetor?

Answer 5

The fuel carburetor’s function is to measure airflow through the engine induction system and dispense the appropriate amount of gasoline into the airflow for all engine operating perimiters and conditions. Must also provide fuel in a state it is vaporized as possible by the time ignition occurs in the engine cylinders

Question 6

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

Answer 6

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

Question 7

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

Answer 7

The mixture becomes richer when carburetor heat is applied

Question 8

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

Answer 8

The mixture would become excessively rich

Question 9

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

Answer 9

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.

Question 10

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

Answer 10

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

Question 11

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

Answer 11

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 into the engine.

Question 12

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

Answer 12

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

Question 13

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

Answer 13

Hydropneumatic and electro-hydromechanical

Question 14

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

Answer 14

A stoichiometric mixture (mix in which all constituents of fuel air mix is 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

Question 15

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

Answer 15

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

Question 16

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

Answer 16

The high unmetered fuel pressure

Question 17

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

Answer 17

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

Question 18

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

Answer 18

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

Question 19

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

Answer 19

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 oped 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

Question 20

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

Answer 20

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

Question 21

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

Answer 21

In the COLD position

Question 22

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

Answer 22

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 though with the ignition switch accidentally on

Question 23

Where is the fuel from a continuous flow fuel injection system discarged?

Answer 23

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

Question 24

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

Answer 24

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

Question 25

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

Answer 25

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

Question 26

When does the acceleration system operate on an aircraft carburetor?

Answer 26

When the throttle is suddenly opened