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Ap > Engine Fuel And Fuel Metering System > Flashcards

Engine Fuel And Fuel Metering System Flashcards

1
Q

Gasoline and other liquid fuels do not burnt at all, unless they are mix with what other elements 

A

Mix with air

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2
Q

Where are the fuel spray nozzle located in a turbine engine?

A

Either externally or internally on the combustion chamber in such a way that fuel can be sprayed into the combustion area

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3
Q

name the heat sources for operation of fuel heaters used in turbine engines

A

Bleeder as air to liquid heat exchanger, engine lubricating oil as liquid to liquid heat exchanger

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4
Q

What engine variables are sensed by Hydro mechanical fuel control

A

Power lever position, rpm, compressor inlet pressure temperature, burner pressure or compressor Discharge pressure and EGT or TIT

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5
Q

In an electrical fuel control system,what are the two import components

A

Electrical and fuel

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6
Q

What are the two most commonly used carburetor in a small reciprocating engine?

A

Float type and pressure type

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7
Q

What type of fuel control unit is used in a turbine engine

A

Both Hydro mechanical and electronic fuel control. Most common unit control is the Hydro mechanical type.

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8
Q

What is meant by trimming a turbine engine?

A

 adjusting fuel control for proper specific gravity of the fuel and for proper idle and full throttle rpm

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9
Q

When should a turbine engine be trimmed?

A

When there is a loss of engine, power or manufacturer specified

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10
Q

What specification are used to trim a turbine engine

A

 Data plate on engine typically contains trimming specification

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11
Q

What are the three type of fuel controls for turbine engines?

A

Supervisory EEC (electronic engine control) ,FADEC and mechanical

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12
Q

What is FADEC

A

full authority digital electronic control is high precision digital electronic fuel control that use electronic engine control and a flight management computer to measure the fuel nozzle that prevent over temperature and over speed conditions. It also sends information to the education system for the aircraft crew.

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13
Q

Does an engine control by FADEC required manual trimming

A

 No, it is self-trimming

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14
Q

What is the purpose of a mixer control in a float type carburetor?

A

Controls the fuel air mixture as air density change with altitude change

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15
Q

What is the purpose of an accelerating system on a flow type carburetor

A

When the throttle is open rapidly, the fuel air mixture will lean out momentarily, to overcome tendency a charge of fuel from the accelerating pump will temporarily enrich the mixture in the Venturi

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16
Q

Describe the purpose and operation of Venturi

A

Is an example of Bernoulli principle as the velocity of a gas or liquid increases, the pressure decrease. Venturi performs three function. 1-proportion to fuel air mixture .
2-lower the pressure at discharge nozzle.
3-and limit the airflow at full throttle. The carburetor depends on differential between the atmospheric pressure, and decreased pressure offered by Venturi

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17
Q

What is the function of a metering jet

A

To limit the fuel flow when the throttle valve is wide open

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18
Q

What is the fuel metering force in a float type carburetor?

A

The differential pressure between the pressure in a flow chamber and at the nozzle

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19
Q

What will be the result of using excessively rich idle mixtures?

A

Carbon fouling of spark plug

20
Q

What is the purpose of economizer system in float type carburetor

A

Valve, which is closed at throttle setting below 60% to 70% rate power, by provide additional fuel for engine cooling to prevent detonation a higher throttle setting above 60%to 70%

21
Q

Where does the pressure injection carburetor obtain fuel pressure

A

Form boost pump for starting and engine driven pump during normal operation

22
Q

What operates an automatic mixture control on a pressure carburetor

A

Seal bellows that expand or contract with changes in atmospheric pressure. The movement of the Bellow operate a Tapered needle that controls the impact air pressure into A chamber of carburetor

23
Q

In what position do you place the mixture control of a pressure injection carburetor to stop engine ?

A

Idle cutoff position

24
Q

What rpm indication should result when the mixture control is placed in the idle cutoff position when the idle mixture is set correctly ?

A

Should be slight drop in rpm, follow by a rapid drop of rpm to zero

25
Q

What is the purpose of filling a pressure injection carburetor full of fuel and allowing it to soak for a period of about eight hours prior to installation

A

To soften the diaphragms and make them as pliable as they were when the carburetor was originally calibrated

26
Q

What are three type of carburetor icing

A

Throttle icing, impact icing and fuel evaporation icing

27
Q

What is the typical fuel pressure in a float type carburetor

A

3-5 psi

28
Q

Name some advantage of direct fuel injection system system over conventional carburetor system

A

Less danger of induction system icing , improve acceleration , improved fuel distribution, reduced overheating of individual cylinders, better fuel economy

29
Q

What is the purpose of filter in a fuel system

A

Prevent foreign matter from entering the carburetor

30
Q

Why do carburetor in aircraft have a mixture control

A

Air density changes with altitude, which affect the air fuel mixture. Mixture control provides a means to adjust for the correct mixture at different attitude

31
Q

What two items are adjusted when setting idling conditions on float carburetor

A

Throttle stop for idle rpm and idle mixture though the idle needle valve

32
Q

What should be looked for when inspecting engine driven pump

A

Look for fuel leak and security of mounting

33
Q

What is the purpose of fuel selector valve?

A

Shutting off fuel flow, crossfeed for tank, engine selection, and for fuel transfer

34
Q

What is the purpose of an engine driven fuel pump?

A

Always deliver continuous supply of fuel add the proper pressure during engine operation

35
Q

What type of fuel pump is generally use with large reciprocating engine

A

Positive displacement, rotary vane type

36
Q

What are the function of the boost pump?

A

Supplies fuel to the engine pump for starting, maintain pressure in the fuel line to prevent fuel from boiling off at altitude and act as a back up if engine driven pump fails

37
Q

What are the three general causes of vapor lock?

A

Low fuel pressure, high fuel temperatures, excessive fuel turbulence

38
Q

Turbine engine fuel pumps may be divided into two distinct system categories

A

Constant displacement and variable displacement

39
Q

What category is a turbine engine driven gear type pump?

A

Constant displacement

40
Q

What type of fuel pump can be made into a vary the fuel flow at any speed

A

Variable displacement pump

41
Q

What part of a gas turbine engine fuel system is very susceptible to formation of ice

A

Fuel filter

42
Q

How is the engine fuel system protected from ice formation?

A

Use fuel heaters

43
Q

Why is a micron filter provided with bypass valve as a necessary safety factor?

A

Small opening in this type of filter makes it very easy to clogging

44
Q

Where are the fuel filter located?

A

At the fuel pump in line with the system. Last chance filter screens are in the fuel control

45
Q

Can you use automotive gasoline in a reciprocating engine in place of avgas?

A

Yes, if you have a STC

46
Q

What is the purpose of pressurizing portion of a pressurizing and dump valve?

A

To provide primary and secondary fuel flow to dual line duplex fuel nozzle

47
Q

What is the divided fuel flow of a turbine engine duplex fuel nozzle produce in the fuel

A

Two spray pattern

Ap (13 decks)

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