Pp Engine Fuel & Fuel Metering

Front 1

what are some of the sources used to heat the fuel in a turbine engine fuel system

Back 1

1. Bleed air
2. engine lubricating oil

Front 2

What are the most common types of fuel metering systems used on small recip engines

Back 2

1. Float type carbs
2. pressure-injection carbs
3. direct fuel injection systems

Front 3

what function does the mixture control perform

Back 3

controls fuel/air mixture

Front 4

what generally causes spark plug fouling

Back 4

operating the engine with an excessively rich mixture at idle

Front 5

what is the purpose of an accelerating system

Back 5

it provides an immediate but brief increase in fuel flow in the venturi to enrich the mixture

Front 6

what is the carburetor economizer system

Back 6

it is a power enrichment system that provides a richer mixture at high power settings, where the excess fuel aids in engine cooling. This system fuctions at throttle settings above cruise power settings

Front 7

when the mixture is placed in the idle cutoff position, a slight rise in RPM is noted prior to the engine decelerating. What does this indicate

Back 7

the idle mixture is set correctly

Front 8

why should engine RPM be accelerated periodically when making carburetor adjustments

Back 8

to clear the engine

Front 9

what maintains the fuel pressure in a pressure injection carburetor

Back 9

an engine-driven fuel pump

Front 10

what happens if the manual mixture control of a pressure injection carburetor is moved to the idle cutoff position

Back 10

the engine stops

Front 11

how does an automatic mixture control (AMC) function

Back 11

A sealed brass bellows connected to the fuel metering system, expands and contracts with changes in pressure and temperature, adjusting the mixture accordingly.

Front 12

what are some of the advantages of fuel injection systems over carburetor systems

Back 12

1. less danger of induction icing
2. better acceleration
3. better fuel distribution
4. better fuel economy
5. reduced overheating of individual cylinders

Front 13

what purpose do turbine engine fuel control units serve

Back 13

they automatically meter fuel to the engine

Front 14

what are the 2 basic types of turbine engine fuel control units

Back 14

1. hydromechanical
2. electronic

Front 15

what are the engine variables detected by the fuel control unit

Back 15

1. power level position
2. engine RPM
3. compressor inlet temperature
4. compressor inlet pressure
5. compressor discharge pressure
6. burner pressure

Front 16

what are the 2 major components of a supervisory electronics engine control

Back 16

1. electronic control unit (computer)
2. hydromechanical fuel control

Front 17

what are some of the advantages of a full-authority digital engine control (FADEC) over a hydromechanical fuel control

Back 17

1. Better fuel economy
2. improved starts
3. requires no engine trimming
4. provides engine limit protection
5. provides constant idle speeds regardless of atmospheric conditions or bleed air requirements
6. fully modulates the active clearence control
7. allows more repeatable engine transients

Front 18

what do turbine engine fuel spray nozzles do

Back 18

inject fuel into the combustion area

Front 19

what are the different engine indications used for trimming a turbine engine

Back 19

either EPR or RPM is used depending on the particular engine

Front 20

what maintenance adjustments are normally allowed on an installed hydromechanical fuel control

Back 20

1. specific gravity for fuel
2. idle RPM
3. max RPM or EPR

Front 21

what type of pump can vary the amount of fuel discharged regardless of speed

Back 21

variable displacement pump

Front 22

what is used to keep water, sediment, and foreign matter out of the carburetor

Back 22

main fuel strainer

Front 23

what is the purpose of a pressure relief valve in a constant displacement pump

Back 23

it returns excess fuel that is not required by the engine to the inlet side of the pump

Front 24

what type of engine-driven fuel pump is widely used other than gear or piston pump

Back 24

rotary vane type

Front 25

what function do fuel boost pumps perform

Back 25

they supply pressurized fuel to the fuel pump, which helps prevent vapor lock and cavitation

Front 26

what is a commonly used type of fuel boost pump

Back 26

centrifugal type

Front 27

what causes vapor lock and why is it of concern

Back 27

Vapor lock is caused by
1. insufficient fuel pressure
2. high fuel temperatures
3. excessive fuel turbulence

which may completely block any fuel flow resulting in engine failure

Front 28

what function does the engine driven pump on a turbine engine perform

Back 28

it provides a continuous supply of fuel at the proper pressure while the engine is running

Front 29

name the 2 categories of turbine engine pumps

Back 29

1. constant
2. variable displacement

Front 30

what category is a gear type pump classified in

Back 30

constant displacement

Front 31

when performing an external inspection of an engine-driven fuel pump, what should you look for

Back 31

1. leaks
2. security of mounting

Front 32

what is the purpose of a shear section of the driveshaft in a dual element constant displacement pump

Back 32

if one element seizes, a portion of the driveshaft seizes, allowing the other element to continue to operate

Front 33

where in a turbine engine fuel system is ice formation likely to occur and how is it prevented

Back 33

the fuel filter is most susceptible to ice formation, so a fuel heater is used that consists of a heat exchanger using either engine oil or bleed air to warm the fuel

Front 34

what is the purpose of a bypass valve in an engine fuel system micron filter

Back 34

it is a safety feature that allows fuel to flow to the engine if the filter becomes blocked

Front 35

what is the purpose of a duplex fuel nozzle

Back 35

a duplex fuel nozzle discharges 2 different spray patterns. The spray pattern is wider during startup & acceleration and narrows when engine speed increases above idle.

Front 36

what are the functions of the pressurizing and dump portions of a pressurizing and dump valve

Back 36

the pressurizing portion provides primary and secondary fuel flow to dual-line duplex fuel nozzles, and the dump portion allows fuel to drain from the manifolds after engine shutdown

Front 37

what purpose do fuel selector valves serve

Back 37

they allow tank & engine selection, and provide a means for shutting off fuel flow