fuel metering systems

Question 1

what are the two types of carburetors most commonly used on small reciprocating engines

Answer 1

float-type carburetors and pressure-type carburetors

Question 2

what is the function of a mixture control on a float-type carburetor

Answer 2

to control the fuel/air mixtures

Question 3

what is the action of a float-type carburetor accelerating system when the throttle is opened with a quick action

Answer 3

a charge of fuel will enrich the mixture in the venture

Question 4

when does the carburetor economizer system needle valve begin to open

Answer 4

above approximately 60 to 70 percent of rated power

Question 5

what is the purpose of a carburetor economizer system

Answer 5

an economizer system provides additional fuel at high power settings for cooling the engine to prevent detonation

Question 6

where does a pressure injection carburetor obtain fuel pressure

Answer 6

from an engine drive fuel pump

Question 7

what operates an automatic mixture control

Answer 7

a sealed bellows that contracts or expands with a change in pressure and temperature

Question 8

what position of a pressure injection carburetor manual mixture control would stop engine operation

Answer 8

idle cutoff position

Question 9

name at the advantages of direct fuel injection systems over conventional carburetor systems

Answer 9

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

Question 10

in a reciprocating engine, what problem is caused by an excessively rich mixture at idle

Answer 10

spark plug fouling

Question 11

what is the RPM indication when an idle mixture is set correctly, and the mixture control is placed to idle cutoff position

Answer 11

a slight rise in RPM prior to decreasing

Question 12

why should engine RPM be accelerated periodically when making carburetor adjustments

Answer 12

to clear the engine

Question 13

what is the function of turbine engine fuel control units

Answer 13

to automatically satisfy fuel requirements of the engine

Question 14

what are two basic types of turbine engine fuel control units

Answer 14

hydromechanical and electronic

Question 15

name the engine variables that may be detected by a turbine engine fuel control unit

Answer 15

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

Question 16

what are two sources used in turbine engine fuel systems for fuel heating

Answer 16

bleed air and engine lubrication oil

Question 17

what turbine engine components inject fuel into the combustion chamber

Answer 17

fuel spray nozzles

Question 18

what is another type of fuel metering system used on reciprocating engines other than carburetors

Answer 18

direct fuel injection

Question 19

depending on the particular engine, trimming is accomplished according to one of two types of (engine) indications. what are they

Answer 19

EPR and RPM

Question 20

name two major components of a supervisory electronic engine control

Answer 20

electronic control unit ( computer) and hydromechanical fuel control

Question 21

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

Answer 21

specific gravity for the fuel
idle RPM
maximum RPM ( or EPR)

Question 22

name the advantages of a full-authority digital electronic control FADEC over hydromechanical fuel control

Answer 22

1. requires no engine trimming
2. improved engine starts
3. Saves Fuel
4. provides engine limit protection
   5.provides constant idle speed with changes in atmospheric conditions and changing bleed air requirements