TOPIC 03.2 - FUEL INJECTION SYSTEMS

Question 1

2 major limitations of carburetors:

Answer 1

• fuel/air mixture is not evenly distributed to the cylinders
• susceptible to carburetor icing

Question 2

When fuel is injected directly into the combustion chamber, the injection system is referred to as _______.

Answer 2

Direct fuel injection system

Question 3

This type of fuel injection system was used on early radial engines and offered benefits of even fuel distribution and a reduced chance of backfiring.

Answer 3

Direct fuel injection system

Question 4

This is the most common type of fuel injection system in reciprocating aircraft engines.

Answer 4

Indirect fuel injection / Continuous-flow fuel injection system

Question 5

This system continuously injects fuel into each intake port instead of mixing the fuel and air in the combustion chamber.

Answer 5

Indirect fuel injection / Continuous-flow fuel injection system

Question 6

In this type of system, a throttle-metering valve varies the pressure of fuel according to airflow to the engine.

Answer 6

Indirect fuel injection / Continuous-flow fuel injection system

Question 7

In this system, mixture strength is varied by a manually operated mixture control valve, which adjusts the fuel pressure for altitude or operating conditions, as necessary, and which is also used to cut off the fuel supply when stopping the engine.

Answer 7

Indirect fuel injection / Continuous-flow fuel injection system

Question 8

In an indirect fuel injection/continuous-flow fuel injection system, this varies the pressure of fuel according to airflow to the engine.

Answer 8

Throttle-metering valve

Question 9

In an indirect fuel injection / continuous-flow fuel injection system, this varies mixture strength, adjusts fuel pressure for altitude or operating conditions, and is used to cut off the fuel supply when stopping the engine.

Answer 9

manually operated mixture control valve

Question 10

Main components of an indirect fuel injection:

Answer 10

• Fuel pump
• Fuel/air control unit
• Fuel manifold valve
• Discharge nozzles
• Throttle valve
• Fuel pressure gauge

Question 11

2 fuel pumps an indirect fuel injection is equipped with:

Answer 11

• Electrical pump
• Engine driven pump

Question 12

This is used in case of a malfunction of the engine driven pump and for engine priming and starting.

Answer 12

Electrical pump

Question 13

Parts in a fuel/air control unit:

Answer 13

• Throttle valve
• Mixture control valve
• Fuel metering valve

Question 14

This is connected to the pilot’s throttle lever and controls the airflow to the engine.

Answer 14

Throttle valve

Question 15

This is connected to the pilot’s mixture control lever, and bleeds off fuel pressure applied to the metering fuel valve

Answer 15

Mixture control valve

Question 16

This can also close completely, acting as the idle cut off control.

Answer 16

Mixture control valve

Question 17

This is mechanically connected to the throttle valve and controls fuel flow from the mixture control valve to the fuel manifold valve, thus, fuel flow to the manifold valve and to injectors is proportioned to airflow.

Answer 17

Fuel metering valve

Question 18

This is the central point for distributing metered fuel to the engine.

Answer 18

Fuel manifold valve

Question 19

When the engine is stopped, what is the position of all the outlet ports?

Answer 19

Closed

Question 20

As the fuel pressure builds up, what happens to all the ports to the discharge nozzles?

Answer 20

Open simultaneously

Question 21

When the inlet pressure drops below a certain level, this closes the fuel inlet, which shuts off all the fuel to the discharge nozzles.

Answer 21

Diaphragm

Question 22

This is located in each cylinder head, with its outlet directed into the inlet port.

Answer 22

Fuel discharge nozzle

Question 23

What kind of engines use a nozzle with a calibrated orifice, which has holes for air entry to the lower chamber?

Answer 23

Normally aspirated engines

Question 24

Nozzles used in this type of engines have turbo-charged output air delivered to a shroud surrounding the nozzle, where output air is forced into the injector to assist in atomizing the fuel spray.

Answer 24

Turbo-charged engines

Question 25

This is a means of preventing manifold air starvation, caused by blockage from icing or other ingested materials.

Answer 25

Alternate air door

Question 26

This will shut off the ram air, and at the same time, admit unfiltered air from inside the cowlings directly into the injector air body throat.

Answer 26

Alternate air door