Fuel Injection

Question 1

What is a key reason for switching from carburetors to fuel injection in modern aero engines?

Answer 1

To achieve more even fuel/air distribution and better performance.

Question 2

What problem does uneven fuel/air distribution in carburetors cause?

Answer 2

Uneven leaning of cylinders.

Question 3

How does fuel injection solve uneven cylinder leaning?

Answer 3

By metering fuel individually to each cylinder.

Question 4

What is the result of uniform fuel distribution in fuel-injected engines?

Answer 4

More power and better fuel efficiency.

Question 5

Where is fuel injected in a fuel-injection system?

Answer 5

Near the intake valve of each cylinder.

Question 6

What happens to fuel after it’s injected near the intake valve?

Answer 6

It vaporizes and is drawn into the cylinder during the intake stroke.

Question 7

What component pumps fuel from the tank in a fuel injection system?

Answer 7

The supply pump.

Question 8

Where is surplus fuel returned after reaching the reservoir?

Answer 8

Back to the fuel tank via a bypass line.

Question 9

What does the bypass line prevent?

Answer 9

Vapour lock in the system.

Question 10

What controls how much fuel enters the fuel injection pump?

Answer 10

The fuel metering valve.

Question 11

What is the function of the fuel injection pump?

Answer 11

It delivers fuel to the nozzles.

Question 12

What do fuel nozzles do?

Answer 12

Atomize the fuel into a fine spray.

Question 13

Where is the atomized fuel discharged?

Answer 13

Into the airstream entering the intake manifold or directly to the inlet ports.

Question 14

How are the throttle and fuel metering valve connected?

Answer 14

Mechanically linked and calibrated together.

Question 15

What ensures the correct fuel/air ratio?

Answer 15

The linked calibration of throttle and fuel metering valve.

Question 16

Where does air enter the fuel injection system?

Answer 16

Through the air intake and air filter.

Question 17

What is a danger to the air filter in flight?

Answer 17

Impact ice buildup.

Question 18

What safety feature bypasses a blocked air filter?

Answer 18

The alternate air source.

Question 19

How is alternate air activated?

Answer 19

By a manual control in the cockpit.

Question 20

What causes hot engine starting problems in fuel-injected engines?

Answer 20

Vaporized fuel in the lines after shutdown.

Question 21

What happens when starting a hot engine with vapor in the lines?

Answer 21

Not enough liquid fuel reaches the cylinders — causes a hard start or flooding.

Question 22

What can clear vaporized fuel from the lines before a hot start?

Answer 22

Activating the booster pump briefly.

Question 23

Where should the pilot check the correct starting procedure for their engine?

Answer 23

The Owner’s Manual.

Question 24

What is one advantage of fuel injection over carburetion?

Answer 24

Elimination of carburetor icing.

Question 25

What kind of ice can still form in a fuel-injected engine?

Answer 25

Throttle ice and impact ice.

Question 26

At what temperature can throttle ice form?

Answer 26

At or below 5°C.

Question 27

What type of fuel delivery does fuel injection use?

Answer 27

Continuous flow near each cylinder’s intake valve.

Question 28

What does fuel injection improve aside from power?

Answer 28

Fuel economy and engine cooling.

Question 29

What pump maintains pressure in the fuel reservoir?

Answer 29

The supply pump (with surplus returned via bypass).

Question 30

What rate does the supply pump deliver fuel?

Answer 30

About twice the rate the engine actually uses.

Question 31

What is vapour lock?

Answer 31

A condition where vaporized fuel blocks fuel flow.

Question 32

How is vapour lock prevented?

Answer 32

By returning surplus fuel to the tank, keeping fuel moving and pressurized.

Question 33

What causes impact ice?

Answer 33

Freezing moisture on cold surfaces like bends and air intakes.

Question 34

Why does fuel injection increase power?

Answer 34

No need to heat the intake air like in carburetor systems.

Question 35

How does fuel injection help cooling?

Answer 35

Eliminates hot lean mixtures in outer cylinders.

Question 36

What is a wobble pump?

Answer 36

A manual backup fuel pump.

Question 37

What does the fuel reservoir do?

Answer 37

Stores pressurized fuel before metering.

Question 38

What happens if the normal air intake is blocked?

Answer 38

The pilot switches to alternate air.

Question 39

What happens when the mixture is too rich during startup?

Answer 39

The engine floods.

Question 40

What does a flooded engine need before it can restart?

Answer 40

Excess fuel must be cleared.

Question 41

What determines the fuel/air ratio in flight?

Answer 41

Throttle position and the calibration with the metering valve.

Question 42

What is atomization?

Answer 42

Breaking fuel into a fine mist for better mixing with air.

Question 43

How is atomization achieved in fuel injection?

Answer 43

By nozzles under high pressure.

Question 44

Why is individual fuel metering important?

Answer 44

Ensures balanced performance across all cylinders.

Question 45

What part adjusts fuel flow in response to throttle movement?

Answer 45

Fuel metering valve.

Question 46

What safety backup exists for fuel supply in flight?

Answer 46

Manual (wobble) and electric booster pumps.

Question 47

What is the function of the fuel distributor?

Answer 47

Splits fuel evenly to all injection nozzles.

Question 48

What ensures fuel delivery stays steady?

Answer 48

Constant fuel circulation and pressurization.

Question 49

What is the main cause of hot-start problems in injected engines?

Answer 49

Fuel vaporizing in the lines due to residual engine heat.

Question 50

What is the biggest operational advantage of fuel injection in aviation?

Answer 50

Greater engine efficiency, reliability, and performance.