Carboretta And Fuel Systems

Question 1

What is the stoichiometric air:fuel ratio?

Answer 1

15:1

Question 2

What is the ISA pressure

Answer 2

1013 hPa

29.92 inches of mercury

Question 3

How does the carburettor work?

Answer 3

Fuel moves up as atmospheric pressure is higher than in the tube

Question 4

What happens to the mixture during the climb?

Answer 4

• Gets richer
• Due to less O2 at a higher altitude

Question 5

What is the purpose of the pressure balance duct?

Answer 5

Ensure that a correct mixture ratio is maintained across a range of airspeeds and flight conditions

Question 6

What is the function of the accelerator pump?

Answer 6

Prevents lean cut

Question 7

What is a risk of the accelerator pump?

Answer 7

It can cause flooding and therefore can cause a fire

Question 8

What is the purpose of the boost lever?

Answer 8

• Provides a rich mixture at high power settings
• Used in high performance A/C

Question 9

What are the three types of pumps used for priming?

Answer 9

• Accelerator pump
• Priming hand pump
• Electric pump

Question 10

What do we have to ensure with the priming hand pump?

Answer 10

Ensure it’s locked after use to prevent excess fuel flow

Question 11

What causes carb icing?

Answer 11

• In Venturi, pressure is low therefore temp is low
• Low temp can cause icing up to a 25 degree decrease
• Evaporation of fuel

Question 12

What are the risks of carb heating?

Answer 12

• 15% reduction in power
• Can create conditions for ice
• Increased risk of detonation in the cylinder