induction system

Question 1

what is induction?

Answer 1

the process of taking outside air and mixing it with fuel to burn efficiently in cylinder

Question 2

what is the intake on induction system?

Answer 2

air is taken in from suitable opening on front of aircraft facing air flow

Question 3

what is the filter on the induction system?

Answer 3

outside air is filtered to remove debris and small particles

Question 4

what is the mixer

Answer 4

used to mix air and fuel to correct ratio

Question 5

what is the ideal fuel to air ratio

Answer 5

1:12

Question 6

what types of mixers are there

Answer 6

carburettor and injection system

Question 7

what is the venturi effect

Answer 7

lower pressure and higher speed in a restriction

Question 8

how do carburettors use the venturi effect to work and what is the result

Answer 8

they use it to produce a pressure drop inside
result is sucking the fuel into airflow from discharge nozzle

Question 9

what is the float chamber

Answer 9

small reservoir of fuel that is kept at a constant level by the float
higher atmospheric pressure

Question 10

what is the throttle lever connected to

Answer 10

butterfly valve

Question 11

how does the throttle increase rpm

Answer 11

allows more fuel/mixture to pass, so more being available to burn in cylinders

Question 12

what is the idle jet

Answer 12

a fuel inlet into manifold past the throttle’s butterfly valve

Question 13

how does the idle jet allow the aircraft to idle

Answer 13

allows enough fuel and air mix to enter the manifold to allow the engine to idle at a slow speed

Question 14

what is the idle jet controlled by

Answer 14

a preset screw that engineers can use to alter the engine idle speed

Question 15

why do we need an accelerator pump?

Answer 15

if throttle opens quickly, the fuel air mix becomes very lean due to inrush of air into carburettor

Question 16

how does the accelerator pump compensate for this?

Answer 16

fuel is forced into venturi under pressure

Question 17

what is the accelerator pump connected to?

Answer 17

the throttle

Question 18

how is the mixture ratio impacted by high power settings?

Answer 18

mixture ratio is made to be more rich and excess fuel is used as a coolant for engine

Question 19

how does increasing altitude impact mixture?

Answer 19

as altitude increases -> air density decreases
–> carburettor still lets in same amount of fuel = rich mixture

Question 20

how to compensate for increasing altitude’s effect on mixture?

Answer 20

use mixture control to adjust amount of fuel being delivered to discharge nozzle
(basically lean mixture by the lever)

Question 21

when do you use mixture control?

Answer 21

only above 3,000ft
only in cruise
only when rpm gauge is available

Question 22

how do you operate mixture control using rpm gauge?

Answer 22

1. note rpm
2. lean mixture until rpm peaks then drops
3. enrich the mixture until rpm peaks again
4. enrich mixture slightly more to maintain rich side of peak rpm

Question 23

what is the EGT gauge

Answer 23

exhaust gas temperature gauge

Question 24

how do you operate mixture control when EGT gauge is available?

Answer 24

1. lean mixture until EGT reaches peak then falls
2. enrich mixture until EGT peaks again
3. richen mixture until EGT falls by POH instructions

Question 25

what are the consequences if the mixture is too rich?

Answer 25

inefficient burn (cool) power reduces engine runs cooler (more fuel being circulated to cool) spark plugs may foul = rpm drop mixture becomes incombustible = engine stops

Question 26

what are the consequences if mixture is too lean?

Answer 26

inefficient burn (hot) power reduces engine runs hotter mixture prone to burning early or quickly engine damage incombustible

Question 27

how does ice form on the carburettor

Answer 27

venturi induces a drop in pressure >> lowers dew point air with reduced pressure cannot support as much water vapour >> air condenses air temperature reduced more by evaporation of fuel at venturi

Question 28

why is air temperature in venturi reduced by evaporation?

Answer 28

for fuel to evaporate, energy is required and this is taken from the air = less kinetic energy = lower temp

Question 29

how much is the air temperature drop inside carburettor venturi

Answer 29

25-30 degrees C

Question 30

how does ice impact the fuel/air mixture

Answer 30

ice restricts venturi so less fuel/air mixture to engine and restricted movement of butterfly valve (throttle ice)

Question 31

true or false - carburettor icing can only happen in cold temperatures

Answer 31

false

Question 32

in what conditions can carburettor ice form

Answer 32

any conditions, as long as there is humidity

Question 33

when is carburettor icing more likely to happen

Answer 33

on warm days -> warm air can hold more moisture

Question 34

what are signs of carburettor icing

Answer 34

decreasing rpm decreasing manifold pressure rough running engine engine failure

Question 35

how do you get rid of carburettor ice

Answer 35

carb heat -> selects different source of intake air thats been warmed via heat exchanger

Question 36

why shouldn't you use carb heat on the ground?

Answer 36

the hot air is unfiltered, so grass etc can get in there

Question 37

what is the effect of carb heat

Answer 37

engine may run rough initially while water mixes with air and fuel, but then it returns to normal

Question 38

what is an alternative to carb heat?

Answer 38

fuel injection

Question 39

how does fuel injection work?

Answer 39

control unit measures out fuel, sends to fuel distributor then to fuel discharge nozzles

Question 40

what is an alternate method to intake air

Answer 40

alternate air: takes warmer air from inside the cowling incase main intake is blocked

Question 41

what are the advantages of fuel injection

Answer 41

reduction in evaporative icing better fuel flow faster throttle response precise control better fuel distribution better cold weather starts

Question 42

what are the disadvantages of fuel injection?

Answer 42

difficulty starting hot engine vapour locks during ground operations on hot days restarting engine that has stopped due to fuel starvation is hard

Question 43

how does priming work

Answer 43

primer cockpit control: inserts neat fuel into intake port just before intake valve

Question 44

what can misuse of primer cause

Answer 44

engine flooding or hydraulic lock

Question 45

how does throttle priming work

Answer 45

by pumping the throttle before start, the accelerator pump will pump fuel into venturi of carburettor

Question 46

what can misuse of throttle priming lead to

Answer 46

engine flooding or fire