Induction System, Carburetor, and Mixture Flashcards
(159 cards)
1
Q
It is designed to supply air to the engine so that, when fuel is added, combustion can take place.
A
induction system
2
Q
Once fuel is added, the fuel/air mixture is delivered into an ________ where it is ducted to the cylinders for combustion.
A
intake manifold
3
Q
On reciprocating engines, outside air passes through an air intake and is then routed to a ______ or other fuel metering device.
A
carburetor
4
Q
Reciprocating engine induction systems can be broadly classified as _________, __________, and __________.
A
normally aspirated, supercharged, turbocharged
5
Q
___________ means that the engine has no supercharger or turbocharger to maintain sea level atmospheric pressure at higher altitudes and, therefore, that it’s maximum available power decreases with ________.
A
Normally aspirated, altitude
6
Q
A standard induction system on a normally aspirated engine consists of four major components, or sections which are:
A
- air intake
- induction air filter
- fuel delivery system
- induction manifold
7
Q
An air intake, sometimes referred to as an _______, is designed to direct outside air into a carburetor or other fuel metering device.
A
air scoop
8
Q
The intake is generally located to take advantage of __________ as much as possible.
A
ram air pressure
9
Q
For an engine to provide a long service life and a reliable operation, the induction air must be free of any kinds of foreign material. To achieve this property, ______ are typically installed in ________ to prevent sand, dust, abrasive materials, and/or other contaminants from entering the engine.
A
induction air filters or filters, air intake ducts
10
Q
The fuel delivery system on a normally aspirated engine can be either a _______ or a _________.
A
carburetor, fuel injection system
11
Q
The purpose of a _________ is to meter the amount of fuel and air that is delivered to the cylinders.
A
fuel delivery system
12
Q
An ________ typically consists of ducting that goes from the fuel metering device to the individual cylinders.
A
intake manifold
13
Q
On a typical horizontally opposed engine, the intake manifold is the ________ of all the individual pipes which deliver air or fuel/air mixture to the cylinders.
A
connecting point
14
Q
One end of each cylinder’s intake pipe is typically bolted to the _______ on each cylinder while the other end is attached to the ______.
A
cylinder intake port, manifold
15
Q
In some installations, the intake manifold goes through the ______ before it branches out to go to each cylinder which increases the temperature of the fuel/air mixture which, in turn, promotes better ________.
A
oil sump, fuel vaporization
16
Q
One very important characteristic of an intake manifold is that it must maintain a ________. If a seal is not maintained, air will leak into the intake manifold and lean out the mixture which will cause the engine to run rough.
A
gastight seal
17
Q
Small induction leaks are most noticeable at idle because the pressure differential between the manifold and atmosphere is greatest at ______.
A
low rpm
18
Q
Two types of Induction System Arrangements
A
Updraft Induction System, Downdraft Induction System
19
Q
______ consists of small particles of hard, abrasive material that can be carried by the air and drawn into the engine cylinders; can collect on the fuel metering elements of the carburetor and fuel injector, upsetting the proper relation between airflow and fuel flow at all engine power settings.
A
dust
20
Q
__________ can be a serious source of trouble to an aircraft engine.
A
dust and dirt
21
Q
_________ act on the cylinder walls by grinding down these surfaces and the piston rings. Then, they contaminate the oil and are carried through the engine, causing further wear on the bearings and gears.
A
dirt particles
22
Q
In extreme cases, dirt accumulation may clog an oil passage and cause _______. Likewise, dirt accumulation on fuel injection nozzles affect the fuel/air mixture delivered to the engine.
A
oil starvation
23
Q
Although dust conditions are most critical at ground level, continued operation under such conditions without ________ results in extreme engine wear and can produce excessive oil consumption.
A
engine protection
24
Q
When operation in a dusty atmosphere is necessary, the engine may be protected by an alternate induction system air inlet that incorporates a ______.
A
dust filter
25
This type of air filter system (dust filter) consists of a ________, a _____, and an __________.
filter element, door, electrically operated actuator
26
When the filter system is operating, air is drawn through a ________ that does not face directly into the airstream. With this entrance location, considerable dust is removed as the air is forced to turn and enter the duct.
louvered access panel
27
Since the dust particles are solid, they tend to continue in a straight line. Most of them are separated at this point, those that are drawn into the louvers are easily removed by the _____.
filter
28
In flight, with air filters operating, consideration must be given to possible icing conditions that may occur from actual surface icing or from freezing of the filter element after it becomes _______.
rain soaked
29
Some installations have a ___________ that automatically opens when the filter is excessively restricted.
spring-loaded filter door
30
The installation of __________ prevents the airflow from being cut off when the filter is clogged with ice or dirt. Other systems use an _______ in the filtered air entrance.
spring-loaded filter door, ice guard
31
The ice guard consists of a _________ located a short distance from the filtered-air entrance. In this location, the screen is directly in the path of incoming air so that the air must pass through or around the screen.
coarse-mesh screen
32
When ice forms on the screen, the air, which has lost its heavy moisture particles, passes around the _____ and into the _______.
iced screen, filter element
33
What must the carburetion system do?
- control air/fuel ratio in response to throttle setting and during ac/deceleration
- function at all altitudes and temperatures in the operating range
- provide for ease of starting; may incorporate a means of shutting off the fuel to stop engine
34
The _____________ is the cheapest and simplest arrangement and is used on many light aircraft, however it is very prone to carburetor icing, and may be affected by flight maneuvers.
float-chamber carburetor
35
The _________ is a more sophisticated device and meters fuel more precisely, thus providing a more accurate air/fuel ratio, it is also less affected by flight maneuvers, and is less prone to icing.
fuel injection system
36
Two principles used in simple float chamber carburetor operation
U-tube principle, Venturi principle
37
In terms of the U-tube principle, explain how the liquid would be in a U-tube with equal pressure and differing pressure.
equal pressure = liquid would be of same level on both legs
differing pressure = cause the liquid to flow
38
In practice one leg of the ‘U’ tube is opened out to form a small tank, a constant level being maintained by a _____________ regulating the flow of fuel from a fuel pump (or pumps) delivering a supply from the main aircraft tanks.
float and valve mechanism
39
Bernoulli's Theorem states that
the total energy per unit mass along any one streamline in a moving fluid is constant
in equation:
P1 + (rho/2)(V1)^2 = P2 + (rho/2)(V2)^2 = C
40
The fluid possesses energy because of its _______, ________, and _______. If one of these changes, one or both of the others must also change to maintain the same overall energy.
pressure, temperature, velocity
41
As the air passes through the restriction of the venturi, its velocity increases, causing a drop in ________ and _________.
pressure, temperature
42
The pressure drop at the throat of the venturi is ________ to the mass airflow, and is used to make fuel flow from the float chamber by placing one leg of the ‘U’ tube in the venturi.
proportional
43
In a float-chamber carburetor, airflow to the engine is controlled by a _______, and fuel flow is controlled by _________.
throttle valve, metering jets
44
________ provides a flow of air from the air intake through a Venturi in the carburetor to the induction manifold.
Engine suction
45
The air speeds up as it passes through the Venturi, and a drop in _________ occurs at this point.
pressure
46
Within the induction manifold however, pressure rises as the throttle is _________.
opened
47
Fuel is contained in a float chamber, which is supplied by ______, or an ___________, or by an _________, and a constant level is maintained in the chamber by a float and needle-valve.
gravity, electrical booster pump, engine-driven fuel pump
48
Where fuel pumps are used, a ________ is included in the system to provide an indication of pump operation.
fuel pressure gauge
49
____________ acts on the fuel in the float chamber, which is connected to a fuel discharge tube located in the throat of the Venturi.
air intake or atmospheric air pressure
50
The difference in pressure between the float chamber and the throat of the Venturi provides the ______ necessary to discharge fuel into the airstream.
force
51
As airflow through the venturi increases, the pressure drop increases, and a higher pressure differential acts on the fuel to increase its ________ in proportion to the airflow.
flow
52
The __________ in the discharge tube determines the quantity of fuel which is discharged at any particular pressure differential, and therefore controls the ________.
size of the main jet, mixture strength
53
Modifications to the Simple Carburetor
pressure balance duct, diffuser well, air bleed diffuser, slow running systems, idle cut-off valve, mixture control
54
In pressure balance duct as modification to carburetor, to maintain the correct rate of discharge of fuel through the main jet, the pressure in the float chamber and the air intake must be _______.
equal
55
Admitting atmospheric pressure in the float chamber by means of a _______ in the float chamber cover plate is not a satisfactory method of ensuring equalized pressure across the carburetor.
drilling
56
Equalized pressure conditions can only be obtained by connecting the float chamber directly to the air intake by a duct which is called the _________.
pressure balance duct
57
As engine speed and airflow through the Venturi increase, the proportion of fuel to air _____ as a result of the different flow characteristics of the two fluids. This causes the mixture to become _______.
rises, richer
58
To overcome the effect which is the mixture becoming richer, some carburetors are fitted with a _________.
diffuser well
59
As engine speed is progressively increased above idling, the fuel level in the diffuser well _____ and progressively uncovers more ________ which allows more air into the discharge tube, and by reducing the pressure differential, prevent enrichment of the air/fuel mixture.
drops, air holes
60
The process of drawing both air and fuel through the discharge tube also has the effect of ____________ more readily, particularly at low engine speeds.
vaporizing the fuel
61
___________ also supplies air to the diffuser and is used in some carburetors to provide altitude mixture control.
Pressure balance duct
62
Pressure balance duct also supplies air to the diffuser and is used in some carburetors to provide __________.
altitude mixture control
63
A ________ applied to a tube immersed in a liquid is sufficient to raise a column of liquid to a certain height up the tube.
suction
64
A suction applied to a tube immersed in a liquid that is sufficient to raise a column of liquid to a certain height up the tube.
air bleed diffuser
65
In an air bleed diffuser, should a small hole be made in the tube, under the same condition, bubbles of air will enter the tube and the liquid will be drawn up the tube in _________ rather than a continuous stream.
smaller drops
66
The liquid will be "diffused" or made to ______ with the air in an air bleed diffuser. The air "bleeds" into the tube and reduces the forces acting on the fuel ________ the flow of liquid through the tube.
intermingle, retarding
67
At low engine speeds, the volume of air passing into the engine is so small that the depression in the choke tube is _________ to draw fuel through the main jet.
insufficient
68
Above the throttle valve, there exists a considerable ________ and this is utilized to effect a second source of fuel supply for slow running conditions.
depression
69
A slow running fuel passage with its own jet leads from the float chamber to an outlet at the lip of the throttle valve. The strong depression at this point gives the necessary _______ to create a fuel flow.
pressure difference
70
The size of the slow-running jet is such that it will provide the rich mixture required for slow-running conditions. An air bleed, opening into the area below the throttle valve, assists ______.
atomization
71
The purpose of the ________ drilled through the throttle valve is to evenly distribute the mixture over the area of the induction manifold.
transverse passage
72
A small hole is drilled into the transverse passage in the __________ side of the throttle valve. It acts as an air bleed to draw some of the fuel through the throttle valve to mix the air passing to the engine.
high pressure
73
As the throttle is opened, the depression at the lip of the throttle valve _______ and the depression in the venturi ______.
decreases, increases
74
As the throttle is opened, the depression at the lip of the throttle valve decreases and the depression in the venturi increases. The main jet starts to ________ and the flow through the slow-running system _______.
deliver fuel, diminishes
75
Carburetors must be carefully tuned in order to obtain a smooth progressive change over between the slow-running and the main system to prevent ‘_________’.
flat spots
76
________ is a period of poor response to throttle opening caused by a temporary weak mixture, it normally makes itself felt as a hesitation during engine acceleration.
flat spot
77
It is usually incorporated in the slow-running passage, and is used when stopping the engine.
idle cut-off valve
78
When the cut-off (idle cut-off valve) is operated, the valve moves over to block the passage to the slow-running delivery, the mixture being delivered to the engine becomes progressively weaker until it will not support _________ and the engine _______.
combustion, stops
79
Operation of the idle cut-off valve prevents any possibility of the engine continuing to run erratically due to _______, and also prevents fuel condensing in the cylinders which would tend to wash the oil from the cylinder walls, causing _________ when the engine is next started.
pre-ignition, lack of lubrication
80
The cut-off may be a separate control or it may be incorporated in the ________.
mixture control lever
81
As altitude increases, the weight of air drawn into the cylinder decreases because the air density ______.
decreases
82
For a given intake velocity, the pressure drop in the Venturi will decrease as ambient density _______.
decreases
83
The fuel flow due to pressure drop will _______ by the same amount and so the mixture will become richer.
not decrease
84
This progressive richness with increased altitude is _______ for economic operation.
unacceptable
85
Types of Mixture Control
needle type mixture control, air bleed mixture control
86
With a __________ mixture control, a cockpit lever is connected to a needle.
needle type
87
In a needle type mixture control, the movement of the cockpit lever inserts or extracts the needle, and varies fuel flow through an orifice to the main jet, thereby controlling the ________.
mixture strength
88
The smallest orifice in the whole fuel system is the _______.
fuel jet
89
To prevent any blockage of the jets by dirt or debris, a ______ can be fitted just before them in the fuel line.
fuel strainer
90
The ________ mixture control operates by controlling the air pressure in the float chamber, thus varying the pressure differential acting on the fuel.
air bleed
91
A small air bleed between the float-chamber and the Venturi tends to reduce air pressure in the float-chamber, and a valve connected to a cockpit lever controls the _________ into the float chamber.
flow of air
92
A small air bleed between the float-chamber and the Venturi tends to reduce air pressure in the float-chamber, and a valve connected to a cockpit lever controls the flow of air into the float chamber. When this valve is fully open the air pressure is greatest, and the mixture is ________.
fully rich
93
A small air bleed between the float-chamber and the Venturi tends to reduce air pressure in the float-chamber, and a valve connected to a cockpit lever controls the flow of air into the float chamber. As this valve is closed, the air pressure decreases, thus reducing the flow of fuel and ________ the mixture.
weakening
94
A small air bleed between the float-chamber and the Venturi tends to reduce air pressure in the float-chamber, and a valve connected to a cockpit lever controls the flow of air into the float chamber. This valve includes a pipe connection to the ________ of the throttle valve. When this pipe is connected to the float-chamber by moving the cockpit control to the ‘_______’ position, float-chamber air pressure is reduced and fuel ceases to flow, thus stopping the engine.
engine side, idle cut-off
95
At power settings above the cruising range, a _________ is required to prevent detonation.
richer mixture
96
The rich mixture required to prevent detonation at power settings above the cruising range may be provided by an ________ or by setting the carburetor to provide a rich mixture for high power and then bleeding off __________ to reduce fuel flow for cruising.
additional fuel supply, float-chamber pressure
97
Some types of carburetor are fitted with an additional needle valve, which may be known as a _________, enrichment jet, or economizer.
power jet
98
The needle valve, which is connected to the throttle control, is fully closed at all throttle settings below that required to give maximum cruising power at sea-level, but as the throttle is opened above this setting the needle valve opens progressively until, at full throttle, it is ________.
fully open
99
A ____________ is used to automatically weaken the mixture for economical cruising.
back-suction economizer
100
When the throttle valve is at a high power setting, the pressure of air flowing past the valve is only slightly below atmospheric pressure, and will have little effect on air pressure in the float chamber, thus a ________ will be provided.
rich mixture
101
As the throttle is closed to the cruising position, air flowing past the throttle valve creates a suction, which is applied to the float-chamber through the _________ and ________.
economizer channel, air jet
102
The reduced float-chamber pressure reduces fuel flow through the main jet to provide the _________ required for cruising.
economical mixture
103
If the throttle valve is opened quickly, airflow responds almost immediately and a larger volume of _____ flows through the carburetor.
air
104
The fuel metering system however, responds less quickly to the changing conditions (throttle valve opening quickly), and a temporary weakening of the mixture will occur, known as a ______ (or at worst causing a ‘______’) before fuel flow again matches airflow.
flat spot, weak cut
105
The fuel metering system responding less quickly to changing conditions is overcome by fitting an _______.
accelerator pump
106
It is linked directly to the throttle; it forces fuel into the Venturi whenever the throttle is opened.
accelerator pump
107
In other pumps, an additional __________ is incorporated to supply an additional quantity of fuel to the engine for a few seconds after throttle movement has ceased.
delayed-action plunger
108
Normally, a _______ would supply fuel to the induction manifold, close to the inlet valve.
priming pump
109
In the absence of a priming pump, it is permissible on some aircraft to prime the engine by __________ (exercising the accelerator pump) several times.
pumping the throttle
110
In the absence of such a device, it is permissible on some aircraft to prime the engine by pumping the throttle (exercising the accelerator pump) several times. This practice must be discouraged in any other circumstances because it increases the chance of __________.
carburetor fires
111
In a simple, light aircraft fuel system, the fuel tanks are rigid tanks fitted in the wings and filled by the ________.
over wing method
112
In a simple, light aircraft fuel system, the fuel is drawn from the tanks by a _________ or _________ fuel pump, through a tank selector, and filter before being delivered to the carburetor.
mechanical, electrical
113
__________ is achieved by use of a priming pump which takes fuel from the filter housing and delivers it to the inlet manifold.
Engine priming
114
The fuel system is monitored for contents and pressure and the fuel drains allow any ______ to be removed before flight.
water
115
Even when an inspection shows that everything is in proper working order and the engine performs perfectly on the ground, ___________ can cause an engine to act erratically and lose power in the air. Many engine troubles commonly attributed to other sources are actually caused by this.
induction system ice
116
It is an operating hazard because it can cut off the flow of the fuel/air charge or vary the fuel/air ratio.
induction system icing
117
_____ can form in the induction system while an aircraft is flying in clouds, fog, rain, sleet, snow, or even clear air that has high moisture content (high humidity).
ice
118
Induction system ice can be prevented or eliminated by raising the temperature of the air that passes through the system, using a _________ located upstream near the induction system inlet and well ahead of the dangerous icing zones.
carburetor heat system
119
Induction System Icing Formations
impact ice, fuel evaporation ice, throttle ice
120
It is caused by visible moisture striking an aircraft and then freezing. Therefore, the air intake and air filter are the areas of an induction system that are most susceptible to this.
impact ice
121
It can also collect at points in an induction system where the airflow changes direction, or where dents and protrusions exist.
impact ice
122
Whenever an induction system encounters this, air flow to the remaining system is restricted. Severe cases of this can cause a total blockage to airflow and complete engine failure.
impact icing
123
sometimes referred to as carburetor ice
fuel evaporation ice
124
It is a result of the temperature drop that occurs when fuel is vaporized.
fuel evaporation ice
125
In a carburetor, as fuel is released into the airstream, it turns into a _______ and absorbs heat from the surrounding air.
vapor
126
In a carburetor, as fuel is released into the airstream, it turns into a vapor and absorbs heat from the surrounding air. This can cause a drop in air temperature of ______. In some cases, this loss of heat is enough to cause the moisture in the air to condense and freeze.
30 deg Fahrenheit or more
127
What part of an aircraft typically accumulates ice before any other part of aircraft in flight?
carburetor
128
Carburetor ice can occur at ambient air temperatures up to ____ and when relative humidity is as low as ____%.
70 deg Fahrenheit, 50
129
Optimum conditions for carburetor ice exist when the outside air temperature is between ___ and ____ and the relative humidity is above _____%.
30 deg Fahrenheit, 40 deg Fahrenheit, 60
130
In a fuel injection system, fuel is injected and vaporized at or near the intake port of each cylinder. In this case, the heat of combustion offsets the temperature drop caused by fuel vaporization. Therefore, __________ is typically not a concern in fuel injected engines.
fuel evaporation icing
131
It is formed on the rear side of the throttle, or butterfly valve when it is in a partially closed position.
throttle ice
132
Why is throttle ice formed on the rear side of the throttle, or butterfly valve when it is in a partially closed position?
It is because as air flows across and around the throttle valve, a _______ is created on the downstream side which has a cooling effect on the fuel/air mixture that causes moisture to accumulate and freeze on the backside of the butterfly valve.
low pressure area
133
basahin mo lang
Since throttle icing typically occurs when the butterfly valve is partially closed, a small amount of ice can cause a relatively large reduction in airflow and a corresponding loss of engine power.
134
In severe cases, a large accumulation of ice can jam the throttle and render it __________.
immovable
135
Since the temperature drop created by the low pressure area is not that great, throttle ice seldom occurs at temperatures above ___°F.
38
136
____________ causes heated air, from the region of the exhaust pipe, to be fed into the induction system. The heated air will then melt ice. The ice then passes through the engine as _________.
Carburetor heat system, water
137
The carburetor heat is operated by a _______ in the cockpit.
push-pull control
138
A ____________ is located below the carburetor for selecting an alternate warm air source (carburetor heat) to prevent carburetor icing.
carburetor heat air valve
139
During normal operation, the carburetor heat valve admits air from the __________.
outside air scoop
140
During icing conditions, the carburetor heat valve admits warm air from the ___________.
engine compartment (cowling)
141
The pilot normally performs a pre-takeoff check of the __________ before each flight. Technicians frequently test the system as part of their engine evaluation during inspections or when performing engine troubleshooting measures.
carburetor heat system
142
A normal response during the application of carburetor heat is a ____________. Should the engine lose more than the normal amount of rpm, a system fault is present.
slight reduction of rpm
143
rich mixture ratio
8:1
144
weak mixture ratio
30:1
145
chemically correct mixture ratio
14.7:1 or 15:1
146
At this ratio, all of the oxygen in the air combines with all of the hydrogen and carbon in the fuel.
14.7:1 or 15:1
147
The _________ does not give the best results because the temperature of combustion is so high that power can be lost through detonation.
chemically correct mixture
148
The chemically correct mixture does not give the best results because the temperature of combustion is so high that power can be lost through _________.
detonation
149
Although the chemically correct mixture strength would theoretically produce the highest temperature and therefore power, in practice, _____________ are less than perfect. This results in some regions being richer and others being weaker than the optimum strength. This variation may exist between one cylinder and another.
mixing and distribution
150
A slightly rich mixture does not have much effect on power since all the oxygen is still consumed and the excess of fuel serves to slightly reduce the effective __________.
volumetric efficiency
151
The cooling effect of the evaporating fuel can be to some extent beneficial preventing ________.
detonation
152
______ mixtures rapidly reduce power since some of the inspired oxygen is not being utilized, and this power reduction is much greater than that resulting from slight richness.
weak
153
It is quite common to run engines (when maximum power rather than best fuel economy is the objective) at somewhat ________ than chemically correct mixtures to ensure that no cylinder is left running at severely reduced power from being unduly weak.
richer
154
A mixture which is weaker than the chemically correct ratio, besides burning at a lower temperatures, also burns at a _________ (because of the greater proportion of nitrogen in the cylinder).
slower rate
155
Power output decreases as the mixture is weakened, but, because of the increase in efficiency resulting from cooler burning, the fall in power is proportionally less than the decrease in fuel consumption. Thus, the specific fuel consumption (S.F.C.), decreases as the mixture strength is weakened below _____.
15:1
156
For economical cruising at moderate power, air/fuel ratios of _____ may be used, an advance in the ignition timing being necessary to allow for the slower rate of combustion.
18:1
157
With extremely weak mixtures, the gases may still be burning when the exhaust valve opens, exposing the valve to high temperatures which may cause the valve to _________.
crack or distort
158
With extremely weak mixtures, the gases may still be burning when the exhaust valve opens. As the inlet valve opens, the heat of the exhaust gases is still so high that it may ignite the mixture in the induction system, and '_______' occurs through the induction manifold.
popping back
159
The slow burning caused by weak mixtures also causes _______, as a certain amount of heat is not converted into work by expansion and has to be dissipated by the cooling system.
overheating
