Chapter 5 - Induction System FAA QUESTIONS

Question 1

An increase in manifold pressure when carburetor heat is applied indicates

Answer 1

ice was forming in the carburetor.

An increase in manifold pressure after carburetor heat is applied indicates that ice has been forming inside the carburetor and the heat has melted it.

Question 2

Is it possible to exceed 100 percent volumetric efficiency of some engines by the use of superchargers of the proper type? Why?

Answer 2

Yes

The volumetric efficiency of an engine is the ratio of the fuel-air charge taken into a cylinder to the charge the cylinder will hold at normal atmospheric pressure.
It is possible, by supercharging, to increase volumetric efficiency to more than 100%.

Question 3

Carburetor icing is most severe at what temperature?

Answer 3

air temperatures between 30 and 40°F.

Carburetor icing is most severe when the air temperature is between 30° and 40°F and the relative humidity is high.
Enough heat is required to change liquid fuel into fuel vapor to drop the temperature of the air, condense out any moisture in the air and freeze it inside the carburetor.

Question 4

Carburetor icing may be eliminated by which method?

Answer 4

Alcohol spray and heated induction air.

Carburetor ice is prevented by heating the induction air, either by routing it around the exhaust, or by picking it up in some warm portion of the engine nacelle.
Impact ice is prevented from forming on the carburetor by the use of an alcohol spray.

Question 5

What directly regulates the speed of a turbocharger?

Answer 5

Waste gate

The amount of exhaust gas passing through the turbine in a turbocharger determines its speed, and the waste gate determines the amount of exhaust gas allowed to pass through the turbine.

Question 6

The action of a carburetor airscoop is to supply air to the carburetor, but it may also

Answer 6

increase the pressure of the incoming air by ram effect.

The carburetor air scoop applies a slight positive pressure to the incoming air by the ram effect caused by the forward movement of the aircraft.

Question 7

What is the purpose of the density controller in a turbocharger system?

Answer 7

Limits the maximum manifold pressure that can be produced by the turbocharger at full throttle.

A density controller is designed to limit the manifold pressure below the turbocharger’s critical altitude. It regulates bleed oil only at the full-throttle position.

Question 8

Into what part of a reciprocating engine induction system is deicing alcohol normally injected?

Answer 8

The airstream ahead of the carburetor.

Deicing alcohol is normally sprayed into the induction system of a reciprocating engine from a spray ring located at the air inlet of the carburetor.

Question 9

What is used to drive a supercharger?

Answer 9

Gear train from the crankshaft.

A supercharger is an air compressor that increases the amount of air an internal combustion engine can take into its induction system. There are two types of superchargers: gear driven and those driven by a turbine powered by the exhaust gases.
In modern terminology, a compressor driven by a gear train from the crankshaft is called a supercharger and one driven by the exhaust gases is called a turbosupercharger, or more simply, a turbocharger.

Question 10

Where would a carburetor air heater be located in a fuel injection system?

Answer 10

None is required.

No carburetor air heater is required for a fuel-injected engine.
However, most engines equipped with fuel injectors have an alternate air system in which warm air from the engine compartment can be taken into the fuel injection system if ice forms on the inlet air filter.

Question 11

What method(s) is/are used to provide clean air to the engines of helicopters and turboprop airplanes that have particle (sand and ice) separators installed?

Answer 11

Sharp airflow directional change to take advantage of inertia and/or centrifugal force, and filters or engine inlet screens.

A centrifugal sand and ice separator removes sand and ice from the air entering the engine by forcing the inlet air to make a sharp change in its direction. Any contaminants in the air are thrown by centrifugal force into a sediment trap where they are held until they can be removed on routine maintenance.

Question 12

The absolute pressure controller on some small engines is designed to sense oil pressure which flows through the waste gate actuator and then through the controllers on the turbocharger system; the pressure between the turbocharger and the throttle valve is called

Answer 12

upper deck pressure.

The air pressure that is present between the turbocharger and the throttle valve is known as the upper-deck pressure.

Question 13

Which of the following would be a factor in the failure of an engine to develop full power at takeoff?

Answer 13

Improper adjustment of carburetor heat valve control linkage.

Improper adjustment of the carburetor heat valve control linkage could prevent the engine from developing full takeoff power.
The density of any heated air taken into the carburetor is so low that it will not furnish enough oxygen to allow the engine to develop full power.

Question 14

Bootstrapping of a turbocharged engine is indicated by

Answer 14

a transient increase in engine power.

Bootstrapping is a transient increase in engine power that causes the turbocharger to speed up, which in turn causes the engine to produce more power. Bootstrapping is indicated by a continual drift in the manifold pressure indication.

Question 15

What indications may shift when a turbofan engine anti-icing (bleed air) system is turned on?

1. Tachometer.
2. EGT.
3. EPR.

Answer 15

1, 2, and 3.

When the anti-icing system is turned on in a turbofan engine there will be a slight rise in the EGT. The EPR and RPM will likely shift their indication because of the change in compression delivered to the combustor.

Question 16

As manifold pressure increases in a reciprocating engine, the

Answer 16

density of air in the cylinder increases.

The manifold pressure is a measure of the absolute pressure of the air inside the induction system of a reciprocating engine.
The higher the manifold pressure, the greater the density of the air being taken into the cylinders.

Question 17

During full power output of an unsupercharged engine equipped with a float-type carburetor, in which of the following areas will the highest pressure exist?

Answer 17

Carburetor air scoop.

The venturi and the intake manifold both have a pressure lower than ambient.
Only the carburetor air scoop has a pressure higher than ambient pressure.

Question 18

What are the three basic regulating components of a sea-level boosted turbocharger system?

1. Exhaust bypass assembly.
2. Compressor assembly.
3. Pump and bearing casing.
4. Density controller.
5. Differential pressure controller.

Answer 18

1, 4, 5.

The three basic regulating components in a sea-level-boosted turbocharger system are the exhaust bypass assembly, the density controller and the differential-pressure controller.

Question 19

On small aircraft engines, fuel vaporization may be increased by

Answer 19

circulating the fuel and air mixture through passages in the oil sump.

On small aircraft reciprocating engines, fuel vaporization is improved by routing the fuel-air mixture from the carburetor through tubes in the oil sump.
Warm oil flows around the tubes and heats the fuel-air mixture.

Question 20

When starting an engine equipped with a carburetor air heater, in what position should the heater be placed?

Answer 20

Cold

The carburetor heater should be placed in the full COLD position when the engine is being started.
Heated air is not filtered. Dirt and other contaminants can be drawn into the engine if it is operated on the ground with the carburetor air heater in the HOT position.

Question 21

A method commonly used to prevent carburetor icing is to

Answer 21

preheat the intake air.

The most commonly used method of preventing carburetor ice is to preheat the intake air.

Question 22

If carburetor or induction system icing is not present when carburetor heat is applied with no change in the throttle setting, the

Answer 22

mixture will become richer.

If carburetor heat is applied when there is no icing present, the heated air, being less dense than cold air, will cause the mixture to become richer.
The use of this richer mixture will cause the engine power to decrease.

Question 23

In addition to causing accelerated wear, dust or sand ingested by a reciprocating engine may also cause

Answer 23

silicon fouling of spark plugs.

Sand that gets into the an engine acts as an abrasive and causes accelerated wear of the cylinder walls. Silica in the sand also forms a silicon glaze on the nose core insulators of the spark plugs. This form of contamination is an insulator at low temperature, but becomes a conductor when it is heated.

Question 24

Vortex dissipator systems are generally activated by

Answer 24

a landing gear switch.

Vortex dissipators are streams of high-velocity compressor bleed air that is directed into the vortex that forms in front of pod-mounted turbine engines.
The compressor bleed air is controlled by a solenoid valve which is actuated by a switch on the landing gear that allows the air to blow only when the aircraft is on the ground.

Question 25

The purpose of an engine/inlet anti-ice system is primarily to

Answer 25

prevent ice formation in engine and/or inlet areas.

An engine inlet anti-ice system is installed on turbine-powered aircraft to prevent the formation of ice on the engine components ahead of the compressor. Any ice that forms in this area can break off and cause serious damage to the compressor

Question 26

A carburetor air pre-heater is not generally used on takeoff unless absolutely necessary because of the

Answer 26

loss of power and possible detonation.

The use of carburetor heat when not necessary can cause a loss of power and possible detonation because of the increased temperature and lower density of the incoming fuel-air charge.

Question 27

If the turbocharger waste gate is completely closed,

Answer 27

all the exhaust gases are directed through the turbine.

When the waste gate of a turbosupercharger is completely closed, all of the exhaust gases flow through the turbine.

Question 28

In an airplane equipped with an alternate air system, if the main air duct air filter becomes blocked or clogged, the

Answer 28

system will automatically allow warm, unfiltered air to be drawn into the engine.

Some aircraft are equipped with a spring-loaded alternate air door. If the main air filter becomes clogged, the door will automatically open, allowing warm unfiltered air to be drawn into the carburetor.

Question 29

If a fire starts in the induction system during the engine starting procedure, what should the operator do?

Answer 29

Continue cranking the engine.

Induction-system fires in an aircraft engine are normally extinguished by keeping the engine running (or by continuing to crank it with the starter) and sucking the fire into the engine to extinguish it.

Question 30

The application of carburetor heat will have which of the following effects?

Answer 30

The mixture will become richer.

The application of carburetor heat will cause the mixture ratio to become richer.
A carburetor meters fuel on the basis of the volume of air passing through its venturi, but the engine burns the fuel on the basis of the weight of the air.
Heated air is less dense (weighs less) than cold air, so the application of carburetor heat will cause the mixture to become richer.

Question 31

What part of an aircraft in flight will begin to accumulate ice before any other?

Answer 31

Carburetor.

The temperature drop inside the carburetor as the fuel is converted from a liquid into a vapor will cause carburetor ice to form even when there is no visible water in the air.
The other types of ice mentioned in this question are atmospheric ice in which the aircraft must be flown through visible moisture.
Carburetor ice can accumulate more readily than these other types.

Question 32

Carburetor icing on an engine equipped with a constant-speed propeller can be detected by

Answer 32

a decrease in manifold pressure with a constant RPM.

Carburetor ice can be detected in an engine equipped with a constant-speed propeller by a drop in manifold pressure as the ice restricts the airflow into the engine.
The constant-speed propeller will hold the engine RPM constant.

Question 33

What is the purpose of a turbocharger system for a small reciprocating aircraft engine?

Answer 33

Compresses air to maintain manifold pressure constant from sea level to the critical altitude of the engine.

The turbocharger system used on a small aircraft compresses the air before it is taken into the induction system.
The engine is able, by using this compressed air, to automatically maintain manifold pressure from sea level to its critical altitude.

Question 34

When an engine with a subsonic divergent type inlet duct is running in place at high speed on the ground, the air pressure within the inlet is

Answer 34

positive.

Air enters the inlet duct of a turbine engine operating on the ground at ambient pressure, but because the duct diverges, the pressure rises to a slightly higher value of positive pressure before the air enters the compressor.

Question 35

The application of carburetor heat during engine operation will

Answer 35

decrease the weight of the fuel/air charge.

The application of carburetor heat will decrease the weight of the fuel-air charge taken into the engine since the heated air is less dense than cold air.
The decreased weight of the fuel-air charge will cause a decrease in the power produced by the engine.

Question 36

The purpose of a bellmouth compressor inlet is to

Answer 36

maximize the aerodynamic efficiency of the inlet.

Bellmouth inlets are used on helicopters, some turboprop engines, and on engine test stands because their shape gives them a high degree of aerodynamic efficiency.

Question 37

The differential pressure controller in a turbocharger system

Answer 37

reduces bootstrapping during part-throttle operation.

The differential-pressure controller reduces the undesirable condition known as bootstrapping during part-throttle operation.
Bootstrapping is an indication of unregulated power changes that result in a continual drift in manifold pressure.

Question 38

The vortex dissipators installed on some turbine-powered aircraft to prevent engine FOD utilize

Answer 38

a stream of engine bleed air blown toward the ground ahead of the engine.

Pod-mounted turbine engines are often so low to the ground that a vortex forms in front of the air inlet. This vortex causes sand and small stones to be drawn into the intake where they can damage the engine. Compressor bleed air is directed in a high velocity stream from a nozzle in the lower part of the engine cowling into the vortex to destroy, or dissipate it.
The compressor bleed air is shut off by a solenoid valve controlled by a switch on the landing gear when the aircraft is in the air.

Question 39

When operating an engine, the application of carburetor heat will have what effect on the fuel/air mixture?

Answer 39

Enriching the mixture until the AMC can make a compensation

The application of carburetor heat increases the volume of the air entering the engine (its density decreases).
Since the amount of fuel metered is a function of the volume of air entering the engine, the mixture will become richer when carburetor heat is applied.
The function of the automatic mixture control (AMC) is to compensate for this change.

Question 40

The use of the carburetor air heater when it is not needed causes

Answer 40

a decrease in power and possibly detonation.

The use of carburetor heat when it is not necessary will decrease the engine power because the engine will be operating with an excessively rich mixture.
There will also be the possibility of detonation because of the hot charge in the cylinders.

Question 41

What is the purpose of the rate-of-change controller in a turbocharger system?

Answer 41

Controls the rate at which the turbocharger discharge pressure will increase.

The rate-of-change controller controls the rate at which the turbocharger compressor discharge pressure will increase.

Question 42

The purpose of a sonic venturi on a turbocharged engine is to

Answer 42

limit the amount of air that can flow from the turbocharger into the cabin for pressurization.

A sonic venturi in a turbocharger installation acts as a flow limiter. When the air passing through the venturi reaches a speed of Mach 1, a shock wave forms that slows down all air passing through it. This limits the amount of air that can enter the pressurization system.

Question 43

Boost manifold pressure is generally considered to be any manifold pressure above

Answer 43

30 inches Hg.

Boost manifold pressure is normally considered to be any pressure above existing ambient pressure.
This is generally thought of as pressure above 30 inches of mercury, absolute.