Chapter 5 - Induction System FAA Questions

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.

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%.

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.

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.

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.

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.

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.

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.

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.

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.

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.

upper deck pressure.

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

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.

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.

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.

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.

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.

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.

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.

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.

preheat the intake air.

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

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.

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.

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

ontrols 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.

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.

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.