Reciprocating Engine Induction and Cooling Systems

8780. 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?

A—Venturi.

B—Intake manifold.

C—Carburetor air scoop.

(C) 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. (AM.III.J.K1) — FAA-H-8083-32

8782. As manifold pressure increases in a reciprocating engine, the

A—volume of air in the cylinder increases.

B—weight of the air-fuel charge decreases.

C—density of air in the cylinder increases.

(C) 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. (AM. III.J.K1) — FAA-H-8083-32

8783. Which of the following statements regarding volumetric efficiency of an engine is true?

A—The volumetric efficiency of an engine will remain the same regardless of the amount of throttle opening.

B—It is impossible to exceed 100 percent volumetric efficiency of any engine regardless of the type of supercharger used.

C—It is possible to exceed 100 percent volumetric efficiency of some engines by the use of superchargers of the proper type.

(C) The volumetric efficiency of an engine is the ratio of the airfuel 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 percent. (AM.III.J.K1) — FAA-H-8083-32

8785. Which of the following would be a factor in the failure of an engine to develop full power at takeoff?

A—Improper adjustment of carburetor heat valve control linkage.

B—Excessively rich setting on the idle mixture adjustment.

C—Failure of the economizer valve to remain closed at takeoff throttle setting.

(A) 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. (AM. III.J.K1) — FAA-H-8083-32

8787. Boost manifold pressure is generally considered to be any manifold pressure above

A—14.7 "Hg.

B—50 "Hg.

C—30 "Hg.

(C) Boost manifold pressure is normally considered to be any pressure above existing ambient pressure. This is generally thought of as pressure above 30 "Hg, absolute. (AM. III.J.K1) — FAA-H-8083-32

8796. The purpose of a bellmouth compressor inlet is to

A—provide an increased ram air effect at low airspeeds.

B—maximize the aerodynamic efficiency of the inlet.

C—provide an increased pressure drop in the inlet

(B) 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. (AM. III.J.K1) — FAA-H-8083-32

8797. 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?

A—Positive and negative charged areas to attract and/ or repel particulates out of the airflow.

B—Air/moisture separators, and “washing” the air clean utilizing water droplets.

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

(C) 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. (AM.III.J.K1) — FAA-H-8083-32

8810. If a fire starts in the induction system during the engine starting procedure, what should the operator do?

A—Turn off the fuel pump switches.

B—Continue cranking the engine.

C—Turn off the magneto switches.

(B) 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. (AM.III.J.K1) — FAA-H-8083-32

8811. On small aircraft engines, fuel vaporization may be increased by

A—cooling the air before it enters the engine.

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

C—heating the fuel before it enters the carburetor.

(B) On small aircraft reciprocating engines, fuel vaporization is improved by routing the air-fuel mixture from the carburetor through tubes in the oil sump. Warm oil flows around the tubes and heats the air-fuel mixture. (AM. III.J.K1) — FAA-H-8083-32

8829. Which of the following defects would likely cause a hot spot on a reciprocating engine cylinder?

A—Too much cooling fin area broken off.

B—A cracked cylinder baffle.

C—Cowling air seal leakage.

(A) If too much cooling fin area is broken off of a cylinder, that particular area in the cylinder will not be properly cooled and it will develop a hot spot. (AM.III.J.K1) — FAAH-8083-32

8830. What part of an air-cooled cylinder assembly has the greatest fin area per square inch?

A—Cylinder barrel.

B—Rear of the cylinder head.

C—Exhaust valve port.

(C) The area around the exhaust valve port on the cylinder head of an air-cooled aircraft engine cylinder has the greatest fin area per square inch. (AM.III.J.K1) — FAAH-8083-32

8831. Reciprocating engines used in helicopters are cooled by

A—the downdraft from the main rotor.

B—a fan mounted on the engine.

C—blast tubes on either side of the engine mount.

(B) Helicopters cool their reciprocating engines with a fan mounted on the engine. This fan pulls air through the fins on the cylinders. (AM.III.J.K1) — FAA-H-8083-32

8832. The greatest portion of heat generated by combustion in a typical aircraft reciprocating engine is

A—converted into useful power.

B—carried out with the exhaust gases.

C—dissipated through the cylinder walls and heads.

(B) Approximately 45 percent of the heat energy in the fuel burned in an aircraft engine is carried out the exhaust with the exhaust gases. Another 20 percent is dissipated through the cylinder heads and walls, and about 5 percent is removed by the oil system. Only about 30 percent is converted into useful power. (AM.III.J.K1) — FAA-H8083-32

8833. A broken cooling fin on a cylinder head

A—is cause for rejection of the head.

B—may be filed to smooth contours if damage and/or repair limits are not exceeded.

C—should be left alone.

(B) A broken cooling fin on a cylinder head can be repaired by filing the edges to a smooth contour. This type of repair can be made only if the amount of fin area remaining after the repair is completed is within the limits allowed by the engine manufacturer. (AM.III.J.K1) — FAA-H-8083-32

8834. An engine becomes overheated due to excessive taxiing or improper ground runup. Prior to shutdown, operation must continue until cylinders have cooled, by running engine at

A—low RPM with oil dilution system activated.

B—idle RPM.

C—high RPM with mixture control in RICH position.

(B) If an engine is overheated from excessive taxiing or improper ground operation, it should be cooled down by operating it at idle RPM for a while before it is shut down. (AM.III.J.K1) — FAA-H-8083-32

8835. Cylinder head temperatures are measured by means of an indicator and a

A—resistance bulb sensing device.

B—wheatstone bridge sensing device.

C—thermocouple sensing device

(C) Cylinder head temperature is normally measured by a thermocouple sensing device. (AM.III.J.K1) — FAA-H8083-32

8836. High cylinder head temperatures are likely to result from

A—a very lean mixture at high power settings.

B—fouled spark plugs.

C—a very rich mixture at high power settings.

(A) An excessively lean mixture will cause a high cylinder head temperature because some of the mixture will be burning when it passes out of the cylinder around the exhaust valve. (AM.III.J.K1) — FAA-H-8083-32

8838. Prolonged idling of an engine will usually result in

A—excessive cylinder head temperatures.

B—increased oil consumption.

C—foreign material buildup on spark plugs.

(C) Prolonged idling of an aircraft engine will normally cause spark plugs to foul by allowing foreign material to accumulate in their firing end cavity. (AM.III.J.K1) — FAA-H8083-32

8839. The most common method and generally the best conduction of heat from the inside of a cylinder barrel to the cooling air is accomplished by

A—machining fins directly on the outside of the barrel.

B—shrinking on a jacket or muff of aluminum cooling fins around a steel cylinder sleeve.

C—machining fins directly on the outside of the barrel and shrinking on a jacket or muff of aluminum cooling fins around a steel cylinder sleeve (on different areas of the barrel).

(A) The most widely used method of conducting heat away from the cylinder barrel of an air-cooled engine is by machining fins directly on the outside of the barrel. (AM. III.J.K1) — FAA-H-8083-32

8840. What is the function of a blast tube as found on aircraft engines?

A—A means of cooling the engine by utilizing the propeller backwash.

B—A tube used to load a cartridge starter.

C—A device to cool an engine accessory.

(C) A blast tube is used on an air-cooled engine to direct a stream of cooling air to some engine accessory, such as a magneto or a generator. (AM.III.J.K1) — FAA-H-8083-32

8842. Which of the following results in a decrease in volumetric efficiency?

A—Cylinder head temperature too low.

B—Part-throttle operation.

C—Short intake pipes of large diameter.

(B) Part-throttle operation lowers the volumetric efficiency of a reciprocating engine. It does not allow a full charge of fuel and air to be drawn into the cylinder as the piston moves down on the intake stroke. (AM.III.J.K1) — FAA-H-8083-32

8843. The undersides of pistons are frequently finned. The principal reason is to

A—provide sludge chambers and sediment traps.

B—provide for greater heat transfer to the engine oil.

C—support ring grooves and piston pins.

(B) The undersides of pistons are frequently finned to provide a greater area for oil to absorb heat from the piston heads. (AM.III.J.K1) — FAA-H-8083-32

8845. Increased engine heat will cause volumetric efficiency to

A—remain the same.

B—decrease.

C—increase.

(B) Increased engine heat decreases volumetric efficiency because it lowers the density of the air entering the cylinders. (AM.III.J.K1) — FAA-H-8083-32

9013. When a fireguard is standing by during an engine start, they should be watching for potential fires that could start

A—close to the battery compartment or starter.

B—in the induction system or the exhaust system.

C—at the ground power receptacle (if connected to a ground power unit).

(B) The fireguard must be familiar with the induction system of the engine so that in case of fire, they can direct the CO2 into the air intake of the engine to extinguish it. A fire could also occur in the exhaust system of the engine from liquid fuel being ignited in the cylinder and expelled during the normal rotation of the engine. (AM.III.J.K1) — FAA-H-8083-32

8772. A method commonly used to prevent carburetor icing is to

A—preheat the intake air.

B—mix alcohol with the fuel.

C—electrically heat the throttle valve.

(A) The most commonly used method of preventing carburetor ice is to preheat the intake air. (AM.III.J.K2) — FAA-H8083-32

8773. Carburetor icing is most severe at

A—air temperatures between 30 and 40°F.

B—high altitudes.

C—low engine temperatures.

(A) 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. (AM.III.J.K2) — FAA-H-8083-32

8774. Into what part of a reciprocating engine induction system is deicing alcohol normally injected?

A—The supercharger or impeller section.

B—The airstream ahead of the carburetor.

C—The low-pressure area ahead of the throttle valve.

(B) 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. (AM.III.J.K2) — FAA-H8083-32

8775. Carburetor icing on an engine equipped with a constant-speed propeller can be detected by

A—a decrease in power output with no change in manifold pressure or RPM.

B—an increase in manifold pressure with a constant RPM.

C—a decrease in manifold pressure with a constant RPM.

(C) 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. (AM.III.J.K2) — FAA-H-8083-32

8776. What part of an aircraft in flight will begin to accumulate ice before any other?

A—Wing leading edge.

B—Propeller spinner or dome.

C—Carburetor.

(C) 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. (AM.III.J.K2) — FAAH-8083-32

8777. Carburetor icing may be eliminated by which of the following methods?

A—Alcohol spray and electrically heated induction duct.

B—Ethylene glycol spray and heated induction air.

C—Alcohol spray and heated induction air.

(C) 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. (AM.III.J.K2) — FAA-H-8083-32

8784. Bootstrapping of a turbocharged engine is indicated by

A—an overboost condition of the engine on takeoff.

B—a transient increase in engine power.

C—a maximum increase in manifold pressure.

(B) 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. (AM.III.J.K4) — AC 43.13-1B

8786. If the turbocharger waste gate is completely closed,

A—none of the exhaust gases are directed through the turbine.

B—the turbocharger is in the OFF position.

C—all the exhaust gases are directed through the turbine.

(C) When the waste gate of a turbosupercharger is completely closed, all of the exhaust gases flow through the turbine. (AM.III.J.K4) — FAA-H-8083-32

8788. What is the purpose of the density controller in a turbocharger system?

A—Limits the maximum manifold pressure that can be produced at other than full throttle conditions.

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

C—Maintains constant air velocity at the carburetor inlet.

(B) 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. (AM.III.J.K4) — FAA-H-8083-32

8789. What is the purpose of the rate-of-change controller in a turbocharger system?

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

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

C—Controls the position of the waste gate after the aircraft has reached its critical altitude.

(B) The rate-of-change controller controls the rate at which the turbocharger compressor discharge pressure will increase. (AM.III.J.K4) — FAA-H-8083-32

8790. What directly regulates the speed of a turbocharger?

A—Turbine.

B—Waste gate.

C—Throttle.

(B) 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. (AM.III.J.K4) — FAA-H-8083-32

8791. What is the purpose of a turbocharger system for a small reciprocating aircraft engine?

A—Compresses the air to hold the cabin pressure constant after the aircraft has reached its critical altitude.

B—Maintains constant air velocity in the intake manifold.

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

(C) 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. (AM.III.J.K4) — FAA-H-8083-32

8792. What are the three basic regulating components of a sea-level boosted turbocharger system?

A—Exhaust bypass assembly, compressor assembly, and density controller.

B—Exhaust bypass assembly, density controller, and differential pressure controller.

C—Pump and bearing casing, compressor assembly, and density controller.

(B) 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. (AM.III.J.K4) — FAA-H-8083-32

8793. The differential pressure controller in a turbocharger system

A—reduces bootstrapping during part-throttle operation.

B—positions the waste gate valve for maximum power.

C—provides a constant fuel-to-air ratio.

(A) 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. (AM.III.J.K4) — FAA-H-8083-32

8793-1. The pressure between the turbocharger and the throttle valve is called

A—turbocharger boost pressure.

B—induction manifold pressure.

C—upper deck pressure.

(C) The air pressure that is present between the turbocharger and the throttle valve is known as the upper-deck pressure. (AM.III.J.K4) — FAA-H-8083-32

8794. The purpose of a sonic venturi on a turbocharged engine is to

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

B—increase the amount of air that can flow from the turbocharger into the cabin for pressurization.

C—increase the velocity of the air-fuel charge.

(A) 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. (AM.III.J.K4) — FAA-H-8083-32

9014. If a turbocharger waste gate is not able to close fully,

A—the aircraft will not be able to reach its critical altitude.

B—the engine is more likely to over boost.

C—none of the exhaust gases will flow through the turbine.

(A) If a turbocharger waste gate will not close fully, then the aircraft will not be able to reach its critical altitude. (AM. III.J.K4) — FAA-H-8083-32

9015. A malfunction that causes the turbocharger waste gate or controller to fluctuate will

A—have no effect on manifold pressure.

B—cause engine surges due to an erratic manifold pressure.

C—cause the oil pressure to the turbocharger to decrease.

(B) If a malfunction occurs causing the waste gate or controller to not be stable, it will cause the engine to surge due to an erratic manifold pressure. (AM.III.J.K4) — FAA-H8083-32

8815. What is the purpose of an augmenter used in some reciprocating engine exhaust systems?

A—To reduce exhaust back pressure.

B—To aid in cooling the engine.

C—To assist in displacing the exhaust gases.

(B) Augmenters are venturi-shaped stainless steel tubes into which the exhaust gases from a reciprocating engine are directed. The augmenters use the venturi effect to draw an increased airflow over the engine to augment (increase) the engine cooling. (AM.III.J.K5) — FAA-H-8083-32

8817. Cracks in cooling fins that do not extend into the cylinder head

A—should be left alone and monitored.

B—may be repaired by removing the affected area and contour filing within limits.

C—may be repaired by adding a stiffener.

(B) If cooling fins are cracked, the affected area may be removed and the fins contour-filed. This repair is permitted only if the finished repair leaves the amount of fin area on the cylinder that is specified by the engine manufacturer. (AM.III.J.K5) — FAA-H-8083-32

8818. Which of the following should a mechanic consult to determine the maximum amount of cylinder cooling fin that could be removed when cracks are found?

A—AC 43.13-1A.

B—Engine manufacturer’s service or overhaul manual.

C—Engine structure repair manual.

(B) Anytime there is a question about what can be done to an aircraft engine, information in the engine manufacturer’s service or overhaul manual must be consulted and complied with. (AM.III.J.K5) — FAA-H-8083-32

8819. A bent cooling fin on an aluminum cylinder head should be

A—sawed off and filed smooth.

B—left alone if no crack has formed.

C—straightened out as much as possible without breaking.

(B) A bent cooling fin on a cast aluminum cylinder head should be left alone if it has not cracked. Attempting to straighten the thin cast fin could cause it to crack. (AM. III.J.K5) — FAA-H-8083-32

8820. Where are cooling fins usually located on aircooled engines?

A—Exhaust side of the cylinder head, inside the pistons, and connecting rods.

B—Cylinder head, cylinder walls, and inside the piston.

C—Cylinder head, cylinder barrel, and inside the piston

(C) Cooling fins on an air-cooled aircraft engine are located on the cylinder head, the cylinder barrel and the inside of the piston heads. (AM.III.J.K5) — FAA-H-8083-32

8823. Generally, a small crack just started in a cylinder baffle

A—requires repair by reinforcing, such as installation of a doubler over the area.

B—requires no action unless it grows or is branched into two cracks.

C—may be stop drilled.

(C) Small cracks in a cylinder baffle that have just started can be stop-drilled to prevent them from growing. (AM. III.J.K5) — FAA-H-8083-32

8828. (1) Some aircraft exhaust systems include an augmenter system to draw additional air over the engine for cooling.

(2) Augmenter systems are used to create a low pressure area at the lower rear of the aircraft engine cowling. Regarding the above statements,

A—only 1 is true.

B—both 1 and 2 are true.

C—only 2 is true.

(B) Statement 1 is true. The augmenter system draws additional air over the engine for cooling.

Statement 2 is also true. Augmenter tubes open into the lower rear of the aircraft engine cowling. Exhaust gases flowing through the tube create a low pressure inside the cowling that draws air from above the engine through the cooling fins. (AM.III.J.K5) — FAA-H-8083-32

8795. What is used to drive a supercharger?

A—Exhaust gases.

B—Gear train from the crankshaft.

C—Belt drive through a pulley arrangement.

(B) 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. (AM.III.J.K6) — FAA-H8083-32

8808. In addition to causing accelerated wear, dust or sand ingested by a reciprocating engine may also cause

A—silicon fouling of spark plugs.

B—sludge formation.

C—acid formation.

(A) Sand that gets into the 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. (AM.III.J.K6) — FAA-H-8083-32

8809. In an airplane equipped with an alternate air system, if the main air duct air filter becomes blocked or clogged, the

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

B—flow of air into the engine will be slowed or cut off unless alternate air is selected.

C—system will automatically allow warm, filtered alternate air to be drawn into the engine.

(A) 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. (AM.III.J.K6) — FAA-H-8083-32

9012. If an engine air filter element is not routinely cleaned and becomes excessively dirty, it can cause

A—the engine to not start.

B—a loss of engine power.

C—both A and B are true.

(C) Periodic removal and cleaning of the filter element is essential to satisfactory engine protection. If the induction system air filter becomes excessively dirty, it will cause a loss of power, or the engine will not start. (AM.III.J.K6) — FAA-H-8083-32

8778. Where would a carburetor air heater be located in a fuel injection system?

A—At the air intake entrance.

B—None is required.

C—Between the air intake and the venturi.

(B) 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. (AM.III.J.K7) — FAA-H-8083-32

8779. An increase in manifold pressure when carburetor heat is applied indicates

A—ice was forming in the carburetor.

B—mixture was too lean.

C—overheating of cylinder heads.

(A) 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. (AM.III.J.K7) — FAA-H-8083-32

8781. The use of the carburetor air heater when it is not needed causes

A—a very lean mixture.

B—excessive increase in manifold pressure.

C—a decrease in power and possibly detonation.

(C) 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. (AM.III.J.K7) — FAA-H-8083-32

8803. If carburetor or induction system icing is not present when carburetor heat is applied with no change in the throttle setting, the

A—mixture will become richer.

B—manifold pressure will increase.

C—engine RPM will increase.

(A) 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. (AM. III.J.K7) — FAA-H-8083-32

8804. When starting an engine equipped with a carburetor air heater, in what position should the heater be placed?

A—HOT.

B—COLD.

C—NEUTRAL.

(B) 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. (AM.III.J.K7) — FAA-H-8083-32

8805. The application of carburetor heat during engine operation will

A—decrease the weight of the air-fuel charge.

B—decrease the volume of air in the cylinder.

C—increase the density of air in the cylinder.

(A) The application of carburetor heat will decrease the weight of the air-fuel charge taken into the engine since the heated air is less dense than cold air. The decreased weight of the air-fuel charge will cause a decrease in the power produced by the engine. (AM.III.J.K7) — FAA-H8083-32

8806. The application of carburetor heat will have which of the following effects?

A—The manifold pressure will be increased.

B—The mixture will become leaner.

C—The mixture will become richer.

(C) 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. (AM.III.J.K7) — FAA-H-8083-32

8807. When operating an engine, the application of carburetor heat will have what effect on the air-fuel mixture?

A—Enriching the mixture because the AMC cannot make a correction for increased temperature.

B—Enriching the mixture until the AMC can make a compensation.

C—Leaning the mixture until the AMC can make a compensation.

(B) 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 AMC is to compensate for this change. (AM.III.J.K7) — FAAH-8083-32

8813. A carburetor air pre-heater is not generally used on takeoff unless absolutely necessary because of the

A—loss of power and possible detonation.

B—possibility of induction system overboost.

C—inability of the engine to supply enough heat to make a significant difference.

(A) 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 air-fuel charge. (AM.III.J.K7) — FAA-H-8083-32

8848. One source commonly used for carburetor air heat is

A—turbocharger heated air.

B—alternate air heat.

C—exhaust gases.

(C) Induction air flows over a portion of the engine exhaust system to receive heat in order to prevent the formation of carburetor ice, and to remove ice that has formed in the induction system. (AM.III.J.K7) — FAA-H-8083-32

8793-2. Which of the following is a function of the differential pressure controller?

A—It limits the maximum manifold pressure that can be produced by the turbocharger at full throttle conditions.

B—It controls all positions of the waste gate except at fully open position.

C—It controls the position of the waste gate after the aircraft has reached its critical altitude.

(B) The differential pressure controller functions during all positions of the waste gate valve other than the fully open position, which is controlled by the density controller. (AM. III.J.K8) — FAA-H-8083-32

8812. The action of a carburetor airscoop is to supply air to the carburetor, but it may also

A—cool the engine.

B—keep fuel lines cool and prevent vapor lock.

C—increase the pressure of the incoming air by ram effect.

(C) 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. (AM.III.J.K8) — FAA-H-8083-32

8821. How do cowl flaps aid in cooling a horizontally opposed aircraft engine?

A—Recirculates air through the engine cylinders.

B—Directs air through the engine cylinders.

C—Controls the amount of air flowing around the cylinders.

(C) The amount of air that can flow through the cylinder fins is determined by the air-pressure differential between the top of the engine and the space below the engine. On most high-powered horizontally opposed engines, this pressure differential can be controlled with cowl flaps. (AM.III.J.K8) — FAA-H-8083-32

8822. The position of the cowl flaps during normal cruise flight conditions is

A—closed.

B—open.

C—neutral.

(A) Cowl flaps should be kept fully open when the engine is run on the ground. In flight, the cowl flaps are closed as there is enough ram air flowing through the engine for adequate cooling. (AM.III.J.K8) — FAA-H-8083-32

8825. During ground operation of an engine, the cowl flaps should be in what position?

A—Fully closed.

B—Fully open.

C—Opened according to ambient conditions

(B) For ground operation of an aircraft reciprocating engine, the cowl flaps should be fully open. (AM.III.J.K8) — FAAH-8083-32

8827. During an operational check of an electrically powered aircraft engine cowl flap system, the motor fails to operate. Which of the following is the first to be checked?

A—Flap actuator motor circuit breaker.

B—Flap actuator control switch.

C—Flap actuator motor.

(A) When any electric motor fails to operate, the first thing to check is its circuit breaker. (AM.III.J.K8) — FAA-H8083-32

8844. What is the position of the cowl flaps during engine starting and warmup operations under normal conditions?

A—Full open at all times.

B—Full closed at all times.

C—Open for starting, closed for warmup.

(A) Cowl flaps on a reciprocating engine should be open anytime the engine is operating on the ground. Open cowl flaps provide maximum engine cooling. (AM.III.J.K8) — FAA-H-8083-32

8814. The primary purpose of baffles and deflectors installed around cylinders of air-cooled aircraft engines is to

A—create a low pressure area aft of the cylinders.

B—force cooling air into close contact with all parts of the cylinders.

C—increase the volume of air used to cool the engine.

(B) Baffles and deflectors force the cooling air into close contact with the fins of an aircraft cylinder head and cylinder barrel. This directed flow of air aids in efficient and uniform cooling of the cylinder. (AM.III.J.K9) — FAA-H-8083-32

8816. Aircraft reciprocating engine cylinder baffles and deflectors should be repaired as required to prevent loss of

A—power.

B—fin area.

C—cooling.

(C) It is extremely important that cylinder baffles and deflectors be kept in a good state of repair. Leaking baffles or improperly oriented deflectors can cause a loss of cooling which can cause engine damage. (AM.III.J.K9) — FAAH-8083-32

8824. Which of the following assists in removing heat from the metal walls and fins of an air-cooled cylinder assembly?

A—An intercooler system.

B—A baffle and cowl arrangement.

C—An engine induction system.

(B) Baffles and a cowling arrangement are used to force cooling air between the fins of an air-cooled cylinder for better cooling. (AM.III.J.K9) — FAA-H-8083-32

8837. The purpose of an intercooler when used with a turbocharger is to cool the

A—exhaust gases before they come in contact with the turbo drive.

B—turbocharger bearings.

C—air entering the carburetor from the turbocharger.

(C) Intercoolers are used with large turbosuperchargers to cool the air that has been heated by compression before it enters the carburetor. (AM.III.J.K10) — FAA-H-8083-32