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(ASA) Powerplant Oral Study Guide TEST 202 3 -2026 ACTUAL
EXAM QUESTIONS AND DETAILED ANSWERS |ALREADY
GRADED A+
What is the main advantage of a horizontally opposed engine over a radial engine for powering modern aircraft? - CORRECT ANSWER The horizontally opposed engine has a much smaller frontal area and is easier to streamline than a radial engine How many throws are there in the crankshaft of a six-cylinder horizontally opposed engine? - CORRECT ANSWER Six What kind of connecting rod arrangement is used in a radial engine? - CORRECT ANSWER A master rod connects the single throw of the crankshaft with a piston. All of the other pistons are connected to the master rod with link rods How does metallic sodium in an exhaust valve aid in transferring heat? - CORRECT ANSWER The sodium melts when the engine is running, and it sloshes up and down as the valve operates. The sodium picks up heat from the valve head and carries it into the stem so it can be transferred to the cylinder head and dissipated into the air How is the structure around a turbine engine protected from excessive heat from the engine? - CORRECT ANSWER An insulating blanket protects the structure from excessive heat What is the function of blast tubes that are installed in a pressure cooling system of a reciprocating engine? - CORRECT ANSWER These blast tubes direct cooling air to the magnetos and the generator Of what material is the insulation blanket made that is used to protect the aircraft structure from the heat produced by a turbine engine? - CORRECT ANSWER Fiberglass sandwich between sheets of metal foil
Of what material are most recip engine exhaust components made? - CORRECT ANSWER Corrosion-resistant steel How is the speed of a turbo controlled? - CORRECT ANSWER By controlling the amount of exhaust gas that flows through the turbine. This is controlled by the position of the waste gate that is in the exhaust pipe What type of actuator is used to control the position of the turbocharger waste gate? - CORRECT ANSWER A hydraulic actuator that uses engine oil pressure to move the piston How does a power recovery turbine increase the power of a recip engine? - CORRECT ANSWER Exhaust-driven velocity turbines are coupled through a hydraulic drive to the engine crankshaft. Energy that would normally be lost is used to drive the turbines, and the turbines assist in turning the crankshaft how tight should the clamps be tightened that hold sections of a recip engine exhaust system together? - CORRECT ANSWER They should not be so tight that they will be damaged when heat expands the exhaust system components What would be the effect on engine performance of an internal failure of a muffler? - CORRECT ANSWER This will increase the exhaust back pressure and cause a loss of engine power What effect on turbine engine operation is caused by a change in the area of the exhaust nozzle? - CORRECT ANSWER Altering the area of the exhaust nozzle affect the compression ratio, the rpm, the mass airflow through the engine, and the EGT. What are two types of thrust reversers that are used with turbojet engines? - CORRECT ANSWER Mechanical blockage (clamshell) and aerodynamic blockage (cascade)
What is done to cause a McCauley prop to feather? - CORRECT ANSWER Oil is allowed to drain out of the prop Does centrifugal twisting moment on a prop blade tent to move the blades toward high pitch or toward low pitch? - CORRECT ANSWER Toward low pitch Do the counterweights on a prop tend to move the blades toward high pitch or toward low pitch? - CORRECT ANSWER Toward high pitch What is the difference between a controllable prop and a constant-speed prop? - CORRECT ANSWER Basically, it is the control system. A controllable-pitch prop uses a manually operated oil valve to control the pitch, and a constant-speed prop uses a governor to control the valve When making a magneto check on an engine equipped with a constant-speed prop, should the prop control be in the low-pitch or the high-pitch position - CORRECT ANSWER It should be in the low-pitch position What can be done to prevent the front cone from bottoming when installing a prop on a splined shaft? - CORRECT ANSWER Install a spacer behind the rear cone to move the prop forward on the shaft What is the purpose of the small holes that are drilled in the end of a wooden prop? - CORRECT ANSWER These holes vent the inside of the prop blade and allow moisture that collects in the wood to be released What is the function of the snap ring inside the hub of a prop that is mounted on a tapered or splined shaft? - CORRECT ANSWER The snap ring allows the prop to be pulled off of the shaft when the retaining nut is backed off What is adjusted inside the governor for a constant speed prop to change the speed at which the prop is operating? - CORRECT ANSWER The compression of the speeder spring
What is the function of the accumulator that is used with some McCauley feathering props? - CORRECT ANSWER The accumulator stores oil under pressure when the engine is operating normally. This oil is used to help the prop blades move toward low pitch when the prop is being unfeathered What is meant by the beta range of operation of a turboshaft prop? - CORRECT ANSWER This is the mode of ground operation, and it includes starting, taxiing, and ground reverse operation What is meant by the alpha range of operation of a turboprop prop? - CORRECT ANSWER This is the in-flight mode of operation from takeoff to landing Is the flat surface of a prop blade the face of the blade or the back of the blade?
- CORRECT ANSWER It is the face of the blade What keeps a McCauley feathering prop from feathering when the engine is shutdown on the ground? - CORRECT ANSWER A spring-loaded latch mechanism prevents the blades moving into the feather position when the engine is shut down on the ground. In the air, aerodynamic forces keep the propeller rotating, and centrifugal force holds the blades unlatched so they can move to the feather position when oil pressure is taken out of the prop Where are most APUs located in modern jet transport aircraft? - CORRECT ANSWER In the tail cone of the fuselage What is the function of the APU? - CORRECT ANSWER An APU provides electric power and compressed air when the main engines are not operating What are two sources of compressed air from an APU? - CORRECT ANSWER From bleed air from the APU turbine compressor, or from a load compressor driven by a free turbine in the engine Where in maintenance information based on the ATA 100 system would you
What is meant by a cam-ground piston? - CORRECT ANSWER A piston that is not perfectly round. Its dimension parallel with the wrist pin is several thousandths of an inch less than its dimension perpendicular to the wrist pin. When the piston reaches operating temperature, the metal in the piston pin boss expands enough that the piston becomes perfectly round Where is the piston in a reciprocating engine when the ignition spark occurs? - CORRECT ANSWER About 30 degrees of crankshaft rotation before the piston reaches top center on the compression stroke What is meant by a full-floating wrist pin? - CORRECT ANSWER A wrist pin that is not clamped in either the piston or the connecting rod. Full-floating wrist pins are kept from scoring the cylinder walls by soft metal plugs in their ends Why do most aircraft reciprocating engines use more than one spring on each valve? - CORRECT ANSWER By using more than one spring and having the wire diameter and pitch of the springs different, valve float is minimized. The springs have different resonant frequencies, so at least one spring will always be exerting a force on the valve Would excessive valve clearance cause the valves to open early or late? - CORRECT ANSWER Excessive clearance will cause the valve to open late and close early What is the purpose of valve overlap in a reciprocating engine? - CORRECT ANSWER Valve overlap allows the inertia of the exhaust gases leaving the cylinder to help the fresh induction charge start flowing into the cylinder What type of piston rings are installed on the pistons of an aircraft reciprocating engine? - CORRECT ANSWER Compression rings, oil control rings, and oil wiper rings Why are some exhaust valves partially filled with metallic sodium? - CORRECT ANSWER The metallic sodium melts at engine operating temperature and sloshes back and forth inside the hollow valve. It picks up heat from the valve head and
transfers it into the valve stem, so it can be transferred to the cylinder head through the valve guide What causes detonation in an aircraft engine? - CORRECT ANSWER Excessive heat and pressure in the engine cylinder causes the fuel-air mixture to reach its critical pressure and temperature. Under these conditions, the mixture explodes rather than burns. This explosion is called detonation Why is a compression check important for determining the condition of an aircraft reciprocating engine? - CORRECT ANSWER A compression check can determine the condition of the seal between the piston rings and the cylinder walls, and the seal between the intake and exhaust valves and their seats What is meant by the compression ratio of a reciprocating engine? - CORRECT ANSWER The ratio of the volume of the cylinder with the piston at the bottom of its stroke to the volume with the piston at the top of its stroke What are the two basic sections of a turbine engine? - CORRECT ANSWER The hot section and the cold section What are the two basic types of compressors that are used in aircraft turbine engines? - CORRECT ANSWER Axial-flow and centrifugal What is the purpose of the stators in an axial-flow compressor? - CORRECT ANSWER The stators convert some velocity energy into pressure energy and change the direction of the air so it is proper for the next stage of rotors What are three types of combustors used on aircraft turbine engines? - CORRECT ANSWER Can-type, annular-type, and can-annular-type How many igniters are there normally in an aircraft turbine engine? - CORRECT ANSWER Two
speed What is meant by a hot start in a turbine engine? - CORRECT ANSWER A start in which ignition occurs, but the internal temperatures go high enough that they can damage the engine What is meant by creep of the turbine blades? - CORRECT ANSWER A condition of permanent elongation of the turbine blades. Creep is caused by the high temperatures and the high centrifugal loading imposed on the blades How is the compressor of a turbine engine cleaned? - CORRECT ANSWER An emulsion-type cleaner is sprayed through the engine while it is being motored by the starter or operated at a low speed. The wash is followed by a clean water rinse. More vigorous cleaning is done by injecting a mild abrasive, such as ground up apricot pits or walnut shells, into the engine while it is operating at low speed Where is water injected into a turbine engine for cooling purposes? - CORRECT ANSWER Into the compressor inlet and into the engine diffuser case At what point in a turbine engine is the temperature the highest? - CORRECT ANSWER At the inlet to the high-pressure turbine What is the function of the interconnect tubes between the cans of a turbine engine that uses can-type combustors? - CORRECT ANSWER These tubes allow the flame to travel from the cans that contain the igniters to all of the other cans when the engine is being started What are the two types of thrust reversers that are used on turbojet engines?
- CORRECT ANSWER The mechanical blockage-type and the aerodynamic blockage-type What is meant by trimming a turbojet engine? - CORRECT ANSWER Adjusting the fuel control to get the correct idling and maximum-thrust RPM
What determines whether or not a 100-hour inspection is required for an aircraft? - CORRECT ANSWER 100-hour inspections are required only on aircraft that carry persons for hire or are used to give flight instruction for hire Where can you find a list of items that should be inspected on a 100-hour and an annual inspection of an aircraft engine? - CORRECT ANSWER in Appendix D of 14 CFR Part 43 In what publication can a mechanic find the operating limitations for an aircraft engine? - CORRECT ANSWER In the TCDS for the engine Who is authorized to perform the powerplant inspection that is required for an annual inspection? - CORRECT ANSWER An A&P mechanic who holds an IA What are two types of compression checks that can be performed on an aircraft reciprocating engine? - CORRECT ANSWER A differential compression check and a direct compression check What items are checked in a hot section inspection of a turbine engine? - CORRECT ANSWER The combustion sections is checked for cracks or distortion. The turbine wheel, the turbine case, and the exhaust section are checked for cracks, indications of overheating, and any indication of warpage, erosion, or burning What is the most common type of damage that is found in the hot section of a turbine engine? - CORRECT ANSWER Cracks that are caused by the high concentration of heat in the hot section Is the use of a checklist required when performing an annual or 100-hour inspection on an aircraft engine? - CORRECT ANSWER Yes What inspection must be performed on an aircraft reciprocating engine if it has been operated on turbine fuel? - CORRECT ANSWER The inside of the cylinders
What type of indicating system is used to measure the EGT of a turbine engine?
- CORRECT ANSWER A set of thermocouples arranged in an averaging circuit. These thermocouples are installed in the tail pipe of the engine What should a thermocouple-type cylinder head temperature indicator read when the engine is not operating? - CORRECT ANSWER The temp of the outside air how does a torquemeter actually measure the torque produced by an engine? - CORRECT ANSWER A torquemeter is actually an oil pressure gage. The pressure it measures is produced in a torque sensor and is proportional to the amount of strain in the torsional shaft that drives the reduction gears of the turboprop engine What two pressures are measured to get the Engine pressure Ratio of a turbojet engine? - CORRECT ANSWER The turbine discharge total pressure and the compressor inlet total pressure Of what two materials are the thermocouples made that are used in a turbine engine EGT system? - CORRECT ANSWER Chromel and alumel What kind of mechanism is normally used to measure oil pressure in a reciprocating engine? - CORRECT ANSWER A bourdon tube mechanism What is measured by the tachometers used on a two-spool gas turbine engine?
- CORRECT ANSWER The N1 tachometer shows the RPM of the low-pressure compressor, and the N2 tachometer shows the RPM of the high-pressure compressor Does the tachometer of a geared reciprocating engine indicate the speed of the crankshaft or of the propeller shaft? - CORRECT ANSWER The speed of the crankshaft Can a thermal switch-type fire detection system indicate a general overheat condition? - CORRECT ANSWER No, this is a spot-type fire detection system, and it cannot indicate an overheat condtion
Can a thermocouple-type fire detection system indicate a general overheat condition? - CORRECT ANSWER No, this is a rate-of-temperature-rise-type of system, and it cannot indicate a general overheat condition How is a thermocouple-type fire detection system checked for operation? - CORRECT ANSWER Current is sent through the heater in the thermal test unit. This heats the thermocouple, which produces enough current to close the sensitive relay. Current through the contacts of the sensitive relay closes the slave relay and turns on the fire warning light Does a break in a continuous-loop fire detection system keep the system from detecting a fire? - CORRECT ANSWER No, the unit will show a fault when it is tested, but it will still warn of a fire Does the pressure-type continuous-element fire detector system detect a general overheat condition, as well as a fire? - CORRECT ANSWER Yes, a high temperature on a small portion of the sensor or a lower temperature over the entire sensor will cause it to release enough gas to close the diaphragm switch and warn of a fire What are the two most commonly used fire extinguishing agents used for engine fires? - CORRECT ANSWER Halogenated hydrocarbon, such as Halon 1301, and carbon dioxide What extinguishing agent is used in the high-rate-discharge fire extinguishing systems installed in most turbojet engine installations? - CORRECT ANSWER Halon 1301 What happens when the pilot pulls the fire-pull T-handle in the cockpit of a jet transport airplane? - CORRECT ANSWER The bottle discharge switch is uncovered and armed, the generator field relay is tripped, fuel is shut off to the engine, hydraulic fluid is shut off to the pump, the engine bleed air is shut off, and the hydraulic pump low-pressure lights are deactivated
Why are the wires in certain electrical installations twisted together? - CORRECT ANSWER By twisting the wires together, the magnetic fields caused by current flowing in the wires are minimized What is used to protect a wire bundle from chafing where it passes through a hole in a bulkhead or frame? - CORRECT ANSWER A grommet around the edges of the hole How are electrical wires protected where they pass through an area of high temperature? - CORRECT ANSWER Wires passing through these areas are insulated with high temperature insulation, and the wires are enclosed in some type of protective conduit What is the minimum separation that is allowed between a wire bundle and a fluid line that carries combustible fluid or oxygen? - CORRECT ANSWER A minimum of six inches What is the significance of the color of the solderless connectors that are used on electrical wires? - CORRECT ANSWER The color of the insulation indicates the size of wire the connector will fit. Red terminals fit 22- through 18-gage wire, blue terminals fit 16- and 14-gage wire, and yellow terminals fit 12- and 10-gage wire What is the maximum number of wire terminals that may be stacked on a single stud in a terminal strip? - CORRECT ANSWER Four What is the purpose of the shielding that is used to encase some electrical wires?
- CORRECT ANSWER Shielding intercepts radiated electromagnet energy and carries it to ground so it will not interfere with any nearby sensitive electronic equipment Why must a switch be derated if it is used in a circuit controlling a DC electric motor? - CORRECT ANSWER The initial current flowing into a DC electric motor is much higher than the current the motor uses after the armature begins to rotate. Because of this high inrush current, the controlling switches must be derated
What is used as the rectifier to produce direct current in a DC generator?
- CORRECT ANSWER Brushes and a commutator How does a vibrator-type voltage regulator control the output voltage of a DC generator? - CORRECT ANSWER The strength of the magnetic field produced in the voltage regulator relay is proportional to the generator ouptut voltage. When the voltage rises above the regulated value, the relay pulls the contacts open and inserts a resistor in the generator field circuit. The contacts vibrate open and closed, putting the resistor in and out of the field circuit to control the amount of voltage the generator produces What is meant by paralleling the generators of a twin-engine aircraft? - CORRECT ANSWER Adjusting the voltage of the generators so they will share the electrical load equally What is meant by flashing the field of a DC generator? - CORRECT ANSWER Restoring the residual magnetism to the frame of a generator by passing battery current through the field coils in the same direction it flows when the generator is producing current What kind of rectifier is used in a DC alternator of the type that is used on most of the modern light airplanes? - CORRECT ANSWER A full-wave, three phase rectifier made up of six silicon diodes What is used to maintain a constant frequency of alternating current that is produced by an AC alternator driven by an aircraft turbine engine? - CORRECT ANSWER A hydraulic constant-speed drive unit between the engine and the alternator What three things must be synchronized before a three-phase AC generator can be connected to a bus that is being served by another generator? - CORRECT ANSWER The voltage, the frequency, and the phase rotation of the generators What must be done to reverse the direction of rotation of the armature of a DC
What is meant by a dry sump lubrication system? - CORRECT ANSWER A lubrication system in which the oil is carried in a tank that is not a part of the engine How is oil temperature controlled in an aircraft reciprocating engine? - CORRECT ANSWER Hot oil is directed through the core of the oil cooler, but cold oil is directed around the outside of the core so it will not be further cooled Is the oil temp shown on the aircraft instrument panel the temp of the oil entering the engine or of the oil leaving the engine? - CORRECT ANSWER It is the temp of the oil entering the engine What is the purpose of oil dilution in a reciprocating engine? - CORRECT ANSWER When very cold weather is anticipated, gasoline can be mixed with the lubricating oil before the engine is shut down. This reduces the viscosity of the oil and makes starting easier. When the engine is running, the gasoline evaporates out of the oil What is the function of the hopper in the oil tanks used with some reciprocating engine? - CORRECT ANSWER Hoppers are a part of the oil dilution system. Only the oil in the hopper is diluted. This speeds up dilution and requires less gasoline What happens to the gasoline that is used to dilute the oil in the crankcase of an aircraft reciprocating engine? - CORRECT ANSWER When the engine is running and the oil is warm, the gasoline evaporates out of it What is the purpose of the sludge plugs in the crankshaft of a reciprocating engine? - CORRECT ANSWER They trap sludge that is in the oil and hold it until the engine is disassembled at overhaul Which pump is the larger in a dry-sump lubricating system, the pressure pump or the scavenger pump - CORRECT ANSWER The scavenger pump has a greater volume Why do full-flow oil filters have a spring-operated bypass valve in them? - CORRECT ANSWER In case the filter should plug up so it cannot pass any oil, the
bypass valve will open and allow unfiltered oil to flow through the system What is the function of a fuel-oil heat exchanger in the lubrication system of a turbojet engine? - CORRECT ANSWER This allows heat from the oil to warm the fuel so ice will not form on the fuel filters What kind of oil is used in most turbojet engines? - CORRECT ANSWER Synthetic oil Where are the last chance oil filters located in a turbojet engine? - CORRECT ANSWER They are located inside the engine just ahead of the nozzles that spray oil onto the bearings Where is the oil tank in a dry-sump reciprocating engine vented? - CORRECT ANSWER To the engine crankcase What information must be displayed around the oil filter opening for a turbojet engine? - CORRECT ANSWER The word "oil" and the permissible oil designations, or references to the Airplane Flight Manual for the permissible oil designations What is the function of the oil control rings on the piston of an aircraft reciprocating engine? - CORRECT ANSWER They maintain the proper quantity of oil between the piston and the cylinder wall What is meant by a spectrometric oil analysis? - CORRECT ANSWER It is a program in which a sample of oil is taken from the engine at regular intervals and sent to a laboratory, where it is burned in an electric arc. The resulting light is analyzed for the wavelengths of the elements that are present in the oil sample. Traces of aluminum, copper, and iron in the oil indicate wear of the pistons or wrist pin plugs (aluminum), cylinder walls or piston rings (iron), main bearings or bushings (copper). A single sample is meaningless. there must be a series of samples taken at regular intervals to measure the change in the amounts of these metals
