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66 Cards in this Set
- Front
- Back
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What is the main advantage of a horizontally opposed engine over a radial engine for powering modern aircraft? |
The horizontally opposed engine has a much smaller frontal area and is easier to streamline than a radial engine
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How many throws are there in a crankshaft of a six-cylinder horizontally opposed engine?
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Six
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What kind of connecting rod arrangement is used in a radial engine?
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A matter 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.
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Of what material are most piston rings made?
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Gray cast iron
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What is the reason for using hydraulic valve lifters in an aircraft engine?
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Hydraulic valve lifters keep all of the clearance out of the valve operating mechanism. This decreases the wear of the valve train components.
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At what speed does the camshaft turn, relative to the crankshaft spec in a horizontally opposed engine?
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The camshaft turns at one half of the crankshaft speed.
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What kind of main bearings are used in a horizontally opposed engine?
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Steel - backed, lead-alloy bearing inserts.
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On what stroke is the piston of a reciprocating engine when the intake valve begins to open? |
On the exhaust stroke |
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On what stroke is the piston of a reciprocating engine when the exhaust valve begins to open? |
On the power stroke |
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Why are both the hot and cold valve clearances given for most radial engines? |
The hot clearance is given for valve timing purposes. The timing is adjusted with the vales in cylinder number one, set with the hot clearance. When the timing is set, all of the valves are adjusted to their cold clearance. |
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What is meant by a cam-ground piston? |
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. |
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Where is the piston in a reciprocating engine when the ignition spark occurs? |
About 30 degrees of crankshaft rotation before the piston reaches top center on the compression stroke. |
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What is meant by a full-floating wrist pin? |
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. |
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Why do most aircraft reciprocating engines use more than one spring on each valve? |
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. |
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Would excessive valve clearance cause the valves to open early or late? |
Excessive clearance will cause the valve to open late and close early. |
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What is the purpose of valve overlap in a reciprocating engine? |
Valve overlap allows the inertia of the exhaust gasses leaving the cylinder to help the fresh induction charge start flowing into the cylinder. |
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What type of piston rings are installed on the pistons of an aircraft reciprocating engine? |
Compression rings, oil control rings, and oil wiper rings. |
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Why are some exhaust valves partially filled with metallic sodium? |
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. |
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What causes detonation in an aircraft engine? |
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. |
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Why is a compression check important for determining the condition of an aircraft reciprocating engine? |
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. |
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What is meant by the compression ratio of a reciprocating engine? |
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. |
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What are the two basic sections of a turbine engine? |
The hot section and the cold section. |
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What are the two basic types of compressors that are used in aircraft turbine engines? |
Axial-flow and centrifugal. |
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What is the purpose of the stators in an axial-flow compressor? |
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. |
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What are three types of combustors used on aircraft turbine engines? |
Can-type, annular-type, and can-annular-type. |
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How any igniters are there normally in an aircraft turbine engine? |
Two |
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What is the main purpose of the turbine nozzle in an aircraft turbine engine? |
The turbine nozzle directs the hot gasses as they leave the combustors so they will turn the turbine wheel with maximum efficiency. |
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What is meant by a free-turbine turboshaft engine? |
A turboshaft engine that has a turbine wheel, or stage of turbine wheels, that is not used to drive the compressor of the gas generator section of the engine. This free turbine drives the propeller in a turboprop engine or the transmission and rotor of a helicopter. |
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Why do some axial-flow turbine engines have more than one set of turbines and compressors? |
A two-spool turbine engine has a low-pressure and a high-pressure compressor, each driven by its own turbine. The two independent systems operate at the speed at which they are most efficient. |
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What kind of bearings are used to support the rotor shaft of an aircraft turbine engine? |
Anti-friction bearings, such as ball bearings or roller bearings. |
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What is meant by a turbofan engine? |
An axial-flow turbine engine in which the first stage of compressor blades are lengthened, so they can force air around the outside of the gas generator portion of the engine |
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Where can you find the limits of repair allowed for the compressor blades of an aircraft turbine engine? |
In the FAA-approved service manual issued by the manufacturer of the engine. |
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Why is it important that a turbojet engine be allowed to cool before it is shut down after it has been operated at a high power setting? |
If the engine is shut down while it is hot, there is a possibility that the shroud will contract around the turbine wheel and seize the rotor. |
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What is meant by a hung start in a turbine engine? |
A start in which ignition occurs, but the engine does not accelerate to a self-sustaining speed. |
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What is meant by a hot start in a turbine engine? |
A start in which ignition occurs, but the internal temperatures go high enough that they can damage the engine. |
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What is meant by creep of the turbine blades? |
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. |
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How is the compressor of a turbine engine cleaned? |
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 low speed. |
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Where is water injected into a turbine engine for cooling purposes? |
Into the compressor inlet and into the engine diffuser case. |
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At what point in a turbine engine is the temperature the highest? |
At the inlet to the high-pressure turbine. |
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What is the function of the interconnect tubes between the cans of a turbine engine that uses can-type combustors? |
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. |
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What are two types of thrust reversers that are used on turbojet engines? |
The mechanical blockage-type and the aerodynamic blockage-type. |
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What is meant by trimming a turbojet engine? |
Adjusting the fuel control to get the correct idling and maximum-thrust RPM. |
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What determines whether or not a 100-hour inspection is required for an aircraft? |
100-hour inspections are required only on aircraft that carry persons for hire or are used to give flight instruction for hire. |
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Where can you find a list of items that should be inspected on a 100-hour and an annual inspection of an aircraft engine? |
In Appendix D of 14 CFR Part 43. |
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In what publication can a mechanic find the operating limitations for an aircraft engine? |
In the Type Certidicate Data Sheets for the engine. |
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Who is authorized to perform the powerplant inspection that is required for an annual inspection? |
An A&P mechanic who holds an Inspection Authorization |
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What are two types of compression checks that can be performed on an aircraft reciprocating engine? |
A differential compression check and a direct compression check. |
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What items are checked in a hot section inspection of a turbine engine? |
The combustion section 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. |
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What is the most common type of damage that is found in the hot section of a turbine engine? |
Cracks that are caused by the high concentration of heat in the hot section. |
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Is the use of a checklist required when performing an annual or 100-hour inspection on an aircraft engine? |
Yes |
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What inspection must be performed on an aircraft reciprocating engine if it has been operated on turbine fuel? |
The inside of the cylinders must be inspected with a borescope. The oil must be changed and the filters examined, and the engine given a careful run-up and operational check. |
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In what units is the tachometer for a reciprocating engine calibrated? |
In hundreds of RPM. |
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In what units is the tachometer for a turbine engine calibrated? |
In percent of the engine's rated takeoff RPM. |
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Where does the manifold pressure gage used on an aircraft reciprocating engine pick up the pressure it measures? |
From the intake manifold of the engine. |
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What are two types of pickups used for measuring the cylinder head temperature of a reciprocating engine? |
The thermocouple can be embedded in a gasket that is installed under the spark plug of the hottest running cylinder, or it can be in a bayonet that is held against the cylinder head by a spring. |
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Why do most engine oil pressure gages have a restrictor in the line between the engine and the instrument? |
The restrictor damps out pressure pulsations in the oil to keep the needle from oscillating. |
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What is used to measure the fuel flow of a horizontally opposed, fuel-injected reciprocating engine? |
A pressure gage that measures the pressure drop across injector nozzles. |
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What is indicated if the needle of a ratiometer-type oil temperature indicator pegs to the high side of the dial as soon as the aircraft master switch is turned on? |
There is an open in the bulb circuit that causes the instrument to see an infinite resistance. The higher the resistance in the bulb circuit, the higher the temperature indication. |
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What type of indicating system is used to measure the exhaust gas temperature of a turbine engine? |
A set of thermocouples arranged in an averaging circuit. These thermocouples are installed in the tail pipe of the engine. |
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What should a thermocouple-type cylinder head temperature indicator read when the engine is not operating? |
The temperature of the outside air. |
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How does a torquemeter actually measure the torque produced by an engine? |
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. |
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What two pressures are measured to get the Engine Pressure Ratio of a turbojet engine? |
The turbine discharge total pressure and the compressor inlet total pressure. |
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Of what two materials are the thermocouples made that are used in a turbine engine exhaust gas temperature system? |
Chromel and alumel. |
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What kind of mechanism is normally used to measure oil pressure in a reciprocating engine? |
A bourdon tube mechanism. |
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What is measured by the tachometers used on a two-spool gas turbine engine? |
The N1 tachometer shows the RPM of the low-pressure compressor, and the N2 tachometer shows the RPM of the high-pressure compressor. |
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Does the tachometer of a geared reciprocating engine indicate the speed of the crankshaft or of the propeller shaft? |
The speed of the crankshaft. |
