Shared Flashcard Set

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A&P Orals Powerplant
The Oral questions for the Airframe and Powerplant tests
253
Aviation
Graduate
04/09/2013

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Cards

Term
1.1 What is the main advantage of a horizontally opposed engine over a radial engine for powering modern aircraft?
Definition
The horizontally opposed engine has a much smaller frontal area and is easier to streamline than a radial engine.
Term
2.1 How many throws are there in the crankshaft of a six-cylinder horizontally opposed engine?
Definition
Six.
Term
3.1 What kind of connecting rod arrangement is used in a radial engine?
Definition
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.
Term
4.1 Of what material are most piston rings made?
Definition
Gray cast iron.
Term
5.1 What is the reason for using hydraulic valve lifters in an aircraft engine?
Definition
Hydraulic valve lifters keep all of the clearance out of the valve operating mechanism. This decreases the wear of the valve train components.
Term
6.1 At what speed does the camshaft turn, relative to the crankshaft speed in a horizontally opposed engine?
Definition
The camshaft turns at one half of the crankshaft speed.
Term
7.1 What kind of main bearings are used in a horizontally opposed engine?
Definition
Steel-backed, lead-alloy bearing inserts.
Term
8.1 On what stroke is the piston of a reciprocating engine when the intake valve begins to open?
Definition
On the exhaust stroke.
Term
9.1 On what stroke is the piston of a reciprocating engine when the exhaust valve begins to open?
Definition
On the power stroke.
Term
10.1 Why are both the hot and cold valve clearances given for most radial engines?
Definition
The hot clearance is given for valve timing purposes. The timing is adjusted with the valves in cylinder number one, set with the hot clearance. When the timing is set, all of the valves are adjusted to their cold clearance.
Term
11.1 What is meant by a cam-ground piston?
Definition
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.
Term
12.1 Where is the piston in a reciprocating engine when the ignition spark occurs?
Definition
About 30 degrees of crankshaft rotation before the piston reaches top center on the compression stroke.
Term
13.1 What is meant by a full-floating wrist pin?
Definition
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.
Term
14.1 Why do most aircraft reciprocating engines use more than one spring on each valve?
Definition
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.
Term
15.1 Would excessive valve clearance cause the valves to open early or late?
Definition
Excessive clearance will cause the valve to open late and close early.
Term
16.1 What is the purpose of valve overlap in a reciprocating engine?
Definition
Valve overlap allows the inertia of the exhaust gases leaving the cylinder to help the fresh induction charge start flowing into the cylinder.
Term
17.1 What type of piston rings are installed on the pistons of an aircraft reciprocating engine?
Definition
Compression rings, oil control rings, and oil wiper rings.
Term
18.1 Why are some exhaust valves partially filled with metallic sodium?
Definition
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.
Term
19.1 What causes detonation in an aircraft engine?
Definition
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.
Term
20.1 Why is a compression check important for determining the condition of an aircraft reciprocating engine?
Definition
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.
Term
21.1 What is meant by the compression ratio of a reciprocating engine?
Definition
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.
Term
1.2 What are the two basic sections of a turbine engine?
Definition
The hot section and the cold section.
Term
2.2 What are the two basic types of compressors that are used in aircraft turbine engines?
Definition
Axial-flow and centrifugal.
Term
3.2 What is the purpose of the stators in an axial-flow compressor?
Definition
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.
Term
4.2 What are three types of combustors used on aircraft turbine engines?
Definition
Can-type, annular-type, and can-annular-type.
Term
5.2 How many igniters are there normally in an aircraft turbine engine?
Definition
Two.
Term
6.2 What is the main purpose of the turbine nozzle in an aircraft turbine engine?
Definition
The turbine nozzle directs the hot gases as they leave the combustors so they will turn the turbine wheel with maximum efficiency.
Term
7.2 What is meant by a free-turbine turboshaft engine?
Definition
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.
Term
8.2 Why do some axial-flow turbine engines have more than one set of turbines and compressors?
Definition
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.
Term
9.2 What kind of bearings are used to support the rotor shaft of an aircraft turbine engine?
Definition
Anti-friction bearings, such as ball bearings or roller bearings.
Term
10.2 What is meant by a turbofan engine?
Definition
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.
Term
11.2 Where can you find the limits of repair allowed for the compressor blades of an aircraft turbine engine?
Definition
In the FAA-approved service manual issued by the manufacturer of the engine.
Term
12.2 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?
Definition
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.
Term
13.2 What is meant by a hung start in a turbine engine?
Definition
A start in which ignition occurs, but the engine does not accelerate to a self-sustaining speed.
Term
14.2 What is meant by a hot start in a turbine engine?
Definition
A start in which ignition occurs, but the internal temperatures go high enough that they can damage the engine.
Term
15.2 What is meant by creep of the turbine blades?
Definition
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.
Term
16.2 How is the compressor of a turbine engine cleaned?
Definition
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.
Term
17.2 Where is water injected into a turbine engine for cooling purposes?
Definition
Into the compressor inlet and into the engine diffuser case.
Term
18.2 At what point in a turbine engine is the temperature the highest?
Definition
At the inlet to the high-pressure turbine.
Term
19.2 What is the function of the interconnect tubes between the cans of a turbine engine that uses can-type combustors?
Definition
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.
Term
20.2 What are two types of thrust reversers that are used on turbojet engines?
Definition
The mechanical blockage-type and the aerodynamic blockage-type.
Term
21.2 What is meant by trimming a turbojet engine?
Definition
Adjusting the fuel control to get the correct idling and maximum-thrust RPM.
Term
1.3 What determines whether or not a 100-hour inspection is required for an aircraft?
Definition
100-hour inspections are required only on aircraft that carry persons for hire or are used to give flight instruction for hire.
Term
2.3 Where can you find a list of items that should be inspected on a 100-hour and an annual inspection of an aircraft engine?
Definition
In Appendix D of 14 CFR Part 43.
Term
3.3 In what publication can a mechanic find the operating limitations for an aircraft engine?
Definition
In the Type Certificate Data Sheets for the engine.
Term
4.3 Who is authorized to perform the powerplant inspection that is required for an annual inspection?
Definition
An A&P mechanic who holds an Inspection Authorization.
Term
5.3 What are two types of compression checks that can be performed on an aircraft reciprocating engine?
Definition
A differential compression check and a direct compression check.
Term
6.3 What items are checked in a hot section inspection of a turbine engine?
Definition
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.
Term
7.3 What is the most common type of damage that is found in the hot section of a turbine engine?
Definition
Cracks that are caused by the high concentration of heat in the hot section.
Term
8.3 Is the use of a checklist required when performing an annual or 100-hour inspection on an aircraft engine?
Definition
Yes.
Term
9.3 What inspection must be performed on an aircraft reciprocating engine if it has been operated on turbine fuel?
Definition
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.
Term
1.4 In what units is the tachometer for a reciprocating engine calibrated?
Definition
In hundreds of RPM.
Term
2.4 In what units is the tachometer for a turbine engine calibrated?
Definition
In percent of the engine's rated takeoff RPM.
Term
3.4 Where does the manifold pressure gage used on an aircraft reciprocating engine pick up the pressure it measures?
Definition
From the intake manifold of the engine.
Term
4.4 What are two types of pickups used for measuring the cylinder head temperature of a reciprocating engine?
Definition
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.
Term
5.4 Why do most engine oil pressure gages have a restrictor in the line between the engine and the instrument?
Definition
The restrictor damps out pressure pulsations in the oil to keep the needle from oscillating.
Term
6.4 What is used to measure the fuel flow of a horizontally opposed, fuel-injected reciprocating engine?
Definition
A pressure gage that measures the pressure drop across injector nozzles.
Term
7.4 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?
Definition
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.
Term
8.4 What type of indicating system is used to measure the exhaust gas temperature of a turbine engine?
Definition
A set of thermocouples arranged in an averaging circuit. These thermocouples are installed in the tail pipe of the engine.
Term
9.4 What should a thermocouple-type cylinder head temperature indicator read when the engine is not operating?
Definition
The temperature of the outside air.
Term
10.4 How does a torquemeter actually measure the torque produced by an engine?
Definition
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.
Term
11.4 What two pressures are measured to get the Engine Pressure Ratio of a turbojet engine?
Definition
The turbine discharge total pressure and the compressor inlet total pressure.
Term
12.4 Of what two materials are the thermocouples made that are used in a turbine engine exhaust gas temperature system?
Definition
Chromel and alumel.
Term
13.4 What kind of mechanism is normally used to measure oil pressure in a reciprocating engine?
Definition
A bourdon tube mechanism.
Term
14.4 What is measured by the tachometers used on a two-spool gas turbine engine?
Definition
The N1 tachometer shows the RPM of the low-pressure compressor, and the N2 tachometer shows the RPM of the high-pressure compressor.
Term
15.4 Does the tachometer of a geared reciprocating engine indicate the speed of the crank shaft or of the propeller shaft?
Definition
The speed of the crankshaft.
Term
1.5 Can a thermal switch-type fire detection system indicate a general overheat condition?
Definition
No, this is a spot-type fire detection system, and it cannot indicate an overheat condition.
Term
2.5 Can a thermocouple-type fire detection system indicate a general overheat condition?
Definition
No, this is a rate-of-temperature-rise-type of system, and it cannot indicate a general overheat condition.
Term
3.5 How is a thermocouple-type fire detection system checked for operation?
Definition
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.
Term
4.5 Does a break in a continuous-loop fire detection system keep the system from detecting a fire?
Definition
No, the unit will show a fault when it is tested, but it will still warn of a fire.
Term
5.5 Does the pressure-type continuous-element fire detector system detect a general overheat condition, as well as a fire?
Definition
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.
Term
6.5 What are the two most commonly used fire extinguishing agents used for engine fires?
Definition
Halogenated hydrocarbon, such as Halon 1301, and carbon dioxide.
Term
7.5 What extinguishing agent is used in the high-rate-discharge fire extinguishing systems installed in most turbojet engine installations?
Definition
Halon 1301.
Term
8.5 What happens when the pilot pulls the fire-pull T-handle in the cockpit of a jet transport airplane?
Definition
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.
Term
9.5 How can a mechanic determine the state of charge of the HRD bottles of fire extinguishing agent?
Definition
A pressure gage on the bottle shows the pressure of the contents of the bottle.
Term
10.5 What method is used to discharge an HRD bottle in a turbine engine installation?
Definition
An electrically ignited powder charge blows a knife through the seal on the bottle and discharges the contents.
Term
11.5 Which type of fire detection system operates on the rate of temperature rise?
Definition
The thermocouple system.
Term
12.5 What is indicated if the yellow blow-out plug of the fire extinguisher system on the side of an engine nacelle is blown out?
Definition
The built-in fire extinguishing system has been discharged by normal operation.
Term
13.5 What is indicated if the red blow-out plug of the fire extinguisher system on the side of an engine nacelle is blown out?
Definition
The built-in fire extinguishing system has been discharged by a high temperature condition.
Term
14.5 How is a pressure-type continuous-element fire detector system checked for operation?
Definition
Low-voltage alternating current is sent through the sheath of the detector element. This heats the element, and it releases enough gas to close the diaphragm switch.
Term
1.6 Why is stranded wire used rather than solid wire in most powerplant electrical systems?
Definition
Solid wire is likely to break when it is subjected to vibration.
Term
2.6 What two things must be considered in selection of wire size when making an electrical installation in an aircraft?
Definition
The current-carrying capability of the wire and the amount of voltage drop that is caused by current flowing through the wire.
Term
3.6 Why are the wires in certain electrical installations twisted together?
Definition
By twisting the wires together, the magnetic fields caused by current flowing in the wires are minimized.
Term
4.6 What is used to protect a wire bundle from chafing where it passes through a hole in a bulkhead or frame?
Definition
A grommet around the edges of the hole.
Term
5.6 How are electrical wires protected where they pass through an area of high temperature?
Definition
Wires passing through these areas are insulated with high temperature insulation, and the wires are enclosed in some type of protective conduit.
Term
6.6 What is the minimum separation that is allowed between a wire bundle and a fluid line that carries combustible fluid or oxygen?
Definition
A minimum of six inches.
Term
7.6 What is the significance of the color of the solderless connectors that are used on electrical wires?
Definition
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.
Term
8.6 What is the maximum number of wire terminals that may be stacked on a single stud in a terminal strip?
Definition
Four.
Term
9.6 What is the purpose of the shielding that is used to encase some electrical wires?
Definition
Shielding intercepts radiated electromagnet energy and carries it to ground so it will not interfere with any nearby sensitive electronic equipment.
Term
10.6 Why must a switch be derated if it is used in a circuit controlling a DC electric motor?
Definition
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.
Term
11.6 What is used as the rectifier to produce direct current in a DC generator?
Definition
Brushes and a commutator.
Term
12.6 How does a vibrator-type voltage regulator control the output voltage of a DC generator?
Definition
The strength of the magnetic field produced in the voltage regulator relay is proportional to the generator output 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.
Term
13.6 What is meant by paralleling the generators of a twin-engine aircraft?
Definition
Adjusting the voltage of the generators so they will share the electrical load equally.
Term
14.6 What is meant by flashing the field of a DC generator?
Definition
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.
Term
15.6 What kind of rectifier is used in a DC alternator of the type that is used on most of the modern light airplanes?
Definition
A full-wave, three-phase rectifier made up of six silicon diodes.
Term
16.6 What is used to maintain a constant frequency of the alternating current that is produced by an AC alternator driven by an aircraft turbine engine?
Definition
A hydraulic constant-speed drive unit between the engine and the alternator.
Term
17.6 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?
Definition
The voltage, the frequency, and the phase rotation of the generators.
Term
18.6 What must be done to reverse the direction of rotation of the armature of a DC electric motor?
Definition
The current flow must be reversed through the armature or the field windings, but not through both of them.
Term
19.6 Does a series-wound DC motor have a high or a low starting torque?
Definition
A high starting torque.
Term
20.6 Which aircraft electrical circuit does not normally contain a fuse or circuit breaker?
Definition
The starter motor circuit.
Term
21.6 When removing a battery from an aircraft, which connection should be removed first?
Definition
The ground connection must be disconnected first and connected last.
Term
22.6 What is meant by the effective voltage of sine wave alternating current?
Definition
The value of the alternating current that is needed to produce the same amount of heat as this value of direct current.
Term
23.6 What is a starter-generator that is used with many of the smaller gas turbine engines?
Definition
A single-engine-mounted component that serves as a starter for starting the turbine engine. When the engine is running, the circuitry can be shifted so it acts as a compound-wound generator.
Term
24.6 When should aircraft wiring be installed in a conduit?
Definition
When the wiring passes through an area in the aircraft where open wiring could likely be damaged, such as through a wheel well.
Term
1.7 What is meant by the viscosity of engine lubricating oil?
Definition
The resistance of the oil to flow.
Term
2.7 What is meant by a wet sump lubrication system?
Definition
A lubrication system in which the oil is carried inside the engine itself.
Term
3.7 What is meant by a dry sump lubrication system?
Definition
A lubrication system in which the oil is carried in a tank that is not a part of the engine.
Term
4.7 How is oil temperature controlled in an aircraft reciprocating engine?
Definition
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.
Term
5.7 Is the oil temperature shown on the aircraft instrument panel the temperature of the oil entering the engine or of the oil leaving the engine?
Definition
It is the temperature of the oil entering the engine.
Term
6.7 What is the purpose of oil dilution in a reciprocating engine?
Definition
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.
Term
7.7 What is the function of the hopper in the oil tanks used with some reciprocating engines?
Definition
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.
Term
8.7 What happens to the gasoline that is used to dilute the oil in the crankcase of an aircraft reciprocating engine?
Definition
When the engine is running and the oil is warm, the gasoline evaporates out of it.
Term
9.7 What is the purpose of the sludge plugs in the crankshaft of a reciprocating engine?
Definition
They trap sludge that is in the oil and hold it until the engine is disassembled at overhaul.
Term
10.7 Which pump is the larger in a dry-sump lubricating system, the pressure pump or the scavenger pump?
Definition
The scavenger pump has the greater volume.
Term
11.7 Why do full-flow oil filters have a spring-operated bypass valve in them?
Definition
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.
Term
12.7 What is the function of a fuel-oil heat exchanger in the lubrication system of a turbojet engine?
Definition
This allows heat from the oil to warm the fuel so ice will not form on the fuel filters.
Term
13.7 What kind of oil is used in most turbojet engines?
Definition
Synthetic oil.
Term
14.7 Where are the last chance oil filters located in a turbojet engine?
Definition
They are located inside the engine just ahead of the nozzles that spray oil onto the bearings.
Term
15.7 Where is the oil tank in a dry-sump reciprocating engine vented?
Definition
To the engine crankcase.
Term
16.7 What information must be displayed around the oil filler opening for a turbojet engine?
Definition
The word "Oil" and the permissible oil designations, or references to the Airplane Flight Manual (AFM) for permissible oil designations.
Term
17.7 What is the function of the oil control rings on the piston of an aircraft reciprocating engine?
Definition
They maintain the proper quantity of oil between the piston and the cylinder wall.
Term
18.7 What is meant by a spectrometric oil analysis?
Definition
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.
Term
19.7 What indication would a pilot have if his oil supply was low?
Definition
The oil temperature would be high and the oil pressure would be low.
Term
20.7 What is meant by a hot-tank lubrication system?
Definition
A lubrication system in which the oil cooler is located in the pressure subsystem.
Term
21.7 What is meant by a cold-tank lubrication system?
Definition
A lubrication system in which the oil cooler is located in the scavenge subsystem. The oil that is returned to the tank has been cooled.
Term
1.8 What is the main advantage of a magneto ignition system over a battery ignition system for an aircraft reciprocating engine?
Definition
A magneto has its own source of electrical energy, and it is not dependent upon the battery.
Term
2.8 What is the function of the capacitor in a magneto?
Definition
The capacitor minimizes arcing at the breaker points, and it speeds up the collapse of the primary current as the breaker points open.
Term
3.8 What is a compensated magneto cam, and on what kind of engine is one used?
Definition
A compensated cam is a special cam used in magnetos mounted on high-performance radial engines. The cam has one lobe for each cylinder, and the lobes are ground in such a way that the breaker points open when the pistons in the different cylinders are the same linear distance from top center.
Term
4.8 What is the significance of the numbers on the distributor of an aircraft magneto?
Definition
These numbers are the sparking order of the magneto, not the firing order of the engine.
Term
5.8 What happens in a magneto ignition system when the ignition switch is placed in the Off position?
Definition
The primary circuit is connected to ground.
Term
6.8 What is the reason for having a low-tension ignition system on some aircraft?
Definition
Low-tension magnetos are used on aircraft that fly at high altitudes where there is a problem with flashover in the high-tension magneto distributor.
Term
7.8 What is the basic difference between a low-tension magneto and a high-tension magneto?
Definition
The low-tension ignition system has only one coil in the magneto, and it uses a carbon-brush-type distributor. Low voltage is distributed to high-tension transformers that are located on the heads of each cylinder.
Term
8.8 What is meant by an All Weather spark plug?
Definition
A shielded spark plug that has a recess in the shielding in which a resilient grommet on the ignition lead forms a watertight seal.
Term
9.8 What is meant by the reach of a spark plug?
Definition
The length of the threads on the spark plug that screw into the cylinder head.
Term
10.8 What is the difference between a hot spark plug and a cold spark plug?
Definition
A hot spark plug has a long path for the heat to travel between the nose core insulator and the spark plug shell. In a cold spark plug, the heat has a shorter distance to travel, and the spark plug operates cooler than a hot spark plug.
Term
11.8 What is checked when a magneto is internally timed?
Definition
Internally timing a magneto consists of adjusting the breaker points so they will open at the instant the rotating magnet is in its E-gap position, and the distributor rotor is in the position to direct the high voltage to cylinder number one.
Term
12.8 What is the purpose of a vernier coupling used on some aircraft magneto drives?
Definition
Magnetos that are base mounted must have a vernier coupling between the magneto drive and the engine. This vernier coupling allows the magneto-to-engine timing to be varied in increments of less than one degree.
Term
13.8 What is the advantage of fine-wire spark plugs over massive electrode spark plugs?
Definition
Fine-wire spark plugs have a firing end that is more open than that of a massive electrode spark plug. The open firing end allows the gases that contain lead to be purged from the spark plug so they will not form solid lead contaminates.
Term
14.8 Why is it important that the spark plugs be kept in numbered holes in a tray when they are removed from an engine?
Definition
Spark plugs tell a good deal about the internal condition of the cylinders from which they were taken. By knowing the cylinder from which each spark plug came, the mechanic can take the proper action when a spark plug indicates such conditions as detonation or overheating.
Term
15.8 What is the purpose of staggered timing between the two magnetos on an aircraft engine?
Definition
Engines in which the exhaust gas scavenging from the cylinders is uneven use staggered ignition timing. The spark plug nearest the exhaust valve, where the fuel-air mixture is diluted, fires before the spark plug on the intake side. By using staggered timing, the flame front caused by the two spark plugs will meet in the center of the piston.
Term
16.8 In what position should the ignition switch be placed when using a timing light on the magnetos?
Definition
In the Both position.
Term
17.8 Why is it important that a torque wrench always be used when installing spark plugs in an aircraft engine?
Definition
If the spark plugs are not put in tight enough, there is the possibility of a poor seal, and if they are put in too tight, there is danger of cracking the insulation.
Term
18.8 Why are pressurized magnetos used on most reciprocating-engine-powered aircraft that fly at high altitudes?
Definition
Pressurized air is a better insulator than less dense air. By pressurizing the distributors, the high voltage is kept from arcing across to the wrong electrode and causing vibration and loss of engine power.
Term
19.8 What type of ignition system is used on most turbine engines?
Definition
High-intensity, intermittent-duty, capacitor discharge ignition systems.
Term
20.8 What is meant by the E-gap in magneto timing?
Definition
The E-gap angle is the position of the rotating magnet when the primary current flowing in the magneto coil is the greatest. The breaker points open when the rotating magnet is in its E-gap position.
Term
21.8 What is the function of an impulse coupling?
Definition
An impulse coupling is a spring-driven coupling between the magneto and the engine. When the engine is being started, the impulse coupling holds the rotating magnet until the piston passes over its top center position and starts down. The impulse coupling releases the magnet and the spring spins it fast so that it produces a hot and late spark.
Term
22.8 What kind of gage should be used to measure the electrode gap in aircraft spark plugs?
Definition
A round wire gage.
Term
23.8 How many igniters are used in most turbine engines?
Definition
Two.
Term
24.8 What are two types of ignition systems used in turbine engines?
Definition
High-voltage systems and low-voltage systems.
Term
25.8 With which type of ignition system is a glow plug igniter used?
Definition
A low-voltage system.
Term
26.8 How is the strength of the magnet in a magneto checked?
Definition
The magneto is put on a test stand and rotated at a specified speed. The breaker points are held open and the primary current is measured. The strength of the magnet determines the amount of primary current.
Term
27.8 In what position is the magnet in a magneto when the greatest change in flux density in the coil core takes place?
Definition
It is a few degrees beyond its neutral position. When it is in this position, the breaker points open and the primary current is interrupted. The flux change in the coil core is the greatest.
Term
28.8 In what position is the magnet in a magneto when the breaker points begin to open?
Definition
In its E-gap position, just a few degrees beyond its neutral position.
Term
29.8 What malfunction in the ignition system would cause an aircraft reciprocating engine to continue to run after the ignition switch is placed in the Off position?
Definition
The ignition switch is not grounding the magneto primary circuit.
Term
30.8 What turns on the autoignition system in a turbo-prop engine?
Definition
A torque pressure switch energizes the system when the engine stops producing torque.
Term
1.9 Where does the fuel metering system of a turbine engine discharge its fuel?
Definition
The fuel is discharged through spray nozzles into the combustion chambers.
Term
2.9 What is adjusted when the fuel control unit of a turbine engine is trimmed?
Definition
The idle speed and the maximum-thrust speed.
Term
3.9 What are two locations water may be injected into a turbine engine?
Definition
At the compressor inlet and at the inlet to the diffuser section.
Term
4.9 What is meant by a duplex nozzle in a turbine engine fuel metering system?
Definition
A duplex fuel nozzle is one that has two fuel discharge passages. A flow divider sends fuel for low-pressure operation through one discharge passage, and when the engine demands more fuel, it is sprayed out through the second discharge passage. The spray pattern keeps the flame centered in the burner for all operating conditions.
Term
5.9 Does the fuel-air mixture provided by a float carburetor become richer or leaner as the aircraft goes up in altitude?
Definition
If the mixture is not adjusted, it will become richer as the aircraft gains in altitude.
Term
6.9 Does the fuel-air mixture provided by a float carburetor become richer or leaner when carburetor heat is applied?
Definition
The mixture becomes richer when carburetor heat is applied.
Term
7.9 What would happen to the fuel-air mixture ratio in a float carburetor if the main air bleed were to become plugged?
Definition
The mixture would become excessively rich.
Term
8.9 How does the automatic mixture control in a pressure carburetor keep the fuel-air mixture constant as the aircraft changes altitude?
Definition
It automatically, and progressively, bleeds the air between the two sides of the air diaphragm and decreases the air metering force. This leans the mixture as the aircraft goes up in altitude.
Term
9.9 What are two purposes of the manifold valve (or flow divider) in the fuel injection system of a horizontally opposed aircraft engine?
Definition
It provides a constant discharge fuel pressure for idling, and it provides a positive shutoff for the fuel when the engine is shut down.
Term
10.9 How does the mixture control change the fuel-air mixture ratio on the Teledyne-Continental fuel injection system?
Definition
When the mixture control is in its Full Rich position, all fuel goes to the manifold valve. When it is in the Idle Cutoff position, all fuel is returned to the pump inlet. Intermediate positions vary the amount of fuel that goes to the engine.
Term
11.9 Why must the diaphragms of a pressure carburetor be soaked before the carburetor is ready for flight?
Definition
Soaking the diaphragms of a pressure carburetor restores them to the condition of flexibility that they had when the carburetor was calibrated.
Term
12.9 What are two basic types of fuel controls for aircraft turbine engines?
Definition
Hydropneumatic and electro-hydromechanical.
Term
13.9 How does the exhaust gas temperature of a reciprocating engine tell anything about the fuel-air mixture being burned by the engine?
Definition
A stoichiometric mixture (a mixture in which all of the constituents of the fuel-air mixture are burned) produces the highest exhaust gas temperature. The mixture is adjusted to get the highest EGT, and then it is enriched to place it on the rich side of stoichiometric.
Term
14.9 What two things are adjusted when adjusting the idling of a reciprocating engine?
Definition
The throttle stop, to get the proper idling RPM, and the idle mixture control, to get the smoothest operation.
Term
15.9 What is controlled by the adjustment of the orifice in the fuel pump of a Teledyne-Continental fuel injection system?
Definition
The high unmetered fuel pressure.
Term
16.9 What is the significance of the letters that are stamped on the flats of a fuel injection nozzle?
Definition
These letters designate the relative size of the orifice in the injector nozzle. The lower the letter in the alphabet, the smaller the amount of fuel the nozzle will flow.
Term
17.9 What is the function of the derichment valve in a pressure carburetor used on an aircraft engine with an antidetonation injection system?
Definition
The derichment valve automatically closes to lean the fuel-air mixture when ADI fluid is flowing. As soon as the ADI fluid stops flowing, the derichment valve opens and the mixture returns to its rich condition.
Term
18.9 What is the function of the economizer system in an aircraft engine carburetor?
Definition
The economizer (or power enrichment) system allows the engine to operate with an economically lean mixture for all conditions other than full power. When the throttle is opened for full power, the power enrichment system automatically enriches the mixture to remove some of the heat that is developed during this type of operation.
Term
19.9 In what position is the mixture control placed for starting an engine that is equipped with a pressure carburetor?
Definition
In the Idle Cutoff position. The engine is started with fuel from the primer system.
Term
20.9 In what position is the carburetor heat control placed when starting an aircraft engine?
Definition
In the Cold position.
Term
21.9 Why is an aircraft reciprocating engine killed by placing the mixture control in the Cutoff position, rather than by using the magneto switch?
Definition
By shutting off the fuel to the cylinders, the combustion chambers are left full of air with no fuel. This makes the engine less likely to fire if the propeller is pulled through with the ignition switch accidentally on.
Term
22.9 Where is the fuel from a continuous-flow fuel injection system discharged?
Definition
It is discharged through injector nozzles screwed into the cylinder heads near the intake valves.
Term
23.9 In which direction relative to the wind should a turbine-powered aircraft be positioned when the fuel control is being trimmed?
Definition
If the wind velocity is less than 10 miles per hour, it can be faced in any direction. If the wind velocity is between 10 and 25 MPH, it should be trimmed facing into the wind. The engine should not be trimmed when the wind velocity is more than 25 MPH.
Term
24.9 What engine parameters are sensed by the fuel control unit of a turbine engine?
Definition
Engine RPM, inlet air pressure, compressor discharge pressure, burner can pressure, and inlet air temperature.
Term
25.9 When does the acceleration system operate on an aircraft carburetor?
Definition
When the throttle is suddenly opened.
Term
1.10 What is the purpose of the bypass valve in an engine-driven fuel pump?
Definition
The bypass valve allows fuel to flow around the engine-driven pump for starting and for emergency operation if the engine-driven pump should fail.
Term
2.10 On which side of the firewall is the engine fuel shutoff valve located?
Definition
The shutoff valve must be on the side of the firewall away from the engine.
Term
3.10 What are three purposes for the boost pumps in an aircraft fuel system?
Definition
To provide fuel pressure for starting the engine, to pressurize the fuel lines to prevent vapor lock, and to transfer fuel from one tank to another.
Term
4.10 What kind of boost pump is used in most aircraft fuel systems?
Definition
Electrically operated centrifugal pumps.
Term
5.10 Where does an engine-driven fuel pump direct the excess fuel from its pressure relief valve?
Definition
Back to the inlet side of the pump.
Term
6.10 What causes a vapor lock in an aircraft fuel system?
Definition
The fuel becomes hot enough that it boils. Vapors are released from the liquid fuel, and these vapors block the fuel lines so the liquid fuel cannot flow to the engine.
Term
7.10 What is done in most aircraft fuel systems to prevent vapor lock?
Definition
Boost pumps in the fuel tank pressurize the fuel in the lines and force the fuel into the fuel metering system.
Term
8.10 What is meant by a compensated relief valve in an engine-driven fuel pump?
Definition
A pressure relief valve that is acted upon by a diaphragm as well as a spring. Atmospheric pressure acting on the diaphragm varies the pump discharge pressure so that it will remain a given amount higher than the pressure of the air entering the carburetor.
Term
9.10 What is the purpose of the pressurizing and dump valve in the fuel system for a turbine engine?
Definition
For normal engine operation, the pressurizing and dump valve acts as a flow divider, directing the fuel into the main or pilot manifold so it will be discharged from the proper orifice in the duplex fuel nozzle.

When the engine is shut down, the dump function of the valve dumps all of the fuel from the manifold.
Term
10.10 What should be done to an aircraft reciprocating engine if it has been operated on turbine engine fuel?
Definition
All of the turbine fuel should be drained out and the system filled with the proper grade of aviation gasoline. The engine should be given a compression check, and all of the cylinders should be inspected with a borescope. The oil should be drained and the filters carefully examined. The engine should be given a complete run-up check.
Term
11.10 What are the two basic types of turbine engine fuel?
Definition
Jet A and A-1, which are a special type of kerosine-base fuel. This is similar to military JP-5.

Jet B is a gasoline-base fuel similar to military JP-4
Term
12.10 Why do some turbine engine fuel systems incorporate a fuel heater?
Definition
The fuel heater keeps the fuel warm enough that any water that precipitates out of the fuel will not freeze on the filters.
Term
13.10 What are two reasons Prist is used in turbine engine fuel?
Definition
Prist is an antifreeze agent that lowers the freezing point of any water that precipitates out of the fuel. It also acts as a biocidal agent that kills the microbial growth that forms scum in fuel tanks. This scum traps and holds water against the aluminum alloy in the fuel tanks and causes corrosion.
Term
14.10 Why do some aircraft fuel filters have a built-in relief valve?
Definition
This relief valve will open and allow unfiltered fuel to flow to the fuel control device if the filter should become plugged with ice or other contaminants.
Term
1.11 Where is the heat taken from that is used to heat the induction air in a reciprocating engine?
Definition
From a muff that is installed around some part of the exhaust system.
Term
2.11 Where does the alternate air come from that is used with a pressure carburetor or a fuel injection system?
Definition
From inside the engine cowling.
Term
3.11 Where does carburetor ice normally form in a carburetor?
Definition
In the throat of the carburetor, on and around the throttle valve.
Term
4.11 Does the application of carburetor heat cause the fuel-air mixture to become richer or to become leaner?
Definition
Heated air causes the fuel-air mixture to become richer.
Term
5.11 What is used to drive most of the external superchargers used on modern reciprocating engines?
Definition
Exhaust gases.
Term
6.11 What controls the speed of a turbocharger compressor?
Definition
The amount of exhaust gas that is forced to flow through the turbine. This is controlled by the position of the waste gate.
Term
7.11 What is meant by a convergent inlet duct for a turbine engine?
Definition
A convergent duct is one whose cross-sectional area becomes smaller in the direction the air flows.
Term
8.11 What is meant by a divergent inlet duct for a turbine engine?
Definition
A divergent duct is one whose cross-sectional area becomes greater in the direction the air flows.
Term
9.11 What kind of inlet duct is often used on turbine-powered helicopters?
Definition
A bell-mouthed inlet duct.
Term
10.11 What is the danger of operating an aircraft reciprocating engine with too high a carburetor air temperature?
Definition
Too high a carburetor air inlet temperature can cause the fuel-air mixture to reach its critical temperature and detonate.
Term
11.11 Why do some turbine engines use variable inlet guide vanes?
Definition
These variable inlet guide vanes are automatically adjusted to direct the air into the engine in such a way that it keeps the RPM vs. velocity proper for the most efficient operation.
Term
12.11 How do some turbine engines prevent ice formation on the inlet guide vanes?
Definition
Hot compressor bleed air flows through hollow inlet guide vanes.
Term
13.11 What is usually installed in a large reciprocating engine between the turbosupercharger and the carburetor?
Definition
An intercooler. This is an air-to-air heat exchanger.
Term
14.11 In what position should the carburetor heat control be placed when starting a reciprocating engine?
Definition
In the Cold position.
Term
15.11 How does an engine air inlet vortex destroyer help prevent foreign object damage to the engine?
Definition
A high-velocity stream of compressor bleed air is blown out in front of the engine to break up the vortices that form in front of the engine when it is operating at high power on the ground.
Term
1.12 What is meant by pressure cooling of an aircraft engine?
Definition
Air cooling in which air is forced to flow through baffles and cylinder fins by a pressure differential across the engine.
Term
2.12 What is the purpose of an augmentor tube in the cooling system of an aircraft reciprocating engine?
Definition
The augmentor tube uses the velocity of the exhaust gases to produce a low pressure on one side of the engine that helps pull cooling air through it.
Term
3.12 Where is the highest temperature located in a turbine engine?
Definition
At the inlet to the high-pressure turbine.
Term
4.12 How are the turbine inlet guide vanes and the first-stage turbine blades in some turbine engines cooled?
Definition
High-pressure compressor bleed air flows through the hollow guide vanes and hollow turbine blades.
Term
5.12 Which side of an air-cooled engine cylinder has the greatest amount of cooling fins?
Definition
The side of the cylinder in which the exhaust valve is located.
Term
6.12 What should be done to repair a bent cooling fin in a cast aluminum cylinder head?
Definition
It is normally best to leave a bent cast fin alone if it does not restrict the flow of air. Cast fins are brittle and could break off.
Term
7.12 What is used in a helicopter to increase the amount of cooling air that flows over the engine cylinders?
Definition
A belt-driven fan.
Term
8.12 What should be the position of the cowl flaps on a reciprocating engine when it is run on the ground?
Definition
They should be wide open when operating the engine on the ground.
Term
9.12 What is the function of the majority of the air that passes through a turbine engine?
Definition
Most of the air is used for cooling.
Term
10.12 How does metallic sodium in an exhaust valve aid in transferring heat?
Definition
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.
Term
11.12 How is the structure around a turbine engine protected from excessive heat from the engine?
Definition
An insulating blanket protects the structure from excessive heat.
Term
12.12 What is the function of blast tubes that are installed in a pressure cooling system of a reciprocating engine?
Definition
These blast tubes direct cooling air to the magnetos and the generator.
Term
13.12 Of what material is the insulation blanket made that is used to protect the aircraft structure from the heat produced by a turbine engine?
Definition
Fiberglass sandwiched between sheets of metal foil.
Term
1.13 Of what material are most reciprocating engine exhaust components made?
Definition
Corrosion-resistant steel.
Term
2.13 How is the speed of a turbocharger controlled?
Definition
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.
Term
3.13 What type of actuator is used to control the position of the turbocharger waste gate?
Definition
A hydraulic actuator that uses engine oil pressure to move the piston.
Term
4.13 How does a power recovery turbine increase the power of a reciprocating engine?
Definition
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.
Term
5.13 How tight should the clamps be tightened that hold sections of a reciprocating engine exhaust system together?
Definition
They should not be so tight that they will be damaged when heat expands the exhaust system components.
Term
6.13 What would be the effect on engine performance of an internal failure of a muffler?
Definition
This will increase the exhaust back pressure and cause a loss of engine power.
Term
7.13 What effect on turbine engine operation is caused by a change in the area of the exhaust nozzle?
Definition
Altering the area of the exhaust nozzle affects the compression ratio, the RPM, the mass airflow through the engine, and the EGT.
Term
8.13 What are two types of thrust reversers that are used with turbojet engines?
Definition
Mechanical blockage (clamshell) and aerodynamic blockage (cascade).
Term
9.13 How does a noise suppressor reduce the amount of noise produced by a turbojet engine?
Definition
It breaks up the low-frequency vibrations in the exhaust stream and converts them into higher frequencies. These high frequencies are dissipated by the air more easily than low frequencies.
Term
10.13 What is the purpose of the ball joints and bellows in the exhaust system of a reciprocating engine?
Definition
The ball joints and bellows allow the exhaust system components to change their dimensions without causing any leaks.
Term
11.13 Why do some supersonic aircraft use a convergent-divergent exhaust duct?
Definition
A CD exhaust duct controls the gas expansion as it leaves the engine so the gases will produce thrust at supersonic velocities.
Term
12.13 Why is it important that a lead pencil never be used to mark on an aircraft exhaust system?
Definition
The graphite in a lead pencil will infuse into the metal when it gets hot. It makes the metal brittle and likely to crack.
Term
13.13 What type of damage is normally found in the hot section of a turbine engine?
Definition
Cracks caused by heat.
Term
1.14 What type of device is used on propeller blades to remove ice that has formed on them?
Definition
Electrically heated deicer boots.
Term
2.14 What is used to prevent ice forming on a propeller blade?
Definition
A mixture of ethylene glycol and isopropyl alcohol slung out along the blades.
Term
3.14 Should an adjustable-pitch propeller be in high pitch or in low pitch for takeoff?
Definition
In low pitch.
Term
4.14 What is done to cause a Hydromatic propeller to feather?
Definition
High-pressure engine oil is directed into the propeller through the governor.
Term
5.14 What is done to cause a McCauley propeller to feather?
Definition
Oil is allowed to drain out of the propeller.
Term
6.14 Does centrifugal twisting moment on a propeller blade tend to move the blades toward high pitch or toward low pitch?
Definition
Toward low pitch.
Term
7.14 Do the counterweights on a propeller tend to move the blades toward high pitch or toward low pitch?
Definition
Toward high pitch.
Term
8.14 What is the difference between a controllable propeller and a constant-speed propeller?
Definition
Basically, it is the control system. A controllable-pitch propeller uses a manually operated oil valve to control the pitch, and a constant-speed propeller uses a governor to control the valve.
Term
9.14 When making a magneto check on an engine equipped with a constant-speed propeller, should the propeller control be in the low-pitch or the high-pitch position?
Definition
It should be in the low-pitch position.
Term
10.14 What can be done to prevent the front cone from bottoming when installing a propeller on a splined shaft?
Definition
Install a spacer behind the rear cone to move the propeller forward on the shaft.
Term
11.14 What is the purpose of the small holes that are drilled in the end of a wooden propeller?
Definition
These holes vent the inside of the propeller blade and allow moisture that collects in the wood to be released.
Term
12.14 What is the function of the snap ring inside the hub of a propeller that is mounted on a tapered or splined shaft?
Definition
The snap ring allows the propeller to be pulled off of the shaft when the retaining nut is backed off.
Term
13.14 What is adjusted inside the governor for a constant-speed propeller to change the speed at which the propeller is operating?
Definition
The compression of the speeder spring.
Term
14.14 What is the function of the accumulator that is used with some McCauley feathering propellers?
Definition
The accumulator stores oil under pressure when the engine is operating normally. This oil is used to help the propeller blades move toward low pitch when the propeller is being unfeathered.
Term
15.14 What is meant by the beta range of operation of a turboprop propeller?
Definition
This is the mode of ground operation, and it includes starting, taxiing, and ground reverse operation.
Term
16.14 What is meant by the alpha range of operation of a turboprop propeller?
Definition
This is the in-flight mode of operation from takeoff to landing.
Term
17.14 Is the flat surface of a propeller blade the face of the blade or the back of the blade?
Definition
It is the face of the blade.
Term
18.14 What keeps a McCauley feathering propeller from feathering when the engine is shutdown on the ground?
Definition
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 propeller.
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