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115 Cards in this Set
- Front
- Back
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Where is the heat taken from that is used to heat the induction air in a reciprocating engine?
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From a muff that is installed around a part of the exhaust system. |
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Where does the alternate air come from that is used with a pressure carburetor or a fuel injection system?
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From inside the engine cowling.
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Where does carburetor ice normally form in a carburetor?
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In the throat and throttle valve of the carburetor |
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What is used to drive most of the external superchargers used on modern reciprocating engines?
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Exhaust gases.
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What controls the speed of a turbocharger compressor?
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The amount of exhaust gas that is forced to flow through the turbine in the turbo housing
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What is meant by a convergent inlet duct for a turbine engine?
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An inlet whose cross–sectional area becomes smaller in the direction the air flows.
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What is meant by a divergent inlet duct for a turbine engine?
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An inlet whose cross–sectional area becomes greater in the direction the air flows.
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What kind of inlet duct is often used on turbine–powered helicopters?
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A bell mouth inlet duct.
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What is the danger of operating an aircraft reciprocating engine with too high a carburetor air temperature?
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Can cause detonation.
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Why do some turbine engines use variable inlet guide vanes?
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Converts velocity energy into pressure energy and directs the flow of air
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How do some turbine engines prevent ice formation on the inlet guide vanes?
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Hot compressor bleed air flows through hollow inlet guide vanes.
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What is usually installed in a large reciprocating engine between the turbosupercharger and the carburetor?
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An intercooler
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How does an engine air inlet vortex destroyer help prevent foreign object damage to the engine?
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A high–velocity stream of compressed bleed air is blown out in front of the engine, to break up the air vortex created in front of the engine when it is operating at high power on the ground.
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Why does ice form in the throat of a float carb?
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When the fuel evaporates it absorbs enough heat from the air to cause condensation, then freezes.
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What happens to engine RPM when carb heat is applied?
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RPM drops
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Why should the use of carb heat be limited when operating an engine with the aircraft on the ground?
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carb heat is applied is not filtered
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Why is a fuel–injected recip not as prone to icing as an engine with a float carb?
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because the fuel evaporates in the intake valve chamber of the hot cylinder head
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How is ice prevented from forming on the nose cowl, nose dome and inlet guide vanes of a turbine engine?
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compressed bleed air flows through passages in these components to keep them too warm for ice to form
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What does a fuel–injected engine have that prevents the loss of induction air, if the air inlet filter should become covered with ice?
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Alternate air valves allow warm air from inside the engine cowling
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What would be the effect on engine operation of an air leak in the intake pipe for one cylinder?
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That cylinder would run lean and detonation could occur
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Why is it very important that the induction air filters be kept clean and replaced as often as the manufacturer recommends?
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Clogged air filters can restrict the air entering the engine resulting in power loss
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What is meant by pressure cooling of an aircraft engine?
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when air is forced to flow through baffles and cylinder fins by a pressure differential across the engine.
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What is the purpose of an augmentor tube in the cooling system of an aircraft reciprocating engine?
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The augmentor tube uses exhaust gases to create low pressure on one side of the engine which helps pull cooling air through it.
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Where is the highest temperature located in a turbine engine?
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At the inlet to the high–pressure turbine.
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How are the turbine inlet guide vanes and the first–stage turbine blades in some turbine engines cooled?
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High–pressure compressor bleed air flows through the hollow guide vanes and hollow turbine blades.
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Which side of an air–cooled engine cylinder has the greatest amount of cooling fins?
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The side with the exhaust valve
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What should be done to repair a bent cooling fin in a cast aluminum cylinder head?
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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.
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What is used in a helicopter to increase the amount of cooling air that flows over the engine cylinders?
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A belt–driven fan.
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What should be the position of the cowl flaps on a reciprocating engine when it is run on the ground?
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They should be wide open
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What is the function of the majority of the air that passes through a turbine engine?
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Most of the air is used for cooling.
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How does metallic sodium in an exhaust valve aid in transferring heat?
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transfers heat from the valve head to the stem
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How is the structure around a turbine engine protected from excessive heat from the engine?
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An insulating blanket
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What is the function of blast tubes that are installed in a pressure cooling system of a reciprocating engine?
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they direct cooling air to the magnetos and the generator.
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Of what material is the insulation blanket made that is used to protect the aircraft structure from the heat produced by a turbine engine?
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Fiberglass sandwiched between sheets of metal foil.
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What must be inspected on the cooling system of an air–cooled engine?
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All baffles and air seals
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Why should an air–cooled engine not be run up to high power without the cowling installed?
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The engine depends on the cowling to force air through the cylinders fins to remove the excess heat
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Why do some air–cooled engine installations have cowl flaps?
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To produce a low pressure on one side of the engine to pull air through the cooling fins on the cylinders
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Where can you find what is the maximum amount of cylinder fin area that can be removed in order to clean out a damaged area?
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Engine overhaul manual
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What document describes the proper use of cowl flaps on an air–cooled engine?
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Pilot's Operating Handbook
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Of what material are most reciprocating engine exhaust components made?
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Corrosion–resistant steel.
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How is the speed of a turbocharger controlled?
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By controlling the amount of exhaust gas that flows through the turbine.
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What type of actuator is used to control the position of the turbocharger waste gate?
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A hydraulic actuator that uses engine oil pressure to move the piston.
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How does a power recovery turbine increase the power of a reciprocating engine?
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Exhaust–driven velocity turbines are coupled through a hydraulic drive to the engine crankshaft.
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How tight should the clamps be tightened that hold sections of a reciprocating engine exhaust system together?
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They should not be so tight that they will be damaged when heat expands the exhaust system components.
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What would be the effect on engine performance of an internal failure of a muffler?
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This will increase the exhaust back pressure and cause a loss of engine power.
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What effect on turbine engine operation is caused by a change in the area of the exhaust nozzle?
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Altering the area of the exhaust nozzle affects the compression ratio, the RPM, the mass airflow through the engine, and the EGT.
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What are two types of thrust reversers that are used with turbojet engines?
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Mechanical blockage (clamshell) and aerodynamic blockage (cascade).
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How does a noise suppressor reduce the amount of noise produced by a turbojet engine?
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It breaks up the low–frequency vibrations in the exhaust stream
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What is the purpose of the ball joints and bellows in the exhaust system of a reciprocating engine?
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The ball joints and bellows allow the exhaust system components to change their dimensions without causing any leaks.
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Why do some supersonic aircraft use a convergent–divergent exhaust duct?
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A CD exhaust duct controls the gas expansion as it leaves the engine so the gases will produce thrust at supersonic velocities.
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Why is it important that a lead pencil never be used to mark on an aircraft exhaust system?
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The graphite in a lead pencil will infuse into the metal when it gets hot. It makes the metal brittle and likely to crack.
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What type of damage is normally found in the hot section of a turbine engine?
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Cracks caused by heat.
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How does a leak appear in an engine exhaust system?
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Gray or black feather–shaped streak coming from a crack or from a location where components are not in perfect alignment
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How can you check an exhaust system for leaks?
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Pressurize the system and wipe soap solution over all joints and then look for bubbles to form
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How do the components in the exhaust of a turbocharged engine allow for expansion and contraction due to heat, and at the same time prevent leakage?
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Bellows and ball joints prevent leakage while allowing contraction and expansion
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What type of damage is most common in the exhaust system of a recip?
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Cracks caused by expansion and contraction
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Should a turbocharged engine be started with the waste gate open or closed?
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Open, so as much exhaust as possible will bypass the turbine
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Why are thrust reversers not normally used when the airplane is moving below approximately 60 knots?
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Danger of recirculating the exhaust gases, and ingesting foreign objects stirred up by the high–velocity gases
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What is a mechanical–blockage thrust reverser?
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It slides a pair of scoop–shaped doors aft and opens them so they block the rearward flow of gases and deflect the gases forward
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How does a cascade–type thrust reverser operate?
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Portion of the fan cowl moves rearward, and a series of blocker doors deflect the fan discharge air
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What type of device is used on propeller blades to remove ice that has formed on them?
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Electrically heated deicer boots.
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What is used to prevent ice forming on a propeller blade?
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A mixture of ethylene glycol and isopropyl alcohol slung out along the blades.
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Should an adjustable–pitch propeller be in high pitch or in low pitch for takeoff?
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In low pitch.
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What is done to cause a Hydromatic propeller to feather?
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High–pressure engine oil is directed into the propeller through the governor.
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What is done to cause a McCauley propeller to feather?
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Oil is allowed to drain out of the propeller.
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Does centrifugal twisting moment on a propeller blade tend to move the blades toward high pitch or toward low pitch?
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Toward low pitch.
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Do the counterweights on a propeller tend to move the blades toward high pitch or toward low pitch?
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Toward high pitch.
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What is the difference between a controllable propeller and a constant–speed propeller?
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A controllable–pitch propeller uses a manually operated oil valve to control the pitch
constant–speed propeller uses a governor to control the valve. |
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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?
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low–pitch position.
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What can be done to prevent the front cone from bottoming when installing a propeller on a splined shaft?
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Install a spacer behind the rear cone to move the propeller forward on the shaft.
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What is the purpose of the small holes that are drilled in the end of a wooden propeller?
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These holes vent the inside of the propeller blade and allow moisture that collects in the wood to be released.
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What is the function of the snap ring inside the hub of a propeller that is mounted on a tapered or splined shaft?
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The snap ring allows the propeller to be pulled off of the shaft after the retaining nut is backed off.
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What is adjusted inside the governor for a constant–speed propeller to change the speed at which the propeller is operating?
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The compression of the speeder spring.
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What is the function of the accumulator that is used with some McCauley feathering propellers?
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The accumulator stores oil under pressure when the engine is operating normally. This oil is used to help feather the propeller blades
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What is meant by the beta range of operation of a turboprop propeller?
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This is the ground operation mode range, and it includes starting, ground reverse and taxiing
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What is meant by the alpha range of operation of a turboprop propeller?
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This is the in–flight operation range from takeoff to landing.
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Is the flat surface of a propeller blade the face of the blade or the back of the blade?
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It is the face of the blade.
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What keeps a McCauley feathering propeller from feathering when the engine is shutdown on the ground?
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A spring–loaded latch mechanism
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What is meant by a slave engine with regard to prop synchronization?
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a multi–engine airplane engine whose RPMs follow those set by the master engine
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What does the pilot do to change the RPM of an engine equipped with a constant–speed prop when it is operating within the constant–speed range?
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Moves the prop pitch control. The change in pitch changes the air load on the prop which changes the RPM
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How can you determine that the electrically heated deicer boots on the prop blades are working as they should?
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Observe the loadmeter to see if the current is flowing to the boot. Feel the boo to see if they are heating. The boots should all have similar heat rise in the same length of time
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How are props on a twin–engine synchronized?
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Prop governor of the master engine is set to the desired RPM. The slave engines stepping motor receives an signal causing it to maintain exactly the same RPM as the master engine
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Where do you find a list of the lubricants that are approved for use in a constant–speed prop?
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Propeller Maintenance manual
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Who or what facility is authorized to perform major repairs to a prop?
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An FAA approved prop repair station that is authorized for the specific prop
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What checks and maintenance is a mechanic with a powerplant rating allowed to make on a prop?
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Check the track and balance the prop
Remove small nicks and scratches Paint the propeller Lubrication |
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What adjustment can a mechanic with a powerplant rating make to a prop governor?
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Adjust the maximum RPM stop
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Why do some aircraft engines have a critical range of operation?
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Engine/prop have a resonant frequency problem in which excessive vibration can occur in a certain range of RPM. The tach is marked in red for this limitation. When it is necessary to pass through this range it must be done as quickly as practical
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Why is a prop indexed to the engine crankshaft?
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Relationship between the prop and the crankshaft is chosen to produce the minimum vibration
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What instrument is used to measure the blade angle of a prop?
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Universal propeller protractor
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Where is the propeller protractor placed to measure the prop blade angle?
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A specific distance from the hub which is specified in the prop maintenance manual
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What is the extent of the repairs a mechanic with a powerplant rating can make to a prop?
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Only minor repairs or minor alterations
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Where can examples of acceptable repairs to aluminum alloy prop blades be found?
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AC 43. 13–1B chapter 8 section 4
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Is it permissible to cold straighten a damaged aluminum alloy prop blade to facilitate shipping it to a repair station?
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No, this could cause hidden damage that may render the blade nonrepairable
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What would be the classification of maintenance for shortening a prop blade?
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Major repair
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May transverse cracks in a metal prop blade be repaired?
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No, transverse crack of any size is reason for rejecting the blade
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What damage to an aluminum alloy prop blade can be repaired by a powerplant mechanic?
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Small roughness, nicks, and scratches in the leading edge of the blades
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How are small nicks removed from the leading edge of a prop blade?
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File them out with a file or stone, leaving a smooth contour
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Who is allowed to reduce the diameter of a type certificated prop?
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FAA–certificated prop repair station with approval for the particular prop
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How can you determine that a surface scratch in an aluminum alloy prop blade is not actually a crack?
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Perform a liquid penetrant NDT test.
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Where are most APUs located in modern jet transport aircraft?
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In the tail cone of the fuselage
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What is the function of an APU?
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Provides electric power and compressed air when the main engines are not operating
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What are two sources of compressed air from an APU?
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From bleed air from the APU turbine compressor, or from a load compressor
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Where in maintenance info based on the ATA–100 system would you find instructions for inspecting and servicing the engine of an airborne APU?
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In section 49 20
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How is most of the troubleshooting done for modern APUs?
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Fault codes generated by the FADEC
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What ensures that a APU will not be shut down while it is too hot?
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An automatic time–delay in FADEC that closes the bleed air valve, reducing the APU temp and load before shutdown
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What prevents the APU exceeding its safe operating limits when the bleed air valve is wide open?
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FADEC monitors the APUs load and regulates its fuel supply
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What document would you use to find the safety procedures to follow when replacing an igniter plug in an APU engine?
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Maintenance manual for the APU
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What places the greatest load on an APU?
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Bleed air loads
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What is used to start an APU?
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Its own electric starter and battery power
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Name two uses for the pneumatic power produced by an APU.
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Engine starting
Air conditioning while on the ground |
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What kind of operating practices could cause heat shock and internal damage to an APU?
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An ubrupt shutdown of the APU while under a heavy load
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What powers the inlet guide vanes to regulate the compressor intake airflow in some APUs?
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Fuel pressure
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What is the typical cool down period for an APU?
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3 minutes
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At what speed does an APU operate?
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The APU will operate near its rated RPM at all times regardless of the load demands.
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Where does an APU get its fuel from?
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One of the aircrafts main tanks |
