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425 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?
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The horizontally opposed engine has a much smaller frontal area & is easier to streamline than a radial engine.
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How many throws are there in the 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 master rod connects the single throw of the crankshaft with the 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 speed 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?
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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?
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On the power stroke.
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Why are both the hot & cold valve clearances given for most radial engines?
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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.
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What is meant by a cam-ground piston?
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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?
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About 30 degrees of crankshaft rotation before the piston reaches top center of the compression stroke.
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What is meant by a full-floating wrist pin?
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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?
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By using more than one spring & having the wire diameter & pitch of the spring 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?
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Excessive valve clearance will cause the valve to open late & close early.
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What is the purpose of valve overlap in a reciprocating engine?
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Valve overlap allows the inertia of the exhaust gases 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?
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Compression rings, oil control rings, & oil wiper rings.
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Why are some exhaust valves partially filled with metallic sodium?
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The metallic sodium melts at engine operating temperature & sloshes back & forth inside the hollow valve. It picks up heat from the valve head & 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?
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Excessive heat & pressure in the engine cylinder causes the fuel-air mixture to reach its critical pressure & 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?
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A compression check can determine the condition of the seal between the piston rings & the cylinder walls, & the seal between the intake & exhaust valves & their seats.
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What is meant by the compression ratio of a reciprocating engine?
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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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In what position should the crankshaft be when a magneto is being timed to the engine?
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The piston in cylinder no. 1 should be in the correct position for ignition to occur. This is normally about 30° before top center on the compression stroke.
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What is the purpose of a cold cylinder check?
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A cold cylinder check determines which cylinder is not firing. Run the engine for a few minutes at the speed, and on the magneto, at which it runs roughest. Shut it down and feel the exhaust stack near the cylinder head. The cylinder with the stack that is not as hot as the others is the cylinder that has not been firing.
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What is checked on engine runup to determine the operational condition of the engine?
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Idling RPM and manifold pressure, engine acceleration, maximum static RPM and manifold pressure, magneto drop, ignition switch safety check, propeller pitch change, propeller feathering, oil pressure, fuel pressure, & fuel flow.
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How can you determine the firing order of an 18-cylinder radial engine?
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Begin with cylinder 1, add 11, and subtract 7, whichever will keep the numbers between 1 and 18. 1-12-5-16-9-2-13-6-17-10-3-14-7-18-11-4-15-8.
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What are two main causes of a cylinder having low compression?
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Piston rings not seating or broken, and valves not seating or burned.
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What is a hydraulic lock in an aircraft engine?
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Oil has drained past the piston rings and filled the combustion chamber of cylinders that are below the center line of the engine. If the crankshaft is turned over with this oil in the cylinder it will lock, and there is a probability that the piston, cylinder, or connecting rod will be damaged.
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How is a hydraulic lock removed from an aircraft engine?
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Remove a spark plug from the locked cylinder and drain all of the oil out. Clean the spark plug and replace it.
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What is a low-tension ignition system?
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It is an ignition system using a magneto with a brush-type distributor and a coil that has no secondary wiring. Low voltage is directed from the magneto to a transformer mounted on the cylinder head. Here the low voltage is boosted to a high voltage and is directed through a very short high-tension lead to a spark plug. There is one transformer for each spark plug.
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What is a floating cam ring on a large radial engine?
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It is a cam ring that rides on a shelf-type bearing with a large amount of clearance between the bearing and the ring. When adjusting the valves on an aircraft engine with a floating cam ring, the pressure of the valve springs on the opposite side of the engine must be removed so the cam ring will be tight against the bearing for the valves being adjusted.
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Why is valve clearance adjusted on radial engines, but not on most horizontally opposed engines?
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Most horizontally opposed engines have hydraulic valve lifters that keep all of the clearance out of the valve train. Radial engines have solid lifters.
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What must be inspected to determine the airworthiness of an engine installation?
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The propeller, lubrication system, ignition system, fuel metering system, cooling system, and the exhaust system.
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What checks should be made to determine the proper operation of a reciprocating engine installation?
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Idle RPM and mixture, static RPM, propeller pitch change operation, magneto check, ignition switch safety check, and carburetor heat check.
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Where can you find the correct grade of fuel and amount of engine lubricating oil for an aircraft engine?
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In the Type Certificate Data Sheets for the aircraft.
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What are the basic steps in troubleshooting an engine installation?
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a. Know how the system should operate. b. Observe how the system is operating. c. Divide the system to find the trouble. d. Look for the obvious problems first.
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Where do you find the procedures to follow when correcting a defective condition in an aircraft engine?
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In the engine maintenance manual.
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Where do you find instructions for removing an engine from an aircraft?
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In the aircraft maintenance manual.
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What must normally be done to a nose-wheel airplane before removing an engine?
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The tail of the airplane must be supported.
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What should be done to the cylinders to protect them from rust and corrosion when preparing the engine for long-time storage?
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Spray a preservative oil inside the cylinders and replace the spark plugs with desiccant plugs.
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What should be used to cover the ends of fuel and oil lines that have been disconnected from the engine?
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The correct plugs or caps. Never cover the end of a line with tape.
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What is meant by a QEC engine assembly?
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An engine that has been prepared for a quick engine change. The engine is on its mount and all of the accessories are installed. A minimum of time is required to change engines. All that is needed is for the controls, wiring, and fluid lines to be connected to the firewall.
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What is meant by rigging the engine controls so they have some cushion?
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The control on the engine component must contact its stop before the control handle in the cockpit reaches its stop. This causes the control handle to spring back a slight amount when it is moved to the extent of its travel.
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What are two ways of pre-oiling an engine?
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a. Before the spark plugs are installed and after the oil tank or sump is fitted, turn the engine over with the starter until oil runs out of the fitting to which the oil pressure gage connects. b. Use a pre-oiler tank. Air pressure forces oil through all of the passages until some of it flows from the oil pressure gage fitting.
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What are the two basic sections of a turbine engine?
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The hot section & the cold section.
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What are the two basic types of compressors that are used in aircraft turbine engines?
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Axial-flow & centrifugal.
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What is the purpose of stators in an axial-flow compressor?
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The stators convert some velocity energy into pressure energy & 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?
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Can-type, annular-type, & can-annular-type.
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How many igniters are there normally in an aircraft turbine engine?
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Two.
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What is the main purpose of the turbine nozzle in an aircraft turbine engine?
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The turbine nozzle directs the hot gases 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?
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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. The free turbine drives the propeller in a turboprop engine or the transmission & rotor of a helicopter.
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Why do some axial-flow turbine engines have more than one set of turbines & compressors?
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A two-spool turbine engine has a low-pressure & 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?
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Anti-friction bearings, such as ball bearings or roller bearings.
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What is meant by a turbofan engine?
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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?
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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?
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If the engine is shut down while it is hot, there is a possibility that the shroud will contract around the turbine wheel & seize the rotor.
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What is meant by a hung start in a turbine engine?
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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?
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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?
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A condition of permanent elongation of the turbine blades. Creep is caused by the high temperatures & the high centrifugal loading imposed on the blades.
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How is the compressor of a turbine engine cleaned?
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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.
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Where is water injected into a turbine engine for cooling purposes?
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Into the compressor inlet & into the engine diffuser case.
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At what point in a turbine engine is the temperature the highest?
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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?
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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?
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The mechanical blockage-type & the aerodynamic blockage-type.
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What is meant by trimming a turbojet engine?
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Adjusting the fuel control to get the correct idling & maximum-thrust RPM.
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What is meant by a hot-section inspection?
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An inspection of the hot section of a turbine engine. The hot section includes the combustors, the turbine, and the exhaust system.
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What is meant by on-condition maintenance of a turbine engine?
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The monitoring of the engine performance at regular intervals and determining when maintenance is required based on certain operating parameters specified by the engine manufacturer.
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What checks of a turbine engine are necessary to verify preflight condition?
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Inspection of the cowling and all air inlet areas and attachment of the engine to the airframe, inspection of the inlet guide vanes and the first stage of the compressor or fan blades, check for unusual noise when the compressor is rotated, inspection of the rear turbine and exhaust system, check the quantity of the lubricating oil for the engine and the constant-speed drive unit, check the ignition system for operation by listening for the sparks.
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What type of equipment should be used to determine that a turbine engine is performing up to the standards specified by the engine manufacturer?
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A JetCal Analyzer/Trimmer has all of the instrumentation and cables to determine the EGT, EPR, and the other parameters specified by the engine manufacturer.
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What determines whether or not a 100-hour inspection is required for an aircraft?
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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?
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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?
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In the Type Certificate Data Sheets for the engine.
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Who is authorized to perform the powerplant inspection that is required for an annual inspection?
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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?
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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?
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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?
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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?
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Yes.
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What inspection must be performed on an aircraft reciprocating engine if it has been operated on turbine fuel?
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The inside of the cylinders must be inspected with a borescope. The oil must be changed & the filters examined, and the engine given a careful run-up and operational check.
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Where can you find the model of magneto that is approved for an engine specified by the examiner?
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In the Type Certificate Data Sheet for the engine.
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What is a Supplemental Type Certificate?
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An approval issued by the FAA for a modification to a type-certificated airframe, engine, or component.
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What paperwork is necessary for the installation of a magneto that was not approved for an engine when it was certificated, but is approved for the engine when installed according to an STC?
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A form FAA 337 must be completed stating that the installation was done in accordance with the specific STC.
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Does the tachometer of a geared reciprocating engine indicate the speed of the crank shaft or of the propeller shaft?
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The speed of the crankshaft.
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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?
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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?
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A set of thermocouples arranged in an averaging circuit. These thermocouples are installed in the tail pipe of the engine.
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In what units is the tachometer for a reciprocating engine calibrated?
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In hundreds of RPM.
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What two pressures are measured to get the Engine Pressure Ratio of a turbojet engine?
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The turbine discharge total pressure and the compressor inlet total pressure.
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What is used to measure the fuel flow of a horizontally opposed, fuel-injected reciprocating engine?
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A pressure gauge that measures the pressure drop across injector nozzles.
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What is measured by the tachometers used on a two-spool gas turbine engine?
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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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In what units is the tachometer for a turbine engine calibrated?
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In percent of the engines rated takeoff RPM.
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What kind of mechanism is normally used to measure oil pressure in a reciprocating engine?
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A bourdon tube mechanism.
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Why do most engine oil pressure gauges have a restrictor in the line between the engine and the instrument?
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The restrictor damps out pressure pulsations in the oil to keep the needle from oscillating
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How does a torquemeter actually measure the torque produced by an engine?
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A torquemeter is actually an oil pressure gauge. 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 are two types of pickups used for the measuring the cylinder head temperature of a reciprocating engine?
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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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What should a thermocouple-type cylinder head temperature indicator read when the engine is not operating?
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The temperature of the outside air.
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Where does the manifold pressure gauge used on an aircraft reciprocating engine pick up the pressure it measures?
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From the intake manifold of the engine.
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Of what two materials are the thermocouples made that are used in a turbine engine exhaust gas temperature system?
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Chromel and alumel.
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What are three types of flow-indicating systems used for turbine engines?
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Vane-type flow meters, synchronous mass-type flow meters, and electronic motorless mass flow meters.
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What do mass flow systems measure?
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The mass of the flow. This is affected by the density of the fuel which is in turn affected by the fuel temperature.
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In what units is an electronic motorless mass flow meter system calibrated?
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Pounds per hour of fuel flow.
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What is indicated in a turbine engine if the fuel flow for all conditions is high?
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If there are instrument abnormalities, there are possibly damaged turbine components.
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Who is authorized to repair a fuel flow indicating system?
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The components can be repaired only by an FAA approved repair station certificated for the particular instruments.
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Where can you find the electrical power requirements for a fuel flow indicating system?
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In the aircraft maintenance manual.
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Where in the fuel system is the fuel flow transmitter located?
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Between the fuel control and the fuel nozzles.
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What kind of indicating system is used to measure oil temperature in a small, single-engine, general aviation airplane?
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A sealed system in which a bulb, partially filled with a highly volatile liquid, is installed inside the oil strainer. The bulb is connected to a pressure gage by a copper tube. The pressure of the gas above the liquid is proportional to the temperature of the oil that surrounds the bulb, and the pressure gage is calibrated in terms of temperature.
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What type of instrument system is used for measuring cylinder-head temperature and exhaust gas temperature?
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A thermocouple system.
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What kind of electrical instrument system is used for measuring oil temperature?
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A ratiometer-type system.
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What should a thermocouple cylinder-head temperature indicator read when the engine is cold?
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The same as the outside air temperature gage.
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What is critical in the installation of the thermocouple leads for a cylinder-head temperature indicator, the length of the leads or their resistance?
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The resistance is critical, it must have the resistance specified on the indicator. This is usually 2 or 8 ohms.
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What should a ratiometer temperature indicator read when the electrical power is off?
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The pointer should be off scale on the low side.
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What kind of tachometer is used on most small single-engine airplanes?
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A magnetic drag tachometer that is similar to an automobile speedometer.
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What would likely cause the pointer of a magnetic drag tachometer to oscillate?
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Either a dry cable connecting the indicator to the engine, or a kink in the cable housing.
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Is it permissible for a mechanic with an airframe and powerplant rating to replace the tachometer cable for a magnetic drag tachometer?
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Yes, this does not constitute a repair to an instrument.
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What kind of tachometer is used on most large multi-engine airplanes?
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A three-phase AC electric tachometer.
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What is measured to indicate the engine RPM with a three-phase AC electric tachometer?
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The frequency of the AC the tachometer generator produces.
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What kind of indicator mechanism is used to measure manifold pressure?
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A differential bellows.
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What should a manifold pressure gage read when the engine is not operating?
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The existing barometric pressure as indicated on the altimeter barometric scale when the altimeter pointers are set to the surveyed field elevation.
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What type of fitting is used to connect an oil pressure gage to the engine?
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A fitting with a restrictor that smoothes out the pulsations and prevents a break in the indicator line, causing a serious loss of engine oil.
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What is used to fill the line between a fuel pressure gage and the fuel metering system?
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A light oil such as kerosine.
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What could cause a fuel pressure gage to fluctuate?
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The loss of the light oil in the line between the gage and the engine.
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Is a certificated mechanic with an airframe and powerplant rating allowed to zero the pointers on a fuel pressure gage?
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No, a mechanic is not allowed to make any repairs or alterations to an aircraft instrument.
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How does a ratiometer-type oil temperature gage measure the temperature of the oil?
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A ratiometer measures the resistance of the temperature bulb. The indicator is calibrated in degrees Fahrenheit or Celsius rather than in ohms.
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What is the range of pressure needed for a fuel pressure gage used with a float carburetor?
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Normally from 1 to 25 psi.
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Can a thermal switch-type fire detection system indicate a general overheat condition?
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No, this is a spot-type fire detection system, & it cannot indicate an overheat condition.
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Can a thermocouple-type fire detection system indicate a general overheat condition?
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No, this is a rate-of-temperature -rise-type of system, & it cannot indicate a general overheat condition.
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How is a thermocouple-type fire detection system checked for operation?
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Press the test switch. This heats the test thermocouple enough for it to close the sensitive relay, which in turn closes the slave relay and activates the fire warning light and bell.
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Does a break in a continuous-loop fire detection system keep the system from detecting a fire?
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No, the unit will show a fault when it is tested, but it will still warn of a fire.
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Does the pressure-type continuous-element fire detector system detect a general overheat condition, as well as a fire?
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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 & warn of a fire.
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What are the two most commonly used fire extinguishing agents used for engine fires?
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Halogenated hydrocarbon, such as Halon 1301, & carbon dioxide.
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What extinguishing agent is used in the high-rate-discharge fire extinguishing systems installed in most turbojet engine installations?
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Halon 1301.
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What happens when the pilot pulls the fire-pull T-handle in the cockpit of a jet transport airplane?
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The bottle discharge switch is uncovered & 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, & the hydraulic pump low-pressure lights are deactivated.
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How can a mechanic determine the state of charge of the HRD bottles of fire extinguishing agent?
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A pressure gage on the bottle shows the pressure of the contents of the bottle.
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What method is used to discharge an HRD bottle in a turbine engine installation?
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An electrically ignited powder charge blows a knife through the seal on the bottle & discharges the contents.
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Which type of fire detection system operates on the rate of temperature rise?
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The thermocouple system.
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What is indicated if the yellow blow-out plug of the fire extinguisher system on the side of the engine nacelle is blown out?
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The built-in fire extinguishing system has been discharged by normal operation.
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What is indicated if the red blow-out of the fire extinguisher system on the side of the engine nacelle is blown out?
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The built-in fire extinguishing system has been discharged by a high temperature condition.
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How is a pressure-type continuous-element fire detector systems checked for operation?
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Low-voltage alternating current is sent through the sheath of the detector element. This heats the element, & it releases enough gas to close the diaphragm switch.
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What are four types of engine fire detection systems?
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Thermoswitch system, thermocouple system, thermistor-type continuous-loop system, pneumatic-type continuous-loop system.
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Why must a reference junction in a thermocouple fire detection system be thermally insulated?
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This is a rate-of-temperature-rise system. The reference junction must be insulated so its temperature will not rise as quickly as that of the measuring junctions if a fire should occur.
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What would likely cause a false fire alarm in a thermistor-type continuous-loop system?
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A kinked or pinched continuous-loop element.
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If there is a break in a single-wire continuous-loop fire detector element, and the systems tests bad, will it indicate the presence of a fire?
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Yes, even though it tests bad, it will still indicate the presence of a fire.
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How is a pneumatic-type continuous-loop fire detection system checked for operation?
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When the test switch is closed, low-voltage AC flows through the tube that encloses the sensitive element. This current heats the element enough for it to release sufficient gas to activate the alarm switch.
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What maintenance is allowed on a continuous-loop fire detection system?
|
Inspect and replace as needed the continuous-loop element, the controller, and the fire warning bell and/or light.
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What is used as a fire extinguishing agent in some older aircraft?
|
Carbon dioxide (CO2).
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What precaution must be taken when checking the electrical circuit for igniting the powder charge in the valve of a high-rate discharge bottle?
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The current used to check the integrity of the electric circuit must not be high enough to ignite the powder charge.
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What color and marking is used to identify the fluid lines that carry the fire extinguishing agent in an aircraft?
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Brown tape with a series of diamonds on it.
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Why is stranded wire used rather than solid wire in most powerplant electrical systems?
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Solid wire is likely to break when it is subjected to vibration.
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What two things must be considered in selection of wire size when making an electrical installation in an aircraft?
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The current-carrying capability of the wire & the amount of voltage drop that is caused by current flowing through the wire.
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Why are the wires in certain electrical installations twisted together?
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By twisting the wires together, the magnetic fields caused by current flowing through the wire are minimized.
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What is used to protect a wire bundle from chafing where it passes through a hole in the bulkhead or frame?
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A grommet around the edges of the hole.
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How are electrical wires protected where they pass through an area of high temperature?
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Wires passing through these areas are insulated with high temperature insulation, & the wires are enclosed in some type of the protective circuit.
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What is the minimum separation that is allowed between a wire bundle & a fluid line that carries combustible fluid or oxygen?
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A minimum of six inches.
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What is the significance of the color of the solderless connectors that are used on electrical connectors?
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The color of the insulation indicates the size of the wire connector will fit. Red terminals fit 22- through 18-gage wire, blue terminals fit 16- & 14-gage wire, & yellow terminals fit 12- & 10-gage wire.
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What is the maximum number of wire terminals that may be stacked on a single stud in a terminal strip?
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Four.
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What is the purpose of the shielding that is used to encase some electrical wires?
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Shielding intercepts radiated electromagnet energy & carries it to ground so it will not interfere with any nearby sensitive electronic equipment.
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Why must a switch be derated if it is used in a circuit controlling a DC electric motor?
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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.
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What is used as the rectifier to produce direct current in a DC generator?
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Brushes & a commutator.
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How does a vibrator-type voltage regulator control the output voltage of a DC generator?
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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 & inserts a resistor in the generator field circuit. The contacts vibrate open & closed, putting the resistor in & out of the field circuit to control the amount of voltage the generator produces.
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What is meant by paralleling the generators of a twin-engine aircraft?
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Adjusting the voltage of the generators so they will share the electrical load equally.
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What is meant by flashing the field of a DC generator?
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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.
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What kind of rectifier is used in a DC alternator of the type that is used on most modern light airplanes?
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A full-wave, three-phase rectifier made up of six silicon diodes.
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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?
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A hydraulic constant-speed drive unit between the engine & the alternator.
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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?
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The voltage, the frequency, & the phase rotation of the generators.
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What must be done to reverse the direction of rotation of the armature of a DC electric motor?
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The current flow must be reversed through the armature or the field windings, but not through both of them.
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Does a series-wound DC motor have a high or a low starting torque?
|
A high starting torque.
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Which aircraft electrical circuit does not contain a fuse or circuit breaker?
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The starter motor circuit.
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When removing a battery from an aircraft, which connection should be removed first?
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The ground connection must be disconnected first & connected last.
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What is meant by the effective voltage of sine wave alternating current?
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The value of the alternating current that is needed to produce the same amount of heat as this value of direct current.
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What is a starter-generator that is used with many of the smaller gas turbine engines?
|
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.
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When should aircraft wiring be installed in a conduit?
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When the wiring passes through an area in the aircraft where open wiring could likely be damaged, such as through a wheel well.
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When should the brushes in a starter motor be replaced?
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When they have worn to one half of their original length.
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Is a starter motor series-wound or shunt-wound?
|
Series wound for maximum stalled-rotor torque.
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What are two ways wires can be attached to the pins in a cannon plug?
|
a. By soldering the wires into pots on the pins and sockets. b. by crimping tapered pins onto the wires and inserting the pins into tapered holes in the pins and sockets.
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What must be done to a DC generator, after it has been overhauled, before it can produce electricity?
|
The field must be flashed to restore residual magnetism to the field frame so it can begin to produce current.
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Why is not necessary to flash the field of a DC alternator after it has been overhauled?
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An alternator field is excited by battery current and residual voltage is not used to start the alternator producing current.
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What is meant by a trip-free circuit breaker?
|
A circuit breaker that opens a circuit any time an excessive amount of current flows, regardless of the position of the circuit breakers operating handle.
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Which way should the toggle of a switch that controls the propeller pitch move to place the propeller in low pitch (high RPM)?
|
Forward.
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Why are protective covers placed over some switches in an aircraft electrical circuit?
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To prevent the switch from being inadvertently actuated.
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What is meant by the viscosity of engine lubricating oil?
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The resistance of the oil to flow.
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What is meant by a wet sump lubrication system?
|
A lubrication system in which the oil is carried inside the engine itself.
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What is meant by a dry sump lubrication system?
|
A lubrication system in which the oil is carried in a tank that is not a part of the engine.
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How is oil temperature controlled in an aircraft reciprocating engine?
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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.
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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?
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It is the temperature of the oil entering the engine.
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What is the purpose of oil dilution in a reciprocating engine?
|
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 & makes starting easier. When the engine is running, the gasoline evaporates out of the oil.
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What is the function of the hopper in the oil tanks used with some reciprocating engines?
|
Hoppers are a part of the oil dilution system. Only the oil in the hopper is diluted. This speeds up dilution & requires less gasoline.
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What happens to the gasoline that is used to dilute the oil in the crankcase of an aircraft reciprocating engine?
|
When the engine is running & the oil is warm, the gasoline evaporates out of it.
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What is the purpose of the sludge plugs in the crankshaft of a reciprocating engine?
|
They trap sludge that is in the oil & hold it until the engine is disassembled at overhaul.
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Which pump is the larger in a dry-sump lubricating system, the pressure pump or the scavenger pump?
|
The scavenger pump has the greater volume.
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Why do full-flow oil filters have a spring-operated bypass valve in them?
|
In case the filter should plug up so it cannot pass any oil, the bypass valve will open & allow unfiltered oil to flow through the system.
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What is the function of a fuel-oil heat exchanger in the lubrication system of a turbojet engine?
|
This allows heat from the oil to warm the fuel so ice will not form on the fuel filters.
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|
What kind of oil is used in most turbojet engines?
|
Synthetic oil.
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Where are the last chance oil filters located in a turbojet engine?
|
They are located inside the engine just ahead of the nozzles that spray oil onto the bearings.
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Where is the oil tank in a dry-sump reciprocating engine vented?
|
To the engine crankcase.
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What information must be displayed around the oil filler opening for a turbojet engine?
|
The word "Oil" & the permissible oil designations, or references to the Airplane Flight Manual (AFM) for permissible oil designations.
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What is the function of the oil control rings on the piston of an aircraft reciprocating engine?
|
They maintain the proper quantity of oil between the piston & the cylinder wall.
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|
What is meant by a spectrometric oil analysis?
|
It is a program in which a sample of oil is taken from the engine at regular intervals & 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.
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|
What indication would a pilot have if his oil supply was low?
|
The oil temperature would be high & the oil pressure would be low.
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What is meant by a hot-tank lubrication system?
|
A lubrication system in which the oil cooler is located in the pressure subsystem.
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|
What is meant by a cold-tank lubrication system?
|
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.
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|
What is straight mineral oil?
|
It is the lubricating oil as obtained by fractional distillation of crude oil. It does not have any additives.
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What is ashless dispersant (AD) oil?
|
A mineral lubricating oil containing additives that disperse the contaminants throughout the oil so they will not clump and clog oil passages. There are no ash-forming additives in AD oil.
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What is synthetic oil?
|
A lubricating oil that is made by chemically changing the nature of an oil base to give it the needed characteristics. Synthetic oil is the primary oil for turbine engines.
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|
Is automotive oil suitable for use in aircraft engines?
|
No, automotive and aviation oils are formulated for entirely different operating conditions.
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What is meant by a multiviscosity oil?
|
It is a lubricating oil with a viscosity index improver that increases the viscosity of the oil when it is hot and decreases the viscosity when it is cold.
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|
What are six functions of the oil in an aircraft engine?
|
a. Reduces friction b. Seals and cushions c. Removes heat d. Cleans inside the engine e. Protects against corrosion f. Performs hydraulic action.
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|
Where can you find the grade of engine oil specified for a particular aircraft?
|
In the Aircraft Flight Manual or the Pilots Operating Handbook for the aircraft.
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|
What components in a reciprocating-engine lubrication system must be inspected on a 100-hour or annual inspection?
|
The oil sump or tank, the oil strainer screen, the oil filter, the oil cooler and the temperature control valve, the oil pressure and temperature gages and any transmitters associated with them, and the entire engine for indication of leaks.
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What two instruments show the condition of a reciprocating-engine lubrication system?
|
Oil pressure and oil temperature gages.
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What must be done to an oil filter when it is removed from the engine?
|
It should be cut open and the pleated element examined to determine the type and amount of contaminant carried by the oil.
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|
What is the purpose of an air-oil separator, or deaerator, in a turbine engine oil tank?
|
In normal operation, the oil picks up a quantity of air and it is swirled as it enters the deaerator. The swirling action releases the air from the oil, and the air is used to pressurize the oil tank.
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|
What type of oil quantity indicator is used in most aircraft engines?
|
A dipstick that measures the quantity of oil in the tank or the sump.
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|
When should the engine oil quantity be checked on a turbine engine?
|
As soon as practical after the engine is shut down.
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|
|
Where is the oil temperature measured on a reciprocating engine?
|
Usually at the oil pressure screen before the oil goes into the engine passages.
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|
How is oil pressure regulated in an aircraft engine?
|
A pressure-relief valve senses the desired pressure and sends all of the oil that caused excessive pressure back into the engine sump.
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|
Why do engine manufacturers recommend that engine lubricating oil be changed at specific intervals?
|
The oil picks up contaminants and carries them through the engine where they can cause wear. The oil also becomes acidic and causes corrosion in the engine.
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|
What is the purpose of the restricted orifice in the line between the oil pressure gage and the engine?
|
The restricted fitting helps dampen any pulsations in the oil pressure caused by the pump.
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|
|
What is a hot-tank lubrication system for a turbojet engine? |
A lubrication system in which the oil cooler is in the pressure subsystem and the scavenged oil is not cooled before it is returned to the tank. |
|
|
What is a cold-tank lubrication system for a turbojet engine? |
A lubrication system in which the oil cooler is in the scavenge subsystem, and the scavenged oil is cooled before it is returned to the tank. |
|
|
What is the main advantage of a magneto ignition system over a battery ignition system for an aircraft reciprocating engine?
|
A magneto has its own source of electrical energy, and it is not dependent upon the battery.
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|
|
What is the function of the capacitor in a magneto?
|
The capacitor minimizes arcing at the breaker points, and it speeds up the collapse of the primary current as the breaker points open.
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|
|
What is a compensated magneto cam, and on what kind of engine is one used?
|
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.
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|
What is the significance of the numbers on the distributor of an aircraft magneto?
|
These numbers are the sparking order of the magneto, not the firing order of the engine.
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|
What happens in a magneto ignition system when the ignition switch is placed in the Off position?
|
The primary circuit is connected to ground.
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|
|
What is the reason for having a low-tension ignition system on some aircraft?
|
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.
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|
|
What is the basic difference between a low-tension magneto and a high-tension magneto?
|
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. A high-tension magneto produces high voltage in the magneto coil, and it is sent to the correct spark plug by the built-in high-voltage distributor.
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|
What is meant by an All Weather spark plug?
|
A shielded spark plug that has a recess in the shielding in which a resilient grommet on the ignition lead forms a watertight seal.
|
|
|
What is meant by the reach of a spark plug?
|
The length of the threads on the spark plug that screw into the cylinder head.
|
|
|
What is the difference between a hot spark plug and a cold spark plug?
|
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.
|
|
|
What is checked when a magneto is internally timed?
|
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.
|
|
|
What is the purpose of a vernier coupling used on some aircraft magneto drives?
|
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.
|
|
|
What is the advantage of fine-wire spark plugs over massive electrode spark plugs?
|
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.
|
|
|
Why is it important that the spark plugs be kept in numbered holes in a tray when they are removed from an engine?
|
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.
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|
|
What is the purpose of staggered timing between the two magnetos on an aircraft engine?
|
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.
|
|
|
In what position should the ignition switch be placed when using a timing light on the magnetos?
|
In the Both position.
|
|
|
Why is it important that a torque wrench always be used when installing spark plugs in an aircraft engine?
|
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.
|
|
|
Why are pressurized magnetos used on most reciprocating-engine-powered aircraft that fly at high altitudes?
|
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.
|
|
|
What type of ignition system is used on most turbine engines?
|
High-intensity, intermittent-duty, capacitor discharge ignition systems.
|
|
|
What is meant by the E-gap in magneto timing?
|
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.
|
|
|
What is the function of an impulse coupling?
|
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 is produces a hot and late spark.
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|
|
What kind of gage should be used to measure the electrode gap in aircraft spark plugs?
|
A round wire gage.
|
|
|
How many igniters are used in most turbine engines?
|
Two.
|
|
|
What are two types of ignition systems used in turbine engines?
|
High-voltage systems and low-voltage systems.
|
|
|
With which type of ignition system is a glow plug igniter used?
|
A low-voltage system.
|
|
|
How is the strength of the magnet in a magneto checked?
|
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.
|
|
|
In what position is the magnet in a magneto when the greatest change in flux density in the coil core takes place?
|
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.
|
|
|
In what position is the magnet in a magneto where the breaker points begin to open?
|
In its E-gap position, just a few degrees beyond its neutral position.
|
|
|
What malfunction in the ignition would cause an aircraft reciprocating engine to continue to run after the ignition switch is placed in the Off position?
|
The ignition switch is not grounding the magneto primary circuit.
|
|
|
What turns on the autoignition system in a turbo-prop engine?
|
A torque pressure switch energizes the system when the engine stops producing torque.
|
|
|
What kind of equipment is used to test an ignition harness for a reciprocating engine?
|
A high-voltage electrical leakage detector.
|
|
|
What kind of electric starting system is used on many of the smaller turbine engines?
|
A starter-generator.
|
|
|
What happens when the start switch for a turbine engine with a starter-generator is placed in the START position?
|
a. Current flows into the starter relay which closes and actuates the ignition exciter. b. Current flows through the series motor coils of the starter generator and rotates the engine until it starts.
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|
|
What happens when the start switch for a turbine engine with a starter-generator is placed in the RUN position?
|
a. The starter relay opens, shutting off current to the ignition exciter and the motor windings in the starter-generator. b. The generator field relay is closed connecting the voltage regulator to the starter-generator. c. The output of the generator flows to the bus through the generator circuit breaker.
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|
What is indicated if the starter relay chatters rather than locks in, when the start switch is placed in the START position?
|
The battery voltage is too low to supply enough current to hold the relay engaged.
|
|
|
Why are air-turbine starters superior to electric starters for large turbine engines?
|
They are light weight for the torque they produce.
|
|
|
Where does an air-turbine starter get its air for starting the engines on a jet transport plane?
|
From an APU, GPU, or from a running engine.
|
|
|
What is the purpose of the shear section in an air-turbine drive shaft?
|
If the ratchet mechanism fails to release and the engine drives the starter to a speed higher than its design speed, the shear section will break and disconnect the starter from the engine.
|
|
|
What prevents too high an air pressure from overspeeding an air-turbine starter?
|
The air shutoff and regulating valve.
|
|
|
Where does an air-turbine starter get it lubricating oil?
|
It has a self-contained lubrication system with the oil held in the starter housing.
|
|
|
What device in an air-turbine starter warns a technician if there are any metal chips or particles in the oil?
|
Magnetic chip detectors warn of any metal contamination in the oil.
|
|
|
Where does the fuel metering system of a turbine engine discharge its fuel?
|
The fuel is discharged through the spray nozzles into the combustion chambers.
|
|
|
What is adjusted when the fuel control unit of a turbine engine is trimmed?
|
The idle speed and the maximum-thrust speed.
|
|
|
What are two locations water may be injected into a turbine engine?
|
At the compressor inlet and at the inlet to the diffuser section
|
|
|
What is meant by a duplex nozzle in a turbine engine fuel metering system?
|
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.
|
|
|
What is the function of a float carburetor?
|
The float carburetors function is to measure airflow through the engine induction system and dispense the appropriate amount of gasoline into the airflow for all engine operating perimeters and conditions. It must also provide the fuel in a state that is as vaporized as possible by the time ignition occurs in the engine cylinders.
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|
Does the fuel-air mixture provided by a float carburetor become richer or leaner as the aircraft goes up in altitude?
|
If the mixture is not adjusted, it will become richer as the aircraft climbs.
|
|
|
Does the fuel-air mixture provided by a float carburetor become richer or leaner when carburetor heat is applied?
|
The mixture becomes richer when carburetor heat is applied.
|
|
|
What would happen to the fuel-air mixture ratio in a float carburetor if the main air bleed were to become plugged?
|
The mixture would become excessively rich.
|
|
|
How does the automatic mixture control in a pressure carburetor keep the fuel-air mixture constant as the aircraft changes altitude?
|
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 climbs.
|
|
|
What are two purposes of the manifold valve (or flow divider) in the fuel injection system of a horizontally opposed aircraft engine?
|
It provides a constant discharge fuel pressure for idling, and it provides a positive shutoff for the fuel when the engine is shut down.
|
|
|
How does the mixture control change the fuel-air mixture ratio on the Teledyne-Continental fuel injection system?
|
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.
|
|
|
Why must the diaphragms of a pressure carburetor be soaked before the carburetor is ready for flight?
|
Soaking the diaphragms of a pressure carburetor restores them to the condition of flexibility that they had when the carburetor was calibrated.
|
|
|
What are two basic types of fuel controls for aircraft turbine engines?
|
Hydropneumatic and electro-hydromechanical.
|
|
|
How does the exhaust gas temperature of a reciprocating engine tell anything about the fuel-air mixture being burned by the engine?
|
A stoichiometric mixture 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.
|
|
|
What two things are adjusted when adjusting the idling of a reciprocating engine?
|
The throttle stop, to get the proper idling RPM, and the idle mixture control, to get the smoothest operation.
|
|
|
What is controlled by the adjustment of the orifice in the fuel pump of a Teledyne-Continental fuel injection system?
|
The high unmetered fuel pressure.
|
|
|
What is the significance of the letters that are stamped on the flats of a fuel injection nozzle?
|
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.
|
|
|
What is the function of the derichment valve in a pressure carburetor used on aircraft engine with an antidetonation injection system?
|
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.
|
|
|
What is the function of the economizer system in an aircraft engine carburetor?
|
The economizer 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.
|
|
|
In what position is the mixture control placed for starting an engine that is equipped with a pressure carburetor?
|
In the idle cutoff position. The engine is started with fuel from the primer system.
|
|
|
In what position is the carburetor heat control placed when starting an aircraft engine?
|
In the cold position.
|
|
|
Why is an aircraft reciprocating engine killed by placing the mixture control in the Cutoff position, rather than by using the magneto switch?
|
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.
|
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Where is the fuel from a continuous-flow fuel injection system discharged?
|
It is discharged through injector nozzles screwed into the cylinder heads near the intake valves.
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In which direction relative to the wind should a turbine-powered aircraft be positioned when the fuel control is being trimmed?
|
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.
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What engine parameters are sensed by the fuel control unit of a turbine engine?
|
Engine RPM, inlet air pressure, compressor discharge pressure, burner can pressure, and inlet air temperature.
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When does the acceleration system operate on an aircraft carburetor?
|
When the throttle is suddenly opened.
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What parameters are normally sensed by a turbine-engine fuel control?
|
a. Power lever angle. b. Compressor inlet total temperature. c. Compressor RPM. d. Burner pressure.
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What is meant by trimming a turbine engine?
|
Adjusting the fuel control for the specific gravity of the fuel and for the proper idle and full throttle RPM.
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What are two types of electronic fuel controls for turbine engines?
|
Supervisory Electronic Engine Control and Full-Authority Digital Electronic Control.
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|
What is FADEC?
|
A Full-Authority Digital Electronic Control (FADEC) is a high-precision digital electronic fuel control that functions during all engine operations. It includes the Electronic Engine Control (EEC) and functions with the Flight Management Computer (FMC) to measure the fuel to the nozzles in such a way that prevents overshooting of power changes and over-temperature conditions. FADEC furnishes information to the Engine Indicating and Crew Alerting System (EICAS).
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Does a turbine engine controlled by a FADEC require manual trimming?
|
No, this is done by the FADEC.
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When should a turbine engine be retrimmed?
|
Any time there is a decrease in engine thrust, and after any maintenance that the manufacturer specifies as requiring trimming.
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Are the instruments installed in an aircraft suitable for use when trimming a turbine engine?
|
No, a special analyzer/trimmer such as JetCal should be used.
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What specifications are used to trim a turbine engine?
|
The data plate specifications for the specific engine. This data was obtained when the engine was calibrated in the manufacturers test cell.
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Where would ambient temperature be measured when trimming a turbine engine?
|
In a shaded area as near the engine inlet as is practical.
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What is the purpose of the bypass valve in an engine-driven fuel pump?
|
The bypass valve allows fuel to flow around the engine-driven pump for starting & for emergency operation if the engine-driven pump should fail.
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On which side of the firewall is the engine fuel shutoff valve located?
|
The shutoff valve must be on the side of the firewall away from the engine.
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What are three purposes for the boost pumps in an aircraft fuel system?
|
To provide fuel pressure for starting the engine, to pressurize the fuel lines to prevent vapor lock, & to transfer fuel from one tank to another.
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What kind of boost pump is used in most aircraft fuel systems?
|
Electrically operated centrifugal pumps.
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Where does an engine-driven fuel pump direct the excess fuel from its pressure relief valve?
|
Back to the inlet side of the pump.
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What causes a vapor lock in an aircraft fuel system?
|
The fuel becomes hot enough that it boils. Vapors are released from the liquid fuel, & these vapors block the fuel lines so the liquid fuel cannot flow to the engine.
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What is done in most aircraft fuel systems to prevent vapor lock?
|
Boost pumps in the fuel tank pressurize the fuel in the lines & force the fuel into the fuel metering system.
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What is meant by a compensated relief valve in an engine-driven fuel pump?
|
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.
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What is the purpose of the pressurizing & dump valve in the fuel system for a turbine engine?
|
For normal engine operation, the pressurizing & dump valve acts 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.
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What should be done to an aircraft reciprocating engine if it has been operated on turbine engine fuel?
|
All of the turbine fuel should be drained out & the system filled with the proper grade of aviation gasoline. The engine should be given a compression check, & all of the cylinders should be inspected with a borescope. The oil should be drained & the filters carefully examined. The engine should be given a complete run-up check.
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What are the two basic types of turbine engine fuel?
|
Jet A & Jet A-1, which are special type of kerosine-base fuel. This is similar to military JP-^Jet B is a gasoline-base fuel similar military JP-4.
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Why do some turbine engine fuel systems incorporate a fuel heater?
|
The fuel heater keeps the fuel warm enough that any water that precipitates out of the fuel will not freeze on the filters.
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What are two reasons Prist is used in turbine engine fuel?
|
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 & holds water against the aluminum alloy in the fuel tanks & causes corrosion.
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Why do some aircraft fuel filters have a built-in relief valve?
|
This relief valve will open & allow unfiltered fuel to flow to the fuel control device if the filter should become plugged with ice or other contaminants.
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What is meant by a compensated fuel pump?
|
It is a fuel pump that senses the ambient air pressure and maintains the fuel pressure a specific amount above this air pressure.
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What would likely cause a reciprocating engine equipped with a float carburetor to hesitate momentarily when the throttle is rapidly advanced from idle to full power?
|
A malfunctioning accelerator pump.
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Why do aircraft fuel metering systems for reciprocating engines have mixture controls?
|
The air density increases as the aircraft ascends, causing the mixture to become richer. The mixture control allows the fuel to be decreased to maintain a fuel-air mixture ratio that produces the desired power.
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|
What are two types of fuel injection systems used on modern reciprocating aircraft engines?
|
Teledyne Continental (TCM) system and Precision Airmotive (Bendix) system.
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|
What is used in the TCM fuel injection system to control the amount of fuel sent to the nozzles?
|
The engine speed determines the injector pump output pressure. The relief valve determines the fuel for low-speed operation, and the adjustable orifice determines the fuel for high-speed operation.
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What is used in the Precision Airmotive system to control the amount of fuel sent to the nozzles?
|
The mass of the air entering the engine acts on air diaphragm that controls a servo ball valve in the line between the regulator and the flow divider.
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|
Where are the fuel strainers normally located in an aircraft fuel system?
|
Finger strainers are located in the tank outlet, the main strainer, located at the lowest point in the fuel system, and strainers in the carburetor or fuel injection system.
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|
What are two types of fuel heaters used in a jet transport aircraft?
|
Air-to-fuel and oil-to-fuel heat exchangers.
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|
What two things are adjusted when setting the idling conditions on a float carburetor?
|
a. Idling RPM by adjusting the throttle stop. b. Idling mixture by adjusting idle needle valve.
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|
Where is the heat taken from that is used to heat the induction air in a reciprocating engine?
|
From a muff that is installed around some 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?
|
From inside the engine cowling.
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|
Where does carburetor ice normally form in a carburetor?
|
In the throat of the carburetor, on & around the throttle valve.
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|
Does the application of carburetor heat cause the fuel-air mixture to become richer or to become leaner?
|
Heated air causes the fuel-air mixture to become richer.
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|
What is used to drive most of the external superchargers used on modern reciprocating engines?
|
Exhaust gases.
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|
What controls the speed of a turbocharger compressor?
|
The amount of exhaust gas that is forced to flow through the turbine. This is controlled by the position of the waste gate.
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|
What is meant by a convergent inlet duct for a turbine engine?
|
A convergent duct is one 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?
|
A divergent duct is one 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?
|
A bell-mouthed inlet duct.
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|
|
What is the danger of operating an aircraft reciprocating engine with too high a carburetor air temperature?
|
Too high a carburetor air inlet temperature can cause the fuel-air mixture to reach its critical temperature & detonate.
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|
Why do some turbine engines use variable inlet guide vanes?
|
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.
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|
How do some turbine engines prevent ice formation on the inlet guide vanes?
|
Hot compressor bled air flows through hollow inlet guide vanes.
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|
What is usually installed in a large reciprocating engine between the turbosupercharger & the carburetor?
|
An intercooler. This is an air-to-air heat exchanger.
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|
|
In what position should the carburetor heat control be placed when starting a reciprocating engine?
|
In the Cold position.
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|
|
How does an engine air inlet vortex destroyer help prevent foreign object damage to the engine?
|
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.
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|
|
Why does ice form in the throat of a float carburetor?
|
When liquid fuel evaporates it absorbs enough heat from the air to cause moisture to condense out and freeze.
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|
|
Does the application of carburetor heat cause the fuel-air mixture to become richer or leaner?
|
The less dense, heated air draws the same amount of fuel from the carburetor as cold air, therefore the mixture becomes richer.
|
|
|
What happens to engine RPM when carburetor heat is applied?
|
The RPM drops.
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|
|
Why should the use of carburetor heat be limited when operating an engine with the aircraft on the ground?
|
The air that flows into the engine when carburetor heat is applied is not filtered.
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|
Why is a fuel-injected reciprocating engine not as prone to icing as an engine equipped with a float carburetor?
|
In a fuel-injected engine, the liquid 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?
|
Hot compressor 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?
|
An alternate air valve allows warm air from inside the engine cowling to flow into the fuel metering system.
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|
|
What would be the effect on engine operation of an air leak in the intake pipe for one cylinder?
|
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?
|
Clogged air filters can restrict the air entering the engine.
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|
What is meant by pressure cooling of an aircraft engine?
|
Air cooling in which air is forced to flow through baffles & 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?
|
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.
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|
|
Where is the highest temperature located in a turbine engine?
|
At the inlet to the high-pressure turbine.
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|
|
How are the turbine inlet guide vanes & the first-stage turbine blades in some turbine engines cooled?
|
High-pressure compressor bleed air flows through the hollow guide vanes & hollow turbine blades.
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|
|
Which side of an air-cooled engine cylinder has the greatest amount of cooling fins?
|
The side of the cylinder in which the exhaust valve is located.
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|
|
What should be done to repair a bent cooling fin in a cast aluminum cylinder head?
|
It is normally best to leave a bent cast fin alone if it does not restrict the flow of air. Cast fins are brittle & 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?
|
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?
|
They should be wide open when operating the engine on the ground.
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|
What is the function of the majority of the air that passes through a turbine engine?
|
Most of the air is used for cooling.
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|
How does metallic sodium in an exhaust valve aid in transferring heat?
|
The sodium melts when the engine is running, & it sloshes up & down as the valve operates. The sodium picks up heat from the valve head & carries it into the stem so it can be transferred to the cylinder head & dissipated into the air.
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|
How is the structure around a turbine engine protected from excessive heat from the engine?
|
An insulating blanket protects the structure from excessive heat.
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|
What is the function of blast tubes that are installed in a pressure cooling system of a reciprocating engine?
|
These blast tubes direct cooling air to the magnetos & 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?
|
Fiberglass sandwiched between sheets of metal foil.
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|
|
What must be inspected on the cooling system of an air-cooled engine?
|
All of the baffles and air seals must be in place and in good condition.
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|
|
Why should an air-cooled engine not be run up to high power without the cowling installed?
|
The engine depends on the cowling to force air through the cylinder fins to remove the excess heat.
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|
|
Why do some air-cooled engine installations have cowl flaps?
|
Cowl flaps 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?
|
In the engine overhaul manual.
|
|
|
What document describes the proper use of cowl flaps on an air-cooled engine?
|
The Pilots Operating Handbook.
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|
|
Of what material are most reciprocating engine exhaust components made?
|
Corrosion-resistant steel.
|
|
|
How is the speed of a turbocharger controlled?
|
By controlling the amount of exhaust gas that flows through the turbine. This is controlled by the position of the waste gate that is in the exhaust pipe.
|
|
|
What type of actuator is used to control the position of the turbocharger waste gate?
|
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?
|
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, & the turbines assist in turning the crankshaft.
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|
|
How tight should the clamps be tightened that hold sections of a reciprocating engine exhaust system together?
|
They should be not 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?
|
This will increase the exhaust back pressure and cause a loss of engine power.
|
|
|
What effect on turbine engine operation is caused by a change in the area of the exhaust nozzle?
|
Altering the area of the exhaust nozzle affects the compression ratio, the RPM, the mass airflow through the engine, & the EGT.
|
|
|
What are two types of thrust reversers that are used with turbojet engines?
|
Mechanical blockage (clamshell) & aerodynamic blockage (cascade)
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|
|
How does a noise suppressor reduce the amount of noise produced by a turbojet engine?
|
It breaks up the low-frequency vibrations in the exhaust stream & converts them into higher frequencies. These high frequencies are dissipated by the air more easily than low frequencies.
|
|
|
What is the purpose of the ball joints & bellows in the exhaust system of a reciprocating engine?
|
The ball joints & bellows allow the exhaust system components to change their dimensions without causing any leaks.
|
|
|
Why do some supersonic aircraft use a convergent-divergent exhaust duct?
|
A CD exhaust duct controls the gas expansion as it leaves the engine so the gases will produce thrust at supersonic velocities.
|
|
|
Why is it important that a lead pencil never be used to mark on an aircraft exhaust system?
|
The graphite in a lead pencil will infuse into the metal when it gets hot. It makes the metal brittle & likely to crack.
|
|
|
What type of damage is normally found in the hot section of a turbine engine?
|
Cracks caused by heat.
|
|
|
How does a leak appear in an engine exhaust system?
|
It normally looks like a gray or black feather-shaped streak coming from a crack or from a location where components are not in perfect alignment.
|
|
|
How can you check an exhaust system for leaks?
|
Pressurize the exhaust system with the discharge from a vacuum cleaner and wipe a soap solution over all joints and suspect areas. A leak will cause bubbles to form.
|
|
|
How do the components in the exhaust system of a turbocharged engine allow for expansion and contraction due to heat, and at the same time prevent leakage?
|
Bellows and ball joints prevent leakage while allowing contraction and expansion.
|
|
|
What type of damage is most common in the exhaust system of a reciprocating engine?
|
Cracks caused by expansion and contraction.
|
|
|
Should a turbocharged engine be started with the waste gate open or closed?
|
Open, so as much exhaust as possible will bypass the turbine.
|
|
|
Why are thrust reversers not normally used when the airplane is moving below approximately 60 knots?
|
There is a danger of recirculating the exhaust gases, and of the engine ingesting foreign objects stirred up by the high-velocity gases.
|
|
|
What is a mechanical-blockage thrust reverser?
|
A thrust reverser that slides a pair of scoop-shaped doors aft and opens them so they block the rearward flow of gases and deflect the gases forward.
|
|
|
How does a cascade-type thrust reverser operate?
|
A portion of the fan cowl moves rearward, and a series of blocker doors deflect the fan discharge air through fan cascades that direct the discharge air forward. At the same time, blocker doors shut off the flow of gases from the core engine and deflect it through cascades that direct it forward.
|
|
|
How is ice removed from propeller blades?
|
An electrothermal deicing system is used. Electrical heating elements are embedded in rubber boots that are bonded to the leading edges of the blades. Low-voltage DC flows from the propeller deicer control through brushes and slip rings to the heating elements. The timer sends current to one propeller for about 90 seconds and then to the other for the next 90 seconds. This allows ice to form and then break loose and blow away.
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|
|
How is ice prevented from forming on propeller blades?
|
A chemical anti-icing system is used. A mixture of ethylene glycol & isopropyl alcohol is pumped into a slinger ring on the back of the propeller hub. From there centrifugal force slings it out along the blades. Ice cannot form on the resulting slick surface.
|
|
|
Should an adjustable-pitch propeller be in high pitch or in low pitch for takeoff?
|
In low pitch.
|
|
|
What is done to cause a Hydromatic propeller to feather?
|
High-pressure engine oil is directed into the propeller through the governor.
|
|
|
What is done to cause a McCauley propeller to feather?
|
Oil is allowed to drain out of the propeller.
|
|
|
Does centrifugal twisting moment on a propeller blade tend to move the blades toward high pitch or toward low pitch?
|
Toward low pitch.
|
|
|
Do the counterweights on a propeller tend to move the blades toward high pitch or toward low pitch?
|
Toward high pitch.
|
|
|
What is the difference between a controllable propeller & constant-speed propeller?
|
Basically, it is the control system. A controllable-pitch propeller uses a manually operated oil valve to control the pitch, & a constant-speed propeller uses a governor to control the valve.
|
|
|
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?
|
It should be in the low-pitch position.
|
|
|
What can be done to prevent the front cone from bottoming when installing a propeller on a splined shaft?
|
Install a spacer behind the rear cone to move the propeller forward on the shaft.
|
|
|
What is the purpose of the small holes that are drilled in the end of a wooden propeller?
|
These holes vent the inside of the propeller blade & allow moisture that collects in the wood to be released.
|
|
|
What is the function of the snap ring inside the hub of a propeller that is mounted on a tapered or splined shaft?
|
The snap ring allows the propeller to be pulled off of the shaft when the retaining nut is backed off.
|
|
|
What is adjusted inside the governor for a constant-speed propeller to change the speed at which the propeller is operating?
|
The compression of the speeder spring.
|
|
|
What is the function of the accumulator that is used with some McCauley feathering propellers?
|
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.
|
|
|
What is meant by the beta range of operation of a turboprop propeller?
|
This is the mode of ground operating, & it includes starting, taxiing, & ground reverse operation.
|
|
|
What is meant by the alpha range of operation of a turboprop propeller?
|
This is the in-flight mode of operation from takeoff to landing.
|
|
|
Is the flat surface of a propeller blade the face of the blade or the back of the blade?
|
It is the face of the blade.
|
|
|
What keeps a McCauley feathering propeller from feathering when the engine is shutdown on the ground?
|
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, & centrifugal force holds the blades unlatched so they can move to the feather position when oil pressure is taken out of the propeller.
|
|
|
What does the pilot do to change the RPM of an engine equipped with a constant-speed propeller when it is operating within the constant-speed range?
|
The pilot moves the propeller pitch control. This changes the compression of the speeder spring inside the governor which moves the pilot valve. The pilot valve directs oil into or out of the propeller to change the pitch of the blades. The change in pitch changes the air load on the propeller which changes the RPM.
|
|
|
What is meant by a slave engine with regard to propeller synchronization?
|
This is the engine in a multi-engine airplane whose RPMs follow those set on the master engine.
|
|
|
How can you determine that the electrically heated deicer boots on the propeller blades are working as they should?
|
Observe the loadmeter or ammeter to see if the proper current is flowing, and follow the sequence of boot heating by feeling with your hands to see which one is heating. The boots should all have a similar heat rise in the same length of time.
|
|
|
How are propellers on a twin-engine airplane synchronized?
|
The propeller governor of the master engine is set to the desired RPM. A signal from the master engine governor is sent to the control box which sends a signal to a stepping motor. The motor adjusts the propeller governor and fuel control of the slave engine causing it to maintain exactly the same RPM as the master engine.
|
|
|
Where do you find a list of the lubricants that are approved for use in constant-speed propeller?
|
In the maintenance manual for the propeller.
|
|
|
Who, or what facility, is authorized to perform major repairs to a propellers?
|
An FAA-approved propeller repair station that is authorized for the specific propeller.
|
|
|
What checks and maintenance is a mechanic with a powerplant rating allowed to make on a propeller?
|
Check the track of the propeller blades, remove small nicks and scratches from the blades, check the dynamic balance of a propeller, lubricate the propeller.
|
|
|
What adjustment can a mechanic with a powerplant rating make to a propeller governor?
|
Adjust the maximum RPM stop.
|
|
|
Why do some aircraft engines have a critical range of operation?
|
The engine and propeller combination have a resonant frequency problem in which excessive vibration can occur in a certain range of RPM. The tachometer for an aircraft with this limitation is marked with a red arc. When it is necessary to pass through this range it must be done as quickly as practical.
|
|
|
Why is a propeller indexed to the engine crankshaft?
|
The relationship between the propeller and the engine crankshaft is chosen to produce the minimum vibration.
|
|
|
What instrument is used to measure the blade angle of a propeller?
|
A universal propeller protractor.
|
|
|
Where is the propeller protractor placed to measure the propeller blade angle?
|
At a distance from the center of the propeller hub. This distance is specified in the propeller maintenance manual in terms of propeller blade stations.
|
|
|
What is the extent of the repairs a mechanic with a powerplant rating can make to a propeller?
|
Only minor repairs or minor alterations.
|
|
|
Where can examples of acceptable repairs to aluminum alloy propeller blades be found?
|
In AC 43.13-1B, Chapter 8, Section 4.
|
|
|
Is it permissible to cold straighten a damaged aluminum alloy propeller blade to facilitate shipping it to a repair station?
|
No, this could cause hidden damage that may render the blade nonrepairable.
|
|
|
What would be the classification of maintenance for shortening a propeller blade?
|
Major repair.
|
|
|
May transverse cracks in a metal propeller blade be repaired?
|
No, a transverse crack of any size is reason for rejecting the blade.
|
|
|
What damage to an aluminum alloy propeller blade can be repaired by a mechanic holding a powerplant rating?
|
Small roughness, nicks, and scratches in the leading edge of the blades.
|
|
|
How are small nicks removed from the leading edge of a propeller blade?
|
File them out with a fine file or stone, leaving a smooth contour.
|
|
|
Who is allowed to reduce the diameter of a type certificated propeller?
|
An FAA-certificated propeller repair station with approval for the particular propeller.
|
|
|
How can you determine that a surface scratch in an aluminum alloy propeller blade is not actually a crack?
|
Clean the damage out to a saucer-shaped depression and spray the area with a dye-penetrant liquid. Allow it time to seep into a crack if one is present, then wipe all of the liquid off the surface. Spray the area with a developer. If the damage is actually a crack, the developer will pull the penetrant out and it will form a visible line.
|
|
|
Where are most APUs located in modern jet transport aircraft?
|
In the tail cone of the fuselage.
|
|
|
What is the function of an APU?
|
An APU provides electric power and compressed air when the main engines are not operating.
|
|
|
What are two sources of compressed air from an APU?
|
From bleed air from the APU turbine compressor, or from a load compressor driven by a free turbine in the engine.
|
|
|
Where in maintenance information based on the ATA-100 system would you find instructions for inspecting and servicing the engine of an airborne APU?
|
In section 49 20.
|
|
|
What ensures that an APU will not be shut down while it is too hot?
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The APU fuel control incorporates an automatic-time delay feature that closes the bleed air valve to remove most of the load and reduce the APU temperature before it is shut down.
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How is most of the troubleshooting done for a modern APU?
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By the fault codes generated by the FADEC.
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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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The FADEC monitors the load and regulates the fuel going to the APU to prevent it from exceeding its safe limits.
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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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The maintenance manual for the APU.
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