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42 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? |
horizontally opposed has smaller frontal area and is easier to streamline than a radial
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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 a piston. All of the other pistons are connected to the master rod with link rods.
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Of what material are most piston rings made
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Gray cast iron.
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What is the reason for using hydraulic valve lifters in an aircraft engine?
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keeps 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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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 and 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 on 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 and having the wire diameter and pitch of the springs different, valve float is minimized. The springs have different resonant frequencies, so at least one spring will always be exerting a force on the valve.
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Would excessive valve clearance cause the valves to open early or late?
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Excessive clearance will cause the valve to open late and close early.
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What is the purpose of valve overlap in a reciprocating engine?
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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, and 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 and sloshes back and forth inside the hollow valve. It picks up heat from the valve head and transfers it into the valve stem, so it can be transferred to the cylinder head through the valve guide.
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What causes detonation in an aircraft engine?
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Excessive heat and pressure in the engine cylinder causes the fuel–air mixture to reach its critical pressure and temperature. Under these conditions, the mixture explodes rather than burns. This explosion is called detonation.
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Why is a compression check important for determining the condition of an aircraft reciprocating engine?
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A compression check can determine the condition of the seal between the piston rings and the cylinder walls, and the seal between the intake and exhaust valves and their seats.
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What is meant by the compression ratio of a reciprocating engine?
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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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Piston in cylinder no.1 should be about 30 degrees before top center on the compression stroke
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What is the purpose of a cold cylinder check?
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Run the engine for a few min. then shut down. Now feel which cylinder is not hot and that is the cylinder not 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/manifold pressure, magneto drop, ignition switch safety check, prop pitch change, prop feathering, oil pressure, fuel pressure, and 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 a aircraft engine?
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Oil has drained past piston rings and filled combustion chamber. If the crankshaft is turned the cylinder will be locked and could cause damage to the piston, cylinder, connecting rod
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How is hydraulic lock removed from an engine?
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Remove a spark plug from the locked cylinder and drain all oil out and rotate the crankshaft. Replace spark plug
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What is a low–tension ignition system?
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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 that is mounted on each cylinder; here it boosted low voltage to high voltage and is directed to the spark plug with a very short high–tension lead wire.
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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 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, lube system, ignition system, fuel metering system, cooling and exhaust systems
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Where can you find the correct grade of fuel and amount of engine lube oil for an engine?
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TCDS for the aircraft
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What are the basic steps in troubleshooting an engine installation?
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1.) Know how the system should operates
2.) Observe how the system is operating 3.) Divide the system to find the trouble 4.) 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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Engine maintenance manual
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Where do you find instructions for removing an engine?
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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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Tail of the aircraft should 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 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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Correct plugs or caps. Never use tape
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What is meant by a Q.E.C. engine assembly?
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It is a quick engine change. The engine is on its mounts and all accessories are installed. A minimum time is required to change out the engine. All it needs are the controls, wiring, and fluid lines to be connected.
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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? |
Before the spark plugs are installed and after the oil tank or sup is filled, turn the engine over with the starter until oil runs out of the fitting to which the oil pressure gage connects |
