Term
POWERPLANT RECIP ENGINES
What is the main advantage of a horizontally opposed engine over a radial engine for powering modern aircraft? |
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Definition
| The horizontally opposed engine has a much smaller frontal area and is easier to streamline than a radial engine. |
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Term
POWERPLANT RECIP ENGINES
How many throws are there in the crankshaft of a six-cylinder horizontally opposed engine? |
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Definition
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Term
POWERPLANT RECIP ENGINES
What kind of connecting rod arrangement is used in a radial engine? |
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Definition
| A master rod connects the single throw of the crankshaft with a piston. All of the other pistons are connected to the master rod with link rods. |
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Term
POWERPLANT RECIP ENGINES
Of what material are most piston rings made? |
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Definition
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Term
POWERPLANT RECIP ENGINES
What is the reason for using hydraulic valve lifters in an aircraft engine? |
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Definition
| 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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Term
POWERPLANT RECIP ENGINES
At what speed does the camshaft turn, relative to the crankshaft speed in a horizontally opposed engine? |
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Definition
| The camshaft turns at one half of the crankshaft speed. |
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Term
POWERPLANT RECIP ENGINES
What kind of main bearings are used in a horizontally opposed engine? |
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Definition
| Steel-backed, lead-alloy bearing inserts. |
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Term
POWERPLANT RECIP ENGINES
On what stroke is the piston of a reciprocating engine when the intake valve begins to open? |
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Definition
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Term
POWERPLANT RECIP ENGINES
On what stroke is the piston of a reciprocating engine when the exhaust valve begins to open? |
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Definition
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Term
POWERPLANT RECIP ENGINES
Why are both the hot and cold valve clearances given for most radial engines? |
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Definition
| Hot clearance is for timing purposes. When timing is set, valves are adjusted to their cold clearances. |
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Term
POWERPLANT RECIP ENGINES
What is meant by a cam-ground piston? |
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Definition
| Not a perfectly round piston, when it reaches operating temp it expands to become perfectly round. |
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Term
POWERPLANT RECIP ENGINES
Where is the piston in a reciprocating engine when the ignition spark occurs? |
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Definition
| About 30 degrees of crankshaft rotation before the piston reaches top center on the compression stroke. |
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Term
POWERPLANT RECIP ENGINES
What is meant by a full-floating wrist pin? |
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Definition
| A wrist pin that is not clamped in either the piston or the connecting rod. Full-floating wrist pins are kept from scoring the cylinder walls by soft metal plugs in their ends. |
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Term
POWERPLANT RECIP ENGINES
Why do most aircraft reciprocating engines use more than one spring on each valve? |
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Definition
| Eliminate valve spring surge, so at least one spring will always be pushing on the valve. |
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Term
POWERPLANT RECIP ENGINES
Would excessive valve clearance cause the valves to open early or late? |
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Definition
| Excessive clearance will cause the valve to open late and close early. |
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Term
POWERPLANT RECIP ENGINES
What is the purpose of valve overlap in a reciprocating engine? |
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Definition
| 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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Term
POWERPLANT RECIP ENGINES
What type of piston rings are installed on the pistons of an aircraft reciprocating engine? |
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Definition
| Compression rings, oil control rings, and oil wiper rings. |
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Term
POWERPLANT RECIP ENGINES
Why are some exhaust valves partially filled with metallic sodium? |
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Definition
| Salt melt ands and picks up heat transfers it to the cylinder head thru the valve guide. Lower operating temps |
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Term
POWERPLANT RECIP ENGINES
What causes detonation in an aircraft engine? |
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Definition
| When F/A mixture reaches critical pressure & temp & explodes instead of burning. |
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Term
POWERPLANT RECIP ENGINES
Why is a compression check important for determining the condition of an aircraft reciprocating engine? |
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Definition
| A compression check can determine the condition of the seal between the piston rings and the cylinder walls, and the seal between the intake and exhaust valves and their seats. |
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Term
POWERPLANT RECIP ENGINES
What is meant by the compression ratio of a reciprocating engine? |
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Definition
| The ratio of the volume of the cylinder with the piston at the bottom of its stroke to the volume with the piston at the top of its stroke. |
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