Reciprocating Engines Flashcards
Which statement is true regarding bearings used in high-powered reciprocating aircraft engines?
There is less rolling friction when ball bearings are used than when roller bearings are employed.
A condition that can occur in radial engines but is unlikely to occur in horizontally opposed engines is what?
Hydraulic lock.
Which condition would be the least likely to be caused by failed or failing engine bearings?
Low oil temperatures.
What is the principal advantage of using propeller reduction gears?
To enable the engine RPM to be increased with an accompanying increase in power and allow the propeller to remain at a lower, more efficient RPM.
Which of the following will decrease volumetric efficiency in a reciprocating engine?
Improper valve timing, sharp bends in the induction system, and high carburetor air temperatures.
Which of the following is a characteristic of a thrust bearing used in most radial engines?
Deep-groove ball.
Which bearing is least likely to be a roller or ball bearing?
Master rod bearing (radial engine).
The operating temperature valve clearance of a radial engine as compared to cold valve clearance is what?
greater.
A nine-cylinder engine with a bore of 5.5 inches and a stroke of 6 inches will have a total piston displacement of what?
1,283 cubic inches.
The five events of a four-stroke cycle engine in the order of their occurrence are what?
intake, compression, ignition, power, and exhaust.
The primary concern in establishing the firing order for an opposed engine is to what?
provide for balance and eliminate vibration to the greatest extent possible.
If fuel-air ratio is proper and ignition timing is correct, the combustion process should be completed…
Just after top center at the beginning of the power stroke.
Grinding the valves of a reciprocating engine to a feather edge is likely to result in what?
preignition and burned valves.
Which statement is correct regarding engine crankshafts?
Moveable counterweights serve to reduce torsional vibrations in an aircraft reciprocating engine.
On which strokes are both valves on a four-stroke cycle reciprocating aircraft engine open?
Exhaust and intake.
Which type of bearings are generally used for connecting rods and cam shafts?
Plain
The actual power delivered to the propeller of an aircraft engine is called what?
brake horsepower.
Cam-ground pistons are installed in some aircraft engines to what?
provide a better fit at operating temperatures.
Using the following information, determine how many degrees the crankshaft will rotate with both the intake and exhaust valves seated.
Intake opens at 15 degrees BTDC
Exhaust opens 70 degrees BBDC
Intake closes 45 degrees ABDC
Exhaust closes 10 degrees ATDC
245 degrees.
Some aircraft engine manufacturers equip their product with chocked or taper-ground cylinders in order to what?
provide a straight cylinder bore at operating temperatures.
An aircraft reciprocating engine using hydraulic valve lifters is observed to have no clearance in its valve operating mechanism after the minimum inlet oil and cylinder head temperatures for takeoff have been reached. When can this condition be expected?
During normal operation.
What tool is generally used to measure the crankshaft rotation in degrees?
Timing disk
If an engine with a stroke of 6 inches is operated at 2,000 RPM, the piston movement within the cylinder will be what?
at maximum velocity 90 degrees after TDC.
If the intake valve is opened too early in the cycle of operation of a four-stroke cycle engine, it may result in what?
backfiring into the induction system.
Some cylinders barrels are hardened by what?
nitriding.
Which statement is correct regarding a four-stroke cycle aircraft engine?
The intake valve closes on the compression stroke.
On which part of the cylinder walls of a normally operating engine will the greatest amount of wear occur?
Near the top of the cylinder.
During overhaul, reciprocating engine exhaust valves are checked for stretch…
with a contour or radius gauge.
When is the fuel/air mixture ignited in a conventional reciprocating engine?
Shortly before the piston reaches the top of the compression stroke.
Ignition occurs at 28 degrees BTDC on a certain four-stroke cycle engine, and the intake valve opens at 15 degrees BTDC. How many degrees of crankshaft travel after ignition does the intake valve open? (Consider one cylinder only.)
373 degrees.
What is the purpose of the safety circlet installed on some valve stems?
To prevent valves from falling into the combustion chamber.
Valve overlap is defined as the number of degrees of crankshaft travel…
during which both valves are off their seats.
The valve clearance of an engine using hydraulic lifters, when the lifters are completely flat, or empty, should not exceed what?
a specified amount above zero.
If the exhaust valve of a four-stroke cycle engine is closed and the intake valve is just closed, the piston is on the what?
compression stroke.
Which of the following are factors in establishing the maximum compression ratio limitations of an aircraft engine?
Detonation characteristics of the fuel, design limitations of the engine, and the degree of supercharging.
Full-floating piston pins are those which allow motion between the pin and what?
both the piston and the small end of the connecting rod.
The primary purpose in setting proper valve timing and overlaps is to what?
obtain the best volumetric efficiency and lower cylinder operating temperatures.
If the hot clearance is used to set the valves when the engine is cold, what will occur during operation of the engine?
The valves will open late and close early.
What is the purpose of installing two or more springs on each valve in an aircraft engine?
To eliminate valve spring vibration or surging.
During overhaul, the disassembled parts of an engine are usually degreased with some form of mineral spirits solvent rather than water-mixed degreasers primarily because what?
water-mixed degreaser residues may cause engine oil contamination in the overhauled engine.
Why does the smoothness of operation of an engine increase with a greater number of cylinders?
The power impulses are spaced closer together.
Compression ratio is the ratio between the what?
Cylinder volume with piston at bottom dead center and at top dead center.
If the crankshaft runout readings on the dial indicator are plus .002 inch and minus .003 inch, the runout is what?
.005 inch.