Subject A - Reciprocating Engines Flashcards
How are conventional reciprocating engines classified?
They are classified according to cylinder arrangement with respect to crankshaft such as in-line, v-type, radial and opposed, or according to method of cooling such as liquid or air cooled
What are different type of piston rings?
they are compression rings, oil control rings and scraper rings
What are the main causes of a cylinder having low compression?
broken piston rings, rings that are not seated properly, burnt valves, and poorly seated valves
What is the purpose of oil control rings
the purpose is to control the thickness of the oil film on cylinder walls
What may be the result of installing piston rings incorrectly?
excessive oil consumption
What type of piston rods are commonly found in radial engines ?
A master and articulating rod assembly.
What types of bearing are generally used in reciprocating engines?
they are roller, plain and ball bearings.
plain are used for crankshaft, camshafts and connecting rods
roller are used primarily as crankshaft main bearings.
ball bearings are used for supercharger impeller shaft bearings and crankshaft thrust bearings on large radial engines.
What is the indication of a valve blow-by?
it is indicated from a hissing or whistling sound upon pulling the propeller through by hand. It can be fixed by running a compression check to find the the faulty cylinder.
What is the purpose of using more than one spring for valve closing?
valve springs surge at certain speeds. To eliminate this problem two springs are placed inside the valve(one inside the other) and each spring will resonate at a different engine speed thus eliminating valve float.
What is the purpose of valve overlap?
it promotes volumetric efficiency and lowers the cylinder operating temp
Describe the inspection you would give valve springs during engine overhaul ?
you would first throughly clean it, than visually inspect it for evidence of overheating, check for broken ends and compression strength
What is the purpose of using valves with sodium filled stems.?
Sodium melts at a relative low temp and is a excellent heat conductor. as the valves move up and down the sodium is circulated carrying the heat from the valve head to the stem and than dissipating to the cylinder head.
what causes engine sudded stoppage
striking an object or engine seizure due to internal damage
What type of inspection must be made after a sudden stoppage of an engine?
Most manufacturers require complete engine tear down and inspection
What is the purpose of the crankshaft dynamic dampers used in aircraft engines?
to overcome forces that` cause deflection of the crankshaft and torsional vibration. Vibration is reduced by placing floating dampers in the counterweight assembly, particularly single-throw type crankshaft.
how would you make a runout check on a crankshaft that is still installed on the engine
first, you would remove the propeller from the crankshaft. Than attach. a dial indicator to the front of the crankcase. Adjust the position of the gauge needle so it is touching the shaft. then rotate the crankshaft and check for misalignment.
What is detonation ?
Fuels have critical limits of temperature and compression and beyond this limit, they will ignite spontaneously and burn with explosive violence. The instantaneous explosive burning of the last portion of the charge is called detonation
What cylinder is engine to magneto timing based on?
the number one cylinder. Timing is usually set to 30 degrees before top dead center on the compression stroke
What is engine sudden speed reduction ?
it occurs when the propeller strikes an object but continues to run. When this occurs a thorough external engine inspection should be carried out, including oil analysis. The propeller should also be checked with a run-out check.
what can be learned about the condition of an engine by studying the result of a compression check .
You can check if the valves, piston rings, and pistons are adequately sealing the combustion chamber
How can a cold cylinder be located on a double row radial engine?
you can use either an old tool called a magic wand, or a more modern infrared laser thermometer.
what instrument can be used to check bore for out of roundness?
a cylinder bore can be checked with a dial indicator, telescopic gauge an outside micrometer, or inside micrometer
what would a cold cylinder indicate?
That there has been no combustion inside the cylinder, normally due to no ignition or clogged fuel nozzle/
where is a crack most likely to occur on a piston?
A crack is most likely to occur where the piston pin/wrist pin connects. The metal is thinnest at this location.
What should be done to a nose wheel airplane before removing the engine?
support the tail of the airplane.
