Subject A - Reciprocating Engines

Question 1

How are conventional reciprocating engines classified?

Answer 1

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

Question 2

What are different type of piston rings?

Answer 2

they are compression rings, oil control rings and scraper rings

Question 3

What are the main causes of a cylinder having low compression?

Answer 3

broken piston rings, rings that are not seated properly, burnt valves, and poorly seated valves

Question 4

What is the purpose of oil control rings

Answer 4

the purpose is to control the thickness of the oil film on cylinder walls

Question 5

What may be the result of installing piston rings incorrectly?

Answer 5

excessive oil consumption

Question 6

What type of piston rods are commonly found in radial engines ?

Answer 6

A master and articulating rod assembly.

Question 7

What types of bearing are generally used in reciprocating engines?

Answer 7

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.

Question 8

What is the indication of a valve blow-by?

Answer 8

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.

Question 9

What is the purpose of using more than one spring for valve closing?

Answer 9

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.

Question 10

What is the purpose of valve overlap?

Answer 10

it promotes volumetric efficiency and lowers the cylinder operating temp

Question 11

Describe the inspection you would give valve springs during engine overhaul ?

Answer 11

you would first throughly clean it, than visually inspect it for evidence of overheating, check for broken ends and compression strength

Question 12

What is the purpose of using valves with sodium filled stems.?

Answer 12

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.

Question 13

what causes engine sudded stoppage

Answer 13

striking an object or engine seizure due to internal damage

Question 14

What type of inspection must be made after a sudden stoppage of an engine?

Answer 14

Most manufacturers require complete engine tear down and inspection

Question 15

What is the purpose of the crankshaft dynamic dampers used in aircraft engines?

Answer 15

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.

Question 16

how would you make a runout check on a crankshaft that is still installed on the engine

Answer 16

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.

Question 17

What is detonation ?

Answer 17

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

Question 18

What cylinder is engine to magneto timing based on?

Answer 18

the number one cylinder. Timing is usually set to 30 degrees before top dead center on the compression stroke

Question 19

What is engine sudden speed reduction ?

Answer 19

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.

Question 20

what can be learned about the condition of an engine by studying the result of a compression check .

Answer 20

You can check if the valves, piston rings, and pistons are adequately sealing the combustion chamber

Question 21

How can a cold cylinder be located on a double row radial engine?

Answer 21

you can use either an old tool called a magic wand, or a more modern infrared laser thermometer.

Question 22

what instrument can be used to check bore for out of roundness?

Answer 22

a cylinder bore can be checked with a dial indicator, telescopic gauge an outside micrometer, or inside micrometer

Question 23

what would a cold cylinder indicate?

Answer 23

That there has been no combustion inside the cylinder, normally due to no ignition or clogged fuel nozzle/

Question 24

where is a crack most likely to occur on a piston?

Answer 24

A crack is most likely to occur where the piston pin/wrist pin connects. The metal is thinnest at this location.

Question 25

What should be done to a nose wheel airplane before removing the engine?

Answer 25

support the tail of the airplane.