Powerplant Theory & Maintenance: Reciprocating Engines 🔊

Question 1

How are conventional reciprocating engines classified?

Answer 1

According to cylinder arrangement with respect to the crankshaft (in-line, v type, radial, and opposed) or according to the method of cooling (liquid cooled or air cooled).

Question 2

What are the different types of piston rings?

Answer 2

Compression, oil control, and scraper.

Question 3

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

Answer 3

Broken piston rings, rings that are not seating properly, burnt valves, and poorly seating valves.

Question 4

What is the purpose of the oil control rings?

Answer 4

To control the thickness of the oil film on the 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 type of bearings are in general use in reciprocating engines?

Answer 7

Plain, roller, and ball bearings.

Question 8

What is the indication of valve blow-by?

Answer 8

It is indicated by hissing or whistling when pulling the propeller through by hand.

Question 9

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

Answer 9

Valve springs will resonate (or surge) at certain engine speeds. If there is only one spring, the valve will float as the spring surges. When two are used, they will resonate at different speeds and eliminate valve floating.

Question 10

What is the purpose of valve overlap?

Answer 10

Better volumetric efficiency and lower cylinder operating temperature.

Question 11

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

Answer 11

They should be cleaned thoroughly then visually inspected for evidence of overheating, cracks, broken ends, and compression strength.

Question 12

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

Answer 12

They are hollow and partially filled with metallic sodium which is an excellent heat conductor. They dissipate heat.

Question 13

What causes engine sudden stoppage?

Answer 13

Striking an object or engine seizure due to internal damage.

Question 14

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

Answer 14

Most manufacturers require a complete engine tear down and inspection.

Question 15

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

Answer 15

Dampers are used to overcome forces which cause deflection of the crankshaft and torsional vibration.

Question 16

How would you make a “runout” check on a crankshaft that is still installed in the engine?

Answer 16

Remove the propeller from the crankshaft and attach a dial indicator gauge to the front of the crankcase. Adjust the position of the gauge needle so it touches the shaft. Rotate the crankshaft and check for misalignment.

Question 17

What is detonation?

Answer 17

Temperature and pressure within cylinders rise at a normal rate as fuel mixtures burn. All fuels have critical limits, beyond this limit they will ignite spontaneously and burn with explosive violence.

Question 18

What cylinder in engine to magneto timing based on?

Answer 18

The number one cylinder.

Question 19

What is engine sudden speed reduction?

Answer 19

This occurs when the propeller strikes an object but the engine continues to run.

Question 20

What can be learned about the condition of an engine by studying the results of a compression check?

Answer 20

You can determine 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

Infrared laser thermometer

Question 22

What instrument can be used to check bore for out of round?

Answer 22

Dial indicator, telescopic gauge and outside micrometer, or inside micrometer.

Question 23

What would a cold cylinder indicate?

Answer 23

There has been no combustion inside the cylinder, usually due to no ignition or a clogged fuel nozzle.

Question 24

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

Answer 24

Where the piston pin/wrist pin connects.

Question 25

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

Answer 25

Support the tail.

Question 26

What is the running valve clearance on engines equipped with hydraulic lifters?

Answer 26

Zero

Question 27

What lever is used to adjust the manifold pressure in a reciprocating engine?

Answer 27

Throttle lever.

Question 28

On an engine with a fixed pitch propeller, what is the relationship between manifold pressure and RPM?

Answer 28

As RPM increases, MAP increases.