Powerplant Theory & Maintenance: Reciprocating Engines 🔊 Flashcards
How are conventional reciprocating engines classified?
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).
What are the different types of piston rings?
Compression, oil control, and scraper.
What are the main causes of a cylinder having low compression?
Broken piston rings, rings that are not seating properly, burnt valves, and poorly seating valves.
What is the purpose of the oil control rings?
To control the thickness of the oil film on the 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 type of bearings are in general use in reciprocating engines?
Plain, roller, and ball bearings.
What is the indication of valve blow-by?
It is indicated by hissing or whistling when pulling the propeller through by hand.
What is the purpose of using more than one spring for valve closing?
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.
What is the purpose of valve overlap?
Better volumetric efficiency and lower cylinder operating temperature.
Describe the inspection you would give the valve springs during engine overhaul.
They should be cleaned thoroughly then visually inspected for evidence of overheating, cracks, broken ends, and compression strength.
What is the purpose of using valves with sodium filled stems?
They are hollow and partially filled with metallic sodium which is an excellent heat conductor. They dissipate heat.
What causes engine sudden stoppage?
Striking an object or engine seizure due to internal damage.
What type of inspection must be made after sudden stoppage of an engine?
Most manufacturers require a complete engine tear down and inspection.
What is the purpose of the crankshaft dynamic dampers used in aircraft engines?
Dampers are used to overcome forces which cause deflection of the crankshaft and torsional vibration.
How would you make a “runout” check on a crankshaft that is still installed in the engine?
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.
What is detonation?
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.
What cylinder in engine to magneto timing based on?
The number one cylinder.
What is engine sudden speed reduction?
This occurs when the propeller strikes an object but the engine continues to run.
What can be learned about the condition of an engine by studying the results of a compression check?
You can determine 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?
Infrared laser thermometer
What instrument can be used to check bore for out of round?
Dial indicator, telescopic gauge and outside micrometer, or inside micrometer.
What would a cold cylinder indicate?
There has been no combustion inside the cylinder, usually due to no ignition or a clogged fuel nozzle.
Where is a crack most likely to occur on a piston?
Where the piston pin/wrist pin connects.
What should be done to a nose wheel airplane before removing the engine?
Support the tail.
What is the running valve clearance on engines equipped with hydraulic lifters?
Zero
What lever is used to adjust the manifold pressure in a reciprocating engine?
Throttle lever.
On an engine with a fixed pitch propeller, what is the relationship between manifold pressure and RPM?
As RPM increases, MAP increases.
