Jeppesen Oral- Chapter 1 (Reciprocating Engine)

Answer 1

They reduce engine vibration

Answer 2

Plain, ball and roller bearings

Answer 3

No. Radial engines use master and articulating rod assemblies

Answer 4

Oil control, compression and oil scraper

Answer 5

Compression ring gaps should be staggered so that they do not align to prevent excessive blow-by

Answer 6

Excessive oil consumption

Answer 7

They regulate the thickness of the oil film on the cylinder walls

Answer 8

Two or more springs are used on each valve

Answer 9

Zero

Answer 10

It allows better volumetric efficiency and lowers cylinder operating temperatures

Question 11

What is the main advantage of a horizontally opposed engine over a radial engine for powering modern aircraft?

Answer 11

The horizontally opposed engine has a much smaller frontal area and is easier to streamline than a radial engine.

Question 12

How many throws are there in the crankshaft of a six-cylinder horizontally opposed engine?

Answer 12

six

Question 13

Of what material are most piston rings made?

Answer 13

Gray cast iron

Question 14

What is the reason for using hydraulic valve lifters in an aircraft engine?

Answer 14

Hydraulic valve lifters keep all of the clearance out of the valve operating mechanism. This decreases the wear of the valve train components.

Question 15

At what speed does the camshaft turn, relative to the crankshaft speed in a horizontally opposed engine?

Answer 15

The camshaft turns at one half of the crankshaft speed.

Question 16

What kind of main bearings are used in a horizontally opposed engine?

Answer 16

Steel-backed, lead alloy bearing inserts.

Question 17

On what stroke is the piston of a reciprocating engine when the intake valve begins to open?

Answer 17

On the exhaust stroke.

Question 18

On what stroke is the piston of a reciprocating engine when the exhaust valve begins to open?

Answer 18

On the power stroke.

Question 19

Why are both the hot and cold valve clearances given for most radial engines?

Answer 19

The hot clearance is given for timing purposes. The timing is adjusted with the valves in cylinder number one, set with the hot clearance. When the timing is set, all of the valves are adjusted to their cold clearance.

Question 20

What is meant by a cam-ground piston?

Answer 20

A piston that is not perfectly round. Its dimension parallel with the wrist pin is several thousandths of an inch less than its dimension perpendicular to the wrist pin. When the piston reaches operating temperature, the metal in the piston boss expands enough that the piston becomes perfectly round.

Question 21

Where is the piston in a reciprocating engine when the ignition spark occurs?

Answer 21

About 30 degrees of crankshaft rotation before the piston reaches top center on the compression stroke.

Question 22

What is meant by a full-floating wrist pin?

Answer 22

A wrist pin that is not clamped in either the piston or the connecting rod. Full-floating wrist pins are kept from scoring the cylinder walls by soft metal plugs in their ends.

Question 23

Why do most aircraft reciprocating engines use more than one spring on each valve?

Answer 23

By using more than one spring and having the wire diameter and pitch of the springs different, valve float is minimized. The springs have different resonant frequencies,so at least one spring will always be exerting a force on the valve.

Question 24

Would excessive valve clearance cause the valves to open early or late?

Answer 24

Excessive clearance will cause the valve to open late and close early.

Question 25

Why are some exhaust valves partially filled with metallic sodium?

Answer 25

The metallic sodium melts at engine operating temperature and sloshes back and forth inside the hollow valve. It picks up heat from the valve head and transfers it into the valve stem, so it can be transferred to the cylinder head through the valve guide.

Question 26

What causes detonation in an aircraft engine?

Answer 26

Excessive heat and pressure in the engine cylinder causes the fuel-air mixture to reach its critical pressure and temperature. Under these conditions, the mixture explodes rather than burns. This explosion is called detonation.

Question 27

What is meant by the compression ratio of a reciprocating engine?

Answer 27

The ratio of the volume of the cylinder with the piston at the bottom of its stroke to the volume with the piston at the top of its stroke.