P Piston Engine Power, Efficiency and Control

Question 1

What 2 factors dictate the power of an engine?

Answer 1

• The mass of charge

- The numbers of times per second that the charge is put into the cylinders

Question 2

What is the power equation?

Answer 2

Power = (force x distance)/time

Question 3

What does power = plane mean?

Answer 3

Power = Pressure x Length of stroke x Area x Number of cylinders x rpm/2

Question 4

What is the total volume of a cylinder?

Answer 4

Volume of cylinder at BDC

Question 5

What is the clearance volume of a cylinder?

Answer 5

Volume of the cylinder at TDC

Question 6

What is the swept volume?

Answer 6

Volume of the cylinder between TDC and BDC

Total volume - Clearance volume = Swept volume

Question 7

What is the compression ratio?

Answer 7

A relationship between total volume and clearance volume

Question 8

What is mechanical efficiency?

Answer 8

Measures the effectiveness of an engine turning the input power to output power. Taking into account friction and vibration most engines are 90-95% mechanically efficient. When factoring in thermal efficiency this falls to around 80%

Question 9

What is thermal efficiency?

Answer 9

Defines how effective the engine is at converting fuel energy into producing mechanical work. All combustion engines are heat engines and heat is always lost, meaning thermal efficiency is 25-35% for a standard engine

Question 10

What is the relationship between thermal efficiency and compression ratio?

Answer 10

As thermal efficiency increases, the compression ratio increases

Question 11

What does the RPM gauge do?

Answer 11

Measures crankshaft RPM

Question 12

What dos the manifold pressure gauge do?

Answer 12

Measures manifold pressure in InHg

Question 13

What does the boost pressure gauge do?

Answer 13

Measures manifold pressure in PSI relative to sea level pressure

Question 14

What does the oil pressure gauge do?

Answer 14

Measures the oil pressure just after the filter

Question 15

What does the oil temperature gauge do?

Answer 15

Measures the oil temperature in the oil return line

Question 16

What does the CHT (cylinder head temperature) gauge do?

Answer 16

Measures the temperature of the hottest cylinder

Question 17

What does the EGT (exhaust gas temperature) gauge do?

Answer 17

Measures the temperature in the exhaust gas stream

Question 18

What does the fuel pressure gauge do?

Answer 18

Measures fuel pump output pressure

Question 19

What does the induction temperature gauge do?

Answer 19

Measures the temperature are the carburettor inlet

Question 20

How to engine controls differ?

Answer 20

By colour and shape

Question 21

What colour and shape is the throttle?

Answer 21

On a panel: round
On a quadrant: cylindrical
Colour: black

Question 22

What colour and shape is the propeller control?

Answer 22

On a panel: round with large grooves
On a quadrant: crown shape with large grooves
Colour: blue

Question 23

What colour and shape is the mixture control?

Answer 23

On a panel: round with small protrusions
On a quadrant: round with small protrusions
Colour: red

Question 24

Why do we check the fuel pre-start?

Answer 24

Check for water contamination

Question 25

Why do we pull through inverted or radial engines before start?

Answer 25

To prevent hydraulicing

Question 26

3 starting procedure precautions

Answer 26

1. Shut down if the start warning light remains on for 30 seconds or more after start 2. Positive engine oil pressure should be indicated within 30 seconds of engine start 3. In very cold conditions increased oil viscosity may make starting more difficult

Question 27

Which 3 after-start checks do we consider?

Answer 27

1. Individually check magnetos to ensure ignition circuits are functional 2. Carburettor heat should be off whilst the engine is running on the ground 3. Prolonged idling should be avoided to reduce risk of spark plug fouling

Question 28

What are the 3 procedures for changing power settings?

Answer 28

1. Slow, smooth throttle movement to reduce engine stress 2. Reduce to max continuous as soon as safely possible after take off 3. Constant speed propellers (rev up, throttle back) (Rev leads throttle when increase, throttle leads revs when decrease power)

Question 29

2 shut down procedures

Answer 29

1. Allow engine to cool at low rpm before shut down | 2. Do a dead cut check to confirm both ignition circuits are properly earthed

Question 30

What does black smoke indicate?

Answer 30

Excessively rich mixture

Question 31

What does blue smoke indicate?

Answer 31

Burning oil - worn or broken piston rings

Question 32

What does a high CHT indicate?

Answer 32

Cowl flaps may be closed

Question 33

What could cause excessive CHT?

Answer 33

Excessively lean mixture

Question 34

What can cause rough running?

Answer 34

- Carburettor icing - Moisture in the ignition circuit - Problems with fuel delivery - Uneven compression in the cylinder