AGK

Question 1

What are the four stokes of the internal combustion engine?

Answer 1

1 Intake
2 Compression
3 Power
4 Exhaust

Question 2

What is valve lead?

Answer 2

When the exhaust valve opens before bottom dead centre. (opens early)

Question 3

What is valve lag?

Answer 3

Inlet valve closes after BDC

Question 4

What is the firing interval for a 4 stroke engine?

Answer 4

720 divided by number of cylinders

Question 5

Define volumetric efficiency?

What reduces VE?

Answer 5

The measure of success achieved drawing gas molecules into the cylinders

Hot days and dry altitudes
Reducing throttle from normal setting
RPM higher than normal setting

Question 6

Why does detonation occur and how can it be managed?

Answer 6

Occurs due to increased temp and pressure of fuel to air mixture that causes instantaneous combustion burning when ignited. Caused by high power with inadequate cooling, high power with lean mixture, high manifold pressure wiht low rpm & use of incorrect fuel.

Cool engine by full rich mixture, reduce power and increase airspeed

Question 7

What is pre ignition?

Answer 7

A hot spot/carbon deposit igniting charge and burn begins before spark plugs fire

Same solution as detonation

Question 8

Compression ratio?

Answer 8

Clearance volume divided by swept volume divided by swept volume

Question 9

What is the oil system responsible for?

Answer 9

Lubricate
Cools
Cleans
Seals
Protects

Question 10

What is viscosity?

Answer 10

The oils resistance to flow.

High viscosity - thick and cold
Low viscosity - warm and runny

Question 11

What is valve overlap?

Answer 11

TDC when inlet valve is opening & exhaust valve is closing

Question 12

What is ashless dispersant oil and why is it used?

Answer 12

Synthetic oil which contains additives

• Prevents sludge bulid up
• Reduces engine wear
• Better compression seal around piston rings
• Reduces oil consumption

Question 13

Straight Mineral Oil?

Answer 13

Contains no additives

• Used for run in periods on new engines
• Used to help piston rings, cylinder walls to wear
• Bedding in process (forms seal to prevent gas from leaking)

Question 14

Oil Quantity characteristics

Answer 14

• less oil the temperature will rise
• fluctuations in oil pressure = low oil
• large or rapid loss may not be noticeable on temp gauge

Question 15

What factors affect engine power output?

Answer 15

Manifold pressure

RPM

Question 16

Semi Rigid rotor system?

Answer 16

Two main blades
-Feather
-Teater
-Flap
(underslung hub reduces mast bumping)

Question 17

Fully articulated System

Answer 17

-Usually more than two blades
-Feathers
-Flaps
-leads (Hunts)
-Drags(lags)
(Prone to ground resonance)

Question 18

Vertical Vibration?

Horizontal Imbalance?

Tail Rotor Imbalance

Answer 18

Blades out of track (Up & Down)Bounce in seat

Stick shake (Cyclic shake)

Felt through pedals (high frequency)

Question 19

What is the difference between a de-icing system and a anti-icing system?

Answer 19

De-icing system is in flight or after it has formed ie inflatable

Anti icing - preventing ice from forming, covering blades etc

Question 20

Define octane rating and how is it increased?

Answer 20

Fuels resistance to detonation
(Higher the rating higher resistance)
Adding lead and Bromine increases resistance

Question 21

Name the four fuels and their colours

Answer 21

100LL - Blue (common piston fuel)
100/130 - Green (Rare piston fuel)
Mogas (80/87) - Red/Purple
AVTUR (Turbine) - Straw colour

Question 22

What does the Stoichiometric mixture measure?

Answer 22

Ratio of fuel to air