AT 103 Second Exam

Question 1

What is the air scoop

Answer 1

opening of airplane facing into airstream that receives ram air

Question 2

What does the air filter do

Answer 2

blocks dirt, abrasive particles, sand, and larger foreign materials

Question 3

What does the alternate air valve do

Answer 3

allows air to flow to engine if filter is clogged

Question 4

how does the carburetor heat valve work

Answer 4

valve closes main air duct and opens duct to heater muff (shroud around exhaust pipe) which heats air

Question 5

what does the intake manifold arrangement on an opposed engine accomplish

Answer 5

cools oil
heats air fuel mixture to aid in vaporization of fuel

Question 6

what does the exhaust system do

Answer 6

removes products of combustion from engine safely and effectively

Question 7

!! What can poor exhaust maintenance lead to !!

Answer 7

nacelle fire
toxic gases entering into cockpit/cabin
damage to parts/structure of nacelle
poor engine performance

Question 8

What makes gasoline good for aviation fuel

Answer 8

high heat value
ability to evaporate when exposed to air
ability to evaporate at ordinary temperature
high volatility

Question 9

What are two solutions to cleaning lead deposits (chemical additives)

Answer 9

Bromine compounds
Tricresyl Phosphate TCP

Question 10

100/130 Gas color

Answer 10

green

Question 11

100 LL color

Answer 11

blue

Question 12

80 Gas color

Answer 12

red

Question 13

Jet gas color

Answer 13

Hay / Clear color

Question 14

What color did fuel use to be / what color are the fuel guys in the navy

Answer 14

purple

Question 15

Why is there dye in the fuel (officially)

Answer 15

to indicate the lead level in the fuel

Question 16

How much lead is in 100 LL compared to 100 high lead

Answer 16

about half as much

Question 17

What gas did the professor develop

Answer 17

UL94 (unleaded)

Question 18

What two types of av gas on the market do not have lead and what is the difference between the two

Answer 18

UL94 and UL91

UL91 is Europe based

Question 19

Why is gasoline bad for aircraft

Answer 19

regular gas is not designed for safety of flight
high vapor pressures in cars are not safe for aircraft applications

Question 20

Why do we check for water in Avgas

Answer 20

large amounts will stop fuel flow and cause engine failure
at high altitude fuel cools below freezing - water turns to ice - ice blocks fuel

Question 21

When did car gas and avgas separate?

Answer 21

1911

Question 22

What is the main fuel system requirement?

Answer 22

Must be capable of delivering continuous flow of clean fuel under positive pressure from fuel tank to engine under all conditions

Question 23

!! What are the requirements for gravity fed fuel systems!!

Answer 23

Must have tanks high enough to provide for 150% of the required fuel flow pressure (takeoff flow)

Question 24

!! What are the requirements for a pump fuel system? !!

Answer 24

Pressure systems must be capable of 125% of the actual takeoff fuel flow of the engine

Question 25

Why is there not a “both” on low wing aircraft

Answer 25

If one tank is on empty, you begin sucking in air and cannot get fuel into the engine

Question 26

When are fuel pumps (boost pumps) required

Answer 26

When fuel tanks cannot be placed the required distance above carburetors or a greater pressure is required for operation

Question 27

What produces the high voltage spark in the contacts of a spark plug

Answer 27

the air gap

Question 28

What are the three major parts of a spark plug

Answer 28

electrodes
ceramic insulator
metal shell

Question 29

What is a massive electrode type

Answer 29

common in aviation
named because of size
copper core

lead can build up in these (lead fowling)

Question 30

What are fine wire types

Answer 30

electrodes made of platinum and iridium
ensure max conductivity and minimum wear
(more expensive)

Question 31

Why is a wrong sized reach on a spark plug bad

Answer 31

Short: not getting the spark in there properly
Long: can total the engine, piston head will slam into it

Question 32

A _____ spark plug goes on a hot engine

Answer 32

cold

Question 33

If a hot spark plug is on a hot engine….

Answer 33

spark plug tip will overheat and cause pre-ignition

Question 34

If a cold spark plug is installed on a cold engine…

Answer 34

spark plug tip will collect unburned carbon and the plugs will be fouled

Question 35

Is a dropped spark plug usable?

Answer 35

nope. Trash it

Question 36

Four principal parts of the induction system:

Answer 36

air scoop
air filter
alternate air valve
carburetor air heat

Question 37

What is the difference in the construction of low and high tension magnetos

Answer 37

Low: wound with only one coil in the field of a permanent magnet
High: primary and secondary winding

Question 37

Why is a base mounted magneto preferred

Answer 37

much more adjustable than the flange

Question 38

What’s the most common kind of mageneto

Answer 38

high tension rotating single base mounted magneto

Question 39

What happens when there is improper oxygen levels in the mixture

Answer 39

Too much: mixture will not burn
Too little: combustion will occur but will not be complete

Question 40

Fuel level must be maintained slightly below the discharge nozzle outlet holes to:

Answer 40

provide correct fuel flow amount
prevent leakage of fuel from nozzle when engine is not running

Question 41

!! what does the needle valve do !!

Answer 41

controls the amount of liquid fuel into the fuel chamber

Question 42

What does the float chamber do

Answer 42

controls valve needle to control level of fuel

When float rises, needle closes and stops fuel flow

Question 43

What are the three functions of the main metering system

Answer 43

proportion air fuel mixture
decrease pressure at discharge nozzle
control airflow at full throttle

Question 44

What is the idling system for

Answer 44

at idle, the airflow through the Venturi is too low for sufficient fuel discharge, so there is a system with an outlet at the end of the throttle valve

delivers fuel only when throttle valve is nearly closed

Question 45

carburetors play an important part in:

Answer 45

engine performance
engine mechanical life
general aircraft efficiency

Question 46

What happens when Carb Heat is applied

Answer 46

RPMs will drop more and engine may sputter

leave carbheat on for 20-30 seconds and give time for the rpm to climb back up

Question 47

!! where do the fuel and air mix in a carb system !!

Answer 47

in the throat of the Venturi

Question 48

what does the throttle do

Answer 48

control how much air is going into the Venturi

Question 49

what system is built into carb systems in the event a throttle is moved quickly and how does it work

Answer 49

Accelerating pump

gives “extra boost” of fuel due to a pump cylinder that fills with fuel when the throttle is closed - piston is forced down with a fast throttle which pushes fuel flow into the main fuel passage

Question 50

What is the economizer system

Answer 50

a system that opens at high speeds to provide an enriched mixture to reduce burning temperatures and prevent detonation

Question 51

Functions of the mixture control system:

Answer 51

prevent mixture from being too rich at high altitudes
economize on fuel during engine operation in low power range

Question 52

What does the idle cutoff do

Answer 52

ensures all fuel within cylinders are used
stops engine - stops flow of fuel from discharge nozzle

Question 53

Carb engine disadvantages

Answer 53

fuel flow disturbances in aircraft maneuvers may interfere with functions of float

during icing conditions, carb ice may accumulate