AT 103 Second Exam Flashcards
What is the air scoop
opening of airplane facing into airstream that receives ram air
What does the air filter do
blocks dirt, abrasive particles, sand, and larger foreign materials
What does the alternate air valve do
allows air to flow to engine if filter is clogged
how does the carburetor heat valve work
valve closes main air duct and opens duct to heater muff (shroud around exhaust pipe) which heats air
what does the intake manifold arrangement on an opposed engine accomplish
cools oil
heats air fuel mixture to aid in vaporization of fuel
what does the exhaust system do
removes products of combustion from engine safely and effectively
!! What can poor exhaust maintenance lead to !!
nacelle fire
toxic gases entering into cockpit/cabin
damage to parts/structure of nacelle
poor engine performance
What makes gasoline good for aviation fuel
high heat value
ability to evaporate when exposed to air
ability to evaporate at ordinary temperature
high volatility
What are two solutions to cleaning lead deposits (chemical additives)
Bromine compounds
Tricresyl Phosphate TCP
100/130 Gas color
green
100 LL color
blue
80 Gas color
red
Jet gas color
Hay / Clear color
What color did fuel use to be / what color are the fuel guys in the navy
purple
Why is there dye in the fuel (officially)
to indicate the lead level in the fuel
How much lead is in 100 LL compared to 100 high lead
about half as much
What gas did the professor develop
UL94 (unleaded)
What two types of av gas on the market do not have lead and what is the difference between the two
UL94 and UL91
UL91 is Europe based
Why is gasoline bad for aircraft
regular gas is not designed for safety of flight
high vapor pressures in cars are not safe for aircraft applications
Why do we check for water in Avgas
large amounts will stop fuel flow and cause engine failure
at high altitude fuel cools below freezing - water turns to ice - ice blocks fuel
When did car gas and avgas separate?
1911
What is the main fuel system requirement?
Must be capable of delivering continuous flow of clean fuel under positive pressure from fuel tank to engine under all conditions
!! What are the requirements for gravity fed fuel systems!!
Must have tanks high enough to provide for 150% of the required fuel flow pressure (takeoff flow)
!! What are the requirements for a pump fuel system? !!
Pressure systems must be capable of 125% of the actual takeoff fuel flow of the engine
Why is there not a “both” on low wing aircraft
If one tank is on empty, you begin sucking in air and cannot get fuel into the engine
When are fuel pumps (boost pumps) required
When fuel tanks cannot be placed the required distance above carburetors or a greater pressure is required for operation
What produces the high voltage spark in the contacts of a spark plug
the air gap
What are the three major parts of a spark plug
electrodes
ceramic insulator
metal shell
What is a massive electrode type
common in aviation
named because of size
copper core
lead can build up in these (lead fowling)
What are fine wire types
electrodes made of platinum and iridium
ensure max conductivity and minimum wear
(more expensive)
Why is a wrong sized reach on a spark plug bad
Short: not getting the spark in there properly
Long: can total the engine, piston head will slam into it
A _____ spark plug goes on a hot engine
cold
If a hot spark plug is on a hot engine….
spark plug tip will overheat and cause pre-ignition
If a cold spark plug is installed on a cold engine…
spark plug tip will collect unburned carbon and the plugs will be fouled
Is a dropped spark plug usable?
nope. Trash it
Four principal parts of the induction system:
air scoop
air filter
alternate air valve
carburetor air heat
What is the difference in the construction of low and high tension magnetos
Low: wound with only one coil in the field of a permanent magnet
High: primary and secondary winding
Why is a base mounted magneto preferred
much more adjustable than the flange
What’s the most common kind of mageneto
high tension rotating single base mounted magneto
What happens when there is improper oxygen levels in the mixture
Too much: mixture will not burn
Too little: combustion will occur but will not be complete
Fuel level must be maintained slightly below the discharge nozzle outlet holes to:
provide correct fuel flow amount
prevent leakage of fuel from nozzle when engine is not running
!! what does the needle valve do !!
controls the amount of liquid fuel into the fuel chamber
What does the float chamber do
controls valve needle to control level of fuel
When float rises, needle closes and stops fuel flow
What are the three functions of the main metering system
proportion air fuel mixture
decrease pressure at discharge nozzle
control airflow at full throttle
What is the idling system for
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
carburetors play an important part in:
engine performance
engine mechanical life
general aircraft efficiency
What happens when Carb Heat is applied
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
!! where do the fuel and air mix in a carb system !!
in the throat of the Venturi
what does the throttle do
control how much air is going into the Venturi
what system is built into carb systems in the event a throttle is moved quickly and how does it work
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
What is the economizer system
a system that opens at high speeds to provide an enriched mixture to reduce burning temperatures and prevent detonation
Functions of the mixture control system:
prevent mixture from being too rich at high altitudes
economize on fuel during engine operation in low power range
What does the idle cutoff do
ensures all fuel within cylinders are used
stops engine - stops flow of fuel from discharge nozzle
Carb engine disadvantages
fuel flow disturbances in aircraft maneuvers may interfere with functions of float
during icing conditions, carb ice may accumulate
