Finale Flashcards
What must be marked on a recip engine fuel system?
The word “avgas” and minimum grade.
What are the requirements for a fuel system?
That it has the proper fuel, that it meets the demands of the regulations.
What must be marked on a turbine engine fuel system?
The words “jet fuel” and designation.
What must be marked on a pressure fueling system?
Maximum fueling and defueling pressures allowed.
What are desirable fuel characteristics?
High heat content, high boiling point , low freezing point, reasonable vapor pressure, free from acids. Free from contaminants, easy to filter, low viscosity.
What is the source of aviation gasolines?
Consists of hydrocarbons in crude petroleum.
What are the different gasoline series?
Paraffin series, cyclo paraffin series, aromatic series, olefin series, alkane series.
What are ratings based on?
Heat energy content, Reid vapor pressure, octane rating or grade.
What is Reid Vapor Pressure?
The amount of pressure required to prevent vapors from escaping a fuel.
The lower the octane rating, the ____ heat released.
Less, but it’s easier to ignite
What is the rating number given by?
The ratio of ISO-octane to heptane
80 octane
Red
100 octane
Green
100LL octane
Blue
115 octane
Purple
Is it ever acceptable to use a gasoline with one octane rating higher?
Yes, but it is never acceptable to use one lower.
Gasoline contaminants?
Sand, dirt, corrosion, surfactants, water, Microorganisms.
Different designations of turbine fuel?
jet A, Jet A-1, jet b.
How much does jet A weigh per gallon?
6.7lbs
How much does avgas weigh per gallon?
6lbs
What is volatility?
The measure of a liquids tendency to change into a gas.
What is vapor pressure?
The amount of pressure above a container of liquid required to keep it from vaporizing
What is detonation?
The spontaneous combustion of the unburned charge ahead of the flame fronts after ignition of the charge.
What is viscosity?
Internal resistance to flow
What is fuel metering?
Measuring the proper amount of fuel and mixing it with the proper amount of air.
What is latent heat?
Energy required to cause a change on a substances state.
what is density?
Weight per unit volume
What is Bernoulli’s principle?
The total energy in a fluid in motion remains constant
Air to fuel ratio?
Ratio of the weight of air to the weight of fuel.
12:1?
Max power
What is specific fuel consumption?
The amount of fuel burned per hour per bhp.
What is map?
Pressure in the induction manifold
What causes detonation?
Pressure too high
Temperature too high
Mixture too lean
What is preignition?
Igniting of the air fuel mixture before the appropriate time.
What causes preignition?
Improperly times magnetos
Too hot of a spark plug
Carbon hot spots
Types of fuel metering systems?
Primitive system, float type carburetor,
Pressure carb, fuel injection.
What is the purpose of a float carburetor?
To provide a place for the fuel to be atomized and mixed with the air, to allow the pilot to control the amount of air fuel to the engine, to provide a uniform mixture to the engine as airflow varies, to allow the pilot to adjust the mixture.
Systems of the float carb?
Main metering system, idle system, acceleration system, power enrichment.
What is the purpose of the throttle valve?
To regulate the amount of air fuel mixture entering the engine.
What does the Venturi do?
Creates a pressure differential in the carburetor to pull fuel into the airstream, and limits the airflow at full throttle.
What is the purpose of the fuel discharge nozzle?
Carries fuel and discharges it into the air stream.
What is the purpose of the main metering jet?
Meters the amount of fuel allowed into the main discharge nozzle.
What is the purpose of air bleed?
Helps proved an even fuel air ratio as airflow through the carburetor changes, and helps atomize the fuel by causing emulsions.
What is the purpose of the float and needle valve?
Controls the level of fuel in the carburetor
What is fuel metering force?
The force required to pull the fuel out of the main discharge nozzle.
What is the purpose of the idle system?
To allow more fuel flow into the engine at speeds so low that there is not enough pressure drop over the metering jet to pull enough fuel out. Usually under 1000 rpm
What is used to adjust the mixture during idle operations?
The idle mixture needle valve.
What is the purpose of the mixture control system?
To allow the pilot to make adjustments to the amount of fuel that flows into the main metering jet.
What are the two methods of mixture control?
Back suction, needle type.
How does the pilot set air fuel ratio in the back suction method?
By adjust the back pressure
How does the pilot set the air fuel ratio in the needle type mixture control?
By controlling the restriction
What is the purpose of the acceleration system?
To compensate for a momentary leaning of the mixture that is caused by the throttle being rapidly advanced.
What are the two methods of operation in an acceleration system?
Acceleration well, acceleration pump.
What is the purpose of the power enrichment system?
To enrich the mix at full throttle operation.
What does having an automatic power enrichment system allow for?
The pilot to use a leaner mixture for normal cruise
What are the two methods of power enrichment?
Needle type and air bleed
Describe the operation of the economizer?
The enrichment valve is spring loaded closed, when the throttle reaches full travel it lifts the valve off its seat
What three things are checked during run up?
Idle rpm, idle mixture and idle cut off
What things are replaced in a carb?2
Bushings, gaskets, float valve and seat, accelerator pump.
What is an injection system?
A fuel metering system which controls the airflow and fuel flow at the injector system body , but does not mix them until right at the cylinder
What are the advantages to an injector system?
More even distribution, not as prone to icing
What are two forms of injection systems?
Direct fuel injection, port injection.
