Chapter 7 - Engine Fuel Systems section A Flashcards
What are the two types of fuel systems?
Gravity-feed
Pressure-feed
What are the typical components of a gravity-feed fuel system?
Two fuel tanks
fuel selector valve
strainer
primer
carburetor
What item is required for pressure-feed fuel system?
Auxiliary Pump
Where can the engine fuel shutoff vlave be NOT located at?
On the engine side of any firewall
The fuel flow rate of a pump-feed fuel system for each reciprocating engine must be at what percentage of the takeoff required fuel flow?
125%
What expansion space must each fuel tank have for unfilled fuel?
2%
The fuel filler opening of an reciprocating and turbine aircraft fuel tank must be mark as what?
Reciprocating aircraft -
- “AVGAS”
- minimum grade of fuel
Turbine aircraft -
- “Jet Fuel”,
- the permissible fuel designation
- maximum permissible fueling and defueling pressures
What is the purpose of an auxiliary fuel pump?
To maintain positve fuel pressure on the inlet side of the engine-driven fuel pump. It is also used to transfer fuel between tanks to redistribute fuel weight and maintain stability.
Define Volatility.
The measure of Avgas’ ability to change from a liquid into a vapor.
Define Reid Vapor Pressure.
The amount of pressure needed to prevent Avgas from changing from a liquid to a vapor.
What is the vapor pressure of 100LL fuel?
7 psi
What is the ideal ratio for the fuel/air mixture?
12(air):1(fuel)
Anything more than 12, mixture becomes lean, anything less mixture becomes rich
What is the proper way to adjust for mixture?
Monitor the RPM guage then idle cut off the mixture. The should be a rise of 10-25 RPM before engine dies. If there was anything more, the mixture was too rich. If there was anything less, the mixture was too lean.
What is Fractional Distillation?
A seperation of mixture into it’s component parts by heating or boiling them to their boiling points at which one or more compound or fraction will vaporize, then cooling the rest to retrieve a different chemical.
What is added to AVGAS to eliminate or reduce detonation? What does this substance do?
Tetraethyl Lead
It is able to retain heat energy for long periods of time without knocking
If fuel changes it state prior to reaching the fuel control unit, what is it called?
Vapor lock
Give three reasons why vapor lock might occur?
routing the fuel line too close to a heat source
Excessive fuel spirals
no fuel
Low fuel pressure
What is unusable fuel?
fuel trapped in the system that can never be used by the f.c.u
Define Viscosity.
A substance internal resistance to flow. (It’s thickness)
Name the different ratings of fuel.
80/87 - Red
90/93 - Clear
100LL - Blue
100/130 - Green
115/130 - Purple
The meaning: Hectane (lean)/Iso Octane (rich)
What formula is used to calculate horsepower?
PLANK
P = Internal Pressure
L = Length of stroke
A = Area of cylinders
N = number of power strokes
K = number of cylinders
ANY CHANGES affects H.P
Avgas ratings higher than 100 is it’s what?
Performance
The heat value of fuel is measured in what?
British Thermal Unit
(BTU)
How much does water weigh?
8 pounds per gallon
What is edge sealer used for?
Sealing the edges of placards
What fuel flow rate is required for gravity feed systems?
150%
What is a micron rated fuel filter?
A filter that only allows particles the size of a micron to filter through.
What does it mean when a Delta-P indicator is protruding?
The filter is blocked
What is the size of a micron?
One millionth of a meter
.000039
Name the three parts of a filter
Housing
Element
Head
What type of valve can be found in the head of a filter?
Relief Valve
Define Vapor Lock.
When fuel changes its state from liquid to gas prior to reaching the fuel control unit and blocks the fuel lines.
What are the advantages of Kerosene
Its has a high heat content and provides lubrication
What is the foundation of all these different types of fuels?
They are all hydrocarbon based.
What system is required for an aircraft that has a designated landing weight?
Jettison
Name a characteristic of a constant displacemnt pump?
It is able to move the same volume of fuel regardless of speed.
Supplies more fluid than the system requires
What is the weight of AVGAS vs Kerosene?
AVGAS = 6 pounds per gallon
Kerosene = 6.5 pounds per gallon
An altitude compensating pump relief valve is vented to the _____ to maintain sea level pressure.
Upper deck pressure
How to you lower pressure if the fuel pressure is too high?
Relief valve
What can be used to prevent vapor lock?
Putting a fire sleeve over the fuel lines
What is the purpose of a lay line?
It provides a visual reference to identify whether a hose is twisted.
Name three requirements for the Jettison System?
It must be free from fire hazards.
It must not alter or effect the flight.
It must be able to dumb fuel and save enough for the aircraft to climb from sea level to 10,000 ft at full power.
What is stoichiometric?
A air/fuel ratio of 15:1
With a stoiciometric mixture, all available fuel and oxygen are used in combustion, releasing the maximum amount of heat from the fuel.
What antimicrobial agent is used to kill microbes, fungi, and bacteria?
What are two benifits of PRIST?
Biobore
PRIST
Two benifits of PRIST: Used for Anti-icing and its a antimicrobial agent.
Define backfiring and afterfiring.
Backfiring - describes the fuel/air mixture burning in the induction system with a lean fuel/air mixture
Afterfiring - is the burning of fuel in the exhaust system because of a rich fuel/air mixture.
What is the process of fuel’s energy transformation?
Chemical -> Heat -> Mechanical
What fuel nozzle is required for turbine engines?
Duplex
What would happen if Kerosene was added to a recipricating engine?
Nothing because the compression ratio of a normal recipricatng engine is not enough to compress the fuel.
What is the purpose of a primer and what are the two types?
Primer - ejects raw fuel into the manifold upstream of the intake valve. It is normally used for cold weather of the first flight of the day.
Two Types:
- Plunger - This is a manual type and brings fuel into the cabin
- Electrical - This is remotely located and draws fuel from the main fuel manifold.
What are the two classifications of heat exchangers?
Liquid to Liquid
Liquid to Air
What are two functions of a P&D Valve?
Pressurizes the fuel manifold
Delivers fuel to the nozzle
What is the final component of the fuel system?
The nozzle
List two functions of a restrictor.
If the diaphram becomes broken, it will limit the fuel sucked out.
If the diaphram becomes broken, it will limit the air sucked in causing pump cavitation
What are the two classifications of pumps
Constant
Variable
What does “Delta P” mean on a filter?
It indicates if there is a change in pressure
Why would some filters be ‘pleated’?
To get more surface area for cleaning
What two places does the relief valve return fuel?
Back to fuel reservior
Inlet side of the pump
Which jet fuel is most common?
What is it’s blend?
Jet B (JP-4) “Raw Cut”
30% Kerosene
70% Gasoline
What is FADEC
Full Authority Digital Engine Control
Where is the fuel nozzle located at?
In the diffuser or inlet of combustion chamber
2 Types of nozzles
Simplex
Duplex
Name the parts of a constant displacement pump
Gears
Vanes
Geo Rotors
Diaphram engine pump is driven by what?
Camshaft
Fuel screens can be found where?
Name four places
Fuel tank outlet
Boot pump inlet
Inline
Inlet of F.C.U
