Fuel Systems Introduction Flashcards
Why does aviation fuel need to be of a higher quality than fuels used in less critical applications?
1) Due to significance in variation in environmental conditions
2) The increased level of performance required.
What are three ways fuel is measured?
1) Fuel Quantity: measured in liters or gallons. 1 gal = 3.79 litres.
2) Fuel mass: measured in kilograms (kg), tonnes or pounds (lb)
3) Fuel flow: measured in kg, lb or USG per hour.
What does the density of a material refer to?
Mass per unit volume
What is the specific gravity (SG) of a substance?
The ratio of a substance’s density in comparison to the density of water.
What is the freezing point of a substance?
Point at which fuel freezes, which can create blockages in the fuel system, severely impacting performance.
What is Fuel System Icing Inhibitor (FSII)?
A fuel additive which is designed to inhibit fuel system icing, while also suppressing fungal growth.
What is the flash point of a substance?
The lowest temperature at which a fuel begins to form a combustible vapour.
What is the volatility of a substance ?
A fuel’s level of volatility can be defined based upon its tendency to turn from a liquid to a gas (or vapour) upon the application of heat.
What is the viscosity of a substance?
Defined as a fuel or oil’s level of resistance to flow.
What is preferred in the fuel for the engine/APU to start at low temperatures?
Low viscosity + high volatility.
What are the two general groups of aviation fuels?
1) Piston engine fuels (AVGAS)
2) Turbine fuels (AVTUR).
What are two main AVGAS fuels and what is their colour?
- 100LL, Blue
- 100/130, Green
What are the main AVTUR fuels and what colors are they?
- Jet A-1
- Jet B
- F 34
- F 35
- F 44
- Colourless/straw colour
What chemical is AVGAS based in?
Petroleum
What chemical are AVTUR fuels based in?
Keresine
What are NATO designations for different aviation fuels?
F-18 for AVGAS 100LL
F34 for Jet A-1 with FSII
F35 for Jet-A-1 without FSII
F-44 which is a high flash point of AVTUR with FSII additive
What are U.S military Jet Fuel codes?
JP-5 = F-44 JP-8 = F34
What are the main functions of fuel?
- Facilitate Engine and/or APU power
- Hydraulic System Cooling
- Centre of Gravity (CoG) maintenance
What are the main two components of the aircraft fuel system?
- Engine fuel supply system
2. Storage System
What does the Engine Fuel Supply System consist of?
- Collector/Negative G tank
- Engine driven fuel pump
- Fuel filtration
- Fuel usage indication
- Engine fuel metering/carburation
What does the Storage System consist of?
- Fuel Tanks
- Motive flow transfer system
- Fuel Tank Pressurization System
- Fuel tank vent system
- Refueling/defueling point
- Fuel storage indication
What are the 4 major variants of internal fuel tanks?
- Integral tanks - Built into A/C wing or fuselage structure
- Rigid Tanks - Plastic, metal or fiberglass construction
- Bladder tanks - collapsible rubber tanks, most commonly used in military A/C applications due to light weight and self sealing properties of components involved.
- Tip Tanks
What are the most common forms of external fuel tanks?
- Conformal tanks - tanks designed to fit closely to the airframe, reducing aerodynamic drag involved.
- Drop Tanks - externally mounted centerline, pylon or wing tanks. Can be jettisoned if required for emergency/combat requirements.
What is the Collector Tank designed to do?
Be a centralized collection point to receive fuel from range of supply tanks to facilitate uninterrupted supply of fuel to the engine during turbulence/combat maneuvers.
What is the Recuperator/Negative G tank designed to do?
- Compensate for the lack of supply from the boost pumps during negative g events.
- Commonly located in the engine fuel supply line.
What is the Low-Pressure Pump (Booster Pump) designed to do?
- Provide backing pressure for intertank transfer and supply of fuel to high pressure pumps located within the engine supply system.
- Electrically or hydraulically driven
What is the Motive Flow Transfer pump designed to do?
Create a venturi effect to create the force required to transfer the volume of fuel required.
What is the Low-Pressure Fuel Cock (LP Cock)?
- An on/off selector that is designed to stop the fuel flow to the engine.
- Acts as the boundary between storage and engine supply segments of an aircraft fuel system.
What is the Filter Unit?
Consists of replaceable elements that remove water and/or particulate contaminants.
What does the engine driven fuel pump do and how does it do it?
- Delivers a continuous supply of fuel across the entirety of the engine’s operational range.
- Regulates supply to ensure the correct pressure and flow rate is maintained for optimal engine performance and efficiency.
For engine/APU supply, what is the typical path of the fuel?
Wing tanks –> Collector Tanks –> Aerobatic Tank –.> Fuel Filter –> Fuel Shut Off Valve –> Firewall –> Engine-Driven Pump –> Engine
What are some common Fuel Storage Management COmponents?
- Fuel transfer metering valves
- Transfer jet ejectors/air control unit
- Flight computer - for automated CoG control.
What are some common Engine Supply Management Components?
For Piston Engine: - Fuel injection metering unit - Carburettor For Gas Turbine: - Engine Driven fuel pump - Electronic Control Unit (ECU) - Fuel Control Unit (FCU) - Full Authority Digital Engine Control (FADEC)
What do fuel indicating systems consist of?
1) Gauges
2) Lights
3) Audio
What are some typical parameters that are monitored in the fuel system?
1) True fuel flow indicators
2) Fuel Temperature
3) Low fuel pressure warning lights
4) Fuel quantity
5) Fuel filter bypass warning lights
