fuels midterms Flashcards
can enter the airplane wing from either the uplifted fuel or through the fuel vent systems.
contamination
three basic types of fuel contamination are:
water, particulate, and microbial growth
JET FUEL’S COMPOSITION ALLOWS WATER TO BE EASILY ABSORBED. WATER CAN BE INTRODUCED IN VARIOUS WAYS INCLUDING THROUGH HUMIDITY IN THE AIR. WATER PRESENT IN THE FUEL IS EITHER SUSPENDED OR IS PRESENT AS A LIQUID. THE DEGREE OF SUSPENSION IS AFFECTED IN PART BY TEMPERATURE.
water contamination
CERTAIN BACTERIA AND FUNGI THRIVE IN WATER WHERE IT INTERFACES WITH JET FUEL. THESE MICROORGANISMS FEED OFF ALKANES AND ADDITIVES IN THE FUEL. THE BYPRODUCT OF THESE ORGANISMS IS A SLUDGE-LIKE SUBSTANCE THAT CAN CAUSE CORROSION ON STEEL AND ALUMINUM SURFACES AND ATTACK RUBBER FUEL SYSTEM COMPONENTS. IT CAN ALSO FOUL FILTERS AND SYSTEM INSTRUMENTATION.
microbial growth
ONE WAY TO CONTROL MICROBIAL GROWTH
ELIMINATING WATER FROM THE FUEL SYSTEM
can be introduced in many different ways. From dirt and sand getting in open ports to degradation of fuel system lines, these are constantly being introduced to fuel systems.
particulates
how to protect open fuel lines
covering all open lines during maintenance, fuel sampling, top off tanks, good housekeeping
CAN HELP REDUCE PROBLEMS WITH MICROBIAL GROWTH AND FREEZING ASSOCIATED WITH WATER IN THE SYSTEM. IT CAN ALSO HELP IDENTIFY IF PARTICULATE CONTAMINATION IS PRESENT
fuel sampling
JET FUEL HAS A TENDENCY TO ABSORB MOISTURE FROM THE ATMOSPHERE. WITH LESS AIR IN THE FUEL CELLS AREAS, THE RATE OF ABSORPTION WILL BE SIGNIFICANTLY LOWERED.
top off tanks
CAN REDUCE CONTAMINATION OF THE FUEL SYSTEM. FUEL STORAGE AND DISPENSING EQUIPMENT SHOULD BE KEPT CLEAN AT ALL TIMES.
good housekeeping
requirements and properties of lubricants
- Keep surfaces separate under all loads, temperatures and speeds, thus minimizing friction and wear.
- Act as a cooling fluid removing the heat produced by friction or from external sources
- Remain adequately stable in order to guarantee constant behavior over the forecasted useful life
- Protect surfaces from the attack of aggressive products formed during operation.
- Show cleaning capability and dirt holding capacity in order to remove residue and debris that may be form during operation.
The main properties of lubricants, which are usually indicated in the technical characteristics of the product, are:
viscosity
viscosity index
pour point
flash point
describes the flow behavior of a fluid. The viscosity of lubricating oils diminishes as temperature rises and consequently is measured at a given temperature (e.g. 40°C).
viscosity
determines the thickness of the layer of oil between metallic surfaces in reciprocal movement.
viscosity
The most widely used unit of measurement of viscosity
centistokes (cSt)
is a characteristic used to indicate variations in the viscosity of lubricating oils with changes in temperature.
viscosity index
The higher the level of the viscosity index,
the lower the variation in viscosity at temperature changes
Consequently, if two lubricants with the same viscosity are considered at a temperature of 40 °C, the one with the higher viscosity index will guarantee:
ØBetter engine start up at low temperatures (lower internal friction)
ØA higher stability of the lubricating film at high temperatures
minimum temperature at which an oil vapor-air-mixture becomes inflammable.
flash point
refers to the minimum temperature at which a lubricant continues to flow. Below this, the oil tends to thicken and to cease to flow freely.
pour point
It is determined by progressively heating the oil-vapor-air-mixture in a standard laboratory receptacle until the mixture ignites.
flash point
often considered to be the life blood of an engine.
lubricating oil
Without it, the friction and wear pro-duced between moving parts would cause an engine to wear at a very rapid rate.
lubricating oil
functions of lubricating oil
reduce friction, absorbs heat, seals, cushions, cleans, protects against corrosion
Many of the metal parts inside an aircraft engine have surfaces which appear smooth to the naked eye. However, if you were to microscopically examine those same parts, you would see a rather rough surface consisting of several peaks and valleys.
reduce friction
oil absorbs some of the heat produced by combustion
as it circulates through the engine. The pistons and
cylinder walls are especially dependent on lubricating oil for cooling.
absorbs heat
basically a heat exchanger that transfers the heat contained in the oil to the outside air.
oil cooler
Oil also exhibits excellent wetting characteristics because the oil film has an ability to evenly coat metal surfaces.
seals
This characteristic of oil makes it a good sealing agent between moving parts.
seals
This helps prevent gas leakage during the combustion process.
seals
helps reduce some of the impact force between a crankshaft and its connecting rods.
cushions
Metal engine parts which are exposed to moist air and various chemicals have a tendency to rust or form other types of surface corrosion.
protects against corrosion
This is especially true for cylinder walls and crankshafts which have been hardened by nitriding.
protects against corrosion
The oil film which coats internal engine parts acts as a barrier, prevent-ing oxygen and moisture from reaching the metal surface and causing it to corrode.
protects against corrosion
types of liquid lubricants
natural oils, mineral oils, synthetic oils
extracted from the ground and is obtained as part of the oil refining process.
mineral/petroleum oils
This type of oil has been around for as long as automobiles have, and it is less expensive than synthetic oils.
mineral/petroleum oils
is a lubricant consisting of chemical compounds or specific additives that are artificially made.
synthetic oil
