Lubrication Systems
What are the two types of oil filters?
- A filter that uses a replaceable laminated paper element. - A filter that uses a fine stainless steel metal mesh.
What are the two types of oil coolers?
- Air-cooled: normally installed at the forward end of the engine and usually included in a dry-sump oil system. - Fuel-cooled: the fuel cools the hot oil and oil heats the fuel for combustion.
Describe the function of the oil tank.
- Although the dry sump systems use an oil tank that contains most of the oil supply, a small sump is usually included on the engine to hold a small supply of oil. - It is designed to furnish a constant supply of oil to the engine during any aircraft attitude.
What is the function of the vent in an oil tank?
- It keeps the pressure within the tank from rising above or falling below that of the outside atmosphere. - The vent maybe routed through a check relief valve that is preset to maintain a slight pressure on the oil to ensure a positive flow of oil to the pump inlet.
Describe the three subsystems found within the regulated and variable-pressure lubrication systems.
- Pressure system supplies oil to the main engine bearings and to the accessory drives. - The scavenger system returns the oil to the engine oil tank that is usually mounted on the compressor case. It is connected to the inlet side of the pressure oil pump and completes the oil flow cycle. - A breather system connecting the individual bearing compartments and the oil tank with the breather pressurising valve completing the lubrication system.
Describe the different uses of check valves in a lubrication system.
- They are sometimes installed in the oil supply lines of dry sump systems to prevent reservoir oil from seeping (by gravity) through the oil pump elements and high-pressure lines into the engine after shutdown. - Check valves, by stopping flow in an opposite direction, prevent accumulations of undue amounts of oil in the accessory gearbox, compressor rear housing and combustion chamber. Such accumulations could cause excessive loading of the accessory drive gears during starts, contamination of the cabin pressurisation air, or internal oil fires.
What is the difference between wet sump engines and dry sump engines?
- Wet sump engines store the lubricating oil in the engine. The oil reservoir may be the accessory gear case or it may be a sump mounted at the bottom of the accessory case. - Dry sump engines use an external tank mounted on the engine or somewhere on the aircraft structure near the engine.
What are the two most common types of oil pumps?
Gear and gerotor.
Where is the oil pressure transmitter located?
In the pressure line between the pump and various points of lubrication.
Describe the operation of the oil pressure regulating valve.
It is a valve held against a seat by a spring. By adjusting the tension(increase) on the spring, you change the pressure at which the valve opens and you increase the system pressure. A screw on the spring adjusts the tension on the valve and the system pressure.
What is the function of the regulating (relief) valve inside an oil pump?
It is located on the discharge side of the oil pump. It limits the output pressure of the pump by bypassing oil to the inlet of the pump when the outlet pressure exceeds a predetermined limit.
What is the function of the oil pressure regulating valve?
It is located on the pressure side of the pressure pump and maintains the system pressure to a limited value.
Where are most oil filters located?
Most filters are located close to the pressure pump.
Most turbine engine oil systems are the ... regulating type system that keeps the pressure fairly ...
Pressure Constant
What is the function of the deaerator in the oil system?
Scavenged oil passes through the deaerator as it enters the oil tank, which separates the air mixed in the return oil. The oil stays in the tank, while the air flows into the accessory gearbox and enters the deoiler.
What is the difference between the deoiler and deaerator?
The deoiler is located in the main accessory gearbox, while the deaerator is located in the oil tank. The deoiler receives air from the bearing compartments, while the deaerator receives air from the scavenged oil returning to the oil tank. Bothe of components vent the air overboard.
What value is measured by the oil pressure gauge?
The pressure of the oil as it leaves the pump and enters the pressure system.
What is the function of thermostatic bypass valves?
They are included in oil systems using an oil cooler. Their purpose is to maintain proper oil temperature by varying the proportion of the total oil flow passing through the oil cooler. The valve is spring-loaded because the pressure drop through the oil cooler could become too great due to denting or clogging of the cooler tubing. In such a case, the valve opens, bypassing oil around the cooler.
What is the location of the oil jets/nozzles inside the engine?
They are located in the pressure lines adjacent to or within the bearing compartments and rotor shaft couplings.
What is the main function of the lubricating system in a turbine engine?
To cool the bearings by taking heat away from the bearings by circulating oil around the bearings. In some engines, air cooling is used in addition to oil cooling the bearing. Air cooling is bleed air provided from the early stages of the compressor where air has enough pressure but has not yet become too warm.
What is the function of the magnetic chip detectors in the oil system?
To detect and catch ferrous (magnetic) particles present in the oil.
Describe the function of the breather pressurising system.
To ensure a proper oil spray pattern from the main bearing oil jets and to provide a pressure head to the scavenge system.
What is the function of the scavenging element inside the oil pump?
To return the oil to the oil tank for reuse.
What is the function of the deoiler in the accessory gearbox?
To separate oil from the air/oil mist and vent the air back to the atmosphere.
What is the function of a finger screen filter?
To strain scavenged oil.
What is the function of last chance filters?
To strain the oil just before it passes from the spray nozzles onto the bearing surfaces.
What is the function of the oil pump located inside the oil tank?
To supply oil under pressure to the parts of the engine that require lubrication, then circulate the oil through coolers as needed, and return the oil to the oil tank. Most oil pumps consist of a pressure supply element and a scavenge element.
What type of pressure system is used on large turbofan engines?
Variable pressure systems in which the pump outlet pressure (oil pressure) depends on engine speed rpm.
What type of lubrication system is used on turbine engines?
Wet or dry sump.
Some engines use an ...-oil mist spray that is produced by tapping high pressure bleed air from the compressor to the oil nozzle outlet. However, the ... oil spray method is considered the better of the two methods.
Air Solid
What is the function of the differential oil pressure switch?
Alerts the flight crew of an impending oil filter bypass because of a clogged filter.
What is the appropriate procedure when metal is found on a chip detector?
An investigation should be carried out to find the source of the metal on the chip.
How do large turbofan oil systems that do not have a regulating valve control system pressure?
By using a relief valve to relieve system pressure only if it exceeds the maximum limit for the system. Whenever pressure exceeds the maximum preset system limit, oil is bypassed back to the inlet side of the oil pump.
Where are magnetic chip detectors located within the oil system?
Chip detectors are placed in the scavenge lines for each scavenge pump, oil tank and in the oil sumps.
Turbine engine's oil systems can also be classified as a pressure relief system that maintains a ... pressure: the full flow type of system in which the pressure varies with engine ...
Constant Speed.
What does FADEC stand for?
Full authority digital engine control.
