Engine Lubrication performance System.pdf

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1. Engine Lubrication and cooling
System (Level 3)
ET-PP31

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REFERENCES
1. Airframe & power plant Mechanics Powerplant
hand book (ac65-12a)
2. Aircraft powerplant by ralph d.Bent & james L.
Mckinley
3. Aviation Maintenance Technician Series Power
plant by Dale Crane

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Table of contents
1. Engine lubrication System
1.1. Principles of Engine Lubrication
1.2. Engine Lubricants
1.3. Gas Turbine Engine Lubrication System
1.4. Lubrication System Maintenance Practices

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Course Objectives
➢ At the end of the course you will be able to:
➢Describe lubrication system specific to gas
turbine engine,
➢Describe engine lubrication maintenance and
servicing.

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Definition of lubrication:
Lubricant is any natural or artificial substance
having greasy or oily properties.
1.1.1. Definition and Importance of Lubrication

Importance of Lubrication:
✓ Since a contact between surfaces moving in relation
to each other produce friction, we need to minimize it
in order to make the best use of the power we
produce.
✓ This can be done by creating a separation between
these sliding surfaces.
✓ The lubricating oil now comes into picture to replace
metal to metal friction with fluid(oil) friction.
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Primary Function:-
➢ Reduces friction
1.1.2. Function of engine lubricants:

Secondary function
✓ provide cooling
✓ perform and facilitate cleaning
✓ enables sealing and cushioning
✓ prevents rust and corrosion
✓ performs hydraulic action
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Types of Friction:
➢ Static friction
is a force between two objects that are not
moving relative to each other.
➢ Kinetic (dynamic) friction
occurs when two objects are moving relative to
each other and rub together.
➢ Sliding
➢ Rolling
➢ Wiping
1.1.3. Friction- Definition, Types and
Factors Affecting

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Factors determining magnitude of friction:
➢ The viscosity of the lubricant
➢ Area of contact surface
➢ Rubbing speed
➢ Material & profile of involved parts
Principles of Engine Lubrication

Bearings and Seals
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Bearing and seals:
✓ Any supporting surface which reduces friction
✓ A bearing is a device to permit constrained relative
motion between two parts, typically rotation or
linear movement.
Types;
✓ Ball bearing
✓ Roller bearing
✓ Plain bearing

Ball bearing
✓ Is a type of rolling-element which uses balls
to maintain the separation between the
moving parts of the bearing.
✓ are used to prevent or minimize rubbing
✓ Used for radial and thrust loads in large gas
turbine engines
✓ Components
▪ Outer race, Inner race, Balls & Retainers
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Ball Bearings
5/12/2024 GAS TURBINE ENGINE
FUNDAMENTALS
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Dual Ball Bearings
FUNDAMENTALS
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Roller bearing
✓ are used to prevent or
minimize rubbing
✓ Used for higher radial loads
than plain bearings with
lower friction

Roller Bearing
FUNDAMENTALS
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Roller Bearing
FUNDAMENTALS
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Plain bearing
✓ The simplest type of bearing, widely used,
relatively high friction, although some use
pumped lubrication most of them are
splash lubricated
✓ Mainly for radial loads, sometimes for
thrust load if they have end flange.
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Oil-
damped
bearing
FUNDAMENTALS
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Radial bearing load
• The load on a bearing perpendicular to the
shaft on which the bearing is mounted.
FUNDAMENTALS
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Axial bearing load
• The load on a bearing parallel to the shaft on
which the bearing is mounted.
5/12/2024 GAS TURBINE ENGINE SYSTEMS 23

Oil-damped bearing
✓ A type of roller bearing installation in which the
outer race is installed in an oil damper
compartment.
✓ Oil damped bearings compensate for slight
misalignment & absorb vibrations of the shaft.
5/12/2024 GAS TURBINE ENGINE SYSTEMS 24

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Seals
✓device preventing the passage of oil
Types
✓ Carbon seal
✓labyrinth seal

Cont…
Carbon seal
➢ is used to prevent the oil from leaking
through the space between a rotating and a
static device and thus reducing the
efficiency
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Ring Type Carbon Oil Seal
FUNDAMENTALS
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Face Type
Carbon Oil
Seal
FUNDAMENTALS
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Cont…
Labyrinth seal
✓ is a mechanical seal that fits around an axle to
prevent the leakage of oil or other fluids.
✓ is used to prevent the gas from leaking through
the space between a rotating and a static
device and thus reducing the efficiency
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FUNDAMENTALS
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Bearings,
Seals and
Lubrication
System
FUNDAMENTALS
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✓ Stated under FAR part 23/25 and FAR part 33
1. General
2. Oil Tanks
– (a) Installation
– (b) Expansion space
– (c) Filler connection
– (d) Vent
– (e) Outlet
1.1.4. Regulation Pertaining to Lubrication
System

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3. Oil Tank Tests
4. Oil Lines and Fittings
5. Oil Strainer or filter
6. Oil System Drains
7. Oil Radiators
8. Propeller Feathering System
Regulation pertaining to lubricating system

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1. General
➢ Each engine must have an independent oil system.
➢ The usable oil tank capacity may not be less than
the product of the endurance of the airplane under
critical operating conditions.
Regulation Pertaining to Lubricating System

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2. Oil Tanks
(a) Installation
✓ Each oil tank must be installed to withstand any
vibration, inertia, and fluid loads expected in operation.
(b) Expansion space
✓ Oil tank expansion space must be provided so that each
oil tank used with a reciprocating engine has an
expansion space of not less than the greater of 10
percent of the tank capacity or 0.5 gallon, and each oil
tank used with a turbine engine has an expansion space
of not less than 10 percent of the tank capacity.

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Oil Tanks …
(c) Filler connection
✓ Each oil tank filler connection must be marked at
or near the filler cap or cover with the word “oil”.
(d) Vent
✓ Each oil tank must be vented to the engine
crankcase from the top part of the expansion
space so that the vent connection is not covered
by oil under any normal flight condition.
(e) Outlet
✓ No oil tank outlet diameter may be less than the
diameter of the engine oil pump inlet.

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3. Oil tank tests
✓ Each oil tank must be tested
a) The applied pressure must be five psi for the tank
construction.
b) For a tank with a nonmetallic liner the test fluid
must be oil rather than fuel.
c) For pressurized tanks used with a turbine engine,
the test pressure may not be less than 5 psi plus
the maximum operating pressure of the tank.

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4. Oil lines and fittings
a) Oil lines
✓ Oil lines must accommodate a flow of oil at a rate
and pressure adequate for proper engine
functioning under any normal operating condition.
b) Breather lines
✓ Breather lines must be arranged so that:
1) condensed water vapor or oil that might freeze
and obstruct the line cannot accumulate at any
point.
2) the breather does not discharge into the engine
air induction system.
3) the breather outlet is protected against blockage
by ice or foreign matter.
Regulation Pertaining to Lubricating System…

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5. Oil strainer or filter
(a)Each turbine engine installation must incorporate
an oil strainer or filter through which all of the
engine oil flows.
(b)Each oil strainer or filter in a powerplant
installation must be constructed and installed so
that oil will flow at the normal rate through the
rest of the system with the strainer or filter
element completely blocked.

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6. Oil system drains
✓ A drain (or drains) must be provided to allow safe
drainage of the oil system. Each drain must :
a) be accessible; and
b) have manual or automatic means for positive
locking in the closed position.

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7. Oil radiators (Oil Coolers)
✓ Each oil radiator and its supporting structures must
be able to withstand the vibration, inertia, and oil
pressure loads to which it would be subjected in
operation.

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8. Propeller feathering system
a) If the propeller feather system depends on engine
oil, there must be means to trap an amount of oil
in the tank if the supply becomes depleted due to
failure of any part of the lubricating system, other
than the tank itself.
b) The amount of trapped oil must be enough to
accomplish feathering and must be available only
to the feathering pump.

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1.2.1. Classification of Lubricant
✓ Oil that meets the requirements for turbine engine
lubrication is a synthetic
✓ It can be made artificially to stand large range of
temperature : from -40oF to 1000oF.
✓ Synthetic product or artificially made
▪ Type I Alkyl diester oils (MIL-L-7808)
▪ Type II Polyolester oils (MIL-L-23699)
✓ Can retain their characteristics at high temperature.
1.2. Engine lubricants

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Synthetic Lubricant
Types
TYPE-I TYPE-II
Aeroshell 300 Aeroshell 500 or 700
Mobil Jet I Mobil Jet II
Stauffer I Stauffer II
Castrol 3c Castrol 205
Enco 15 Enco 2380
Exxon 15 Exxon 25
Exxon 2389 Exxon 2380
Caltex 15 Caltex 2380
Shell 307 Texaco 7388,Starjet-5
Exxon 274 Caltex Starjet-5
Cheveron jet-5
Sinclair type-2
Castrol 5000

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Viscosity of Synthetic Oils
✓ Expressed in units of CGS (centimeter gram second)
system
✓ Coefficient of Absolute Viscosity is expressed in
Poise(P) or Centipoise (cp)
✓ Kinematic Viscosity is expressed in Stokes(St) or
Centistokes(cSt)
1.2.2. Properties of Lubricating Oil

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Viscosity Index (VI)
✓Is a number which expresses the rate at
which the viscosity of an oil will change with
temperature.
✓Effect of temperature on viscosity
✓High index ratings are desirable.
✓Parafinic oil has viscosity index of 100 and
zero for highly naphtalic oils.
Lubrication oil properties

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Flash Point & Fire Point
✓ Flash point show the
temperature at which a
liquid will begin to give off
ignitable vapors.
✓ Fire point the lowest
temperature at which an oil
ignites and continues to
burn for at least 5 sec. Cleveland open cup tester

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Cloud Point & Pour Point
✓ The cloud point of an oil is
the temperature at which
its wax content, normally
held in solution, begins to
solidify and separate into
tiny crystals, causing the
oil to appear cloudy or
hazy.
✓ Pour point is the lowest
temperature at which it will
flow or can be poured.
Apparatus for cloud-point and pour-point tests

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Spectrometric analysis
✓Identifies engine oil contaminants
✓Is used to identify internal engine failure.
E. Lubrication oil properties

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Oil spectrometer

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Spectrometric oil analysis report

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✓ For an oil to perform properly, it must have these
characteristics:
▪ Low viscosity - It must be able to flow readily under
all temperature conditions.
▪ High viscosity index - It must not change its
viscosity appreciably with changes in its temperature.
▪ High film strength - It must not break down under
the loads imposed by the accessory gear tooth
pressures.
▪ Low volatility - It must not evaporate at the low air
pressures of high altitude.
1.2.3. Lubricants Requirements

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▪ High flash point -It must not release vapors that
would ignite at the temperatures inside the engine.
▪ Low pour point-It must be pourable at low
temperatures.
▪ Good antifoaming characteristics- It must be able
to easily release all the air it accumulates as it passes
through the engine.
▪ Low carbon deposit formation - It must not deposit
coke or hard carbon deposits on hot engine parts. The
carbon that forms must be held in the oil until
removed by the filters.
Lubricants Requirements …

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1.3. Gas Turbine Engine Lubrication system

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1.3.1. Methods of Lubrication
✓Pressure
✓Splash
✓Combination of both

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a) Dry Sump Lubrication System Operation
✓ Hot tank
✓ Cold tank
b) Wet-Sump Lubrication System Operation
1.3.2. System Layout and Operation

E.GTE Lubrication System
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Hot Tank Dry-Sump Lubrication System
5/12/2024

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Cold Tank Dry-Sump Lubrication System
5/12/2024

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a) Oil tank
➢Furnish a constant supply of oil to the engine
during any aircraft attitude.
1.3.3. System Components

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✓ Vent system inside the tank vents the airspace at all
times
✓ An expansion space:
▪ allows for expansion of the oil after heat is
absorbed from the bearings and gears and after
the oil foams as a result oil circulating through the
system.
✓ De-aerator tray
▪ Used for separating air from the oil returned to
the top of the tank by the scavenger system.
▪ air released is carried out through the vent system
in the top of the tank.
System Components: Oil tank

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b) Oil Pump
✓ designed to supply oil under pressure to the parts
of the engine
✓ oil pumps may consist of:
▪ Both pressure supply and scavenge elements, or
▪ either supply or scavenge the oil.
▪ The scavenge elements have a greater pumping
capacity
▪ A relief valve in the discharge side of the pump
➢limits the output pressure of the pump by
bypassing oil to the pump inlet when the
outlet pressure exceeds a predetermined limit.
System Components…

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c)Oil Filter
✓ Components of a typical main oil filter include:
➢a housing, having integral relief (or bypass) valve
and, the filtering element.
➢The bypass valve opens
whenever a certain pressure is reached. If this
occurs, the filtering action is lost, allowing
unfiltered oil to be pumped to the bearings.
System Components …

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Filters
✓ they remove foreign particles that may be in the
oil.
✓ common types of oil filter
➢ replaceable laminated paper element ,
➢ filter element made up of a series of spacers
and screens ,
➢ main oil strainer (filtering element interior is
made of stainless steel),
Secondary filters
✓ fine-mesh screens, called “last chance” filters, for
straining the oil just before it passes from the
spray nozzles onto the bearing surfaces.

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Bowl type cleanable stainless
steel mesh, pleated oil filter

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H. ENGINE LUBRICATION SYSTEM

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e) Oil Pressure Relief Valve
✓ Found in the pressure oil line to limit the
maximum pressure within the system.
✓ whenever the pressure exceeds the preset limit
▪ It relieves pressure and bypass the oil back
to the inlet side of the oil pump
System Components …

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Types of
gearbox
mounted oil
filters

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Cleanable wafer screen type filter

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Screen and spacer oil filter

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2. Gas Turbine Engine
– Oil subsystems
• Supply section
• Pressure section
• Scavenge section
• Breather Section
• Drain section

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➢ Oil Jets (nozzles):
➢are located in the pressure lines adjacent to, or within,
the bearing compartments and rotor shaft couplings.
➢Oil from nozzles is delivered in the form of an
atomized spray.
➢high-pressure bleed- air from the compressor is
tapped for air-oil mist spray.
➢last-chance filters found prior to nozzles removes any
dirt
➢Oil jets are cleaned only during engine overhaul

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➢ Can be installed in the
➢Scavenge pump,
➢Oil tank,
➢Accessory case,
➢ Indicates the presence of metal
contamination without opening oil filter.
➢Picks up ferrous-metal particles.
Magnetic chip detector

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➢ oil pressure gage
– measures the pressure of the lubricant as it
leaves the pump on its way to the oil jets.
– located in the pressure line between the pump
and the various points of lubrication.

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➢ Oil temperature indications
– Two of the most common methods
(1) A thermocouple fitting in the oil line or
(2) an oil temperature bulb inserted in the oil line.
– is located in the pressure inlet to the engine

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➢ Lubrication System Vents
• Vents or breathers are lines or openings in the oil tanks or
accessory cases of the various engines,
• In the accessory case the vent (or breather)
is a screen-protected opening, which allows accumulated
air pressure within the accessory case to escape to the
atmosphere.

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➢ Lubrication System Vents
➢The scavenged oil carries air into the accessory
case and this air must be vented;
• otherwise, the pressure buildup within the accessory
case would stop the flow of oil draining from the bearing,

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➢ Lubrication System Check Valve (anti-leakage valve)
• are the spring-loaded, ball-and socket type
• prevent reservoir oil from seeping (by gravity) through the
oil pump elements and high-pressure lines into the engine
after shutdown.

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Lubrication System Check Valve (anti-leakage
valve)
• stop flow in an opposite direction,
prevent accumulations of undue amounts of oil in the
accessory gearbox, compressor rear housing, and
combustion chamber.
• the valves generally require from 2 to 5 p.s.i. to permit oil to
flow to the bearings.

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➢ Thermostatic Bypass Valves
➢Used to maintain proper oil temperature by varying the
proportion of the total oil flow passing through the oil
cooler.
➢consists of
a valve body, having two inlet ports and one outlet
port, and
a spring-loaded thermostatic element valve.
➢It is spring loaded
✓valve opens, to bypass the oil around the cooler.

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Oil Coolers
➢ Used to reduce the temperature of the oil to a degree suitable for
recirculation through the system.
➢ Two basic types of oil coolers
1. Air cooled oil cooler
2. Fuel cooled oil cooler
✓ The air-cooled oil cooler
• Cools the oil by air.

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Oil Coolers
✓ The fuel-cooled oil cooler (fuel/oil heat exchanger
).
➢fuel cools the oil and the oil heats the fuel.
➢The fuel/oil heat exchanger
• consists of a series of joined tubes with an inlet
and outlet port.
• The oil enters the inlet port, moves around the
fuel tubes, and goes out the oil outlet port.

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Fuel oil heat exchanger cooler.

E.GAS TURBINE ENGINE
LUBRICATION SYSTEM
Basics Powerplant Systems 94
Oil Cooler
5/12/2024

Fuel-Oil Heat Exchanger
5/12/2024 95

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➢ DRY-SUMP LUBRICATION SYSTEM
➢It consists of the
➢Pressure,
➢Scavenge, and
➢Breather subsystems.

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➢The pressure system
➢ supplies oil to the main engine bearings and to the accessory
drives.
➢ The pressure pump receives engine oil at its lower (inlet) side
and
➢ discharges pressurized oil to an oil filter

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The pressure system
➢Oil from the filter housing passes to
• engine rear bearings and to front compressor front
bearing and front accessory drive gears.
• Then lubricate the front compressor rear bearing
and the rear compressor front bearing
• Pressure relief valve maintain a proper pressure to
the oil metering jets in the engine.

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The pressure system
➢Oil from the filter housing passes to
• Pressurized oil distributed to the engine main
bearings is sprayed on the bearings through fixed
orifice nozzles

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JT8D turbofan lubrication system (Hot Tank)

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➢ Scavenge System
➢ scavenges
main bearing compartments and,
circulates the scavenged oil through the oil cooler (s) and back
to the tank.

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➢ Breather Pressurizing System
➢ Ensures
➢a proper oil spray pattern from the main bearing oil jets,
and
➢furnishes a pressure head to the scavenge system.
➢Pressurization is provided by compressor air which leaks
by the seals and enters the oil system.
➢Breather tubes are found
➢in the compressor inlet case, the oil tank, the diffuser
case and the turbine exhaust case are connected to
external tubing at the top of the engine.

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➢ The breather pressurizing valve
➢ Ensures a proper oil spray pattern and furnishes a pressure
head to the scavenge system
➢consists of
an aneroid-operated (spring and bellows) valve and
a spring-loaded blow off valve.
➢ is open at sea level pressure,
➢ It closes gradually with increasing altitude and maintains an
oil system pressure,
➢ A pressure-equalizing valve
➢limits the pressure supplied to the carbon air/oil seal.

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➢ Reasons for oil change
➢Decrease in lubricating qualities
➢Contamination due to
➢Gasoline,moisture,acids,dirt or
dust,carbon,metallic particles
J. LUBRICATION SYSTEM SERVICING

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➢Oil system servicing
➢General
➢Before servicing an engine’s oil system,the
technician should refer to the following publications
➢Engine –type certificate data sheet
➢Aircraft – type certificate data sheet
➢Operations manual for the correct oil
➢Regulating bodies publications

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➢ Cleaning oil system (flushing)
➢Flushing means reservicing and draining a second
time after motoring the engine over with the starter
and no ignition
➢In the event of inadvertent mixing of
incompatible lubricants
➢When changing to another approved oil

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➢Cleaning oil filters and screens
➢At a certain time interval
➢When the filter clogged
➢When the oil changed
➢Note:-during cleaning, residue in the screen and
housing should be checked for metal particles or
chips which would indicate internal failure in the
engine

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➢Adding oil between flights
➢Oil servicing should be accomplished within a
short time after engine shutdown in order to
prevent over servicing ( 5 minutes)
➢Oil consumption of gas turbine engines is very low

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➢ A typical oil change interval for GTE is 300 to 400
operating hours or 6 months on a calendar interval
➢ Larger GTEs consume no more than 0.2 to 0.5 quart per
operating hour
➢ By comparison, an 18-cylinder radial engine could
consume as much as 20 quarts per operating hour and
still be considered airworthy

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• For example,the maximum oil consumption limit for all
Textron Lycoming engines can be calculated using the
formula:
• 0.006 x BHP X 4II 7.4= Quarts per hour
• An important consideration after oil servicing is recording
the amount of oil serviced

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➢ Quantity or level check
➢ Marking an oil filler cap
➢ Oil pressure adjustment

Thank You
FUNDAMENTALS
114

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