The document discusses lubrication and cooling functions for engines. It describes the primary functions of engine oil including lubrication and various properties important for oil including viscosity, flash point, and types of oil. It also discusses engine cooling systems, liquid cooled vs air cooled engines, and the pilot's role in maintaining proper engine temperatures.

1. LUBRICATION AND COOLING

2. FUNCTIONS OF ENGINE OIL
• Lubrication (Primary function)
• Wear-reduction
• Protection
• Cooling
• Cleaning
• Corrosion protection
• Hydraulic action

3. Lubricating Oil Properties
• Gravity
• Flash Point
• Viscosity
• Cloud Point
• Pour Point
• Carbon-Residue Test
• Ash Test
• Precipitation number

4. Gravity
• The gravity of petroleum oil is a numerical value
which serves as an index of the weight of a
measured volume of this product

5. Flash Point
• The flash point of an oil is the temperature to which the oil must
be heated in order to give off enough vapor to form a combustible
mixture above the surface that will momentarily flash or burn
when the vapor is brought into contact with a very small flame.

6. Viscosity
• Viscosity is technically defined as the fluid
friction of an oil
• To put it more simply, it is the resistance an oil
offers to flowing
• Heavy-bodied oil is high in viscosity and pours or
flows slowly
• Oils are typically classified by viscosity. SAE 30
is a reflection of the oils viscosity. The higher the
number the higher the viscosity.

7. Multiviscosity Oils
• When you see a W on a viscosity rating it means that this oil viscosity has
been tested at a Colder temperature. The numbers without the W are all
tested at 210° F or 100° C which is considered an approximation of engine
operating temperature. In other words, a SAE 30 motor oil is the same
viscosity as a 10w-30 or 5W-30 at 210° (100° C).
• The difference is when the viscosity is tested at a much colder temperature.
For example, a 5W-30 motor oil performs like a SAE 5 motor oil would perform
at the cold temperature specified, but still has the SAE 30 viscosity at 210° F
(100° C) which is engine operating temperature. This allows the engine to get
quick oil flow when it is started cold verses dry running until lubricant either
warms up sufficiently or is finally forced through the engine oil system. The
advantages of a low W viscosity number is obvious. The quicker the oil flows
cold, the less dry running. Less dry running means much less engine wear.

8. Cloud Point
• The cloud point is the temperature at which the separation of wax
becomes visible in certain oils under prescribed testing conditions
• When such oils are tested, the cloud point is slightly above the
solidification point

9. Pour Point
• The pour point of an oil is the temperature at
which the oil will just flow without disturbance
when chilled

10. Carbon-Residue Test
• The purpose of the carbon-residue test is to
study the carbon-forming properties of a
lubricating oil.

11. Ash Test
• The ash test is an extension of the carbon-
residue test
• If an unused oil leaves almost no ash, it is
regarded as pure
• The ash content is a percentage (by weight) of
the residue after all carbon and all carbonaceous
matter have been evaporated and burned

12. Precipitation number
• The precipitation number recommended by the
ASTM (American Society for Testing and
Materials) is the number of milliliters of
precipitate formed when 10 mL of lubricating oil
is mixed with 90 mL of petroleum naphtha under
specific conditions and then centrifuged

13. Lubricating Oil Types
• Straight Mineral Oil
• Ashless Dispersant Mineral Oil
• Synthetic Oil
• Mineral/Synthetic Blends

14. Straight Mineral Oil
• Straight mineral oil is one of many types of oil
used in aircraft reciprocating engines
• It is blended from selected high-viscosity-index
base stocks
• These oils do not contain additives, except for a
small amount of pour-point depressant for
improved fluidity at cold temperatures
• Often used after engine overhaul or when new to
facilitate seating of the piston rings (wear-in).

15. Ashless Dispersant Oil
• Most aircraft oils other than straight mineral oils
contain a dispersant that suspends
contamination such as carbon, lead compound
and dirt
• The dispersant helps prevent these
contaminants from gathering into clumps and
forming sludge or plugging oil passageways

16. Synthetic Oil
• Because of the high operating temperatures of
gas-turbine engines, it became necessary to
develop lubricants which would retain their
characteristics at temperatures that cause
petroleum lubricants to evaporate and break
down
• Synthetic lubricants do not break down easily
and do not produce coke or other deposits

17. Multiviscosity Oil
• In certain circumstances, all single-grade oils
have short comings
• In cold-weather starts, single grade oil generally
flows slowly to the upper reaches and vital parts
of the engine
• Multigrade oils have viscosity characteristics that
allow for better flow characteristics at engine
start

18. Characteristics of Aircraft
Lubricating Oil
• It should have the proper body (viscosity)
• High antifriction characteristics
• Maximum fluidity at low temperatures
• Minimum changes in viscosity with changes in
temperature
• High antiwear properties
• Maximum cooling abilities
• Maximum resistance to oxidation
• Noncorrosive

19. Characteristics of Lubrication
Systems
• Pressure Lubrication
• Splash Lubrication and Combination Systems
• Principal Components of a Lubrication System
• Oil Capacity

20. Pressure Lubrication
• In a pressure lubrication system, a mechanical
pump supplies oil under pressure to the bearings
• Oil flows into the inlet of the pump through the
pump and into an oil manifold which distributes it
to the crankshaft bearings

21. Splash Lubrication and
Combination Systems
• Although pressure lubrication is the principle
method of lubrication on all aircraft engines,
some engines use splash lubrication also
• Splash lubrication is never used by itself
• All lubrication systems are pressure systems or
combination pressure/splash systems

22. Components of Lubrication
Systems
• Plumbing for Lubrication Systems
• Temperature Regulator (Oil Cooler)
• Oil Viscosity Valve
• Oil Pressure Relief Valves
• Oil Separator
• Oil Pressure Gauge
• Oil Temperature Gauge
• Oil Pressure Pumps
• Scavenge Pumps
• Oil Dilution System

23. Plumbing for Lubrication
Systems
• Oil plumbing is essentially the same as is used
in oil and hydraulic systems
• When the lines will not be subject to bending,
aluminum tubing is used
• Synthetic hose is often used near the engine
and other places on the aircraft that are subject
to vibration or other movement

24. Temperature Regulator (Oil
Cooler)
• An oil temperature regulator is designed to
maintain the temperature of the oil for an
operating engine at the correct level
• These regulators are often called oil coolers
since cooling of engine oil is one of their main
functions

25. Oil Viscosity Valve
• The oil viscosity valve is generally considered a
part of the oil temperature regulator unit and is
employed in some oil systems
• The viscosity valve consists essentially of an
aluminum alloy housing and a thermostatic
control element
• The oil viscosity valve works with the oil cooler
valve to maintain a desired temperature and
keep the viscosity within required limits

26. Oil Pressure Relief Valves
• The purpose of the oil pressure relief valve is to
control and limit the lubricating pressure in the
oil system
• This is necessary to prevent damage caused by
excessive system pressure and to ensure that
engine parts are not deprived of fuel due to a
system failure

27. Oil Separator
• Air systems where oil or oil mist is present may
require the use of an oil separator
• These are often used on vacuum pump outlets
• The oil separator contains baffle plates which
cause the air to swirl and it deposits on the
baffles

28. Oil Pressure Gauge
• An oil pressure gauge is an essential component
of any engine oil system
• These gauges generally use a bourdon tube to
measure the pressure
• They are designed to measure a wide range of
pressures

29. Oil Temperature Gauge
• The temperature probe for the oil temperature
gauge in the oil inlet line or passage between
the pressure pump and the engine system
• On some installations the temperature probe is
located in the oil filter housing
• These are normally electric or electronic

30. Oil Pressure Pumps
• Oil pressure pumps may either be of the gear
type or vane type
• The gear type pump is used in the majority of
reciprocating engines and uses close fitting
gears that rotate and push the oil through the
system

31. Scavenge Pumps
• Scavenge pumps are driven in the same manner
as the pressure pumps but have a greater
capacity
• This higher capacity is because the oil in the
sump is foamy which means it has a much
greater volume than air-free oil

32. Oil Dilution System
• The purpose of the oil dilution system is to
provide thinner oil during engine start
• This allows faster lubrication of engine
components
• Oil dilution is accomplished by pumping a small
amount of fuel into the oil

33. Sludge Chambers
• Some reciprocating engines have sludge
chambers which are in the hollowed out
connecting-rod journals
• These journals accumulate carbon sludge and
dirt particles as they are designed to
• During engine overhaul these must be replaced

34. Typical Lubrication Systems
• Oil System for Wet-Sump Engine
• Oil System for Dry-Sump Engine
• Oil Tanks

35. Wet Sump System
• In a wet sump system the oil is housed within
the crankcase.
• This is not possible in a turbine engine
application because of the high operating
temperatures.

36. Oil Tanks
• Dry sump engine lubrication systems require a separate tank for
each engine system
• These tanks can be constructed in three different ways:
• Welded sheet aluminum
• Riveted aluminum
• Stainless steel
• Some aircraft are equipped with synthetic rubber tanks

37. Troubleshooting
• Symptom: Oil pressure decrease, oil temp.
increase.
• Cause: loss of oil causing temp. to rise, engine
failure imminent.
• Action: reduce power to maximize engine life.

38. Troubleshooting
• Symptom: Oil pressure decrease, oil temp.
steady
• Cause: Oil pressure gauge malfunction.
• Action: monitor engine instruments.

39. Troubleshooting
• Symptom: Slight drop in oil pressure, steady or
slight rise in oil temp.
• Cause: possible filter blockage, by-pass valve
restricts flow.
• Action: inform maintenance.

40. Usage Monitoring
• It is important to monitor oil usage trends in
order to detect problems before they become
critical.
• Each company will have specific trend
monitoring procedures.

41. Engine Cooling Systems
• Cowling
• Baffles
• Cooling fins
• Cowl flaps
• Augmenters

42. Liquid Cooled Cylinder

43. Air Cooled Engine

44. Engine Cooling Airflow

45. Pilot Handling
• It is the pilots responsibility to ensure engine
operating temperatures remain in the normal
operating range.
• Temperature can be controlled by adjusting:
• Cowl flaps
• Power setting
• Airspeed
• Fuel mixture

46. Thermal Shock
• Thermal shock occurs when an engine operating
at high temperatures is allowed to cool quickly.
• Some parts cool more rapidly than others and
causes stress cracks in the cylinder head.
• Pilot handling can prevent thermal shock by
avoiding rapid power reductions, especially in
cold outside air temps.