After combustion in an engine, 2/3 of the heat energy is lost through the exhaust, friction, and heating of metal walls. To prevent overheating of parts, the formation of oil films and proper lubrication is needed. Both low and high temperatures can cause issues like metal-to-metal contact from changes in oil viscosity or part clearances. Maintaining proper operating temperatures is important for engine performance and reliability.

2. After the combustion process , only 1/3 of the heat
energy from the fuel changes into mechanical
energy , & the rest :
• Hot exhaust gases
• Frictional heat from the rubbing surfaces
• Heating of the metal walls

3. to prevent :
• Overheating and the resulting breakdown of
lubricating oil film
• Overheating and the resulting loss of strength of
the metal itself
• Excessive stresses in or between the engine
parts resulting from unequal temperatures

4.  Theformation of an oil film depends on the
viscosity of the oil …
And the
viscosity
the oil
depends on
The
Temperature

6.  Will
decrease the oil viscosity which will
cause : metal-to-metal contact and
resulting excessive wear of the load-
bearing parts .

7.  Willlead to condensation in the crankcase
, causing acids and sludge to form in the
lubrication oil , and condensation of
corrosive gases in the cylinder walls .

8. At low Temp :
Excessive clearances between
parts will cause pounding
Excessive clearances between
the bearings and the Journals
will allows the oil to escape .

9.  AtHigh Temp: the parts will expand and
insufficient clearances between the moving parts
will result .
As the clearances are
Reduced , inadequate
Lubrication will cause
metal-to-metal contact.

10.  High temperatures change the strength and
physical properties of the various metals used in
an engine.
Excessive expansion of the metal, which may
result in shearing of the cylinder-head bolts.

11.  Thecomplete induction system for an aircraft
engine includes three principal sections :
 The air scoop and ducting
 The carburetor or air-control section
 The intake manifold and pipes

12.  Air Scoop is simply an opening facing into the
airstream.
 This scoop receives ram air , usually augmented
by the propeller slipstream
 The effect of the air scoop
and ducting is in
increasing the power
in 5 percent .

13.  Overheating can cook the seals in the
engine

14.  The ducting system comprises four principal
parts :
 The air scoop
 Air filter

15.  Alternateair valve(operated
By means of the carburetor
Heat control in the cockpit)
 The carburetor air heater
or muff

17.  The typical opposed-type or flat-type aircraft
engine has an induction system with an
individual pipe leading to each cylinder .
 The 2 purposes of intake manifolds are :
 -it cools the oil slightly
 -it increases the temperature
of the fuel-air mixture slightly
for a better vaporization of
the fuel

18. The type of induction system used on a radial-
type engine principally depends on the
horsepower output desired from the eingine

19.  On a small radial engine of low output , the air is
drawn through the carburetor , mixed with fuel in
the carburetor, and then carried to the cylinders
through individual intake pipes .

20.  Ina typical high-output engine, an internal
blower or a supercharge is located in the rear
section of the engine . The fuel-air mixture
passes from the carburetor through the
supercharge or blower and the then flows out
through the diffuser section and individual intake
pipes to the engine cylinders

21.  The portion of the intake system of an engine
between the carburetor and the cylinders must
be installed gastight to provide proper engine
operation.
the gasket should be
between the the pipe
and the cylinder , and
secured rigidly by
bolts and nuts .

22.  Icecan form anywhere from the inlet of the
induction system to the intake manifold
between the carburetor and the intake port
of the cylinder.
 Thenature of the ice formation depends
on atmospheric temperature and humidity

23.  In
fixed-pitch propeller , the engine rpm will
decrease .
 Witha constant-speed propeller , the manifold
pressure will decrease and the engine power will
drop.

24.  Theformation of ice in an induction system is
prevented by the use of carburetor heat .
 Insome older installations for large engines ,
alcohol was sprayed into the inlet air duct to
reduce the formations of ice