08/04/2020

 Considered to be the heart of an aircraft.

P O W E R P L A N T
Powerplant  Absence of it makes an aircraft a glider.
Lecturer: Engr. Kris Aileen B. Cortez

KACortez

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Thermodynamics The Reciprocating Engine

Design Concepts of Engines
P O W E R P L A N T

P O W E R P L A N T

 The name was derived from the ‘back-

Types of Engine and-forth’ movement or linear motion of
Performance pistons that produces a rotary motion of the
Functions of Engine Components crankshaft to produce thrust.
Limitations  Converts chemical energy to mechanical
Engine Failure Prevention energy

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Heat The Propulsion Chain

Heat is energy transferred due to temperature
P O W E R P L A N T

P O W E R P L A N T

differences only.
a. It alters system states; Energy Source Heat Mechanical Useful Work
b. Bodies don’t contain heat but identified as it come (chemical, (combustion (work, electric (propulsive
across system boundaries; nuclear, etc.) process) power) force)
c. Amount of heat needed to go from one state to
another is path dependent;
d. Adiabatic processes are ones in which no heat is
transferred.
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Temperature Scales
P O W E R P L A N T

P O W E R P L A N T
𝐾 = 273.15 + °𝐶
- or -
𝑅 = 459.9 + °𝐹

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Work Work
P O W E R P L A N T

P O W E R P L A N T

A means of changing the energy of a system. a. 𝑑𝑊 . =𝐹 . 𝑥 𝑑𝑙

.
b. 𝑑𝑊 . = 𝑥 𝐴 𝑥 𝑑𝑙
Effects that the system has on its surroundings. c. 𝐹 =𝑝
. . 𝑥 𝑑𝑉
d. 𝐹 . = 𝑝 𝑥 𝑑𝑉
e. 𝑑𝑊 . = ∫ 𝑝 𝑑𝑉
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Representation of
Work
Thermodynamic Cycles
P O W E R P L A N T

P O W E R P L A N T

f. 𝑑𝑊 . = ∫ (𝑝 ± 𝑑𝑝)𝑑𝑉 Transfer of heat from a high temperature

reservoir to a device, which does work on the
g. 𝑑𝑊 . = ∫ 𝑝 𝑑𝑉 ± 𝑑𝑝𝑑𝑉 surroundings, followed by a rejection of heat
from that device to a low temperature
h. 𝑊 = ∫ 𝑝 𝑑𝑉 reservoir.
i. 𝑊 = 𝑚 ∫ 𝑝 𝑑𝑣
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Operating Cycles of a
Generalized Heat Engine
Reciprocating Engine
P O W E R P L A N T

P O W E R P L A N T
1. Otto Cycle
2. Diesel Cycle
By-product

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Four Stroke (Five Event) Cycle Four Stroke (Five Event) Cycle
P O W E R P L A N T

P O W E R P L A N T

Inventor of the first Concept of the four strokes with vital

internal – combustion compression of the mixture before ignition
engine to efficiently was invented and patented by Alphonse
burn fuel directly in a Beau de Roches, Otto made it practical.
piston chamber.

Nikolaus August Otto

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Otto Cycle Otto Cycle

P O W E R P L A N T

P O W E R P L A N T

Fuel/air mixture 1. Ingest a mixture of

subjected to changes fuel and air
in pressure,
temperature, volume,
addition of heat and
removal of heat.
Ideal Otto Cycle Ideal Otto Cycle
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Piston and Valves in a Four-Stroke

Sketch of an Actual Otto Cycle Internal Combustion Engine
P O W E R P L A N T

P O W E R P L A N T
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Piston and Valves in a Four-Stroke

Internal Combustion Engine
Four Stroke (Five Event) Cycle
P O W E R P L A N T

P O W E R P L A N T

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Diesel Cycle Diesel Cycle

P O W E R P L A N T

P O W E R P L A N T

 Compression ignition  Can operate with a higher compression

engine. ratio that the Otto cycle as air is compressed
 Fuel sprayed into the without the risk of auto-ignition of the fuel.
cylinder at 𝑃 when  It can have higher efficiency than Otto
compression is cycle when operated at compression ratio
complete, and there is that might be achieved in practice.
ignition without spark. Ideal Diesel Cycle

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Diesel Cycle Thermal Efficiency Diesel Cycle

P O W E R P L A N T

P O W E R P L A N T
𝑸 𝑪 (𝑻 𝑻𝟒 )
a. 𝜼𝑫𝒊𝒆𝒔𝒆𝒍 = 𝟏 + 𝑸 𝑳 = 𝟏 + 𝑪𝒗 (𝑻𝟏
𝑯 𝒑 𝟑 𝑻𝟐 )
𝑻𝟒
𝑻𝟏 𝟏
𝑻𝟏
b. 𝜼𝑫𝒊𝒆𝒔𝒆𝒍 = 𝟏 − 𝑻𝟐 𝑻𝟑
𝟏
𝑻𝟐

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Valve Timing Otto Cycle vs. Diesel Cycle

The spark plug fires twice as often in a two-stroke
P O W E R P L A N T

P O W E R P L A N T

 Valve Lead engine -- once per every revolution of the

 Valve Lag crankshaft, versus once for every two revolutions
 Valve Overlap in a four-stroke engine. This means that a two-
stroke engine has the potential to produce twice
as much power as a four-stroke engine of the
same size.

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Design Concept Design

P O W E R P L A N T

P O W E R P L A N T

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Spark Ignition Compression Ignition

P O W E R P L A N T

P O W E R P L A N T
 Reduced operating costs  Variable alternative
 Simplified designs  Jet fuel for jet engines
 Improved reliability  Utilizes readily available and lower cost
 Utilizes spark plug to ignite a pre-mixed diesel or jet fuel (advantage)
fuel/air mixture.

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Types of Reciprocating Engines Radial Engine

P O W E R P L A N T

P O W E R P L A N T

 Classified according to piston

arrangement.
1. Radial
2. Inline
3. V-Type
4. Opposed

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Inline Engine V-Type Engine

P O W E R P L A N T

P O W E R P L A N T

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Opposed Engine Firing Order

Radial Engine V-Type Engine
P O W E R P L A N T

P O W E R P L A N T
1-3-5-2-4 1-3-4-2
1-3-5-7-2-4-6 1-6-5-4-3-2
1-3-5-7-9-2-4-6-8 1-3-7-2-6-5-4-8
Inline Engine
1-2-3 Opposed
1-3-4-2 1-3-4-2
1-5-3-6-2-4 1-3-5-6-4-2
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Engine Identification Piston Volume Displacement

P O W E R P L A N T

P O W E R P L A N T

O – Horizontally Opposed G – Geared Nose Section

R – Radial L – Left – hand Rotation
𝟐
I – Inline (multi-engine installations) 𝒃𝒐𝒓𝒆
𝑷𝒊𝒔𝒕𝒐𝒏 𝑫𝒊𝒔𝒑𝒍𝒂𝒄𝒆𝒎𝒆𝒏𝒕 = 𝝅 𝒙 (𝒔𝒕𝒓𝒐𝒌𝒆)
V – V-Type H – Horizontal Mounting 𝟐
T – Turbocharged (helicopters)
I – Fuel Injected V – Vertical Mounting
S - Supercharged A – Modified for Aerobatics

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Total Piston Displacement

P O W E R P L A N T

P O W E R P L A N T

𝟐
𝒃𝒐𝒓𝒆
𝑻𝒐𝒕𝒂𝒍 𝑷𝒊𝒔𝒕𝒐𝒏 𝑫𝒊𝒔𝒑𝒍𝒂𝒄𝒆𝒎𝒆𝒏𝒕 = 𝝅 𝒙 (𝒔𝒕𝒓𝒐𝒌𝒆)(# 𝒐𝒇 𝒄𝒚𝒍𝒊𝒏𝒅𝒆𝒓𝒔)
𝟐

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Parts of the Engine Parts of the Engine

P O W E R P L A N T

P O W E R P L A N T
 Crankshaft
 Connecting Rod
 Piston
 Intake Valve
 Exhaust Valve
 Cylinder
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Factors Affecting Propeller

Parts of a Propeller
Efficiency
P O W E R P L A N T

P O W E R P L A N T

 Propeller Blades  Propeller Blade Angle – angle between the

 Leading Edge chord line of the propeller and the plane of
 Trailing Edge rotation.
 Tip
 Propeller Hub
 Spinner
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Factors Affecting Propeller Factors Affecting Propeller

Efficiency Efficiency
P O W E R P L A N T

P O W E R P L A N T

 Propeller Twist– tapers towards the tips  Propeller Twist– the tip of the propeller rotates
which appears to twist. in a larger arc than the hub. Therefore, travels a
greater speed that would produce more angle of
attack.

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Factors Affecting Propeller

Propeller Performance
Efficiency
 Tip Speed
P O W E R P L A N T

P O W E R P L A N T
 Tip Speed – flutter or 𝑉 = 𝜋𝑑𝑛
vibration may be caused
by the tip of the propeller 𝑇=  Thrust
blade travelling at a rate of
speed of sound which w= −𝑉 + 𝑉 +  Induced Velocity
causes stress to develop.
𝜂 =  Ideal Prop. Efficiency

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Propeller Performance Propeller Efficiency

P O W E R P L A N T

P O W E R P L A N T

𝜂 = 𝜂 .𝜂  New Ideal Prop. Eff.  Ratio of thrust

Δ=𝜂 −𝜂  Change in Prop. Eff. horsepower to brake
horsepower.
 Varies from 50% - 87%
depending on propeller
slippage.

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Horsepower Calculation Geometric Pitch

P O W E R P L A N T

P O W E R P L A N T

𝐻𝑃 =  HP Required  Theoretical distance a propeller should

advance in one revolution.
𝐻𝑃 =  BHP (crankshaft power)
𝐼𝐻𝑃 =  IHP
,

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Effective Pitch Propeller Slippage

P O W E R P L A N T

P O W E R P L A N T
 Distance a propeller actually advances  Also known as propeller slip.
 Difference between the geometric pitch of
the propeller and its effective pitch.

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Types of Propellers
P O W E R P L A N T

P O W E R P L A N T

 Fixed Pitch
 Ground Adjustable
 Controllable Pitch
 Constant Speed

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Fixed Pitch Ground Adjustable Pitch

P O W E R P L A N T

P O W E R P L A N T

 Usually efficient at one RPM and speed setting.  Pitch setting is done on
 At a constant RPM, a fixed pitch propeller with the ground when the
increasing forward speed would result in a aircraft is not flying or
decrease of propeller and angle of attack. engine is not running.

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Controllable Pitch Constant Speed

 Pilot can change the  Also referred to as
P O W E R P L A N T

P O W E R P L A N T
pitch in-flight. automatic propeller.
 Types of Controllable  Automatically
Pitch Propeller adjusts the propeller
1. Two-Position pitch to maintain a
Propeller selected propeller
2. Multi-Position
Propeller rpm.
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Constant Speed Constant Speed

 Hydromechanical or
P O W E R P L A N T

P O W E R P L A N T

electrically pitch-
changing mechanism
called propeller
governor.
 Converts a high
percentage of engine’s
power to thrust.
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Manifold Pressure
P O W E R P L A N T

P O W E R P L A N T

 Power output is controlled

by the throttle and indicated
on the MAP gauge.
 The gauge measures the
absolute pressure of the
fuel/air mixture inside the
intake manifold.
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Manifold Pressure Induction System

P O W E R P L A N T

P O W E R P L A N T
 Increased throttle  Fuel/Air Ratio
setting, more fuel and air  Rich Mixture
is flowing to the engine  Lean Mixture
and MAP increases.  Stoichiometric Ratio
 For any given RPM, MAP
should not be exceeded.

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Benefits of a Properly Leaned

Induction System
Mixture
Mixture Knob
P O W E R P L A N T

P O W E R P L A N T

 Better Engine Performance

 Fuel Efficient

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Disadvantages of Improperly
Leaning Type
Leaned Engines
P O W E R P L A N T

P O W E R P L A N T

 Rich of Peak  Mixture too Lean  Mixture too Rich

 Slightly rich of maximum power  High engine  Lower engine output
 Better engine cooling temperatures.  High fuel consumption
 Lower engine output.
 Lean of Peak  Possible spark plug
 Rough engine and can
cause detonation and fouling
 Slightly lean of maximum power
pre-ignition.
 Better efficiency

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Carburetor Icing Carburetor Icing

P O W E R P L A N T

P O W E R P L A N T
 Formation at temperature below 70 °F or  Detection
21 °C.  Engine roughness in
 Relative humidity is above 80%. fixed pitch propeller
 reduced manifold
pressure but no
reduction in rpm

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Carburetor Heat Application of Carburetor Heat

P O W E R P L A N T

P O W E R P L A N T

 Preheats air  Reduction of engine power

 Hot air makes  Used below green arc of tachometer
mixture richer since  For presence of ice, slight increase in rpm
hot air is less dense. after applying Carb Heat.
 If no presence of ice, rpm will decrease and
remain constant.
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Indication of Successful Use of

Carburetor Heat
P O W E R P L A N T

P O W E R P L A N T

 Increase in rpm after ice is melted.

 Increase in manifold pressure after
carburetor ice is melted.

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Superchargers and
Effects of Carburetor Heat
Turbochargers
P O W E R P L A N T

P O W E R P L A N T
 Decrease in engine power  Increases engine’s power
 Alternate source of intake filter clogs  Both compresses air as it enters the intake
 Avoid use in dusty environments manifold to increase the air density.
 ‘Rich mixture’ is one of its major effects
 Below the green arc

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Propulsive Efficiency of Engines Supercharger

P O W E R P L A N T

P O W E R P L A N T

 Relies on engine-
driven air compressor to
compress the air.
 Placed between fuel
metering device and
intake manifold.

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Supercharger Supercharger
P O W E R P L A N T

P O W E R P L A N T

 Provides sea level  Disadvantage

pressures to increase  Gear-driven
aircraft performance up supercharger uses a
to 18,000 ft. large amount of engine’s
power output for the
amount of power
increase produced.
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Turbocharger Turbocharger
P O W E R P L A N T

P O W E R P L A N T
 Utilizes exhaust stream that runs through a  Can maintain control
turbine which in turn spins the compressor. over an engine’s rated
 External devices are driven by the engine sea level horsepower
exhaust system which compresses fuel/air from sea level up to the
mixture. engine’s critical altitude.
 Most efficient method of increasing
horsepower which uses exhaust gases.
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Turbocharger Turbocharger
 Critical Altitude
P O W E R P L A N T

P O W E R P L A N T

 Avoids using a large

amount of engine’s  Maximum altitude at
power output (to obtain which a turbocharged
engine can produce its
an increase in the power rated horsepower.
output).  Above the critical
altitude, power output
begins to decrease.
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Overboost
P O W E R P L A N T

P O W E R P L A N T

 A condition where the compressor feeds too much

pressure on the engine due to:
 Malfunctioning waste gate
 Inadequate oil flow to waste gate
 Abrupt throttle advances
 Most turbocharger systems are fitted with
automated controls to prevent overboosting.

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Turbocharger Turbolag
P O W E R P L A N T

P O W E R P L A N T
 Since EGT rises when  The time that a
compressed, intercooler turbocharger needs to
is used to reduce the stabilize which requires
temperature of air and smooth and slow throttle
lower the risk of movements.
detonation.

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Ignition System Magneto Check

P O W E R P L A N T

P O W E R P L A N T

 Magnetos  Shuts down half of the engine’s spark

 Engine driven and uses a permanent magnet plugs and tests each magneto
to generate electrical current. independently.
 Generates high voltage to jump a spark  A smooth drop is normal.
across the spark plug in each cylinder.
 Continues to operate whenever the
 Magneto differential = 50rpm
crankshaft is rotating.  Magneto drop = 125 rpm
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Benefits of Magneto Check Ignition Switch Positions

OFF
P O W E R P L A N T

P O W E R P L A N T

 Higher power output.  No magnetos are connected

L
 Efficient burning capability.  Only left magneto is connected
 Fail safe mechanism in the event one R
 Only right magneto is connected
magneto fails. Both
 Both magnetos are connected
Start
 Both magnetos are connected
 Initiates an electric starter motor to rotate the crankshaft

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Distributor
P O W E R P L A N T

P O W E R P L A N T
 Distributes electrical current from
magnetos to the spark plugs.
 Spark plugs in different cylinders received
current at different times.

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Ground Wire
P O W E R P L A N T

P O W E R P L A N T

 If the “Ground Wire” between the

magneto and ignition switch becomes
disconnected or grounded, the engine could
accidentally start if the propeller is moved
with residual fuel in the cylinder/continue to
run even when the switch is in the OFF
position.
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Starter System Starting System

P O W E R P L A N T

P O W E R P L A N T

Electric Starter Motor

 Cranks the crankshaft to move the piston
inside the cylinders.
 Initiates Otto Cycle

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Fuel System Gravity – Feed System

P O W E R P L A N T

P O W E R P L A N T
 Designed to provide uninterrupted flow of  Generally used by high-wing aircrafts in
clean fuel from the fuel tanks to the engine. the general aviation.
 Utilizes gravitational force to transfer fuel.
Types of Fuel System  Ex. On high-wing aircrafts, fuel tanks are
1. Gravity – Feed installed on the wings.
2. Fuel - Pump
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Gravity – Feed System Fuel – Pump System

P O W E R P L A N T

P O W E R P L A N T

 Main pump system is engine driven.

 Auxiliary pump which is electrically
powered and is used for engine startup.

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Fuel – Pump System Fuel Related Problems

P O W E R P L A N T

P O W E R P L A N T

Pre-ignition
 Fuel/air mixture ignites
prior to engine’s normal
ignition event.
 Ignition of the fuel/air
mixture ahead of the spark
provided by the spark plugs.

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Fuel Related Problems Fuel Related Problems

P O W E R P L A N T

P O W E R P L A N T
Pre-ignition Detonation
Causes:  Uncontrolled, explosive
 Premature burning by a residual hot spot in the ignition of the fuel/air
cylinder which is often created by a small carbon mixture within the
deposit on a spark plug. cylinder’s combustion
chamber.
 Using a lower than prescribed octane rating.

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Fuel Related Problems Fuel Related Problems

Detonation Detonation
P O W E R P L A N T

P O W E R P L A N T

 Causes:  Causes:
 Use of a lower fuel  Operation of the
grade than that engine at high power
specified by the aircraft settings with an
manufacturer. excessively lean
 Operation of the mixture.
engine with extremely  Maintaining extended
high manifold ground operations or
pressures in steep climbs in which
conjunction with low cylinder cooling is
rpm. required.

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Fuel Related Problems Fuel Related Problems

Fuel Contamination
P O W E R P L A N T

P O W E R P L A N T

How to Avoid Detonation

 Keep cowl flaps open on the ground.  Fuel tanks contain moisture that condenses when
the OAT cools.
 Use proper grade of fuel.  Solution: Empty space inside the fuel tanks
 Use rich fuel setting during takeoff and contains moisture that condenses when the outside
air temperature cools.
initial climb.  Another solution: Refilling the fuel tanks to full
 Avoid high power, and steep climb. levels at the end of each day.
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Fuel Types Fuel Types

AVGAS 80
P O W E R P L A N T

P O W E R P L A N T
 Very low lead content
 Only suitable for low compression engines
 Red in color
AVGAS 100
 High lead content
 Suitable for high compression engines
 Green in color
AVGAS 100LL
 Has low lead content
 Blue in color

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Fuel Grade Fuel Grade

P O W E R P L A N T

P O W E R P L A N T

 STC issued by the FAA

 “If the proper fuel grade is not available,
use the next higher grade as a substitute.”

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MOGAS MOGAS
 Cheaper than AVGAS.
P O W E R P L A N T

P O W E R P L A N T

 Low Compression Engine – uses low fuel

 It tends to cause vapor locks in pipelines at grades (ignites at lower temperature).
high temperature and altitude.  High Compression Engine – uses high fuel
 Carbureted engines using this fuel are grades (ignites at higher temperature).
more susceptible to carburetor icing.
 Low lead content which can lead to pre-
ignition and detonation.
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Fuel Injected Engines Fuel Injected Engines

P O W E R P L A N T

P O W E R P L A N T
Fuel Injection System Auxiliary Fuel Pump
 Fuel is injected directly into the  Provides fuel under pressure to the fuel/air
cylinders, or just ahead of the intake valve. control unit for engine starting and/or
emergency use.
Fuel Pump
Engine Driven Fuel Pump
 Provides fuel from the tanks to the FCU.
 Used after starting the engine, and provides
the fuel/air control unit.
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Fuel Injected Engines

P O W E R P L A N T

P O W E R P L A N T

FCU
 Replaces the carburetor, meters fuel based
on the mixture control setting and sends it to
the fuel manifold valve at a rate controlled by
the throttle.
Fuel Manifold Valve
 Distributes the mixture to individual nozzles
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Fuel Injected Engines Fuel Injected Engines

P O W E R P L A N T

P O W E R P L A N T

Discharge Nozzles Metering Fuel Valve

 Atomizes fuel into fine mist and inject  Controls fuel flow going in the manifold valve via
directly into each cylinder intake port. throttle control.
 Provides correct fuel/air ratio.
Throttle Valve
Mixture Control Valve
 Controls airflow to the engine.
 Connected to mixture control lever.
 Regulates amount of fuel entering the system.

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Fuel Injected Engines Fuel Injected Engines

P O W E R P L A N T

P O W E R P L A N T
Fuel Pressure Gauge
 Allows mixture to be adjusted according to
altitude and power setting.

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Fuel Injected Engines Fuel Injected Engines

Advantages Disadvantages
P O W E R P L A N T

P O W E R P L A N T

 Reduction in evaporative icing  Difficulty in starting a hot engine

 Better fuel flow and distribution  Vapor locks during ground operations on
 Faster throttle response hot days
 Precise control of mixture  Problems associated with restarting an
 Easier cold weather starts engine that quits because of fuel
starvation
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Fuel Injected Engines

Vapor Lock
P O W E R P L A N T

P O W E R P L A N T

 Prominent in fuel injected aircraft after

shutting down a hot engine.
 Atomized fuel evaporates into fuel lines,
preventing fuel from reaching the engine
during start-up.
 Solution: use auxiliary fuel pump
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Cooling System Cooling System

Air Cooled
P O W E R P L A N T

P O W E R P L A N T
 Air Cooled
 Spinner – redirects air into the nacelles
 Water Cooled  Baffles – redirects cold air to the parts of the
engine which would not normally be cooled
 Cooling Fins – expands the surface area to
improve cooling
 Cowl Flaps – air vents outside the engine to
improve cooling
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Oil System Oil System

Properties of Aircraft Oil
P O W E R P L A N T

P O W E R P L A N T

Functions
 Cooling  High viscosity – resistance to flow
 Low pour points – temperature at which fluid
 Lubrication solidifies
 Functions as a seal in pistons  High flash point – does not vaporize or catch
 Carries away contaminants fire easily
 Low carbon content
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Oil System Wet Sump Oil System

P O W E R P L A N T

P O W E R P L A N T

Types of Oil System

 Dry Sump – oil is contained in a separate
tank
 Wet Sump – oil is located in a sump

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Dry Sump Oil System Oil System Malfunctions

P O W E R P L A N T

P O W E R P L A N T
Rapid Oil Loss
 Decrease in pressure
 Increase in temperature
Oil Blockage
 Increase in pressure
 Increase in temperature
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Things to Remember for

Oil Gauges
the Oil System
P O W E R P L A N T

P O W E R P L A N T

Pressure  Do not mix oil with different grades

 60 – 90 psi  If no oil pressure rise within 30 seconds of
Temperature engine operation, shut down engine.
 100 – 245°F  It could be a sign of oil leak.

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Exhaust System Exhaust System

 Scavenges hot exhaust gases out of the Exhaust Gases
P O W E R P L A N T

P O W E R P L A N T

engine cylinders.  Contains large amount of carbon monoxide.

EGT Probe
 Vents burned combusted gases overboard  Measures the temperature of gases at the exhaust
and provides heated air for cabin heat and manifold which can also be used for regulating the fuel/air
carburetor heat. mixture.
 Prevents the escape of these potentially EGT Gauge
 Measures the temperature of gases at the exhaust
harmful gases into the airframe/cabin. manifold.
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Two Types of Exhaust System Short Stack System

P O W E R P L A N T

P O W E R P L A N T
 Short Stacks System  Used on low powered, non-turbocharged engines.
 Collector System  Simplicity of design in:
 Each side has its own collector tube/downstack
from each cylinder;
 An exhaust collector tube on each side of the
engine, and;
 An exhaust ejector on each side of the cowling

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Collector System Factors Affecting Power

 MAP
P O W E R P L A N T

P O W E R P L A N T

 Exhaust is collected to drive the

 Detonation and Preignition
turbocharger.
 Compression Ratio
 Ignition Timing
 Engine Speed
 SFC
 Altitude
 Fuel/Air Ratio
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