Aircraft Systems

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Aircraft Systems
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Engine Types

• Turbine Engine
• Found in transport Category aircraft
• Relatively costly but extremely powerful
• Reciprocating Engine
• Found in general aviation
• Economical, but still very reliable

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Cadet Engine

• Horizontally Opposed
• Direct Drive
• Air Cooled
• 4 cylinder

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Engine Operation

• Four Stroke Operating Cycle

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Intake

• When the piston moves away form the cylinder head
• Intake valve opens
• Fuel/Air mixture is drawn into the combustion
  chamber

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Compression

• Piston moves back toward the cylinder head
• Intake valve closes
• Fuel/Air Mixture is compressed

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Power

• Compression nearly complete
• Spark pugs fire
• Compressed mixture is ignited
• Rapidly expanding gases drive the piston,
  providing the power that rotates the crankshaft

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Exhaust

• Expels the burned gases through the exauhst
  valve, which opens at the end of the power stroke

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Induction System

• Brings outside air into the engine, mixes it with
  fuel in the proper proportion and deliver it to
  the cylinders where combustion occurs.
• Throttle
• Mixture
• Intake Port

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Throttle

• Controls Engine Speed
• Regulates the amount of fuel/air mixture that
  flows into the cylinders

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Mixture

• Controls the fuel/air ratio

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Intake Port

• Where outside air enters the induction system
• Normally contains an air filter to keep out dust
  and FOD

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Carburetor

• Mixes the incoming air with fuel and delivers it
  to the combustion chamber

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Carburetor

• Air passes through a venturi, increases velocity
  and decreases pressure
• Fuel enters from a float chamber where it is
  maintained at a nearly constant level by a float
  device
• Discharge nozzle is located in an area of low
  pressure created by the venturi
• the fuel is forced through the discharge nozze by
  the higher atmospheric pressure in the float
  chamber

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Overly Rich Mixture

• As altitude increases, the mixture will get
  progressively richer due to the decrease in air
  density.
• Can result in engine roughness excessive carbon
  buildup on the spark plug will cause them to
  foul.
• High elevation airports, climb or cruise at high
  elevation

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Overly Lean Mixture

• May result in high engine temperatures causing
  excessive wear or even failure
• Enrichen Mixture on descents from high altitudes
• Watch engine temperature

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Carburetor Ice

• Occurs due to the effect of fuel vaporization and
  decreasing pressure in the venturi which causes a
  sharp temperature drop in the carburetor
• If water vapor in the air condenses when the
  carburetor temperature is at or below freezing,
  ice may form on internal surfaces of the
  carburetor, including the throttle valve
• Likely below 21C (70F), humidity above 80

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Carburetor Ice Indications

• Drop in engine RPM
• Engine Roughness
• Fuel starvation

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Carburetor Heat

• Especially Dangerous when operating at low power
  settings, may go unnoticed until power is added
• Carburetor heat routes air across a heat source
  befor it enters the carburetor
• Causes a slight decrease in engine power (heated
  air is less dense)
• If ice is present, there will be a decrease
  followed by a gradual increase in rpm

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Fuel Injection

• No carburetor
• More Precise in metering and distributing
  fuel/air mixture
• Injects the fuel directly into each cylinder
  separately
• Lower fuel consumption, increased Horsepower,
  lower operating temperatures, longer engine life

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High Altitude Flight

• Supercharger
• Compresses the incoming air to the engine using a
  pump driven by the engine
• Turbocharger
• Pressurizes the air into the engine using a
  mechanism driven by exhaust gases

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Ignition System

• Provides spark that ignites the fuel/air mixture
  in the cylinders
• Magnetos
• Spark Plugs
• Interconnecting wires
• Ignition Switch

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Magneto

• Self contained
• Engine driven
• Supplies electrical current to the spark plugs
• Uses permanent magnet for electrical current that
  is completely separate from the electrical system
• Begins when you engage starter
• Operates whenever the crankshaft turns
• Normally two for redundancy/ improves combustion

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Ignition Switch

• Controls the operation of the magneto from the
  cockpit
• Can select left, right or both
• Engine can still fire even with the battery and
  master switches off, if the magnetos are left on
  and the prop is moved because no outside
  electrical power is required

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Abnormal Combustion

• Detonation
• Pre-ignition

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Detonation

• Explosive ignition of the fuel/air mixture within
  the cylinders combustion chamber
• Uncontrolled
• Engine overheating, roughness or loss of power
• Excessive temperatures and pressures leading to
  failure of piston, cylinder or valves
• Engine overheat or lower than recommended fuel
  grade

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Pre-ignition

• Detonation can lead to pre ignition
• Fuel/Air mixture is ignited in advance of the
  normal timed ignition
• Caused by a residual hot spot in the cylinder
  such as a small carbon deposit on a spark plug ,
  cracked ceramic spark plug insulator, or any
  damage around the combustion chamber

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Fuel System
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Fuel-Pump System

• Engine Driven Pump
• Electric Fuel pump
• Provides fuel under pressure from the fuel tanks
  to the engine
• Low wing airplanes

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Fuel-Pump System

• Fuel Pressure Gauge
• Gives and exact reading of the pressure the fuel
  pump is providing the engine
• Helpful in detecting fuel pump malfunctions

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Fuel-Pump System

• Vapor Lock
• When air enters the fuel system and does not
  allow the fuel to flow to the engine

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Gravity Feed System

• Fuel flows to the engine by gravity from the fuel
  tanks
• High wing aircraft

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Primer

• Used to pump fuel directly into the intake system
  prior to engine start
• Useful in cold weather when fuel in the
  carburetor is difficult to vaporize

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Fuel Tanks

• Usually located on the wings
• Vented to allow for changes in pressure inside
  the tank, prevents vacuum

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Fuel Quantity Gauges

• Located on the instrument panel
• Shows the amount of fuel in each fuel tank

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Fuel Selector Valve

• Allows you to select fuel from various tanks
• Some may only have Left, Right and OFF must
  monitor

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Fuel Strainer

• Removes moisture and other sediments that might
  be in the system
• In cold weather, moisture is hazardous because it
  can freeze and block fuel lines
• In warm weather, it can flow into the carburetor
  and stop the engine
• Fill tanks should be filled each evening to
  prevent condensation

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Re- Fueling

• Red 80/87 octane
• Green 100/130
• Blue 100LL
• Clear Jet
• In emergency, always use next higher grade (but
  never jet)

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Oil System

• Lubricates
• Cleans
• Seals
• Cools
• Protects

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Dry- Sump System

• Oil is contained in a separate tank
• Circulated through the engine by pumps

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Wet Sump System

• Oil is carried in a sump
• Integral part of the engine
• Found on most small general aviation aircraft

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Oil Pressure Gauge

• Provides direct indication of the oil system
  operation
• Below normal pressure may mean that the oil pump
  is not putting out enough pressure to circulate
  oil throughout the engine.
• Above normal may indicate a clogged oil line
• Shut down engine if oil pressure does not begin
  to rise within 30 seconds for warm starts/60
  seconds cold starts

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Oil Temperature Gauge

• Measures temperature of the oil as it enters the
  engine
• Slow changes

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Cooling Systems

• Excessively high engine temperatures can result
  in a loss of power, high oil consumption and
  engine damage.
• Internal cooling is done by oil, but more is
  needed to maintain normal temperatures
• Remaining heat dissipated by exhaust and through
  outside air flowing around the engine

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Cowl Flaps

• Create a large path for air to escape from the
  engine compartment
• Flaps that open on the bottom of the engine
  cowling
• Increases cooling air flow

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Cylinder Head Temperature Gauge

• Usually in airplanes with Cowl Flaps
• Direct temperature reading from one of the
  cylinders
• Reducing Engine Temperatures
• Enrichen mixture
• Reduce rate of climb
• Increase airspeed
• Decrease power setting

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Exhaust System

• Vent burned gases
• Provide heat for cabin
• Directs exhaust out below the engine compartment
  through a muffler and tailpipe
• As the hot exhaust gases heat the muffler, metal
  shrouds around the muffler capture the heat and
  duct it to the cabin.

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Propellers

• Provides thrust to propel the airplane through
  the air.
• Each blade is an airfoil that acts like a
  rotating wing
• Amount of thrust produced is a function of shape,
  rotation speed and position relative to the
  relative wind

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Propellers

• Each small section of blade is set at a different
  angle to the plane of rotation
• Gradual decrease in blade angle gives twisted
  appearance
• Allows the propeller to provide more uniform
  thrust throughout most of the length of the blade

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Climb Propeller

• Low blade angle
• Best performance for takeoff and climb

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Cruise Propeller

• High blade angle
• High speed cruise
• High altitude flight

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Fixed Pitch Propeller

• Blade angle is selected on the basis of what is
  best for the primary function of the airplane
• Cannot be changed by the pilot

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Constant Speed Propeller

• Pilot can adjust the blade angle for the most
  efficient operation

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Electrical System
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Definitions

• Amp flow rate
• Volt measure of electromagnetic force. Volts are
  pressure that push amps to give power
• Volts X Amps Watts

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Alternators v. Generators

• Alternators
• Produces sufficient amount of electrical current
  at slower RPM by producing AC current that is
  converted to DC
• More constant at different ranges of engine
  speeds
• Lighter weight
• Less costly to maintain
• Less prone to overloading

• Generators
• Do not produce enough electrical current at low
  engine RPM to operate entire electrical system.
• Electrical needs often rely on battery, which is
  quickly depleted

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Alternator

• Engine Driven
• Supplies engine when running with electrical
  supply
• Usually 14-28 volt

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Alternating Current (AC)

• Type of current produced by an alternator
• Current that changes direction

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Direct Current (DC)

• Current that flows in one direction
• Aircraft run off of direct current
• AC must be converted to DC
• Battery is DC current

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Battery

• Main purpose is to provide a means of starting
  the engine
• Limited operation of electrical components
  (Clock, hourmeters)
• Source of standby or emergency electrical power
  in case of alternator malfunction

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Ammeter

• Used to monitor the electrical current in amperes
  within the system
• Positive value means battery is being charged
• Negative value means you are drawing off of the
  battery
• Two types
• One reflects current flowing to or from the
  battery
• Other type displays the load placed on the
  alternator and is often called a loadmeter

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Master Switch

• Controls the entire electrical system
• Except battery and magnetos
• Battery and Alternator Switches
• Similar to Master
• You can turn of the Alternator in the event of
  failure, at which point all current will be drawn
  the battery. At that point, you will need to load
  shed

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Circuit Breakers/Fuses

• Protect various components from overloads
• Resetting a breaker will usually re-activate the
  circuit
• In the event of an alternator failure, you may
  have to reduce the load on the battery by pulling
  certain non essential circuit breakers.

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Bus Bars
Tie Bus
Avionics (40)
Non Essential (40)l
Main Bus (60)
AP Com. 1
Rec. lts Heater
Strobe Pitot
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Voltage Regulator

• Controls the rate of charge to the battery by
  stabilizing generator/alternator electrical
  output.
• Alternator voltage is normally slightly higher
  than battery (otherwise, the battery would be
  charging the alternator)

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Overvoltage Relay

• Located in alternator
• Takes the alternator offline if the output
  exceeds a predetermined value

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Questions