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Aircraft Systems
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
 Cessna Engine
 Horizontally Opposed
 Direct Drive
 Air Cooled
 4 cylinder
Engine Operation
What are the four strokes of an engine?
 Four Strokes on an Engine
 Intake
 When the piston moves away form the cylinder head
 Intake valve opens
 Fuel/Air mixture is drawn into the combustion chamber
 Compression
 Piston moves back toward the cylinder head
 Intake valve closes
 Fuel/Air Mixture is compressed
 Power
 Compression nearly complete
 Spark plugs fire
Compressed mixture is ignited
 Rapidly expanding gases drive the piston, providing the power that rotates the crankshaft
 Exhaust
 Expels the burned gases through the exhaust valve, which opens at the end of the power stroke
 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
 Throttle
Controls Engine Speed
 Regulates the amount of fuel/air mixture that flows into the cylinders
 Mixture
 Controls the fuel/air ratio
 Intake Port
 Where outside air enters the induction system
 Normally contains an air filter to keep out dust and FOD
 Carburetor
 Mixes the incoming air with fuel and delivers it to the combustion chamber
 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
 Fuel is forced through the discharge nozzel by the higher atmospheric pressure in the float chamber
 Overly Rich Mixture
What does it mean to have a “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
 Overly Lean Mixture
 What does it mean to have a “Lean” mixture?
– May result in high engine temperatures causing excessive wear or even failure
– Enrichen Mixture on descents from high altitudes
– Watch engine temperature
 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%
 Carburetor Ice
 Carburetor Ice
 Carburetor Ice Indications
 Why can Carburetor Ice be dangerous?
 What are some indications of Carb Ice?
– Drop in engine RPM
– Engine Roughness
– Fuel starvation
 What can we do to get rid of carburetor ice or even prevent it from happening in the first place?
– Carburetor Heat
 Carburetor Heat
 Carburetor ice is especially dangerous when operating at low power settings, may go unnoticed until power is added
– How does carburetor heat work?
– Carburetor heat routes air across a heat source before it enters the carburetor
– How will carb heat affect engine performance?
– 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
 Carburetor Heat
 Fuel Injection
What is the benefit of a fuel injected fuel system?
– No carburetor
– More precision 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
 Fuel Injection
 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
 Turbocharger
 Ignition System
What does the ignition system do?
– Provides spark that ignites the fuel/air mixture in the cylinders
 List the parts of the ignition system.
– Magnetos
– Spark Plugs
– Interconnecting wires
– Ignition Switch
Magneto
What is a 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
 If you lose your battery/alternator in flight, will your engine stop working?