engine intro & basic induction presented by: will miller
TRANSCRIPT
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
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
Intake Port
Where outside air enters the induction system
Normally contains an air filter to keep out dust and FOD
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 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